DOTS T. Reddy, Ed.
Internet-Draft McAfee
Intended status: Standards Track M. Boucadair, Ed.
Expires: July 22, 2019 Orange
P. Patil
Cisco
A. Mortensen
Arbor Networks, Inc.
N. Teague
Verisign, Inc.
January 18, 2019
Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal
Channel Specification
draft-ietf-dots-signal-channel-27
Abstract
This document specifies the DOTS signal channel, a protocol for
signaling the need for protection against Distributed Denial-of-
Service (DDoS) attacks to a server capable of enabling network
traffic mitigation on behalf of the requesting client.
A companion document defines the DOTS data channel, a separate
reliable communication layer for DOTS management and configuration
purposes.
Editorial Note (To be removed by RFC Editor)
Please update these statements within the document with the RFC
number to be assigned to this document:
o "This version of this YANG module is part of RFC XXXX;"
o "RFC XXXX: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Signal Channel Specification";
o "| [RFCXXXX] |"
o reference: RFC XXXX
Please update this statement with the RFC number to be assigned to
the following documents:
o "RFC YYYY: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Data Channel Specification (used to be
[I-D.ietf-dots-data-channel])
Reddy, et al. Expires July 22, 2019 [Page 1]
Internet-Draft DOTS Signal Channel Protocol January 2019
Please update TBD/TBD1/TBD2 statements with the assignments made by
IANA to DOTS Signal Channel Protocol.
Also, please update the "revision" date of the YANG modules.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 22, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6
4. DOTS Signal Channel: Messages & Behaviors . . . . . . . . . . 9
4.1. DOTS Server(s) Discovery . . . . . . . . . . . . . . . . 9
4.2. CoAP URIs . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . 9
4.4. DOTS Mitigation Methods . . . . . . . . . . . . . . . . . 11
4.4.1. Request Mitigation . . . . . . . . . . . . . . . . . 12
Reddy, et al. Expires July 22, 2019 [Page 2]
Internet-Draft DOTS Signal Channel Protocol January 2019
4.4.2. Retrieve Information Related to a Mitigation . . . . 26
4.4.2.1. DOTS Servers Sending Mitigation Status . . . . . 31
4.4.2.2. DOTS Clients Polling for Mitigation Status . . . 34
4.4.3. Efficacy Update from DOTS Clients . . . . . . . . . . 35
4.4.4. Withdraw a Mitigation . . . . . . . . . . . . . . . . 37
4.5. DOTS Signal Channel Session Configuration . . . . . . . . 38
4.5.1. Discover Configuration Parameters . . . . . . . . . . 40
4.5.2. Convey DOTS Signal Channel Session Configuration . . 44
4.5.3. Configuration Freshness and Notifications . . . . . . 49
4.5.4. Delete DOTS Signal Channel Session Configuration . . 50
4.6. Redirected Signaling . . . . . . . . . . . . . . . . . . 51
4.7. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 53
5. DOTS Signal Channel YANG Modules . . . . . . . . . . . . . . 54
5.1. Tree Structure . . . . . . . . . . . . . . . . . . . . . 54
5.2. IANA DOTS Signal Channel YANG Module . . . . . . . . . . 56
5.3. IETF DOTS Signal Channel YANG Module . . . . . . . . . . 60
6. YANG/JSON Mapping Parameters to CBOR . . . . . . . . . . . . 70
7. (D)TLS Protocol Profile and Performance Considerations . . . 73
7.1. (D)TLS Protocol Profile . . . . . . . . . . . . . . . . . 73
7.2. (D)TLS 1.3 Considerations . . . . . . . . . . . . . . . . 74
7.3. DTLS MTU and Fragmentation . . . . . . . . . . . . . . . 75
8. Mutual Authentication of DOTS Agents & Authorization of DOTS
Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 78
9.1. DOTS Signal Channel UDP and TCP Port Number . . . . . . . 78
9.2. Well-Known 'dots' URI . . . . . . . . . . . . . . . . . . 78
9.3. Media Type Registration . . . . . . . . . . . . . . . . . 78
9.4. CoAP Content-Formats Registration . . . . . . . . . . . . 79
9.5. CBOR Tag Registration . . . . . . . . . . . . . . . . . . 79
9.6. DOTS Signal Channel Protocol Registry . . . . . . . . . . 80
9.6.1. DOTS Signal Channel CBOR Key Values Sub-Registry . . 80
9.6.1.1. Registration Template . . . . . . . . . . . . . . 80
9.6.1.2. Initial Sub-Registry Content . . . . . . . . . . 81
9.6.2. Status Codes Sub-Registry . . . . . . . . . . . . . . 82
9.6.3. Conflict Status Codes Sub-Registry . . . . . . . . . 84
9.6.4. Conflict Cause Codes Sub-Registry . . . . . . . . . . 86
9.6.5. Attack Status Codes Sub-Registry . . . . . . . . . . 86
9.7. DOTS Signal Channel YANG Modules . . . . . . . . . . . . 87
10. Security Considerations . . . . . . . . . . . . . . . . . . . 88
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 90
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 90
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 90
13.1. Normative References . . . . . . . . . . . . . . . . . . 90
13.2. Informative References . . . . . . . . . . . . . . . . . 93
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 97
Reddy, et al. Expires July 22, 2019 [Page 3]
Internet-Draft DOTS Signal Channel Protocol January 2019
1. Introduction
A distributed denial-of-service (DDoS) attack is a distributed
attempt to make machines or network resources unavailable to their
intended users. In most cases, sufficient scale for an effective
attack can be achieved by compromising enough end-hosts and using
those infected hosts to perpetrate and amplify the attack. The
victim in this attack can be an application server, a host, a router,
a firewall, or an entire network.
Network applications have finite resources like CPU cycles, the
number of processes or threads they can create and use, the maximum
number of simultaneous connections they can handle, the limited
resources of the control plane, etc. When processing network
traffic, such applications are supposed to use these resources to
provide the intended functionality in the most efficient manner.
However, a DDoS attacker may be able to prevent an application from
performing its intended task by making the application exhaust its
finite resources.
A TCP DDoS SYN-flood [RFC4987], for example, is a memory-exhausting
attack while an ACK-flood is a CPU-exhausting attack. Attacks on the
link are carried out by sending enough traffic so that the link
becomes congested, thereby likely causing packet loss for legitimate
traffic. Stateful firewalls can also be attacked by sending traffic
that causes the firewall to maintain an excessive number of states
that may jeopardize the firewall's operation overall, besides likely
performance impacts. The firewall then runs out of memory, and can
no longer instantiate the states required to process legitimate
flows. Other possible DDoS attacks are discussed in [RFC4732].
In many cases, it may not be possible for network administrators to
determine the cause(s) of an attack. They may instead just realize
that certain resources seem to be under attack. This document
defines a lightweight protocol that allows a DOTS client to request
mitigation from one or more DOTS servers for protection against
detected, suspected, or anticipated attacks. This protocol enables
cooperation between DOTS agents to permit a highly-automated network
defense that is robust, reliable, and secure. Note that "secure"
means the support of the features defined in Section 2.4 of
[I-D.ietf-dots-requirements].
An example of a network diagram that illustrates a deployment of DOTS
agents is shown in Figure 1. In this example, a DOTS server is
operating on the access network. A DOTS client is located on the LAN
(Local Area Network), while a DOTS gateway is embedded in the CPE
(Customer Premises Equipment).
Reddy, et al. Expires July 22, 2019 [Page 4]
Internet-Draft DOTS Signal Channel Protocol January 2019
Network
Resource CPE router Access network __________
+-----------+ +--------------+ +-------------+ / \
| |___| |____| |___ | Internet |
|DOTS client| | DOTS gateway | | DOTS server | | |
| | | | | | | |
+-----------+ +--------------+ +-------------+ \__________/
Figure 1: Sample DOTS Deployment (1)
DOTS servers can also be reachable over the Internet, as depicted in
Figure 2.
Network DDoS mitigation
Resource CPE router __________ service
+-----------+ +-------------+ / \ +-------------+
| |___| |____| |___ | |
|DOTS client| |DOTS gateway | | Internet | | DOTS server |
| | | | | | | |
+-----------+ +-------------+ \__________/ +-------------+
Figure 2: Sample DOTS Deployment (2)
In typical deployments, the DOTS client belongs to a different
administrative domain than the DOTS server. For example, the DOTS
client is embedded in a firewall protecting services owned and
operated by a customer, while the DOTS server is owned and operated
by a different administrative entity (service provider, typically)
providing DDoS mitigation services. The latter might or might not
provide connectivity services to the network hosting the DOTS client.
The DOTS server may (not) be co-located with the DOTS mitigator. In
typical deployments, the DOTS server belongs to the same
administrative domain as the mitigator. The DOTS client can
communicate directly with a DOTS server or indirectly via a DOTS
gateway.
The document adheres to the DOTS architecture
[I-D.ietf-dots-architecture]. The requirements for DOTS signal
channel protocol are documented in [I-D.ietf-dots-requirements].
This document satisfies all the use cases discussed in
[I-D.ietf-dots-use-cases].
This document focuses on the DOTS signal channel. This is a
companion document of the DOTS data channel specification
[I-D.ietf-dots-data-channel] that defines a configuration and a bulk
data exchange mechanism supporting the DOTS signal channel.
Reddy, et al. Expires July 22, 2019 [Page 5]
Internet-Draft DOTS Signal Channel Protocol January 2019
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
(D)TLS is used for statements that apply to both Transport Layer
Security [RFC5246][RFC8446] and Datagram Transport Layer Security
[RFC6347]. Specific terms are used for any statement that applies to
either protocol alone.
The reader should be familiar with the terms defined in
[I-D.ietf-dots-requirements].
The meaning of the symbols in YANG tree diagrams is defined in
[RFC8340].
3. Design Overview
The DOTS signal channel is built on top of the Constrained
Application Protocol (CoAP) [RFC7252], a lightweight protocol
originally designed for constrained devices and networks. The many
features of CoAP (expectation of packet loss, support for
asynchronous Non-confirmable messaging, congestion control, small
message overhead limiting the need for fragmentation, use of minimal
resources, and support for (D)TLS) makes it a good candidate to build
the DOTS signaling mechanism from.
The DOTS signal channel is layered on existing standards (Figure 3).
+---------------------+
| DOTS Signal Channel |
+---------------------+
| CoAP |
+----------+----------+
| TLS | DTLS |
+----------+----------+
| TCP | UDP |
+----------+----------+
| IP |
+---------------------+
Figure 3: Abstract Layering of DOTS Signal Channel over CoAP over
(D)TLS
Reddy, et al. Expires July 22, 2019 [Page 6]
Internet-Draft DOTS Signal Channel Protocol January 2019
By default, a DOTS signal channel MUST run over port number TBD as
defined in Section 9.1, for both UDP and TCP, unless the DOTS server
has a mutual agreement with its DOTS clients to use a different port
number. DOTS clients MAY alternatively support means to dynamically
discover the ports used by their DOTS servers (e.g.,
[I-D.boucadair-dots-server-discovery]). In order to use a distinct
port number (as opposed to TBD), DOTS clients and servers SHOULD
support a configurable parameter to supply the port number to use.
The rationale for not using the default port number 5684 ((D)TLS
CoAP) is to allow for differentiated behaviors in environments where
both a DOTS gateway and an IoT gateway (e.g., Figure 3 of [RFC7452])
are present.
The signal channel uses the "coaps" URI scheme defined in Section 6
of [RFC7252] and the "coaps+tcp" URI scheme defined in Section 8.2 of
[RFC8323] to identify DOTS server resources accessible using CoAP
over UDP secured with DTLS and CoAP over TCP secured with TLS,
respectively.
The signal channel is initiated by the DOTS client (Section 4.4).
Once the signal channel is established, the DOTS agents periodically
send heartbeats to keep the channel active (Section 4.7). At any
time, the DOTS client may send a mitigation request message to a DOTS
server over the active channel. While mitigation is active (because
of the higher likelihood of packet loss during a DDoS attack), the
DOTS server periodically sends status messages to the client,
including basic mitigation feedback details. Mitigation remains
active until the DOTS client explicitly terminates mitigation, or the
mitigation lifetime expires.
DOTS signaling can happen with DTLS over UDP and TLS over TCP.
Likewise, DOTS requests may be sent using IPv4 or IPv6 transfer
capabilities. A Happy Eyeballs procedure for DOTS signal channel is
specified in Section 4.3.
Messages exchanged between DOTS agents are serialized using Concise
Binary Object Representation (CBOR) [RFC7049], a binary encoding
scheme designed for small code and message size. CBOR-encoded
payloads are used to carry signal channel-specific payload messages
which convey request parameters and response information such as
errors. In order to allow reusing data models across protocols,
[RFC7951] specifies the JavaScript Object Notation (JSON) encoding of
YANG-modeled data. A similar effort for CBOR is defined in
[I-D.ietf-core-yang-cbor].
DOTS agents primarily determine that a CBOR data structure is a DOTS
signal channel object from the application context, such as from the
port number assigned to the DOTS signal channel. The other method
Reddy, et al. Expires July 22, 2019 [Page 7]
Internet-Draft DOTS Signal Channel Protocol January 2019
DOTS agents use to indicate that a CBOR data structure is a DOTS
signal channel object is the use of the "application/dots+cbor"
content type (Section 9.3).
This document specifies a YANG module for representing DOTS
mitigation scopes, DOTS signal channel session configuration data,
and DOTS redirected signalling (Section 5). Representing these data
as CBOR data can either follow the rules in [I-D.ietf-core-yang-cbor]
or those in [RFC7951] combined with JSON/CBOR conversion rules in
[RFC7049]; both approaches produce a valid encoding. All parameters
in the payload of the DOTS signal channel are mapped to CBOR types as
specified in Section 6.
In order to prevent fragmentation, DOTS agents must follow the
recommendations documented in Section 4.6 of [RFC7252]. Refer to
Section 7.3 for more details.
DOTS agents MUST support GET, PUT, and DELETE CoAP methods. The
payload included in CoAP responses with 2.xx Response Codes MUST be
of content type "application/dots+cbor". CoAP responses with 4.xx
and 5.xx error Response Codes MUST include a diagnostic payload
(Section 5.5.2 of [RFC7252]). The Diagnostic Payload may contain
additional information to aid troubleshooting.
In deployments where multiple DOTS clients are enabled in a network
(owned and operated by the same entity), the DOTS server may detect
conflicting mitigation requests from these clients. This document
does not aim to specify a comprehensive list of conditions under
which a DOTS server will characterize two mitigation requests from
distinct DOTS clients as conflicting, nor recommend a DOTS server
behavior for processing conflicting mitigation requests. Those
considerations are implementation- and deployment-specific.
Nevertheless, the document specifies the mechanisms to notify DOTS
clients when conflicts occur, including the conflict cause
(Section 4.4).
In deployments where one or more translators (e.g., Traditional NAT
[RFC3022], CGN [RFC6888], NAT64 [RFC6146], NPTv6 [RFC6296]) are
enabled between the client's network and the DOTS server, DOTS signal
channel messages forwarded to a DOTS server MUST NOT include internal
IP addresses/prefixes and/or port numbers; external addresses/
prefixes and/or port numbers as assigned by the translator MUST be
used instead. This document does not make any recommendation about
possible translator discovery mechanisms. The following are some
(non-exhaustive) deployment examples that may be considered:
o Port Control Protocol (PCP) [RFC6887] or Session Traversal
Utilities for NAT (STUN) [RFC5389] may be used to retrieve the
Reddy, et al. Expires July 22, 2019 [Page 8]
Internet-Draft DOTS Signal Channel Protocol January 2019
external addresses/prefixes and/or port numbers. Information
retrieved by means of PCP or STUN will be used to feed the DOTS
signal channel messages that will be sent to a DOTS server.
o A DOTS gateway may be co-located with the translator. The DOTS
gateway will need to update the DOTS messages, based upon the
local translator's binding table.
4. DOTS Signal Channel: Messages & Behaviors
4.1. DOTS Server(s) Discovery
This document assumes that DOTS clients are provisioned with the
reachability information of their DOTS server(s) using any of a
variety of means (e.g., local configuration, or dynamic means such as
DHCP). The description of such means is out of scope of this
document.
Likewise, it is out of scope of this document to specify the behavior
to be followed by a DOTS client to send DOTS requests when multiple
DOTS servers are provisioned (e.g., contact all DOTS servers, select
one DOTS server among the list).
4.2. CoAP URIs
The DOTS server MUST support the use of the path-prefix of "/.well-
known/" as defined in [RFC5785] and the registered name of "dots".
Each DOTS operation is indicated by a path-suffix that indicates the
intended operation. The operation path (Table 1) is appended to the
path-prefix to form the URI used with a CoAP request to perform the
desired DOTS operation.
+-----------------------+----------------+-------------+
| Operation | Operation Path | Details |
+-----------------------+----------------+-------------+
| Mitigation | /mitigate | Section 4.4 |
+-----------------------+----------------+-------------+
| Session configuration | /config | Section 4.5 |
+-----------------------+----------------+-------------+
Table 1: Operations and their Corresponding URIs
4.3. Happy Eyeballs for DOTS Signal Channel
[I-D.ietf-dots-requirements] mentions that DOTS agents will have to
support both connectionless and connection-oriented protocols. As
such, the DOTS signal channel is designed to operate with DTLS over
UDP and TLS over TCP. Further, a DOTS client may acquire a list of
Reddy, et al. Expires July 22, 2019 [Page 9]
Internet-Draft DOTS Signal Channel Protocol January 2019
IPv4 and IPv6 addresses (Section 4.1), each of which can be used to
contact the DOTS server using UDP and TCP. The following specifies
the procedure to follow to select the address family and the
transport protocol for sending DOTS signal channel messages.
Such procedure is needed to avoid experiencing long connection
delays. For example, if an IPv4 path to reach a DOTS server is
functional, but the DOTS server's IPv6 path is non-functional, a
dual-stack DOTS client may experience a significant connection delay
compared to an IPv4-only DOTS client, in the same network conditions.
The other problem is that if a middlebox between the DOTS client and
DOTS server is configured to block UDP traffic, the DOTS client will
fail to establish a DTLS association with the DOTS server and, as a
consequence, will have to fall back to TLS over TCP, thereby
incurring significant connection delays.
To overcome these connection setup problems, the DOTS client attempts
to connect to its DOTS server(s) using both IPv6 and IPv4, and tries
both DTLS over UDP and TLS over TCP in a manner similar to the Happy
Eyeballs mechanism [RFC8305]. These connection attempts are
performed by the DOTS client when it initializes, or in general when
it has to select an address family and transport to contact its DOTS
server. The results of the Happy Eyeballs procedure are used by the
DOTS client for sending its subsequent messages to the DOTS server.
Note that the DOTS client after successfully establishing a
connection must cache information regarding the outcome of each
connection attempt for a specific time period, and it uses that
information to avoid thrashing the network with subsequent attempts.
The order of preference of the DOTS signal channel address family and
transport protocol (most preferred first) is: UDP over IPv6, UDP over
IPv4, TCP over IPv6, and finally TCP over IPv4. This order adheres
to the address preference order specified in [RFC6724] and the DOTS
signal channel preference which privileges the use of UDP over TCP
(to avoid TCP's head of line blocking).
In reference to Figure 4, the DOTS client sends two TCP SYNs and two
DTLS ClientHello messages at the same time over IPv6 and IPv4. In
this example, it is assumed that the IPv6 path is broken and UDP
traffic is dropped by a middlebox but has little impact to the DOTS
client because there is no long delay before using IPv4 and TCP. The
DOTS client periodically repeats the mechanism to discover whether
DOTS signal channel messages with DTLS over UDP becomes available
from the DOTS server, so the DOTS client can migrate the DOTS signal
channel from TCP to UDP. Such probing SHOULD NOT be done more
frequently than every 24 hours and MUST NOT be done more frequently
than every 5 minutes.
Reddy, et al. Expires July 22, 2019 [Page 10]
Internet-Draft DOTS Signal Channel Protocol January 2019
A single DOTS signal channel between DOTS agents can be used to
exchange multiple DOTS signal messages. To reduce DOTS client and
DOTS server workload, DOTS clients SHOULD re-use the (D)TLS session.
+-----------+ +-----------+
|DOTS client| |DOTS server|
+-----------+ +-----------+
| |
|--DTLS ClientHello, IPv6 ---->X |
|--TCP SYN, IPv6-------------->X |
|--DTLS ClientHello, IPv4 ---->X |
|--TCP SYN, IPv4--------------------------------------->|
|--DTLS ClientHello, IPv6 ---->X |
|--TCP SYN, IPv6-------------->X |
|<-TCP SYNACK-------------------------------------------|
|--DTLS ClientHello, IPv4 ---->X |
|--TCP ACK--------------------------------------------->|
|<------------Establish TLS Session-------------------->|
|----------------DOTS signal--------------------------->|
| |
Figure 4: DOTS Happy Eyeballs (Sample Flow)
4.4. DOTS Mitigation Methods
The following methods are used by a DOTS client to request, withdraw,
or retrieve the status of mitigation requests:
PUT: DOTS clients use the PUT method to request mitigation from a
DOTS server (Section 4.4.1). During active mitigation, DOTS
clients may use PUT requests to carry mitigation efficacy
updates to the DOTS server (Section 4.4.3).
GET: DOTS clients may use the GET method to subscribe to DOTS
server status messages, or to retrieve the list of its
mitigations maintained by a DOTS server (Section 4.4.2).
DELETE: DOTS clients use the DELETE method to withdraw a request for
mitigation from a DOTS server (Section 4.4.4).
Mitigation request and response messages are marked as Non-
confirmable messages (Section 2.2 of [RFC7252]).
DOTS agents SHOULD follow the data transmission guidelines discussed
in Section 3.1.3 of [RFC8085] and control transmission behavior by
not sending more than one UDP datagram per round-trip time (RTT) to
the peer DOTS agent on average.
Reddy, et al. Expires July 22, 2019 [Page 11]
Internet-Draft DOTS Signal Channel Protocol January 2019
Requests marked by the DOTS client as Non-confirmable messages are
sent at regular intervals until a response is received from the DOTS
server. If the DOTS client cannot maintain an RTT estimate, it
SHOULD NOT send more than one Non-confirmable request every 3
seconds, and SHOULD use an even less aggressive rate whenever
possible (case 2 in Section 3.1.3 of [RFC8085]).
JSON diagnostic notation is used to illustrate the various methods
defined in the following sub-sections. Also, the examples use the
Labels defined in Sections 9.6.2, 9.6.3, 9.6.4, and 9.6.5.
4.4.1. Request Mitigation
When a DOTS client requires mitigation for some reason, the DOTS
client uses the CoAP PUT method to send a mitigation request to its
DOTS server(s) (Figures 5 and 6).
If a DOTS client is entitled to solicit the DOTS service, the DOTS
server enables mitigation on behalf of the DOTS client by
communicating the DOTS client's request to a mitigator (which may be
colocated with the DOTS server) and relaying the feedback of the
thus-selected mitigator to the requesting DOTS client.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
...
}
Figure 5: PUT to Convey DOTS Mitigation Requests
The order of the Uri-Path options is important as it defines the CoAP
resource. In particular, 'mid' MUST follow 'cuid'.
The additional Uri-Path parameters to those defined in Section 4.2
are as follows:
cuid: Stands for Client Unique Identifier. A globally unique
identifier that is meant to prevent collisions among DOTS clients,
especially those from the same domain. It MUST be generated by
DOTS clients.
Reddy, et al. Expires July 22, 2019 [Page 12]
Internet-Draft DOTS Signal Channel Protocol January 2019
Implementations SHOULD set 'cuid' to the output of a cryptographic
hash algorithm whose input is the Distinguished Encoding Rules
(DER)-encoded Abstract Syntax Notation One (ASN.1) representation
of the Subject Public Key Info (SPKI) of the DOTS client X.509
certificate [RFC5280], the DOTS client raw public key [RFC7250],
or the "Pre-Shared Key (PSK) identity" used by the DOTS client in
the TLS ClientKeyExchange message. In this version of the
specification, the recommended cryptographic hash algorithm is
SHA-256 [RFC6234]. The output of the cryptographic hash algorithm
is truncated to 16 bytes; truncation is done by stripping off the
final 16 bytes. The truncated output is base64url encoded.
The 'cuid' is intended to be stable when communicating with a
given DOTS server, i.e., the 'cuid' used by a DOTS client SHOULD
NOT change over time. Distinct 'cuid' values MAY be used by a
single DOTS client per DOTS server.
DOTS servers MUST return 4.09 (Conflict) error code to a DOTS peer
to notify that the 'cuid' is already in-use by another DOTS
client. Upon receipt of that error code, a new 'cuid' MUST be
generated by the DOTS peer (e.g., using [RFC4122]).
Client-domain DOTS gateways MUST handle 'cuid' collision directly
and it is RECOMMENDED that 'cuid' collision is handled directly by
server-domain DOTS gateways.
DOTS gateways MAY rewrite the 'cuid' used by peer DOTS clients.
Triggers for such rewriting are out of scope.
This is a mandatory Uri-Path parameter.
mid: Identifier for the mitigation request represented with an
integer. This identifier MUST be unique for each mitigation
request bound to the DOTS client, i.e., the 'mid' parameter value
in the mitigation request needs to be unique (per 'cuid' and DOTS
server) relative to the 'mid' parameter values of active
mitigation requests conveyed from the DOTS client to the DOTS
server.
In order to handle out-of-order delivery of mitigation requests,
'mid' values MUST increase monotonically.
If the 'mid' value has reached 3/4 of (2**32 - 1) (i.e.,
3221225471) and no attack is detected, the DOTS client MUST reset
'mid' to 0 to handle 'mid' rollover. If the DOTS client maintains
mitigation requests with pre-configured scopes, it MUST re-create
them with the 'mid' restarting at 0.
Reddy, et al. Expires July 22, 2019 [Page 13]
Internet-Draft DOTS Signal Channel Protocol January 2019
This identifier MUST be generated by the DOTS client.
This is a mandatory Uri-Path parameter.
'cuid' and 'mid' MUST NOT appear in the PUT request message body
(Figure 6).
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"string"
],
"target-port-range": [
{
"lower-port": number,
"upper-port": number
}
],
"target-protocol": [
number
],
"target-fqdn": [
"string"
],
"target-uri": [
"string"
],
"alias-name": [
"string"
],
"lifetime": number,
"trigger-mitigation": true|false
}
]
}
}
Figure 6: PUT to Convey DOTS Mitigation Requests (Message Body
Schema)
The parameters in the CBOR body (Figure 6) of the PUT request are
described below:
Reddy, et al. Expires July 22, 2019 [Page 14]
Internet-Draft DOTS Signal Channel Protocol January 2019
target-prefix: A list of prefixes identifying resources under
attack. Prefixes are represented using Classless Inter-Domain
Routing (CIDR) notation [RFC4632].
As a reminder, the prefix length must be less than or equal to 32
(resp. 128) for IPv4 (resp. IPv6).
The prefix list MUST NOT include broadcast, loopback, or multicast
addresses. These addresses are considered as invalid values. In
addition, the DOTS server MUST validate that target prefixes are
within the scope of the DOTS client's domain. Other validation
checks may be supported by DOTS servers.
This is an optional attribute.
target-port-range: A list of port numbers bound to resources under
attack.
A port range is defined by two bounds, a lower port number (lower-
port) and an upper port number (upper-port). When only 'lower-
port' is present, it represents a single port number.
For TCP, UDP, Stream Control Transmission Protocol (SCTP)
[RFC4960], or Datagram Congestion Control Protocol (DCCP)
[RFC4340], a range of ports can be, for example, 0-1023,
1024-65535, or 1024-49151.
This is an optional attribute.
target-protocol: A list of protocols involved in an attack. Values
are taken from the IANA protocol registry [proto_numbers].
If 'target-protocol' is not specified, then the request applies to
any protocol.
This is an optional attribute.
target-fqdn: A list of Fully Qualified Domain Names (FQDNs)
identifying resources under attack [RFC8499].
How a name is passed to an underlying name resolution library is
implementation- and deployment-specific. Nevertheless, once the
name is resolved into one or multiple IP addresses, DOTS servers
MUST apply the same validation checks as those for 'target-
prefix'.
The use of FQDNs may be suboptimal because:
Reddy, et al. Expires July 22, 2019 [Page 15]
Internet-Draft DOTS Signal Channel Protocol January 2019
* It induces both an extra load and increased delays on the DOTS
server to handle and manage DNS resolution requests.
* It does not guarantee that the DOTS server will resolve a name
to the same IP addresses that the DOTS client does.
This is an optional attribute.
target-uri: A list of Uniform Resource Identifiers (URIs) [RFC3986]
identifying resources under attack.
The same validation checks used for 'target-fqdn' MUST be followed
by DOTS servers to validate a target URI.
This is an optional attribute.
alias-name: A list of aliases of resources for which the mitigation
is requested. Aliases can be created using the DOTS data channel
(Section 6.1 of [I-D.ietf-dots-data-channel]), direct
configuration, or other means.
An alias is used in subsequent signal channel exchanges to refer
more efficiently to the resources under attack.
This is an optional attribute.
lifetime: Lifetime of the mitigation request in seconds. The
RECOMMENDED lifetime of a mitigation request is 3600 seconds --
this value was chosen to be long enough so that refreshing is not
typically a burden on the DOTS client, while still making the
request expire in a timely manner when the client has unexpectedly
quit. DOTS clients MUST include this parameter in their
mitigation requests. Upon the expiry of this lifetime, and if the
request is not refreshed, the mitigation request is removed. The
request can be refreshed by sending the same request again.
A lifetime of '0' in a mitigation request is an invalid value.
A lifetime of negative one (-1) indicates indefinite lifetime for
the mitigation request. The DOTS server MAY refuse indefinite
lifetime, for policy reasons; the granted lifetime value is
returned in the response. DOTS clients MUST be prepared to not be
granted mitigations with indefinite lifetimes.
The DOTS server MUST always indicate the actual lifetime in the
response and the remaining lifetime in status messages sent to the
DOTS client.
Reddy, et al. Expires July 22, 2019 [Page 16]
Internet-Draft DOTS Signal Channel Protocol January 2019
This is a mandatory attribute.
trigger-mitigation: If the parameter value is set to 'false', DDoS
mitigation will not be triggered for the mitigation request unless
the DOTS signal channel session is lost.
If the DOTS client ceases to respond to heartbeat messages, the
DOTS server can detect that the DOTS signal channel session is
lost.
The default value of the parameter is 'true' (that is, the
mitigation starts immediately). If 'trigger-mitigation' is not
present in a request, this is equivalent to receiving a request
with 'trigger-mitigation' set to 'true'.
This is an optional attribute.
In deployments where server-domain DOTS gateways are enabled,
identity information about the origin source client domain SHOULD be
propagated to the DOTS server. That information is meant to assist
the DOTS server to enforce some policies such as grouping DOTS
clients that belong to the same DOTS domain, limiting the number of
DOTS requests, and identifying the mitigation scope. These policies
can be enforced per-client, per-client domain, or both. Also, the
identity information may be used for auditing and debugging purposes.
Figure 7 shows an example of a request relayed by a server-domain
DOTS gateway.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cdid=7eeaf349529eb55ed50113"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
...
}
Figure 7: PUT for DOTS Mitigation Request as Relayed by a DOTS
Gateway
A server-domain DOTS gateway SHOULD add the following Uri-Path
parameter:
Reddy, et al. Expires July 22, 2019 [Page 17]
Internet-Draft DOTS Signal Channel Protocol January 2019
cdid: Stands for Client Domain Identifier. The 'cdid' is conveyed
by a server-domain DOTS gateway to propagate the source domain
identity from the gateway's client-facing-side to the gateway's
server-facing-side, and from the gateway's server-facing-side to
the DOTS server. 'cdid' may be used by the final DOTS server for
policy enforcement purposes (e.g., enforce a quota on filtering
rules). These policies are deployment-specific.
Server-domain DOTS gateways SHOULD support a configuration option
to instruct whether 'cdid' parameter is to be inserted.
In order to accommodate deployments that require enforcing per-
client policies, per-client domain policies, or a combination
thereof, server-domain DOTS gateways instructed to insert the
'cdid' parameter MUST supply the SPKI hash of the DOTS client
X.509 certificate, the DOTS client raw public key, or the hash of
the "PSK identity" in the 'cdid', following the same rules for
generating the hash conveyed in 'cuid', which is then used by the
ultimate DOTS server to determine the corresponding client's
domain. The 'cdid' generated by a server-domain gateway is likely
to be the same as the 'cuid' except if the DOTS message was
relayed by a client-domain DOTS gateway or the 'cuid' was
generated from a rogue DOTS client.
If a DOTS client is provisioned, for example, with distinct
certificates as a function of the peer server-domain DOTS gateway,
distinct 'cdid' values may be supplied by a server-domain DOTS
gateway. The ultimate DOTS server MUST treat those 'cdid' values
as equivalent.
The 'cdid' attribute MUST NOT be generated and included by DOTS
clients.
DOTS servers MUST ignore 'cdid' attributes that are directly
supplied by source DOTS clients or client-domain DOTS gateways.
This implies that first server-domain DOTS gateways MUST strip
'cdid' attributes supplied by DOTS clients. DOTS servers SHOULD
support a configuration parameter to identify DOTS gateways that
are trusted to supply 'cdid' attributes.
Only single-valued 'cdid' are defined in this document.
This is an optional Uri-Path. When present, 'cdid' MUST be
positioned before 'cuid'.
A DOTS gateway MAY add the CoAP Hop-Limit Option
[I-D.ietf-core-hop-limit].
Reddy, et al. Expires July 22, 2019 [Page 18]
Internet-Draft DOTS Signal Channel Protocol January 2019
Because of the complexity to handle partial failure cases, this
specification does not allow for including multiple mitigation
requests in the same PUT request. Concretely, a DOTS client MUST NOT
include multiple entries in the 'scope' array of the same PUT
request.
FQDN and URI mitigation scopes may be thought of as a form of scope
alias, in which the addresses associated with the domain name or URI
(as resolved by the DOTS server) represent the full scope of the
mitigation.
In the PUT request at least one of the attributes 'target-prefix',
'target-fqdn','target-uri', or 'alias-name' MUST be present.
Attributes and Uri-Path parameters with empty values MUST NOT be
present in a request and render the entire request invalid.
Figure 8 shows a PUT request example to signal that TCP port numbers
80, 8080, and 443 used by 2001:db8:6401::1 and 2001:db8:6401::2
servers are under attack (illustrated in JSON diagnostic notation).
The presence of 'cdid' indicates that a server-domain DOTS gateway
has modified the initial PUT request sent by the DOTS client. Note
that 'cdid' MUST NOT appear in the PUT request message body.
Reddy, et al. Expires July 22, 2019 [Page 19]
Internet-Draft DOTS Signal Channel Protocol January 2019
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cdid=7eeaf349529eb55ed50113"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-port-range": [
{
"lower-port": 80
},
{
"lower-port": 443
},
{
"lower-port": 8080
}
],
"target-protocol": [
6
],
"lifetime": 3600
}
]
}
}
Figure 8: PUT for DOTS Mitigation Request (An Example)
The corresponding CBOR encoding format for the payload is shown in
Figure 9.
Reddy, et al. Expires July 22, 2019 [Page 20]
Internet-Draft DOTS Signal Channel Protocol January 2019
A1 # map(1)
01 # unsigned(1)
A1 # map(1)
02 # unsigned(2)
81 # array(1)
A3 # map(3)
06 # unsigned(6)
82 # array(2)
74 # text(20)
323030313A6462383A363430313A3A312F313238
74 # text(20)
323030313A6462383A363430313A3A322F313238
07 # unsigned(7)
83 # array(3)
A1 # map(1)
08 # unsigned(8)
18 50 # unsigned(80)
A1 # map(1)
08 # unsigned(8)
19 01BB # unsigned(443)
A1 # map(1)
08 # unsigned(8)
19 1F90 # unsigned(8080)
0A # unsigned(10)
81 # array(1)
06 # unsigned(6)
0E # unsigned(14)
19 0E10 # unsigned(3600)
Figure 9: PUT for DOTS Mitigation Request (CBOR)
In both DOTS signal and data channel sessions, the DOTS client MUST
authenticate itself to the DOTS server (Section 8). The DOTS server
MAY use the algorithm presented in Section 7 of [RFC7589] to derive
the DOTS client identity or username from the client certificate.
The DOTS client identity allows the DOTS server to accept mitigation
requests with scopes that the DOTS client is authorized to manage.
The DOTS server couples the DOTS signal and data channel sessions
using the DOTS client identity and optionally the 'cdid' parameter
value, so the DOTS server can validate whether the aliases conveyed
in the mitigation request were indeed created by the same DOTS client
using the DOTS data channel session. If the aliases were not created
by the DOTS client, the DOTS server MUST return 4.00 (Bad Request) in
the response.
The DOTS server couples the DOTS signal channel sessions using the
DOTS client identity and optionally the 'cdid' parameter value, and
Reddy, et al. Expires July 22, 2019 [Page 21]
Internet-Draft DOTS Signal Channel Protocol January 2019
the DOTS server uses 'mid' and 'cuid' Uri-Path parameter values to
detect duplicate mitigation requests. If the mitigation request
contains the 'alias-name' and other parameters identifying the target
resources (such as 'target-prefix', 'target-port-range', 'target-
fqdn', or 'target-uri'), the DOTS server appends the parameter values
in 'alias-name' with the corresponding parameter values in 'target-
prefix', 'target-port-range', 'target-fqdn', or 'target-uri'.
The DOTS server indicates the result of processing the PUT request
using CoAP response codes. CoAP 2.xx codes are success. CoAP 4.xx
codes are some sort of invalid requests (client errors). COAP 5.xx
codes are returned if the DOTS server is in an error state or is
currently unavailable to provide mitigation in response to the
mitigation request from the DOTS client.
Figure 10 shows an example response to a PUT request that is
successfully processed by a DOTS server (i.e., CoAP 2.xx response
codes). This version of the specification forbids 'cuid' and 'cdid'
(if used) to be returned in a response message body.
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"mid": 123,
"lifetime": 3600
}
]
}
}
Figure 10: 2.xx Response Body
If the request is missing a mandatory attribute, does not include
'cuid' or 'mid' Uri-Path options, includes multiple 'scope'
parameters, or contains invalid or unknown parameters, the DOTS
server MUST reply with 4.00 (Bad Request). DOTS agents can safely
ignore comprehension-optional parameters they don't understand.
A DOTS server that receives a mitigation request with a lifetime set
to '0' MUST reply with a 4.00 (Bad Request).
If the DOTS server does not find the 'mid' parameter value conveyed
in the PUT request in its configuration data, it MAY accept the
mitigation request by sending back a 2.01 (Created) response to the
DOTS client; the DOTS server will consequently try to mitigate the
attack. A DOTS server could reject mitigation requests when it is
Reddy, et al. Expires July 22, 2019 [Page 22]
Internet-Draft DOTS Signal Channel Protocol January 2019
near capacity or needs to rate-limit a particular client, for
example.
If the DOTS server finds the 'mid' parameter value conveyed in the
PUT request in its configuration data bound to that DOTS client, it
MAY update the mitigation request, and a 2.04 (Changed) response is
returned to indicate a successful update of the mitigation request.
The relative order of two mitigation requests, having the same
'trigger-mitigation' type, from a DOTS client is determined by
comparing their respective 'mid' values. If two mitigation requests
with the same 'trigger-mitigation' type have overlapping mitigation
scopes, the mitigation request with the highest numeric 'mid' value
will override the other mitigation request. Two mitigation requests
from a DOTS client have overlapping scopes if there is a common IP
address, IP prefix, FQDN, URI, or alias-name. To avoid maintaining a
long list of overlapping mitigation requests (i.e., requests with the
same 'trigger-mitigation' type and overlapping scopes) from a DOTS
client and avoid error-prone provisioning of mitigation requests from
a DOTS client, the overlapped lower numeric 'mid' MUST be
automatically deleted and no longer available at the DOTS server.
For example, if the DOTS server receives a mitigation request which
overlaps with an existing mitigation with a higher numeric 'mid', the
DOTS server rejects the request by returning 4.09 (Conflict) to the
DOTS client. The response includes enough information for a DOTS
client to recognize the source of the conflict as described below in
the 'conflict-information' subtree with only the relevant nodes
listed:
conflict-information: Indicates that a mitigation request is
conflicting with another mitigation request. This optional
attribute has the following structure:
conflict-cause: Indicates the cause of the conflict. The
following values are defined:
1: Overlapping targets. 'conflict-scope' provides more details
about the conflicting target clauses.
conflict-scope: Characterizes the exact conflict scope. It may
include a list of IP addresses, a list of prefixes, a list of
port numbers, a list of target protocols, a list of FQDNs, a
list of URIs, a list of alias-names, or a 'mid'.
If the DOTS server receives a mitigation request which overlaps with
an active mitigation request, but both having distinct 'trigger-
mitigation' types, the DOTS server MUST deactivate (absent explicit
policy/configuration otherwise) the mitigation request with 'trigger-
Reddy, et al. Expires July 22, 2019 [Page 23]
Internet-Draft DOTS Signal Channel Protocol January 2019
mitigation' set to false. Particularly, if the mitigation request
with 'trigger-mitigation' set to false is active, the DOTS server
withdraws the mitigation request (i.e., status code is set to '7' as
defined in Table 2) and transitions the status of the mitigation
request to '8'.
Upon DOTS signal channel session loss with a peer DOTS client, the
DOTS server MUST withdraw (absent explicit policy/configuration
otherwise) any active mitigation requests overlapping with mitigation
requests having 'trigger-mitigation' set to false from that DOTS
client, as the loss of the session implictily activates these
preconfigured mitigation requests and they take precedence. Note
that active-but-terminating period is not observed for mitigations
withdrawn at the initiative of the DOTS server.
DOTS clients may adopt various strategies for setting the scopes of
immediate and pre-configured mitigation requests to avoid potential
conflicts. For example, a DOTS client may tweak pre-configured
scopes so that the scope of any overlapping immediate mitigation
request will be a subset of the pre-configured scopes. Also, if an
immediate mitigation request overlaps with any of the pre-configured
scopes, the DOTS client sets the scope of the overlapping immediate
mitigation request to be a subset of the pre-configured scopes, so as
to get a broad mitigation when the DOTS signal channel collapses and
maximize the chance of recovery.
If the request is conflicting with an existing mitigation request
from a different DOTS client, the DOTS server may return 2.01
(Created) or 4.09 (Conflict) to the requesting DOTS client. If the
DOTS server decides to maintain the new mitigation request, the DOTS
server returns 2.01 (Created) to the requesting DOTS client. If the
DOTS server decides to reject the new mitigation request, the DOTS
server returns 4.09 (Conflict) to the requesting DOTS client. For
both 2.01 (Created) and 4.09 (Conflict) responses, the response
includes enough information for a DOTS client to recognize the source
of the conflict as described below:
conflict-information: Indicates that a mitigation request is
conflicting with another mitigation request(s) from other DOTS
client(s). This optional attribute has the following structure:
conflict-status: Indicates the status of a conflicting mitigation
request. The following values are defined:
1: DOTS server has detected conflicting mitigation requests
from different DOTS clients. This mitigation request is
currently inactive until the conflicts are resolved.
Another mitigation request is active.
Reddy, et al. Expires July 22, 2019 [Page 24]
Internet-Draft DOTS Signal Channel Protocol January 2019
2: DOTS server has detected conflicting mitigation requests
from different DOTS clients. This mitigation request is
currently active.
3: DOTS server has detected conflicting mitigation requests
from different DOTS clients. All conflicting mitigation
requests are inactive.
conflict-cause: Indicates the cause of the conflict. The
following values are defined:
1: Overlapping targets. 'conflict-scope' provides more details
about the conflicting target clauses.
2: Conflicts with an existing accept-list. This code is
returned when the DDoS mitigation detects source addresses/
prefixes in the accept-listed ACLs are attacking the
target.
3: CUID Collision. This code is returned when a DOTS client
uses a 'cuid' that is already used by another DOTS client.
This code is an indication that the request has been
rejected and a new request with a new 'cuid' is to be re-
sent by the DOTS client. Note that 'conflict-status',
'conflict-scope', and 'retry-timer' MUST NOT be returned in
the error response.
conflict-scope: Characterizes the exact conflict scope. It may
include a list of IP addresses, a list of prefixes, a list of
port numbers, a list of target protocols, a list of FQDNs, a
list of URIs, a list of alias-names, or references to
conflicting ACLs (by an 'acl-name', typically
[I-D.ietf-dots-data-channel]).
retry-timer: Indicates, in seconds, the time after which the DOTS
client may re-issue the same request. The DOTS server returns
'retry-timer' only to DOTS client(s) for which a mitigation
request is deactivated. Any retransmission of the same
mitigation request before the expiry of this timer is likely to
be rejected by the DOTS server for the same reasons.
The retry-timer SHOULD be equal to the lifetime of the active
mitigation request resulting in the deactivation of the
conflicting mitigation request. The lifetime of the
deactivated mitigation request will be updated to (retry-timer
+ 45 seconds), so the DOTS client can refresh the deactivated
mitigation request after retry-timer seconds before expiry of
lifetime and check if the conflict is resolved.
Reddy, et al. Expires July 22, 2019 [Page 25]
Internet-Draft DOTS Signal Channel Protocol January 2019
As an active attack evolves, DOTS clients can adjust the scope of
requested mitigation as necessary, by refining the scope of resources
requiring mitigation. This can be achieved by sending a PUT request
with a new 'mid' value that will override the existing one with
overlapping mitigation scopes.
For a mitigation request to continue beyond the initial negotiated
lifetime, the DOTS client has to refresh the current mitigation
request by sending a new PUT request. This PUT request MUST use the
same 'mid' value, and MUST repeat all the other parameters as sent in
the original mitigation request apart from a possible change to the
lifetime parameter value.
4.4.2. Retrieve Information Related to a Mitigation
A GET request is used by a DOTS client to retrieve information
(including status) of DOTS mitigations from a DOTS server.
'cuid' is a mandatory Uri-Path parameter for GET requests.
Uri-Path parameters with empty values MUST NOT be present in a
request.
The same considerations for manipulating 'cdid' parameter by server-
domain DOTS gateways specified in Section 4.4.1 MUST be followed for
GET requests.
The 'c' (content) parameter and its permitted values defined in
[I-D.ietf-core-comi] can be used to retrieve non-configuration data
(attack mitigation status), configuration data, or both. The DOTS
server MAY support this optional filtering capability. It can safely
ignore it if not supported. If the DOTS client supports the optional
filtering capability, it SHOULD use "c=n" query (to get back only the
dynamically changing data) or "c=c" query (to get back the static
configuration values) when the DDoS attack is active to limit the
size of the response.
The DOTS client can use Block-wise transfer [RFC7959] to get the list
of all its mitigations maintained by a DOTS server, it can send
Block2 Option in a GET request with NUM = 0 to aid in limiting the
size of the response. If the representation of all the active
mitigation requests associated with the DOTS client does not fit
within a single datagram, the DOTS server MUST use the Block2 Option
with NUM = 0 in the GET response. The Size2 Option may be conveyed
in the response to indicate the total size of the resource
representation. The DOTS client retrieves the rest of the
representation by sending additional GET requests with Block2 Options
containing NUM values greater than zero. The DOTS client MUST adhere
Reddy, et al. Expires July 22, 2019 [Page 26]
Internet-Draft DOTS Signal Channel Protocol January 2019
to the block size preferences indicated by the DOTS server in the
response. If the DOTS server uses the Block2 Option in the GET
response and the response is for a dynamically changing resource
(e.g. "c=n" or "c=a" query), the DOTS server MUST include the ETag
Option in the response. The DOTS client MUST include the same ETag
value in subsequent GET requests to retrieve the rest of the
representation.
The following examples illustrate how a DOTS client retrieves active
mitigation requests from a DOTS server. In particular:
o Figure 11 shows the example of a GET request to retrieve all DOTS
mitigation requests signaled by a DOTS client.
o Figure 12 shows the example of a GET request to retrieve a
specific DOTS mitigation request signaled by a DOTS client. The
configuration data to be reported in the response is formatted in
the same order as was processed by the DOTS server in the original
mitigation request.
These two examples assume the default of "c=a"; that is, the DOTS
client asks for all data to be reported by the DOTS server.
Header: GET (Code=0.01)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Observe: 0
Figure 11: GET to Retrieve all DOTS Mitigation Requests
Header: GET (Code=0.01)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=12332"
Observe: 0
Figure 12: GET to Retrieve a Specific DOTS Mitigation Request
If the DOTS server does not find the 'mid' Uri-Path value conveyed in
the GET request in its configuration data for the requesting DOTS
client, it MUST respond with a 4.04 (Not Found) error response code.
Likewise, the same error MUST be returned as a response to a request
to retrieve all mitigation records (i.e., 'mid' Uri-Path is not
defined) of a given DOTS client if the DOTS server does not find any
Reddy, et al. Expires July 22, 2019 [Page 27]
Internet-Draft DOTS Signal Channel Protocol January 2019
mitigation record for that DOTS client. As a reminder, a DOTS client
is identified by its identity (e.g., client certificate, 'cuid') and
optionally the 'cdid'.
Figure 13 shows a response example of all active mitigation requests
associated with the DOTS client as maintained by the DOTS server.
The response indicates the mitigation status of each mitigation
request.
Reddy, et al. Expires July 22, 2019 [Page 28]
Internet-Draft DOTS Signal Channel Protocol January 2019
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"mid": 12332,
"mitigation-start": "1507818434",
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-protocol": [
17
],
"lifetime": 1756,
"status": "attack-successfully-mitigated",
"bytes-dropped": "134334555",
"bps-dropped": "43344",
"pkts-dropped": "333334444",
"pps-dropped": "432432"
},
{
"mid": 12333,
"mitigation-start": "1507818393",
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-protocol": [
6
],
"lifetime": 1755,
"status": "attack-stopped",
"bytes-dropped": "0",
"bps-dropped": "0",
"pkts-dropped": "0",
"pps-dropped": "0"
}
]
}
}
Figure 13: Response Body to a GET Request
The mitigation status parameters are described below:
mitigation-start: Mitigation start time is expressed in seconds
relative to 1970-01-01T00:00Z in UTC time (Section 2.4.1 of
Reddy, et al. Expires July 22, 2019 [Page 29]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC7049]). The CBOR encoding is modified so that the leading tag
1 (epoch-based date/time) MUST be omitted.
This is a mandatory attribute when an attack mitigation is active.
Particularly, 'mitigation-start' is not returned for a mitigation
with 'status' code set to 8.
lifetime: The remaining lifetime of the mitigation request, in
seconds.
This is a mandatory attribute.
status: Status of attack mitigation. The various possible values of
'status' parameter are explained in Table 2.
This is a mandatory attribute.
bytes-dropped: The total dropped byte count for the mitigation
request since the attack mitigation is triggered. The count wraps
around when it reaches the maximum value of unsigned integer64.
This is an optional attribute.
bps-dropped: The average number of dropped bytes per second for the
mitigation request since the attack mitigation is triggered. This
average SHOULD be over five-minute intervals.
This is an optional attribute.
pkts-dropped: The total number of dropped packet count for the
mitigation request since the attack mitigation is triggered. The
count wraps around when it reaches the maximum value of unsigned
integer64.
This is an optional attribute.
pps-dropped: The average number of dropped packets per second for
the mitigation request since the attack mitigation is triggered.
This average SHOULD be over five-minute intervals.
This is an optional attribute.
Reddy, et al. Expires July 22, 2019 [Page 30]
Internet-Draft DOTS Signal Channel Protocol January 2019
+-----------+-------------------------------------------------------+
| Parameter | Description |
| Value | |
+-----------+-------------------------------------------------------+
| 1 | Attack mitigation setup is in progress (e.g., |
| | changing the network path to redirect the inbound |
| | traffic to a DOTS mitigator). |
+-----------+-------------------------------------------------------+
| 2 | Attack is being successfully mitigated (e.g., traffic |
| | is redirected to a DDoS mitigator and attack traffic |
| | is dropped). |
+-----------+-------------------------------------------------------+
| 3 | Attack has stopped and the DOTS client can withdraw |
| | the mitigation request. This status code will be |
| | transmitted for immediate mitigation requests till |
| | the mitigation is withdrawn or the lifetime expires. |
| | For mitigation requests with pre-configured scopes |
| | (i.e., 'trigger-mitigation' set to 'false'), this |
| | status code will be transmitted 4 times and then |
| | transition to "8". |
+-----------+-------------------------------------------------------+
| 4 | Attack has exceeded the mitigation provider |
| | capability. |
+-----------+-------------------------------------------------------+
| 5 | DOTS client has withdrawn the mitigation request and |
| | the mitigation is active but terminating. |
+-----------+-------------------------------------------------------+
| 6 | Attack mitigation is now terminated. |
+-----------+-------------------------------------------------------+
| 7 | Attack mitigation is withdrawn (by the DOTS server). |
| | If a mitigation request with 'trigger-mitigation' set |
| | to false is withdrawn because it overlaps with an |
| | immediate mitigation request, this status code will |
| | be transmitted 4 times and then transition to "8" for |
| | the mitigation request with pre-configured scopes. |
+-----------+-------------------------------------------------------+
| 8 | Attack mitigation will be triggered for the |
| | mitigation request only when the DOTS signal channel |
| | session is lost. |
+-----------+-------------------------------------------------------+
Table 2: Values of 'status' Parameter
4.4.2.1. DOTS Servers Sending Mitigation Status
The Observe Option defined in [RFC7641] extends the CoAP core
protocol with a mechanism for a CoAP client to "observe" a resource
on a CoAP server: The client retrieves a representation of the
Reddy, et al. Expires July 22, 2019 [Page 31]
Internet-Draft DOTS Signal Channel Protocol January 2019
resource and requests this representation be updated by the server as
long as the client is interested in the resource. DOTS
implementations MUST use the Observe Option for both 'mitigate' and
'config' (Section 4.2).
A DOTS client conveys the Observe Option set to '0' in the GET
request to receive asynchronous notifications of attack mitigation
status from the DOTS server.
Unidirectional mitigation notifications within the bidirectional
signal channel enables asynchronous notifications between the agents.
[RFC7641] indicates that (1) a notification can be sent in a
Confirmable or a Non-confirmable message, and (2) the message type
used is typically application dependent and may be determined by the
server for each notification individually. For DOTS server
application, the message type MUST always be set to Non-confirmable
even if the underlying COAP library elects a notification to be sent
in a Confirmable message.
Due to the higher likelihood of packet loss during a DDoS attack, the
DOTS server periodically sends attack mitigation status to the DOTS
client and also notifies the DOTS client whenever the status of the
attack mitigation changes. If the DOTS server cannot maintain an RTT
estimate, it SHOULD NOT send more than one asynchronous notification
every 3 seconds, and SHOULD use an even less aggressive rate whenever
possible (case 2 in Section 3.1.3 of [RFC8085]).
When conflicting requests are detected, the DOTS server enforces the
corresponding policy (e.g., accept all requests, reject all requests,
accept only one request but reject all the others, ...). It is
assumed that this policy is supplied by the DOTS server administrator
or it is a default behavior of the DOTS server implementation. Then,
the DOTS server sends notification message(s) to the DOTS client(s)
at the origin of the conflict (refer to the conflict parameters
defined in Section 4.4.1). A conflict notification message includes
information about the conflict cause, scope, and the status of the
mitigation request(s). For example,
o A notification message with 'status' code set to '7 (Attack
mitigation is withdrawn)' and 'conflict-status' set to '1' is sent
to a DOTS client to indicate that an active mitigation request is
deactivated because a conflict is detected.
o A notification message with 'status' code set to '1 (Attack
mitigation is in progress)' and 'conflict-status' set to '2' is
sent to a DOTS client to indicate that this mitigation request is
in progress, but a conflict is detected.
Reddy, et al. Expires July 22, 2019 [Page 32]
Internet-Draft DOTS Signal Channel Protocol January 2019
Upon receipt of a conflict notification message indicating that a
mitigation request is deactivated because of a conflict, a DOTS
client MUST NOT resend the same mitigation request before the expiry
of 'retry-timer'. It is also recommended that DOTS clients support
means to alert administrators about mitigation conflicts.
A DOTS client that is no longer interested in receiving notifications
from the DOTS server can simply "forget" the observation. When the
DOTS server sends the next notification, the DOTS client will not
recognize the token in the message and thus will return a Reset
message. This causes the DOTS server to remove the associated entry.
Alternatively, the DOTS client can explicitly deregister itself by
issuing a GET request that has the Token field set to the token of
the observation to be cancelled and includes an Observe Option with
the value set to '1' (deregister). The latter is RECOMMENDED.
Figure 14 shows an example of a DOTS client requesting a DOTS server
to send notifications related to a mitigation request. Note that for
mitigations with pre-configured scopes (i.e., 'trigger-mitigation'
set to 'false'), the state will need to transition from 3 (attack-
stopped) to 8 (attack-mitigation-signal-loss).
Reddy, et al. Expires July 22, 2019 [Page 33]
Internet-Draft DOTS Signal Channel Protocol January 2019
+-----------+ +-----------+
|DOTS client| |DOTS server|
+-----------+ +-----------+
| |
| GET /<mid> |
| Token: 0x4a | Registration
| Observe: 0 |
+----------------------------------------->|
| |
| 2.05 Content |
| Token: 0x4a | Notification of
| Observe: 12 | the current state
| status: "attack-mitigation-in-progress" |
| |
|<-----------------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 44 | a state change
| status: "attack-successfully-mitigated" |
| |
|<-----------------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 60 | a state change
| status: "attack-stopped" |
|<-----------------------------------------+
| |
...
Figure 14: Notifications of Attack Mitigation Status
4.4.2.2. DOTS Clients Polling for Mitigation Status
The DOTS client can send the GET request at frequent intervals
without the Observe Option to retrieve the configuration data of the
mitigation request and non-configuration data (i.e., the attack
status). The frequency of polling the DOTS server to get the
mitigation status SHOULD follow the transmission guidelines in
Section 3.1.3 of [RFC8085].
If the DOTS server has been able to mitigate the attack and the
attack has stopped, the DOTS server indicates as such in the status.
In such case, the DOTS client recalls the mitigation request by
issuing a DELETE request for this mitigation request (Section 4.4.4).
A DOTS client SHOULD react to the status of the attack as per the
information sent by the DOTS server rather than performing its own
detection that the attack has been mitigated. This ensures that the
Reddy, et al. Expires July 22, 2019 [Page 34]
Internet-Draft DOTS Signal Channel Protocol January 2019
DOTS client does not recall a mitigation request prematurely because
it is possible that the DOTS client does not sense the DDoS attack on
its resources, but the DOTS server could be actively mitigating the
attack because the attack is not completely averted.
4.4.3. Efficacy Update from DOTS Clients
While DDoS mitigation is in progress, due to the likelihood of packet
loss, a DOTS client MAY periodically transmit DOTS mitigation
efficacy updates to the relevant DOTS server. A PUT request is used
to convey the mitigation efficacy update to the DOTS server. This
PUT request is treated as a refresh of the current mitigation.
The PUT request used for efficacy update MUST include all the
parameters used in the PUT request to carry the DOTS mitigation
request (Section 4.4.1) unchanged apart from the 'lifetime' parameter
value. If this is not the case, the DOTS server MUST reject the
request with a 4.00 (Bad Request).
The If-Match Option (Section 5.10.8.1 of [RFC7252]) with an empty
value is used to make the PUT request conditional on the current
existence of the mitigation request. If UDP is used as transport,
CoAP requests may arrive out-of-order. For example, the DOTS client
may send a PUT request to convey an efficacy update to the DOTS
server followed by a DELETE request to withdraw the mitigation
request, but the DELETE request arrives at the DOTS server before the
PUT request. To handle out-of-order delivery of requests, if an If-
Match Option is present in the PUT request and the 'mid' in the
request matches a mitigation request from that DOTS client, the
request is processed by the DOTS server. If no match is found, the
PUT request is silently ignored by the DOTS server.
An example of an efficacy update message, which includes an If-Match
Option with an empty value, is depicted in Figure 15.
Reddy, et al. Expires July 22, 2019 [Page 35]
Internet-Draft DOTS Signal Channel Protocol January 2019
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
If-Match:
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-port-range": [
{
"lower-port": 80
},
{
"lower-port": 443
},
{
"lower-port": 8080
}
],
"target-protocol": [
6
],
"attack-status": "under-attack"
}
]
}
}
Figure 15: An Example of Efficacy Update
The 'attack-status' parameter is a mandatory attribute when
performing an efficacy update. The various possible values contained
in the 'attack-status' parameter are described in Table 3.
Reddy, et al. Expires July 22, 2019 [Page 36]
Internet-Draft DOTS Signal Channel Protocol January 2019
+-----------+-------------------------------------------------------+
| Parameter | Description |
| value | |
+-----------+-------------------------------------------------------+
| 1 | The DOTS client determines that it is still under |
| | attack. |
+-----------+-------------------------------------------------------+
| 2 | The DOTS client determines that the attack is |
| | successfully mitigated (e.g., attack traffic is not |
| | seen). |
+-----------+-------------------------------------------------------+
Table 3: Values of 'attack-status' Parameter
The DOTS server indicates the result of processing a PUT request
using CoAP response codes. The response code 2.04 (Changed) is
returned if the DOTS server has accepted the mitigation efficacy
update. The error response code 5.03 (Service Unavailable) is
returned if the DOTS server has erred or is incapable of performing
the mitigation. As specified in [RFC7252], 5.03 uses Max-Age option
to indicate the number of seconds after which to retry.
4.4.4. Withdraw a Mitigation
DELETE requests are used to withdraw DOTS mitigation requests from
DOTS servers (Figure 16).
'cuid' and 'mid' are mandatory Uri-Path parameters for DELETE
requests.
The same considerations for manipulating 'cdid' parameter by DOTS
gateways, as specified in Section 4.4.1, MUST be followed for DELETE
requests. Uri-Path parameters with empty values MUST NOT be present
in a request.
Header: DELETE (Code=0.04)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Figure 16: Withdraw a DOTS Mitigation
If the DELETE request does not include 'cuid' and 'mid' parameters,
the DOTS server MUST reply with a 4.00 (Bad Request).
Reddy, et al. Expires July 22, 2019 [Page 37]
Internet-Draft DOTS Signal Channel Protocol January 2019
Once the request is validated, the DOTS server immediately
acknowledges a DOTS client's request to withdraw the DOTS signal
using 2.02 (Deleted) response code with no response payload. A 2.02
(Deleted) Response Code is returned even if the 'mid' parameter value
conveyed in the DELETE request does not exist in its configuration
data before the request.
If the DOTS server finds the 'mid' parameter value conveyed in the
DELETE request in its configuration data for the DOTS client, then to
protect against route or DNS flapping caused by a DOTS client rapidly
removing a mitigation, and to dampen the effect of oscillating
attacks, the DOTS server MAY allow mitigation to continue for a
limited period after acknowledging a DOTS client's withdrawal of a
mitigation request. During this period, the DOTS server status
messages SHOULD indicate that mitigation is active but terminating
(Section 4.4.2).
The initial active-but-terminating period SHOULD be sufficiently long
to absorb latency incurred by route propagation. The active-but-
terminating period SHOULD be set by default to 120 seconds. If the
client requests mitigation again before the initial active-but-
terminating period elapses, the DOTS server MAY exponentially
increase (the exponent is 2) the active-but-terminating period up to
a maximum of 300 seconds (5 minutes).
Once the active-but-terminating period elapses, the DOTS server MUST
treat the mitigation as terminated, as the DOTS client is no longer
responsible for the mitigation. For example, if there is a financial
relationship between the DOTS client and server domains, the DOTS
client stops incurring cost at this point.
If a mitigation is triggered due to a signal channel loss, the DOTS
server relies upon normal triggers to stop that mitigation
(typically, receipt of a valid DELETE request, expiry of the
mitigation lifetime, or scrubbing the traffic to the attack target).
In particular, the DOTS server MUST NOT consider the signal channel
recovery as a trigger to stop the mitigation.
4.5. DOTS Signal Channel Session Configuration
A DOTS client can negotiate, configure, and retrieve the DOTS signal
channel session behavior with its DOTS peers. The DOTS signal
channel can be used, for example, to configure the following:
a. Heartbeat interval (heartbeat-interval): DOTS agents regularly
send heartbeats (CoAP Ping/Pong) to each other after mutual
authentication is successfully completed in order to keep the
DOTS signal channel open. Heartbeat messages are exchanged
Reddy, et al. Expires July 22, 2019 [Page 38]
Internet-Draft DOTS Signal Channel Protocol January 2019
between DOTS agents every 'heartbeat-interval' seconds to detect
the current status of the DOTS signal channel session.
b. Missing heartbeats allowed (missing-hb-allowed): This variable
indicates the maximum number of consecutive heartbeat messages
for which a DOTS agent did not receive a response before
concluding that the session is disconnected or defunct.
c. Acceptable signal loss ratio: Maximum retransmissions,
retransmission timeout value, and other message transmission
parameters for the DOTS signal channel.
The same or distinct configuration sets may be used during times when
a mitigation is active ('mitigating-config') and when no mitigation
is active ('idle-config'). This is particularly useful for DOTS
servers that might want to reduce heartbeat frequency or cease
heartbeat exchanges when an active DOTS client has not requested
mitigation. If distinct configurations are used, DOTS agents MUST
follow the appropriate configuration set as a function of the
mitigation activity (e.g., if no mitigation request is active, 'idle-
config'-related values must be followed). Additionally, DOTS agents
MUST automatically switch to the other configuration upon a change in
the mitigation activity (e.g., if an attack mitigation is launched
after a peacetime, the DOTS agent switches from 'idle-config' to
'mitigating-config'-related values).
CoAP Requests and responses are indicated for reliable delivery by
marking them as Confirmable messages. DOTS signal channel session
configuration requests and responses are marked as Confirmable
messages. As explained in Section 2.1 of [RFC7252], a Confirmable
message is retransmitted using a default timeout and exponential
back-off between retransmissions, until the DOTS server sends an
Acknowledgement message (ACK) with the same Message ID conveyed from
the DOTS client.
Message transmission parameters are defined in Section 4.8 of
[RFC7252]. The DOTS server can either piggyback the response in the
acknowledgement message or, if the DOTS server cannot respond
immediately to a request carried in a Confirmable message, it simply
responds with an Empty Acknowledgement message so that the DOTS
client can stop retransmitting the request. Empty Acknowledgement
messages are explained in Section 2.2 of [RFC7252]. When the
response is ready, the server sends it in a new Confirmable message
which in turn needs to be acknowledged by the DOTS client (see
Sections 5.2.1 and 5.2.2 of [RFC7252]). Requests and responses
exchanged between DOTS agents during peacetime are marked as
Confirmable messages.
Reddy, et al. Expires July 22, 2019 [Page 39]
Internet-Draft DOTS Signal Channel Protocol January 2019
Implementation Note: A DOTS client that receives a response in a
Confirmable message may want to clean up the message state right
after sending the ACK. If that ACK is lost and the DOTS server
retransmits the Confirmable message, the DOTS client may no longer
have any state that would help it correlate this response: from
the DOTS client's standpoint, the retransmission message is
unexpected. The DOTS client will send a Reset message so it does
not receive any more retransmissions. This behavior is normal and
not an indication of an error (see Section 5.3.2 of [RFC7252] for
more details).
4.5.1. Discover Configuration Parameters
A GET request is used to obtain acceptable (e.g., minimum and maximum
values) and current configuration parameters on the DOTS server for
DOTS signal channel session configuration. This procedure occurs
between a DOTS client and its immediate peer DOTS server. As such,
this GET request MUST NOT be relayed by a DOTS gateway.
Figure 17 shows how to obtain acceptable configuration parameters for
the DOTS server.
Header: GET (Code=0.01)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Figure 17: GET to Retrieve Configuration
The DOTS server in the 2.05 (Content) response conveys the current,
minimum, and maximum attribute values acceptable by the DOTS server
(Figure 18).
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"max-value": number,
"min-value": number,
"current-value": number
},
"missing-hb-allowed": {
"max-value": number,
"min-value": number,
"current-value": number
},
"max-retransmit": {
Reddy, et al. Expires July 22, 2019 [Page 40]
Internet-Draft DOTS Signal Channel Protocol January 2019
"max-value": number,
"min-value": number,
"current-value": number
},
"ack-timeout": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
},
"ack-random-factor": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
}
},
"idle-config": {
"heartbeat-interval": {
"max-value": number,
"min-value": number,
"current-value": number
},
"missing-hb-allowed": {
"max-value": number,
"min-value": number,
"current-value": number
},
"max-retransmit": {
"max-value": number,
"min-value": number,
"current-value": number
},
"ack-timeout": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
},
"ack-random-factor": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
}
}
}
}
Figure 18: GET Configuration Response Body Schema
The parameters in Figure 18 are described below:
Reddy, et al. Expires July 22, 2019 [Page 41]
Internet-Draft DOTS Signal Channel Protocol January 2019
mitigating-config: Set of configuration parameters to use when a
mitigation is active. The following parameters may be included:
heartbeat-interval: Time interval in seconds between two
consecutive heartbeat messages.
'0' is used to disable the heartbeat mechanism.
This is an optional attribute.
missing-hb-allowed: Maximum number of consecutive heartbeat
messages for which the DOTS agent did not receive a response
before concluding that the session is disconnected.
This is an optional attribute.
max-retransmit: Maximum number of retransmissions for a message
(referred to as MAX_RETRANSMIT parameter in CoAP).
This is an optional attribute.
ack-timeout: Timeout value in seconds used to calculate the
initial retransmission timeout value (referred to as
ACK_TIMEOUT parameter in CoAP).
This is an optional attribute.
ack-random-factor: Random factor used to influence the timing of
retransmissions (referred to as ACK_RANDOM_FACTOR parameter in
CoAP).
This is an optional attribute.
idle-config: Set of configuration parameters to use when no
mitigation is active. This attribute has the same structure as
'mitigating-config'.
Figure 19 shows an example of acceptable and current configuration
parameters on a DOTS server for DOTS signal channel session
configuration. The same acceptable configuration is used during
mitigation and idle times.
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"max-value": 240,
Reddy, et al. Expires July 22, 2019 [Page 42]
Internet-Draft DOTS Signal Channel Protocol January 2019
"min-value": 15,
"current-value": 30
},
"missing-hb-allowed": {
"max-value": 9,
"min-value": 3,
"current-value": 5
},
"max-retransmit": {
"max-value": 15,
"min-value": 2,
"current-value": 3
},
"ack-timeout": {
"max-value-decimal": "30.00",
"min-value-decimal": "1.00",
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"max-value-decimal": "4.00",
"min-value-decimal": "1.10",
"current-value-decimal": "1.50"
}
},
"idle-config": {
"heartbeat-interval": {
"max-value": 240,
"min-value": 15,
"current-value": 30
},
"missing-hb-allowed": {
"max-value": 9,
"min-value": 3,
"current-value": 5
},
"max-retransmit": {
"max-value": 15,
"min-value": 2,
"current-value": 3
},
"ack-timeout": {
"max-value-decimal": "30.00",
"min-value-decimal": "1.00",
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"max-value-decimal": "4.00",
"min-value-decimal": "1.10",
Reddy, et al. Expires July 22, 2019 [Page 43]
Internet-Draft DOTS Signal Channel Protocol January 2019
"current-value-decimal": "1.50"
}
}
}
}
Figure 19: Example of a Configuration Response Body
4.5.2. Convey DOTS Signal Channel Session Configuration
A PUT request (Figures 20 and 21) is used to convey the configuration
parameters for the signal channel (e.g., heartbeat interval, maximum
retransmissions). Message transmission parameters for CoAP are
defined in Section 4.8 of [RFC7252]. The RECOMMENDED values of
transmission parameter values are ack-timeout (2 seconds), max-
retransmit (3), ack-random-factor (1.5). In addition to those
parameters, the RECOMMENDED specific DOTS transmission parameter
values are 'heartbeat-interval' (30 seconds) and 'missing-hb-allowed'
(5).
Note: heartbeat-interval should be tweaked to also assist DOTS
messages for NAT traversal (SIG-011 of
[I-D.ietf-dots-requirements]). According to [RFC8085], keepalive
messages must not be sent more frequently than once every 15
seconds and should use longer intervals when possible.
Furthermore, [RFC4787] recommends NATs to use a state timeout of 2
minutes or longer, but experience shows that sending packets every
15 to 30 seconds is necessary to prevent the majority of
middleboxes from losing state for UDP flows. From that
standpoint, this specification recommends a minimum heartbeat-
interval of 15 seconds and a maximum heartbeat-interval of 240
seconds. The recommended value of 30 seconds is selected to
anticipate the expiry of NAT state.
A heartbeat-interval of 30 seconds may be considered as too chatty
in some deployments. For such deployments, DOTS agents may
negotiate longer heartbeat-interval values to prevent any network
overload with too frequent keepalives.
Different heartbeat intervals can be defined for 'mitigating-
config' and 'idle-config' to reduce being too chatty during idle
times. If there is an on-path translator between the DOTS client
(standalone or part of a DOTS gateway) and the DOTS server, the
'mitigating-config' heartbeat-interval has to be smaller than the
translator session timeout. It is recommended that the 'idle-
config' heartbeat-interval is also smaller than the translator
session timeout to prevent translator traversal issues, or
Reddy, et al. Expires July 22, 2019 [Page 44]
Internet-Draft DOTS Signal Channel Protocol January 2019
disabled entirely. Means to discover the lifetime assigned by a
translator are out of scope.
When a Confirmable "CoAP Ping" is sent, and if there is no response,
the "CoAP Ping" is retransmitted max-retransmit number of times by
the CoAP layer using an initial timeout set to a random duration
between ack-timeout and (ack-timeout*ack-random-factor) and
exponential back-off between retransmissions. By choosing the
recommended transmission parameters, the "CoAP Ping" will timeout
after 45 seconds. If the DOTS agent does not receive any response
from the peer DOTS agent for 'missing-hb-allowed' number of
consecutive "CoAP Ping" Confirmable messages, it concludes that the
DOTS signal channel session is disconnected. A DOTS client MUST NOT
transmit a "CoAP Ping" while waiting for the previous "CoAP Ping"
response from the same DOTS server.
If the DOTS agent wishes to change the default values of message
transmission parameters, it SHOULD follow the guidance given in
Section 4.8.1 of [RFC7252]. The DOTS agents MUST use the negotiated
values for message transmission parameters and default values for
non-negotiated message transmission parameters.
The signal channel session configuration is applicable to a single
DOTS signal channel session between DOTS agents, so the 'cuid' Uri-
Path MUST NOT be used.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Uri-Path: "sid=123"
Content-Format: "application/dots+cbor"
{
...
}
Figure 20: PUT to Convey the DOTS Signal Channel Session
Configuration Data
The additional Uri-Path parameter to those defined in Table 1 is as
follows:
sid: Session Identifier is an identifier for the DOTS signal channel
session configuration data represented as an integer. This
identifier MUST be generated by DOTS clients. 'sid' values MUST
increase monotonically (when a new PUT is generated by a DOTS
client to convey the configuration parameters for the signal
channel).
Reddy, et al. Expires July 22, 2019 [Page 45]
Internet-Draft DOTS Signal Channel Protocol January 2019
This is a mandatory attribute.
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"current-value": number
},
"missing-hb-allowed": {
"current-value": number
},
"max-retransmit": {
"current-value": number
},
"ack-timeout": {
"current-value-decimal": "string"
},
"ack-random-factor": {
"current-value-decimal": "string"
}
},
"idle-config": {
"heartbeat-interval": {
"current-value": number
},
"missing-hb-allowed": {
"current-value": number
},
"max-retransmit": {
"current-value": number
},
"ack-timeout": {
"current-value-decimal": "string"
},
"ack-random-factor": {
"current-value-decimal": "string"
}
}
}
}
Figure 21: PUT to Convey the DOTS Signal Channel Session
Configuration Data (Message Body Schema)
The meaning of the parameters in the CBOR body (Figure 21) is defined
in Section 4.5.1.
Reddy, et al. Expires July 22, 2019 [Page 46]
Internet-Draft DOTS Signal Channel Protocol January 2019
At least one of the attributes 'heartbeat-interval', 'missing-hb-
allowed', 'max-retransmit', 'ack-timeout', and 'ack-random-factor'
MUST be present in the PUT request. Note that 'heartbeat-interval',
'missing-hb-allowed', 'max-retransmit', 'ack-timeout', and 'ack-
random-factor', if present, do not need to be provided for both
'mitigating-config', and 'idle-config' in a PUT request.
The PUT request with a higher numeric 'sid' value overrides the DOTS
signal channel session configuration data installed by a PUT request
with a lower numeric 'sid' value. To avoid maintaining a long list
of 'sid' requests from a DOTS client, the lower numeric 'sid' MUST be
automatically deleted and no longer available at the DOTS server.
Figure 22 shows a PUT request example to convey the configuration
parameters for the DOTS signal channel. In this example, the
heartbeat mechanism is disabled when no mitigation is active, while
the heartbeat interval is set to '91' when a mitigation is active.
Reddy, et al. Expires July 22, 2019 [Page 47]
Internet-Draft DOTS Signal Channel Protocol January 2019
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Uri-Path: "sid=123"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"current-value": 91
},
"missing-hb-allowed": {
"current-value": 3
},
"max-retransmit": {
"current-value": 3
},
"ack-timeout": {
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"current-value-decimal": "1.50"
}
},
"idle-config": {
"heartbeat-interval": {
"current-value": 0
},
"max-retransmit": {
"current-value": 3
},
"ack-timeout": {
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"current-value-decimal": "1.50"
}
}
}
}
Figure 22: PUT to Convey the Configuration Parameters
The DOTS server indicates the result of processing the PUT request
using CoAP response codes:
Reddy, et al. Expires July 22, 2019 [Page 48]
Internet-Draft DOTS Signal Channel Protocol January 2019
o If the request is missing a mandatory attribute, does not include
a 'sid' Uri-Path, or contains one or more invalid or unknown
parameters, 4.00 (Bad Request) MUST be returned in the response.
o If the DOTS server does not find the 'sid' parameter value
conveyed in the PUT request in its configuration data and if the
DOTS server has accepted the configuration parameters, then a
response code 2.01 (Created) MUST be returned in the response.
o If the DOTS server finds the 'sid' parameter value conveyed in the
PUT request in its configuration data and if the DOTS server has
accepted the updated configuration parameters, 2.04 (Changed) MUST
be returned in the response.
o If any of the 'heartbeat-interval', 'missing-hb-allowed', 'max-
retransmit', 'target-protocol', 'ack-timeout', and 'ack-random-
factor' attribute values are not acceptable to the DOTS server,
4.22 (Unprocessable Entity) MUST be returned in the response.
Upon receipt of this error code, the DOTS client SHOULD retrieve
the maximum and minimum attribute values acceptable to the DOTS
server (Section 4.5.1).
The DOTS client may re-try and send the PUT request with updated
attribute values acceptable to the DOTS server.
A DOTS client may issue a GET message with 'sid' Uri-Path parameter
to retrieve the negotiated configuration. The response does not need
to include 'sid' in its message body.
4.5.3. Configuration Freshness and Notifications
Max-Age Option (Section 5.10.5 of [RFC7252]) SHOULD be returned by a
DOTS server to associate a validity time with a configuration it
sends. This feature allows the update of the configuration data if a
change occurs at the DOTS server side. For example, the new
configuration may instruct a DOTS client to cease heartbeats or
reduce heartbeat frequency.
It is NOT RECOMMENDED to return a Max-Age Option set to 0.
Returning a Max-Age Option set to 2**32-1 is equivalent to
associating an infinite lifetime with the configuration.
If a non-zero value of Max-Age Option is received by a DOTS client,
it MUST issue a GET request with 'sid' Uri-Path parameter to retrieve
the current and acceptable configuration before the expiry of the
value enclosed in the Max-Age option. This request is considered by
the client and the server as a means to refresh the configuration
Reddy, et al. Expires July 22, 2019 [Page 49]
Internet-Draft DOTS Signal Channel Protocol January 2019
parameters for the signal channel. When a DDoS attack is active,
refresh requests MUST NOT be sent by DOTS clients and the DOTS server
MUST NOT terminate the (D)TLS session after the expiry of the value
returned in Max-Age Option.
If Max-Age Option is not returned in a response, the DOTS client
initiates GET requests to refresh the configuration parameters each
60 seconds (Section 5.10.5 of [RFC7252]). To prevent such overload,
it is RECOMMENDED that DOTS servers return a Max-Age Option in GET
responses. Considerations related to which value to use and how such
value is set, are implementation- and deployment-specific.
If an Observe Option set to 0 is included in the configuration
request, the DOTS server sends notifications of any configuration
change (Section 4.2 of [RFC7641]).
If a DOTS server detects that a misbehaving DOTS client does not
contact the DOTS server after the expiry of Max-Age and retrieve the
signal channel configuration data, it MAY terminate the (D)TLS
session. A (D)TLS session is terminated by the receipt of an
authenticated message that closes the connection (e.g., a fatal alert
(Section 6 of [RFC8446])).
4.5.4. Delete DOTS Signal Channel Session Configuration
A DELETE request is used to delete the installed DOTS signal channel
session configuration data (Figure 23).
Header: DELETE (Code=0.04)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Uri-Path: "sid=123"
Figure 23: Delete Configuration
The DOTS server resets the DOTS signal channel session configuration
back to the default values and acknowledges a DOTS client's request
to remove the DOTS signal channel session configuration using 2.02
(Deleted) response code.
Upon bootstrapping or reboot, a DOTS client MAY send a DELETE request
to set the configuration parameters to default values. Such a
request does not include any 'sid'.
Reddy, et al. Expires July 22, 2019 [Page 50]
Internet-Draft DOTS Signal Channel Protocol January 2019
4.6. Redirected Signaling
Redirected DOTS signaling is discussed in detail in Section 3.2.2 of
[I-D.ietf-dots-architecture].
If a DOTS server wants to redirect a DOTS client to an alternative
DOTS server for a signal session, then the response code 5.03
(Service Unavailable) will be returned in the response to the DOTS
client.
The DOTS server can return the error response code 5.03 in response
to a request from the DOTS client or convey the error response code
5.03 in a unidirectional notification response from the DOTS server.
The DOTS server in the error response conveys the alternate DOTS
server's FQDN, and the alternate DOTS server's IP address(es) values
in the CBOR body (Figure 24).
{
"ietf-dots-signal-channel:redirected-signal": {
"alt-server": "string",
"alt-server-record": [
"string"
]
}
Figure 24: Redirected Server Error Response Body Schema
The parameters are described below:
alt-server: FQDN of an alternate DOTS server.
This is a mandatory attribute.
alt-server-record: A list of IP addresses of an alternate DOTS
server.
This is an optional attribute.
The DOTS server returns the Time to live (TTL) of the alternate DOTS
server in a Max-Age Option. That is, the time interval that the
alternate DOTS server may be cached for use by a DOTS client. A Max-
Age Option set to 2**32-1 is equivalent to receiving an infinite TTL.
This value means that the alternate DOTS server is to be used until
the alternate DOTS server redirects the traffic with another 5.03
response which encloses an alternate server.
Reddy, et al. Expires July 22, 2019 [Page 51]
Internet-Draft DOTS Signal Channel Protocol January 2019
A Max-Age Option set to '0' may be returned for redirecting
mitigation requests. Such value means that the redirection applies
only for the mitigation request in progress. Returning short TTL in
a Max-Age Option may adversely impact DOTS clients on slow links.
Returning short values should be avoided under such conditions.
If the alternate DOTS server TTL has expired, the DOTS client MUST
use the DOTS server(s), that was provisioned using means discussed in
Section 4.1. This fall back mechanism is triggered immediately upon
expiry of the TTL, except when a DDoS attack is active.
Requests issued by misbehaving DOTS clients which do not honor the
TTL conveyed in the Max-Age Option or react to explicit re-direct
messages can be rejected by DOTS servers.
Figure 25 shows a 5.03 response example to convey the DOTS alternate
server 'alt-server.example' together with its IP addresses
2001:db8:6401::1 and 2001:db8:6401::2.
{
"ietf-dots-signal-channel:redirected-signal": {
"alt-server": "alt-server.example",
"alt-server-record": [
"2001:db8:6401::1",
"2001:db8:6401::2"
]
}
Figure 25: Example of Redirected Server Error Response Body
When the DOTS client receives 5.03 response with an alternate server
included, it considers the current request as failed, but SHOULD try
re-sending the request to the alternate DOTS server. During a DDoS
attack, the DNS server may be the target of another DDoS attack,
alternate DOTS server's IP addresses conveyed in the 5.03 response
help the DOTS client skip DNS lookup of the alternate DOTS server, at
the cost of trusting the first DOTS server to provide accurate
information. The DOTS client can then try to establish a UDP or a
TCP session with the alternate DOTS server. The DOTS client MAY
implement a method to construct IPv4-embedded IPv6 addresses
[RFC6052]; this is required to handle the scenario where an IPv6-only
DOTS client communicates with an IPv4-only alternate DOTS server.
If the DOTS client has been redirected to a DOTS server to which it
has already communicated with within the last five (5) minutes, it
MUST ignore the redirection and try to contact other DOTS servers
listed in the local configuration or discovered using dynamic means
Reddy, et al. Expires July 22, 2019 [Page 52]
Internet-Draft DOTS Signal Channel Protocol January 2019
such as DHCP or SRV procedures. It is RECOMMENDED that DOTS clients
support means to alert administrators about redirect loops.
4.7. Heartbeat Mechanism
To provide an indication of signal health and distinguish an 'idle'
signal channel from a 'disconnected' or 'defunct' session, the DOTS
agent sends a heartbeat over the signal channel to maintain its half
of the channel. The DOTS agent similarly expects a heartbeat from
its peer DOTS agent, and may consider a session terminated in the
prolonged absence of a peer agent heartbeat. Concretely, while the
communication between the DOTS agents is otherwise quiescent, the
DOTS client will probe the DOTS server to ensure it has maintained
cryptographic state and vice versa. Such probes can also keep
firewalls and/or stateful translators bindings alive. This probing
reduces the frequency of establishing a new handshake when a DOTS
signal needs to be conveyed to the DOTS server.
DOTS servers MAY trigger their heartbeat requests immediately after
receiving heartbeat probes from peer DOTS clients. As a reminder, it
is the responsibility of DOTS clients to ensure that on-path
translators/firewalls are maintaining a binding so that the same
external IP address and/or port number is retained for the DOTS
signal channel session.
In case of a massive DDoS attack that saturates the incoming link(s)
to the DOTS client, all traffic from the DOTS server to the DOTS
client will likely be dropped, although the DOTS server receives
heartbeat requests in addition to DOTS messages sent by the DOTS
client. In this scenario, the DOTS agents MUST behave differently to
handle message transmission and DOTS signal channel session
liveliness during link saturation:
o The DOTS client MUST NOT consider the DOTS signal channel session
terminated even after a maximum 'missing-hb-allowed' threshold is
reached. The DOTS client SHOULD keep on using the current DOTS
signal channel session to send heartbeat requests over it, so that
the DOTS server knows the DOTS client has not disconnected the
DOTS signal channel session.
After the maximum 'missing-hb-allowed' threshold is reached, the
DOTS client SHOULD try to resume the (D)TLS session. The DOTS
client SHOULD send mitigation requests over the current DOTS
signal channel session, and in parallel, for example, try to
resume the (D)TLS session or use 0-RTT mode in DTLS 1.3 to
piggyback the mitigation request in the ClientHello message.
Reddy, et al. Expires July 22, 2019 [Page 53]
Internet-Draft DOTS Signal Channel Protocol January 2019
As soon as the link is no longer saturated, if traffic from the
DOTS server reaches the DOTS client over the current DOTS signal
channel session, the DOTS client can stop (D)TLS session
resumption or if (D)TLS session resumption is successful then
disconnect the current DOTS signal channel session.
o If the DOTS server does not receive any traffic from the peer DOTS
client, then the DOTS server sends heartbeat requests to the DOTS
client and after maximum 'missing-hb-allowed' threshold is
reached, the DOTS server concludes the session is disconnected.
In DOTS over UDP, heartbeat messages MUST be exchanged between the
DOTS agents using the "CoAP Ping" mechanism defined in Section 4.2 of
[RFC7252]. Concretely, the DOTS agent sends an Empty Confirmable
message and the peer DOTS agent will respond by sending a Reset
message.
In DOTS over TCP, heartbeat messages MUST be exchanged between the
DOTS agents using the Ping and Pong messages specified in Section 5.4
of [RFC8323]. That is, the DOTS agent sends a Ping message and the
peer DOTS agent would respond by sending a single Pong message.
5. DOTS Signal Channel YANG Modules
This document defines a YANG [RFC7950] module for DOTS mitigation
scope, DOTS signal channel session configuration data, and DOTS
redirection signalling.
This YANG module (ietf-dots-signal-channel) defines the DOTS client
interaction with the DOTS server as seen by the DOTS client. A DOTS
server is allowed to update the non-configurable 'ro' entities in the
responses. This YANG module is not intended to be used via NETCONF/
RESTCONF for DOTS server management purposes; such module is out of
the scope of this document. It serves only to provide a data model
and encoding, but not a management data model.
A companion YANG module is defined to include a collection of types
defined by IANA: "iana-dots-signal-channel" (Section 5.2).
5.1. Tree Structure
This document defines the YANG module "ietf-dots-signal-channel"
(Section 5.3), which has the following tree structure. A DOTS signal
message can either be a mitigation or a configuration message.
module: ietf-dots-signal-channel
+--rw dots-signal
+--rw (message-type)?
Reddy, et al. Expires July 22, 2019 [Page 54]
Internet-Draft DOTS Signal Channel Protocol January 2019
+--:(mitigation-scope)
| +--rw scope* [cuid mid]
| +--rw cdid? string
| +--rw cuid string
| +--rw mid uint32
| +--rw target-prefix* inet:ip-prefix
| +--rw target-port-range* [lower-port]
| | +--rw lower-port inet:port-number
| | +--rw upper-port? inet:port-number
| +--rw target-protocol* uint8
| +--rw target-fqdn* inet:domain-name
| +--rw target-uri* inet:uri
| +--rw alias-name* string
| +--rw lifetime? int32
| +--rw trigger-mitigation? boolean
| +--ro mitigation-start? uint64
| +--ro status? iana-signal:status
| +--ro conflict-information
| | +--ro conflict-status? iana-signal:conflict-status
| | +--ro conflict-cause? iana-signal:conflict-cause
| | +--ro retry-timer? uint32
| | +--ro conflict-scope
| | +--ro target-prefix* inet:ip-prefix
| | +--ro target-port-range* [lower-port]
| | | +--ro lower-port inet:port-number
| | | +--ro upper-port? inet:port-number
| | +--ro target-protocol* uint8
| | +--ro target-fqdn* inet:domain-name
| | +--ro target-uri* inet:uri
| | +--ro alias-name* string
| | +--ro acl-list* [acl-name]
| | | +--ro acl-name
| | | | -> /ietf-data:dots-data/dots-client/acls/
| | | | acl/name
| | | +--ro acl-type?
| | | -> /ietf-data:dots-data/dots-client/acls/
| | | acl/type
| | +--ro mid? -> ../../../mid
| +--ro bytes-dropped? yang:zero-based-counter64
| +--ro bps-dropped? yang:zero-based-counter64
| +--ro pkts-dropped? yang:zero-based-counter64
| +--ro pps-dropped? yang:zero-based-counter64
| +--rw attack-status? iana-signal:attack-status
+--:(signal-config)
| +--rw sid uint32
| +--rw mitigating-config
| | +--rw heartbeat-interval
| | | +--ro max-value? uint16
Reddy, et al. Expires July 22, 2019 [Page 55]
Internet-Draft DOTS Signal Channel Protocol January 2019
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw missing-hb-allowed
| | | +--ro max-value? uint16
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw max-retransmit
| | | +--ro max-value? uint16
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw ack-timeout
| | | +--ro max-value-decimal? decimal64
| | | +--ro min-value-decimal? decimal64
| | | +--rw current-value-decimal? decimal64
| | +--rw ack-random-factor
| | +--ro max-value-decimal? decimal64
| | +--ro min-value-decimal? decimal64
| | +--rw current-value-decimal? decimal64
| +--rw idle-config
| +--rw heartbeat-interval
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw missing-hb-allowed
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw max-retransmit
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw ack-timeout
| | +--ro max-value-decimal? decimal64
| | +--ro min-value-decimal? decimal64
| | +--rw current-value-decimal? decimal64
| +--rw ack-random-factor
| +--ro max-value-decimal? decimal64
| +--ro min-value-decimal? decimal64
| +--rw current-value-decimal? decimal64
+--:(redirected-signal)
+--ro alt-server string
+--ro alt-server-record* inet:ip-address
5.2. IANA DOTS Signal Channel YANG Module
<CODE BEGINS> file "iana-dots-signal-channel@2019-01-17.yang"
module iana-dots-signal-channel {
yang-version 1.1;
Reddy, et al. Expires July 22, 2019 [Page 56]
Internet-Draft DOTS Signal Channel Protocol January 2019
namespace "urn:ietf:params:xml:ns:yang:iana-dots-signal-channel";
prefix iana-signal;
organization
"IANA";
contact
"Internet Assigned Numbers Authority
Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
United States of America
Tel: +1 310 301 5800
<mailto:iana@iana.org>";
description
"This module contains a collection of YANG data types defined
by IANA and used for DOTS signal channel protocol.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision 2019-01-17 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel Specification";
}
typedef status {
type enumeration {
enum attack-mitigation-in-progress {
value 1;
description
"Attack mitigation setup is in progress (e.g., changing
the network path to re-route the inbound traffic
to DOTS mitigator).";
}
Reddy, et al. Expires July 22, 2019 [Page 57]
Internet-Draft DOTS Signal Channel Protocol January 2019
enum attack-successfully-mitigated {
value 2;
description
"Attack is being successfully mitigated (e.g., traffic
is redirected to a DDoS mitigator and attack
traffic is dropped or blackholed).";
}
enum attack-stopped {
value 3;
description
"Attack has stopped and the DOTS client can
withdraw the mitigation request.";
}
enum attack-exceeded-capability {
value 4;
description
"Attack has exceeded the mitigation provider
capability.";
}
enum dots-client-withdrawn-mitigation {
value 5;
description
"DOTS client has withdrawn the mitigation
request and the mitigation is active but
terminating.";
}
enum attack-mitigation-terminated {
value 6;
description
"Attack mitigation is now terminated.";
}
enum attack-mitigation-withdrawn {
value 7;
description
"Attack mitigation is withdrawn.";
}
enum attack-mitigation-signal-loss {
value 8;
description
"Attack mitigation will be triggered
for the mitigation request only when
the DOTS signal channel session is lost.";
}
}
description
"Enumeration for status reported by the DOTS server.";
}
Reddy, et al. Expires July 22, 2019 [Page 58]
Internet-Draft DOTS Signal Channel Protocol January 2019
typedef conflict-status {
type enumeration {
enum request-inactive-other-active {
value 1;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
This mitigation request is currently inactive
until the conflicts are resolved. Another
mitigation request is active.";
}
enum request-active {
value 2;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
This mitigation request is currently active.";
}
enum all-requests-inactive {
value 3;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients. All
conflicting mitigation requests are inactive.";
}
}
description
"Enumeration for conflict status.";
}
typedef conflict-cause {
type enumeration {
enum overlapping-targets {
value 1;
description
"Overlapping targets. conflict-scope provides
more details about the exact conflict.";
}
enum conflict-with-acceptlist {
value 2;
description
"Conflicts with an existing accept-list.
This code is returned when the DDoS mitigation
detects that some of the source addresses/prefixes
listed in the accept-list ACLs are actually
attacking the target.";
}
Reddy, et al. Expires July 22, 2019 [Page 59]
Internet-Draft DOTS Signal Channel Protocol January 2019
enum cuid-collision {
value 3;
description
"Conflicts with the cuid used by another
DOTS client.";
}
}
description
"Enumeration for conflict causes.";
}
typedef attack-status {
type enumeration {
enum under-attack {
value 1;
description
"The DOTS client determines that it is still under
attack.";
}
enum attack-successfully-mitigated {
value 2;
description
"The DOTS client determines that the attack is
successfully mitigated.";
}
}
description
"Enumeration for attack status codes.";
}
}
<CODE ENDS>
5.3. IETF DOTS Signal Channel YANG Module
This module uses the common YANG types defined in [RFC6991] and types
defined in [I-D.ietf-dots-data-channel].
<CODE BEGINS> file "ietf-dots-signal-channel@2019-01-17.yang"
module ietf-dots-signal-channel {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel";
prefix signal;
import ietf-inet-types {
prefix inet;
reference "Section 4 of RFC 6991";
}
import ietf-yang-types {
Reddy, et al. Expires July 22, 2019 [Page 60]
Internet-Draft DOTS Signal Channel Protocol January 2019
prefix yang;
reference "Section 3 of RFC 6991";
}
import ietf-dots-data-channel {
prefix ietf-data;
reference
"RFC YYYY: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Data Channel Specification";
}
import iana-dots-signal-channel {
prefix iana-signal;
}
organization
"IETF DDoS Open Threat Signaling (DOTS) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/dots/>
WG List: <mailto:dots@ietf.org>
Editor: Konda, Tirumaleswar Reddy
<mailto:TirumaleswarReddy_Konda@McAfee.com>
Editor: Mohamed Boucadair
<mailto:mohamed.boucadair@orange.com>
Author: Prashanth Patil
<mailto:praspati@cisco.com>
Author: Andrew Mortensen
<mailto:amortensen@arbor.net>
Author: Nik Teague
<mailto:nteague@verisign.com>";
description
"This module contains YANG definition for the signaling
messages exchanged between a DOTS client and a DOTS server.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
Reddy, et al. Expires July 22, 2019 [Page 61]
Internet-Draft DOTS Signal Channel Protocol January 2019
the RFC itself for full legal notices.";
revision 2019-01-17 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel Specification";
}
/*
* Groupings
*/
grouping mitigation-scope {
description
"Specifies the scope of the mitigation request.";
list scope {
key "cuid mid";
description
"The scope of the request.";
leaf cdid {
type string;
description
"The cdid should be included by a server-domain
DOTS gateway to propagate the client domain
identification information from the
gateway's client-facing-side to the gateway's
server-facing-side, and from the gateway's
server-facing-side to the DOTS server.
It may be used by the final DOTS server
for policy enforcement purposes.";
}
leaf cuid {
type string;
description
"A unique identifier that is
generated by a DOTS client to prevent
request collisions. It is expected that the
cuid will remain consistent throughout the
lifetime of the DOTS client.";
}
leaf mid {
type uint32;
description
"Mitigation request identifier.
Reddy, et al. Expires July 22, 2019 [Page 62]
Internet-Draft DOTS Signal Channel Protocol January 2019
This identifier must be unique for each mitigation
request bound to the DOTS client.";
}
uses ietf-data:target;
leaf-list alias-name {
type string;
description
"An alias name that points to a resource.";
}
leaf lifetime {
type int32;
units "seconds";
default "3600";
description
"Indicates the lifetime of the mitigation request.
A lifetime of '0' in a mitigation request is an
invalid value.
A lifetime of negative one (-1) indicates indefinite
lifetime for the mitigation request.";
}
leaf trigger-mitigation {
type boolean;
default "true";
description
"If set to 'false', DDoS mitigation will not be
triggered unless the DOTS signal channel
session is lost.";
}
leaf mitigation-start {
type uint64;
config false;
description
"Mitigation start time is represented in seconds
relative to 1970-01-01T00:00:00Z in UTC time.";
}
leaf status {
type iana-signal:status;
config false;
description
"Indicates the status of a mitigation request.
It must be included in responses only.";
}
container conflict-information {
config false;
description
"Indicates that a conflict is detected.
Reddy, et al. Expires July 22, 2019 [Page 63]
Internet-Draft DOTS Signal Channel Protocol January 2019
Must only be used for responses.";
leaf conflict-status {
type iana-signal:conflict-status;
description
"Indicates the conflict status.";
}
leaf conflict-cause {
type iana-signal:conflict-cause;
description
"Indicates the cause of the conflict.";
}
leaf retry-timer {
type uint32;
units "seconds";
description
"The DOTS client must not re-send the
same request that has a conflict before the expiry of
this timer.";
}
container conflict-scope {
description
"Provides more information about the conflict scope.";
uses ietf-data:target {
when "../conflict-cause = 'overlapping-targets'";
}
leaf-list alias-name {
when "../../conflict-cause = 'overlapping-targets'";
type string;
description
"Conflicting alias-name.";
}
list acl-list {
when "../../conflict-cause = 'conflict-with-acceptlist'";
key "acl-name";
description
"List of conflicting ACLs as defined in the DOTS data
channel. These ACLs are uniquely defined by
cuid and acl-name.";
leaf acl-name {
type leafref {
path "/ietf-data:dots-data/ietf-data:dots-client/"
+"ietf-data:acls/ietf-data:acl/ietf-data:name";
}
description
"Reference to the conflicting ACL name bound to
a DOTS client.";
}
leaf acl-type {
Reddy, et al. Expires July 22, 2019 [Page 64]
Internet-Draft DOTS Signal Channel Protocol January 2019
type leafref {
path "/ietf-data:dots-data/ietf-data:dots-client/"
+ietf-data:acls/ietf-data:acl/ietf-data:type";
}
description
"Reference to the conflicting ACL type bound to
a DOTS client.";
}
}
leaf mid {
when "../../conflict-cause = 'overlapping-targets'";
type leafref {
path "../../../mid";
}
description
"Reference to the conflicting 'mid' bound to
the same DOTS client.";
}
}
}
leaf bytes-dropped {
type yang:zero-based-counter64;
units "bytes";
config false;
description
"The total dropped byte count for the mitigation
request since the attack mitigation is triggered.
The count wraps around when it reaches the maximum value
of counter64 for dropped bytes.";
}
leaf bps-dropped {
type yang:zero-based-counter64;
config false;
description
"The average number of dropped bits per second for
the mitigation request since the attack
mitigation is triggered. This should be a
five-minute average.";
}
leaf pkts-dropped {
type yang:zero-based-counter64;
config false;
description
"The total number of dropped packet count for the
mitigation request since the attack mitigation is
triggered. The count wraps around when it reaches
the maximum value of counter64 for dropped packets.";
}
Reddy, et al. Expires July 22, 2019 [Page 65]
Internet-Draft DOTS Signal Channel Protocol January 2019
leaf pps-dropped {
type yang:zero-based-counter64;
config false;
description
"The average number of dropped packets per second
for the mitigation request since the attack
mitigation is triggered. This should be a
five-minute average.";
}
leaf attack-status {
type iana-signal:attack-status;
description
"Indicates the status of an attack as seen by the
DOTS client.";
}
}
}
grouping config-parameters {
description
"Subset of DOTS signal channel session configuration.";
container heartbeat-interval {
description
"DOTS agents regularly send heartbeats to each other
after mutual authentication is successfully
completed in order to keep the DOTS signal channel
open.";
leaf max-value {
type uint16;
units "seconds";
config false;
description
"Maximum acceptable heartbeat-interval value.";
}
leaf min-value {
type uint16;
units "seconds";
config false;
description
"Minimum acceptable heartbeat-interval value.";
}
leaf current-value {
type uint16;
units "seconds";
default "30";
description
"Current heartbeat-interval value.
Reddy, et al. Expires July 22, 2019 [Page 66]
Internet-Draft DOTS Signal Channel Protocol January 2019
'0' means that heartbeat mechanism is deactivated.";
}
}
container missing-hb-allowed {
description
"Maximum number of missing heartbeats allowed.";
leaf max-value {
type uint16;
config false;
description
"Maximum acceptable missing-hb-allowed value.";
}
leaf min-value {
type uint16;
config false;
description
"Minimum acceptable missing-hb-allowed value.";
}
leaf current-value {
type uint16;
default "5";
description
"Current missing-hb-allowed value.";
}
}
container max-retransmit {
description
"Maximum number of retransmissions of a Confirmable
message.";
leaf max-value {
type uint16;
config false;
description
"Maximum acceptable max-retransmit value.";
}
leaf min-value {
type uint16;
config false;
description
"Minimum acceptable max-retransmit value.";
}
leaf current-value {
type uint16;
default "3";
description
"Current max-retransmit value.";
}
}
Reddy, et al. Expires July 22, 2019 [Page 67]
Internet-Draft DOTS Signal Channel Protocol January 2019
container ack-timeout {
description
"Initial retransmission timeout value.";
leaf max-value-decimal {
type decimal64 {
fraction-digits 2;
}
units "seconds";
config false;
description
"Maximum ack-timeout value.";
}
leaf min-value-decimal {
type decimal64 {
fraction-digits 2;
}
units "seconds";
config false;
description
"Minimum ack-timeout value.";
}
leaf current-value-decimal {
type decimal64 {
fraction-digits 2;
}
units "seconds";
default "2";
description
"Current ack-timeout value.";
}
}
container ack-random-factor {
description
"Random factor used to influence the timing of
retransmissions.";
leaf max-value-decimal {
type decimal64 {
fraction-digits 2;
}
config false;
description
"Maximum acceptable ack-random-factor value.";
}
leaf min-value-decimal {
type decimal64 {
fraction-digits 2;
}
config false;
Reddy, et al. Expires July 22, 2019 [Page 68]
Internet-Draft DOTS Signal Channel Protocol January 2019
description
"Minimum acceptable ack-random-factor value.";
}
leaf current-value-decimal {
type decimal64 {
fraction-digits 2;
}
default "1.5";
description
"Current ack-random-factor value.";
}
}
}
grouping signal-config {
description
"DOTS signal channel session configuration.";
leaf sid {
type uint32;
mandatory true;
description
"An identifier for the DOTS signal channel
session configuration data.";
}
container mitigating-config {
description
"Configuration parameters to use when a mitigation
is active.";
uses config-parameters;
}
container idle-config {
description
"Configuration parameters to use when no mitigation
is active.";
uses config-parameters;
}
}
grouping redirected-signal {
description
"Grouping for the redirected signaling.";
leaf alt-server {
type string;
config false;
mandatory true;
description
"FQDN of an alternate server.";
}
Reddy, et al. Expires July 22, 2019 [Page 69]
Internet-Draft DOTS Signal Channel Protocol January 2019
leaf-list alt-server-record {
type inet:ip-address;
config false;
description
"List of records for the alternate server.";
}
}
/*
* Main Container for DOTS Signal Channel
*/
container dots-signal {
description
"Main container for DOTS signal message.
A DOTS signal message can be a mitigation, a configuration,
or a redirected signal message.";
choice message-type {
description
"Can be a mitigation, a configuration, or a redirect
message.";
case mitigation-scope {
description
"Mitigation scope of a mitigation message.";
uses mitigation-scope;
}
case signal-config {
description
"Configuration message.";
uses signal-config;
}
case redirected-signal {
description
"Redirected signaling.";
uses redirected-signal;
}
}
}
}
<CODE ENDS>
6. YANG/JSON Mapping Parameters to CBOR
All parameters in the payload of the DOTS signal channel MUST be
mapped to CBOR types as shown in Table 4 and are assigned an integer
key to save space. The CBOR key values are divided into two types:
comprehension-required and comprehension-optional. DOTS agents can
Reddy, et al. Expires July 22, 2019 [Page 70]
Internet-Draft DOTS Signal Channel Protocol January 2019
safely ignore comprehension-optional values they don't understand,
but cannot successfully process a request if it contains
comprehension-required values that are not understood. The 4.00
response SHOULD include a diagnostic payload describing the unknown
comprehension-required CBOR key values. The initial set of CBOR key
values defined in this specification are of type comprehension-
required.
+----------------------+-------------+-----+---------------+--------+
| Parameter Name | YANG | CBOR| CBOR Major | JSON |
| | Type | Key | Type & | Type |
| | | | Information | |
+----------------------+-------------+-----+---------------+--------+
| ietf-dots-signal-cha | | | | |
| nnel:mitigation-scope| container | 1 | 5 map | Object |
| scope | list | 2 | 4 array | Array |
| cdid | string | 3 | 3 text string | String |
| cuid | string | 4 | 3 text string | String |
| mid | uint32 | 5 | 0 unsigned | Number |
| target-prefix | leaf-list | 6 | 4 array | Array |
| | inet: | | | |
| | ip-prefix | | 3 text string | String |
| target-port-range | list | 7 | 4 array | Array |
| lower-port | inet: | | | |
| | port-number| 8 | 0 unsigned | Number |
| upper-port | inet: | | | |
| | port-number| 9 | 0 unsigned | Number |
| target-protocol | leaf-list | 10 | 4 array | Array |
| | uint8 | | 0 unsigned | Number |
| target-fqdn | leaf-list | 11 | 4 array | Array |
| | inet: | | | |
| | domain-name| | 3 text string | String |
| target-uri | leaf-list | 12 | 4 array | Array |
| | inet:uri | | 3 text string | String |
| alias-name | leaf-list | 13 | 4 array | Array |
| | string | | 3 text string | String |
| lifetime | int32 | 14 | 0 unsigned | Number |
| | | | 1 negative | Number |
| mitigation-start | uint64 | 15 | 0 unsigned | String |
| status | enumeration | 16 | 0 unsigned | String |
| conflict-information | container | 17 | 5 map | Object |
| conflict-status | enumeration | 18 | 0 unsigned | String |
| conflict-cause | enumeration | 19 | 0 unsigned | String |
| retry-timer | uint32 | 20 | 0 unsigned | Number |
| conflict-scope | container | 21 | 5 map | Object |
| acl-list | list | 22 | 4 array | Array |
| acl-name | leafref | 23 | 3 text string | String |
| acl-type | leafref | 24 | 3 text string | String |
Reddy, et al. Expires July 22, 2019 [Page 71]
Internet-Draft DOTS Signal Channel Protocol January 2019
| bytes-dropped | yang:zero- | | | |
| | based- | | | |
| | counter64 | 25 | 0 unsigned | String |
| bps-dropped | yang:zero- | | | |
| | based- | | | |
| | counter64 | 26 | 0 unsigned | String |
| pkts-dropped | yang:zero- | | | |
| | based- | | | |
| | counter64 | 27 | 0 unsigned | String |
| pps-dropped | yang:zero- | | | |
| | based- | | | |
| | counter64 | 28 | 0 unsigned | String |
| attack-status | enumeration | 29 | 0 unsigned | String |
| ietf-dots-signal- | | | | |
| channel:signal-config| container | 30 | 5 map | Object |
| sid | uint32 | 31 | 0 unsigned | Number |
| mitigating-config | container | 32 | 5 map | Object |
| heartbeat-interval | container | 33 | 5 map | Object |
| max-value | uint16 | 34 | 0 unsigned | Number |
| min-value | uint16 | 35 | 0 unsigned | Number |
| current-value | uint16 | 36 | 0 unsigned | Number |
| missing-hb-allowed | container | 37 | 5 map | Object |
| max-retransmit | container | 38 | 5 map | Object |
| ack-timeout | container | 39 | 5 map | Object |
| ack-random-factor | container | 40 | 5 map | Object |
| max-value-decimal | decimal64 | 41 | 6 tag 4 | |
| | | | [-2, integer]| String |
| min-value-decimal | decimal64 | 42 | 6 tag 4 | |
| | | | [-2, integer]| String |
| current-value-decimal| decimal64 | 43 | 6 tag 4 | |
| | | | [-2, integer]| String |
| idle-config | container | 44 | 5 map | Object |
| trigger-mitigation | boolean | 45 | 7 bits 20 | False |
| | | | 7 bits 21 | True |
| ietf-dots-signal-cha | | | | |
|nnel:redirected-signal| container | 46 | 5 map | Object |
| alt-server | string | 47 | 3 text string | String |
| alt-server-record | leaf-list | 48 | 4 array | Array |
| | inet: | | | |
| | ip-address | | 3 text string | String |
+----------------------+-------------+-----+---------------+--------+
Table 4: CBOR Key Values Used in DOTS Signal Channel Messages & Their
Mappings to JSON and YANG
Reddy, et al. Expires July 22, 2019 [Page 72]
Internet-Draft DOTS Signal Channel Protocol January 2019
7. (D)TLS Protocol Profile and Performance Considerations
7.1. (D)TLS Protocol Profile
This section defines the (D)TLS protocol profile of DOTS signal
channel over (D)TLS and DOTS data channel over TLS.
There are known attacks on (D)TLS, such as man-in-the-middle and
protocol downgrade attacks. These are general attacks on (D)TLS and,
as such, they are not specific to DOTS over (D)TLS; refer to the
(D)TLS RFCs for discussion of these security issues. DOTS agents
MUST adhere to the (D)TLS implementation recommendations and security
considerations of [RFC7525] except with respect to (D)TLS version.
Since DOTS signal channel encryption relying upon (D)TLS is virtually
a green-field deployment, DOTS agents MUST implement only (D)TLS 1.2
or later.
When a DOTS client is configured with a domain name of the DOTS
server, and connects to its configured DOTS server, the server may
present it with a PKIX certificate. In order to ensure proper
authentication, a DOTS client MUST verify the entire certification
path per [RFC5280]. The DOTS client additionally uses [RFC6125]
validation techniques to compare the domain name with the certificate
provided.
A key challenge to deploying DOTS is the provisioning of DOTS
clients, including the distribution of keying material to DOTS
clients to enable the required mutual authentication of DOTS agents.
Enrollment over Secure Transport (EST) [RFC7030] defines a method of
certificate enrollment by which domains operating DOTS servers may
provide DOTS clients with all the necessary cryptographic keying
material, including a private key and a certificate to authenticate
themselves. One deployment option is DOTS clients behave as EST
clients for certificate enrollment from an EST server provisioned by
the mitigation provider. This document does not specify which EST or
other mechanism the DOTS client uses to achieve initial enrollment.
The Server Name Indication (SNI) extension [RFC6066] defines a
mechanism for a client to tell a (D)TLS server the name of the server
it wants to contact. This is a useful extension for hosting
environments where multiple virtual servers are reachable over a
single IP address. The DOTS client may or may not know if it is
interacting with a DOTS server in a virtual server hosting
environment, so the DOTS client SHOULD include the DOTS server FQDN
in the SNI extension.
Implementations compliant with this profile MUST implement all of the
following items:
Reddy, et al. Expires July 22, 2019 [Page 73]
Internet-Draft DOTS Signal Channel Protocol January 2019
o DTLS record replay detection (Section 3.3 of [RFC6347]) or an
equivalent mechanism to protect against replay attacks.
o DTLS session resumption without server-side state to resume
session and convey the DOTS signal.
o At least one of raw public keys [RFC7250] or PSK handshake
[RFC4279] with (EC)DHE key exchange which reduces the size of the
ServerHello, and can be used by DOTS agents that cannot obtain
certificates.
Implementations compliant with this profile SHOULD implement all of
the following items to reduce the delay required to deliver a DOTS
signal channel message:
o TLS False Start [RFC7918] which reduces round-trips by allowing
the TLS client's second flight of messages (ChangeCipherSpec) to
also contain the DOTS signal.
o Cached Information Extension [RFC7924] which avoids transmitting
the server's certificate and certificate chain if the client has
cached that information from a previous TLS handshake.
o TCP Fast Open [RFC7413] can reduce the number of round-trips to
convey DOTS signal channel message.
7.2. (D)TLS 1.3 Considerations
TLS 1.3 provides critical latency improvements for connection
establishment over TLS 1.2. The DTLS 1.3 protocol
[I-D.ietf-tls-dtls13] is based upon the TLS 1.3 protocol and provides
equivalent security guarantees. (D)TLS 1.3 provides two basic
handshake modes the DOTS signal channel can take advantage of:
o A full handshake mode in which a DOTS client can send a DOTS
mitigation request message after one round trip and the DOTS
server immediately responds with a DOTS mitigation response. This
assumes no packet loss is experienced.
o 0-RTT mode in which the DOTS client can authenticate itself and
send DOTS mitigation request messages in the first message, thus
reducing handshake latency. 0-RTT only works if the DOTS client
has previously communicated with that DOTS server, which is very
likely with the DOTS signal channel.
The DOTS client has to establish a (D)TLS session with the DOTS
server during peacetime and share a PSK.
Reddy, et al. Expires July 22, 2019 [Page 74]
Internet-Draft DOTS Signal Channel Protocol January 2019
During a DDoS attack, the DOTS client can use the (D)TLS session
to convey the DOTS mitigation request message and, if there is no
response from the server after multiple retries, the DOTS client
can resume the (D)TLS session in 0-RTT mode using PSK.
Section 8 of [RFC8446] discusses some mechanisms to implement to
limit the impact of replay attacks on 0-RTT data. If the DOTS
server accepts 0-RTT, it MUST implement one of these mechanisms.
A DOTS server can reject 0-RTT by sending a TLS HelloRetryRequest.
A simplified TLS 1.3 handshake with 0-RTT DOTS mitigation request
message exchange is shown in Figure 26.
DOTS Client DOTS Server
ClientHello
(0-RTT DOTS signal message)
-------->
ServerHello
{EncryptedExtensions}
{Finished}
<-------- [DOTS signal message]
(end_of_early_data)
{Finished} -------->
[DOTS signal message] <-------> [DOTS signal message]
Note that:
() Indicates messages protected 0-RTT keys
{} Indicates messages protected using handshake keys
[] Indicates messages protected using 1-RTT keys
Figure 26: A Simplified TLS 1.3 Handshake with 0-RTT
7.3. DTLS MTU and Fragmentation
To avoid DOTS signal message fragmentation and the subsequent
decreased probability of message delivery, DOTS agents MUST ensure
that the DTLS record MUST fit within a single datagram. If the path
MTU is not known to the DOTS server, an IP MTU of 1280 bytes SHOULD
be assumed. The DOTS client must consider the amount of record
expansion expected by the DTLS processing when calculating the size
of CoAP message that fits within the path MTU. Path MTU MUST be
greater than or equal to [CoAP message size + DTLS 1.2 overhead of 13
octets + authentication overhead of the negotiated DTLS cipher suite
+ block padding] (Section 4.1.1.1 of [RFC6347]). If the total
request size exceeds the path MTU then the DOTS client MUST split the
DOTS signal into separate messages; for example, the list of
Reddy, et al. Expires July 22, 2019 [Page 75]
Internet-Draft DOTS Signal Channel Protocol January 2019
addresses in the 'target-prefix' parameter could be split into
multiple lists and each list conveyed in a new PUT request.
Implementation Note: DOTS choice of message size parameters works
well with IPv6 and with most of today's IPv4 paths. However, with
IPv4, it is harder to safely make sure that there is no IP
fragmentation. If the IPv4 path MTU is unknown, implementations may
want to limit themselves to more conservative IPv4 datagram sizes
such as 576 bytes, as per [RFC0791]. IP packets whose size does not
exceed 576 bytes should never need to be fragmented: therefore,
sending a maximum of 500 bytes of DOTS signal over a UDP datagram
will generally avoid IP fragmentation.
8. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients
(D)TLS based upon client certificate can be used for mutual
authentication between DOTS agents. If, for example, a DOTS gateway
is involved, DOTS clients and DOTS gateways must perform mutual
authentication; only authorized DOTS clients are allowed to send DOTS
signals to a DOTS gateway. The DOTS gateway and the DOTS server must
perform mutual authentication; a DOTS server only allows DOTS signal
channel messages from an authorized DOTS gateway, thereby creating a
two-link chain of transitive authentication between the DOTS client
and the DOTS server.
The DOTS server should support certificate-based client
authentication. The DOTS client should respond to the DOTS server's
TLS CertificateRequest message with the PKIX certificate held by the
DOTS client. DOTS client certificate validation must be performed as
per [RFC5280] and the DOTS client certificate must conform to the
[RFC5280] certificate profile. If a DOTS client does not support TLS
client certificate authentication, it must support pre-shared key
based or raw public key based client authentication.
Reddy, et al. Expires July 22, 2019 [Page 76]
Internet-Draft DOTS Signal Channel Protocol January 2019
+-----------------------------------------------+
| example.com domain +---------+ |
| | AAA | |
| +---------------+ | Server | |
| | Application | +------+--+ |
| | server +<-----------------+ ^ |
| | (DOTS client) | | | |
| +---------------+ | | |
| V V | example.net domain
| +-----+----+--+ | +---------------+
| +--------------+ | | | | |
| | Guest +<-----x----->+ DOTS +<------>+ DOTS |
| | (DOTS client)| | gateway | | | server |
| +--------------+ | | | | |
| +----+--------+ | +---------------+
| ^ |
| | |
| +----------------+ | |
| | DDoS detector | | |
| | (DOTS client) +<---------------+ |
| +----------------+ |
+-----------------------------------------------+
Figure 27: Example of Authentication and Authorization of DOTS Agents
In the example depicted in Figure 27, the DOTS gateway and DOTS
clients within the 'example.com' domain mutually authenticate. After
the DOTS gateway validates the identity of a DOTS client, it
communicates with the AAA server in the 'example.com' domain to
determine if the DOTS client is authorized to request DDoS
mitigation. If the DOTS client is not authorized, a 4.01
(Unauthorized) is returned in the response to the DOTS client. In
this example, the DOTS gateway only allows the application server and
DDoS attack detector to request DDoS mitigation, but does not permit
the user of type 'guest' to request DDoS mitigation.
Also, DOTS gateways and servers located in different domains must
perform mutual authentication (e.g., using certificates). A DOTS
server will only allow a DOTS gateway with a certificate for a
particular domain to request mitigation for that domain. In
reference to Figure 27, the DOTS server only allows the DOTS gateway
to request mitigation for 'example.com' domain and not for other
domains.
Reddy, et al. Expires July 22, 2019 [Page 77]
Internet-Draft DOTS Signal Channel Protocol January 2019
9. IANA Considerations
9.1. DOTS Signal Channel UDP and TCP Port Number
IANA is requested to assign the port number TBD to the DOTS signal
channel protocol for both UDP and TCP from the "Service Name and
Transport Protocol Port Number Registry" available at
https://www.iana.org/assignments/service-names-port-numbers/service-
names-port-numbers.xhtml.
The assignment of port number 4646 is strongly suggested, as 4646 is
the ASCII decimal value for ".." (DOTS).
9.2. Well-Known 'dots' URI
This document requests IANA to register the 'dots' well-known URI
(Table 5) in the Well-Known URIs registry
(https://www.iana.org/assignments/well-known-uris/well-known-
uris.xhtml) as defined by [RFC5785]:
+----------+----------------+---------------------+-----------------+
| URI | Change | Specification | Related |
| suffix | controller | document(s) | information |
+----------+----------------+---------------------+-----------------+
| dots | IETF | [RFCXXXX] | None |
+----------+----------------+---------------------+-----------------+
Table 5: 'dots' well-known URI
9.3. Media Type Registration
This document requests IANA to register the "application/dots+cbor"
media type in the "Media Types" registry [IANA.MediaTypes] in the
manner described in [RFC6838], which can be used to indicate that the
content is a DOTS signal channel object:
o Type name: application
o Subtype name: dots+cbor
o Required parameters: N/A
o Optional parameters: N/A
o Encoding considerations: binary
o Security considerations: See the Security Considerations section
of [RFCXXXX]
o Interoperability considerations: N/A
o Published specification: [RFCXXXX]
o Applications that use this media type: DOTS agents sending DOTS
messages over CoAP over (D)TLS.
o Fragment identifier considerations: N/A
Reddy, et al. Expires July 22, 2019 [Page 78]
Internet-Draft DOTS Signal Channel Protocol January 2019
o Additional information:
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A
o Person & email address to contact for further information:
IESG, iesg@ietf.org
o Intended usage: COMMON
o Restrictions on usage: none
o Author: See Authors' Addresses section.
o Change controller: IESG
o Provisional registration? No
9.4. CoAP Content-Formats Registration
This document requests IANA to register the CoAP Content-Format ID
for the "application/dots+cbor" media type in the "CoAP Content-
Formats" registry [IANA.CoAP.Content-Formats] (0-255 range):
o Media Type: application/dots+cbor
o Encoding: -
o Id: TBD1
o Reference: [RFCXXXX]
9.5. CBOR Tag Registration
This section defines the DOTS CBOR tag as another means for
applications to declare that a CBOR data structure is a DOTS signal
channel object. Its use is optional and is intended for use in cases
in which this information would not otherwise be known. DOTS CBOR
tag is not required for DOTS signal channel protocol version
specified in this document. If present, the DOTS tag MUST prefix a
DOTS signal channel object.
This document requests IANA to register the DOTS signal channel CBOR
tag in the "CBOR Tags" registry [IANA.CBOR.Tags] using the 24-255
range:
o CBOR Tag: TBD2 (please assign the same value as the Content-
Format)
o Data Item: DDoS Open Threat Signaling (DOTS) signal channel object
o Semantics: DDoS Open Threat Signaling (DOTS) signal channel
object, as defined in [RFCXXXX]
o Description of Semantics: [RFCXXXX]
Reddy, et al. Expires July 22, 2019 [Page 79]
Internet-Draft DOTS Signal Channel Protocol January 2019
9.6. DOTS Signal Channel Protocol Registry
The document requests IANA to create a new registry, entitled "DOTS
Signal Channel Registry". The following sections define sub-
registries.
9.6.1. DOTS Signal Channel CBOR Key Values Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel CBOR Key Values".
The structure of this sub-registry is provided in Section 9.6.1.1.
Section 9.6.1.2 provides how the registry is initially populated with
the values in Table 4.
9.6.1.1. Registration Template
Parameter name:
Parameter name as used in the DOTS signal channel.
CBOR Key Value:
Key value for the parameter. The key value MUST be an integer in
the 1-65535 range. The key values of the comprehension-required
range (0x0001 - 0x3FFF) and of the comprehension-optional range
(0x8000 - 0xBFFF) are assigned by IETF Review [RFC8126]. The key
values of the comprehension-optional range (0x4000 - 0x7FFF) are
assigned by Designated Expert [RFC8126] and of the comprehension-
optional range (0xC000 - 0xFFFF) are reserved for Private Use
[RFC8126].
CBOR Major Type:
CBOR Major type and optional tag for the parameter.
Change Controller:
For Standards Track RFCs, list the "IESG". For others, give the
name of the responsible party. Other details (e.g., email
address) may also be included.
Specification Document(s):
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
Reddy, et al. Expires July 22, 2019 [Page 80]
Internet-Draft DOTS Signal Channel Protocol January 2019
9.6.1.2. Initial Sub-Registry Content
+----------------------+-------+-------+------------+---------------+
| Parameter Name | CBOR | CBOR | Change | Specification |
| | Key | Major | Controller | Document(s) |
| | Value | Type | | |
+----------------------+-------+-------+------------+---------------+
| ietf-dots-signal-chan| 1 | 5 | IESG | [RFCXXXX] |
| nel:mitigation-scope | | | | |
| scope | 2 | 4 | IESG | [RFCXXXX] |
| cdid | 3 | 3 | IESG | [RFCXXXX] |
| cuid | 4 | 3 | IESG | [RFCXXXX] |
| mid | 5 | 0 | IESG | [RFCXXXX] |
| target-prefix | 6 | 4 | IESG | [RFCXXXX] |
| target-port-range | 7 | 4 | IESG | [RFCXXXX] |
| lower-port | 8 | 0 | IESG | [RFCXXXX] |
| upper-port | 9 | 0 | IESG | [RFCXXXX] |
| target-protocol | 10 | 4 | IESG | [RFCXXXX] |
| target-fqdn | 11 | 4 | IESG | [RFCXXXX] |
| target-uri | 12 | 4 | IESG | [RFCXXXX] |
| alias-name | 13 | 4 | IESG | [RFCXXXX] |
| lifetime | 14 | 0/1 | IESG | [RFCXXXX] |
| mitigation-start | 15 | 0 | IESG | [RFCXXXX] |
| status | 16 | 0 | IESG | [RFCXXXX] |
| conflict-information | 17 | 5 | IESG | [RFCXXXX] |
| conflict-status | 18 | 0 | IESG | [RFCXXXX] |
| conflict-cause | 19 | 0 | IESG | [RFCXXXX] |
| retry-timer | 20 | 0 | IESG | [RFCXXXX] |
| conflict-scope | 21 | 5 | IESG | [RFCXXXX] |
| acl-list | 22 | 4 | IESG | [RFCXXXX] |
| acl-name | 23 | 3 | IESG | [RFCXXXX] |
| acl-type | 24 | 3 | IESG | [RFCXXXX] |
| bytes-dropped | 25 | 0 | IESG | [RFCXXXX] |
| bps-dropped | 26 | 0 | IESG | [RFCXXXX] |
| pkts-dropped | 27 | 0 | IESG | [RFCXXXX] |
| pps-dropped | 28 | 0 | IESG | [RFCXXXX] |
| attack-status | 29 | 0 | IESG | [RFCXXXX] |
| ietf-dots-signal- | 30 | 5 | IESG | [RFCXXXX] |
| channel:signal-config| | | | |
| sid | 31 | 0 | IESG | [RFCXXXX] |
| mitigating-config | 32 | 5 | IESG | [RFCXXXX] |
| heartbeat-interval | 33 | 5 | IESG | [RFCXXXX] |
| min-value | 34 | 0 | IESG | [RFCXXXX] |
| max-value | 35 | 0 | IESG | [RFCXXXX] |
| current-value | 36 | 0 | IESG | [RFCXXXX] |
| missing-hb-allowed | 37 | 5 | IESG | [RFCXXXX] |
| max-retransmit | 38 | 5 | IESG | [RFCXXXX] |
| ack-timeout | 39 | 5 | IESG | [RFCXXXX] |
Reddy, et al. Expires July 22, 2019 [Page 81]
Internet-Draft DOTS Signal Channel Protocol January 2019
| ack-random-factor | 40 | 5 | IESG | [RFCXXXX] |
| min-value-decimal | 41 | 6tag4 | IESG | [RFCXXXX] |
| max-value-decimal | 42 | 6tag4 | IESG | [RFCXXXX] |
| current-value- | 43 | 6tag4 | IESG | [RFCXXXX] |
| decimal | | | | |
| idle-config | 44 | 5 | IESG | [RFCXXXX] |
| trigger-mitigation | 45 | 7 | IESG | [RFCXXXX] |
| ietf-dots-signal-chan| 46 | 5 | IESG | [RFCXXXX] |
| nel:redirected-signal| | | | |
| alt-server | 47 | 3 | IESG | [RFCXXXX] |
| alt-server-record | 48 | 4 | IESG | [RFCXXXX] |
+----------------------+-------+-------+------------+---------------+
Table 6: Initial DOTS Signal Channel CBOR Key Values Registry
9.6.2. Status Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Status Codes". Codes in this registry are used
as valid values of 'status' parameter.
The registry is initially populated with the following values:
+-----+----------------------------------+--------------+-----------+
| Cod | Label | Description | Reference |
| e | | | |
+-----+----------------------------------+--------------+-----------+
| 1 | attack-mitigation-in-progress | Attack | [RFCXXXX] |
| | | mitigation | |
| | | setup is in | |
| | | progress | |
| | | (e.g., | |
| | | changing the | |
| | | network path | |
| | | to redirect | |
| | | the inbound | |
| | | traffic to a | |
| | | DOTS | |
| | | mitigator). | |
| 2 | attack-successfully-mitigated | Attack is | [RFCXXXX] |
| | | being | |
| | | successfully | |
| | | mitigated | |
| | | (e.g., | |
| | | traffic is | |
| | | redirected | |
| | | to a DDoS | |
| | | mitigator | |
Reddy, et al. Expires July 22, 2019 [Page 82]
Internet-Draft DOTS Signal Channel Protocol January 2019
| | | and attack | |
| | | traffic is | |
| | | dropped). | |
| 3 | attack-stopped | Attack has | [RFCXXXX] |
| | | stopped and | |
| | | the DOTS | |
| | | client can | |
| | | withdraw the | |
| | | mitigation | |
| | | request. | |
| 4 | attack-exceeded-capability | Attack has | [RFCXXXX] |
| | | exceeded the | |
| | | mitigation | |
| | | provider | |
| | | capability. | |
| 5 | dots-client-withdrawn-mitigation | DOTS client | [RFCXXXX] |
| | | has | |
| | | withdrawn | |
| | | the | |
| | | mitigation | |
| | | request and | |
| | | the | |
| | | mitigation | |
| | | is active | |
| | | but | |
| | | terminating. | |
| 6 | attack-mitigation-terminated | Attack | [RFCXXXX] |
| | | mitigation | |
| | | is now | |
| | | terminated. | |
| 7 | attack-mitigation-withdrawn | Attack | [RFCXXXX] |
| | | mitigation | |
| | | is | |
| | | withdrawn. | |
| 8 | attack-mitigation-signal-loss | Attack | [RFCXXXX] |
| | | mitigation | |
| | | will be | |
| | | triggered | |
| | | for the | |
| | | mitigation | |
| | | request only | |
| | | when the | |
| | | DOTS signal | |
| | | channel | |
| | | session is | |
| | | lost. | |
+-----+----------------------------------+--------------+-----------+
Reddy, et al. Expires July 22, 2019 [Page 83]
Internet-Draft DOTS Signal Channel Protocol January 2019
New codes can be assigned via Standards Action [RFC8126].
9.6.3. Conflict Status Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Conflict Status Codes". Codes in this registry
are used as valid values of 'conflict-status' parameter.
The registry is initially populated with the following values:
Reddy, et al. Expires July 22, 2019 [Page 84]
Internet-Draft DOTS Signal Channel Protocol January 2019
+------+-------------------------------+----------------+-----------+
| Code | Label | Description | Reference |
+------+-------------------------------+----------------+-----------+
| 1 | request-inactive-other-active | DOTS server | [RFCXXXX] |
| | | has detected | |
| | | conflicting | |
| | | mitigation | |
| | | requests from | |
| | | different DOTS | |
| | | clients. This | |
| | | mitigation | |
| | | request is | |
| | | currently | |
| | | inactive until | |
| | | the conflicts | |
| | | are resolved. | |
| | | Another | |
| | | mitigation | |
| | | request is | |
| | | active. | |
| 2 | request-active | DOTS server | [RFCXXXX] |
| | | has detected | |
| | | conflicting | |
| | | mitigation | |
| | | requests from | |
| | | different DOTS | |
| | | clients. This | |
| | | mitigation | |
| | | request is | |
| | | currently | |
| | | active. | |
| 3 | all-requests-inactive | DOTS server | [RFCXXXX] |
| | | has detected | |
| | | conflicting | |
| | | mitigation | |
| | | requests from | |
| | | different DOTS | |
| | | clients. All | |
| | | conflicting | |
| | | mitigation | |
| | | requests are | |
| | | inactive. | |
+------+-------------------------------+----------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
Reddy, et al. Expires July 22, 2019 [Page 85]
Internet-Draft DOTS Signal Channel Protocol January 2019
9.6.4. Conflict Cause Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Conflict Cause Codes". Codes in this registry
are used as valid values of 'conflict-cause' parameter.
The registry is initially populated with the following values:
+------+--------------------------+---------------------+-----------+
| Code | Label | Description | Reference |
+------+--------------------------+---------------------+-----------+
| 1 | overlapping-targets | Overlapping | [RFCXXXX] |
| | | targets. | |
| 2 | conflict-with-acceptlist | Conflicts with an | [RFCXXXX] |
| | | existing accept- | |
| | | list. This code is | |
| | | returned when the | |
| | | DDoS mitigation | |
| | | detects source | |
| | | addresses/prefixes | |
| | | in the accept- | |
| | | listed ACLs are | |
| | | attacking the | |
| | | target. | |
| 3 | cuid-collision | CUID Collision. | [RFCXXXX] |
| | | This code is | |
| | | returned when a | |
| | | DOTS client uses a | |
| | | 'cuid' that is | |
| | | already used by | |
| | | another DOTS | |
| | | client. | |
+------+--------------------------+---------------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
9.6.5. Attack Status Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Attack Status Codes". Codes in this registry
are used as valid values of 'attack-status' parameter.
The registry is initially populated with the following values:
Reddy, et al. Expires July 22, 2019 [Page 86]
Internet-Draft DOTS Signal Channel Protocol January 2019
+------+-------------------------------+----------------+-----------+
| Code | Label | Description | Reference |
+------+-------------------------------+----------------+-----------+
| 1 | under-attack | The DOTS | [RFCXXXX] |
| | | client | |
| | | determines | |
| | | that it is | |
| | | still under | |
| | | attack. | |
| 2 | attack-successfully-mitigated | The DOTS | [RFCXXXX] |
| | | client | |
| | | determines | |
| | | that the | |
| | | attack is | |
| | | successfully | |
| | | mitigated. | |
+------+-------------------------------+----------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
9.7. DOTS Signal Channel YANG Modules
This document requests IANA to register the following URIs in the
"ns" subregistry within the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:iana-dots-signal-channel
Registrant Contact: IANA.
XML: N/A; the requested URI is an XML namespace.
This document requests IANA to register the following YANG modules in
the "YANG Module Names" subregistry [RFC7950] within the "YANG
Parameters" registry.
name: ietf-signal
namespace: urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel
maintained by IANA: N
prefix: signal
reference: RFC XXXX
name: iana-signal
namespace: urn:ietf:params:xml:ns:yang:iana-dots-signal-channel
maintained by IANA: Y
prefix: iana-signal
reference: RFC XXXX
Reddy, et al. Expires July 22, 2019 [Page 87]
Internet-Draft DOTS Signal Channel Protocol January 2019
This document defines the initial version of the IANA-maintained
iana-dots-signal-channel YANG module. IANA is requested to add this
note:
Status, conflict status, conflict cause, and attack status values
must not be directly added to the iana-dots-signal-channel YANG
module. They must instead be respectively added to the "DOTS
Status Codes", "DOTS Conflict Status Codes", "DOTS Conflict Cause
Codes", and "DOTS Attack Status Codes" registries.
When a 'status', 'conflict-status', 'conflict-cause', or 'attack-
status' value is respectively added to the "DOTS Status Codes", "DOTS
Conflict Status Codes", "DOTS Conflict Cause Codes", or "DOTS Attack
Status Codes" registry, a new "enum" statement must be added to the
iana-dots-signal-channel YANG module. The following "enum"
statement, and substatements thereof, should be defined:
"enum": Replicates the label from the registry.
"value": Contains the IANA-assigned value corresponding to the
'status', 'conflict-status', 'conflict-cause', or
'attack-status'.
"description": Replicates the description from the registry.
"reference": Replicates the reference from the registry and add the
title of the document.
When the iana-dots-signal-channel YANG module is updated, a new
"revision" statement must be added in front of the existing revision
statements.
IANA is requested to add this note to "DOTS Status Codes", "DOTS
Conflict Status Codes", "DOTS Conflict Cause Codes", and "DOTS Attack
Status Codes" registries:
When this registry is modified, the YANG module iana-dots-signal-
channel must be updated as defined in [RFCXXXX].
10. Security Considerations
High-level DOTS security considerations are documented in
[I-D.ietf-dots-requirements] and [I-D.ietf-dots-architecture].
Authenticated encryption MUST be used for data confidentiality and
message integrity. The interaction between the DOTS agents requires
Datagram Transport Layer Security (DTLS) or Transport Layer Security
(TLS) with a cipher suite offering confidentiality protection, and
Reddy, et al. Expires July 22, 2019 [Page 88]
Internet-Draft DOTS Signal Channel Protocol January 2019
the guidance given in [RFC7525] MUST be followed to avoid attacks on
(D)TLS. The (D)TLS protocol profile used for the DOTS signal channel
is specified in Section 7.
If TCP is used between DOTS agents, an attacker may be able to inject
RST packets, bogus application segments, etc., regardless of whether
TLS authentication is used. Because the application data is TLS
protected, this will not result in the application receiving bogus
data, but it will constitute a DoS on the connection. This attack
can be countered by using TCP-AO [RFC5925]. If TCP-AO is used, then
any bogus packets injected by an attacker will be rejected by the
TCP-AO integrity check and therefore will never reach the TLS layer.
An attack vector that can be achieved if the 'cuid' is guessable is a
misbehaving DOTS client from within the client's domain which uses
the 'cuid' of another DOTS client of the domain to delete or alter
active mitigations. For this attack vector to happen, the
misbehaving client needs to pass the security validation checks by
the DOTS server, and eventually the checks of a client-domain DOTS
gateway.
A similar attack can be achieved by a compromised DOTS client which
can sniff the TLS 1.2 handshake, use the client certificate to
identify the 'cuid' used by another DOTS client. This attack is not
possible with TLS 1.3 because most of the TLS handshake is encrypted
and the client certificate is not visible to eavesdroppers.
Rate-limiting DOTS requests, including those with new 'cuid' values,
from the same DOTS client defends against DoS attacks that would
result in varying the 'cuid' to exhaust DOTS server resources. Rate-
limit policies SHOULD be enforced on DOTS gateways (if deployed) and
DOTS servers.
In order to prevent leaking internal information outside a client-
domain, DOTS gateways located in the client-domain SHOULD NOT reveal
the identification information that pertains to internal DOTS clients
(e.g., source IP address, client's hostname) unless explicitly
configured to do so.
DOTS servers MUST verify that requesting DOTS clients are entitled to
trigger actions on a given IP prefix. That is, only actions on IP
resources that belong to the DOTS client' domain MUST be authorized
by a DOTS server. The exact mechanism for the DOTS servers to
validate that the target prefixes are within the scope of the DOTS
client's domain is deployment-specific.
Reddy, et al. Expires July 22, 2019 [Page 89]
Internet-Draft DOTS Signal Channel Protocol January 2019
The presence of DOTS gateways may lead to infinite forwarding loops,
which is undesirable. To prevent and detect such loops, this
document uses the Hop-Limit Option.
CoAP-specific security considerations are discussed in Section 11 of
[RFC7252], while CBOR-related security considerations are discussed
in Section 8 of [RFC7049].
11. Contributors
The following individuals have contributed to this document:
o Jon Shallow, NCC Group, Email: jon.shallow@nccgroup.trust
o Mike Geller, Cisco Systems, Inc. 3250 Florida 33309 USA, Email:
mgeller@cisco.com
o Robert Moskowitz, HTT Consulting Oak Park, MI 42837 United States,
Email: rgm@htt-consult.com
o Dan Wing, Email: dwing-ietf@fuggles.com
12. Acknowledgements
Thanks to Christian Jacquenet, Roland Dobbins, Roman D. Danyliw,
Michael Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang
Xia, Gilbert Clark, Xialiang Frank, Jim Schaad, Klaus Hartke and
Nesredien Suleiman for the discussion and comments.
Thanks to the core WG for the recommendations on Hop-Limit and
redirect signaling.
Special thanks to Benjamin Kaduk for the detailed AD review.
13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
Reddy, et al. Expires July 22, 2019 [Page 90]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <https://www.rfc-editor.org/info/rfc4632>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010,
<https://www.rfc-editor.org/info/rfc5785>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
Reddy, et al. Expires July 22, 2019 [Page 91]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/info/rfc7641>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Reddy, et al. Expires July 22, 2019 [Page 92]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets",
RFC 8323, DOI 10.17487/RFC8323, February 2018,
<https://www.rfc-editor.org/info/rfc8323>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
13.2. Informative References
[I-D.boucadair-dots-server-discovery]
Boucadair, M., K, R., and P. Patil, "Distributed-Denial-
of-Service Open Threat Signaling (DOTS) Server Discovery",
draft-boucadair-dots-server-discovery-05 (work in
progress), October 2018.
[I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
Management Interface", draft-ietf-core-comi-04 (work in
progress), November 2018.
[I-D.ietf-core-hop-limit]
Boucadair, M., K, R., and J. Shallow, "Constrained
Application Protocol (CoAP) Hop Limit Option", draft-ietf-
core-hop-limit-02 (work in progress), December 2018.
[I-D.ietf-core-yang-cbor]
Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A.
Minaburo, "CBOR Encoding of Data Modeled with YANG",
draft-ietf-core-yang-cbor-07 (work in progress), September
2018.
[I-D.ietf-dots-architecture]
Mortensen, A., Andreasen, F., K, R., Teague, N., Compton,
R., and c. christopher_gray3@cable.comcast.com,
"Distributed-Denial-of-Service Open Threat Signaling
(DOTS) Architecture", draft-ietf-dots-architecture-10
(work in progress), December 2018.
Reddy, et al. Expires July 22, 2019 [Page 93]
Internet-Draft DOTS Signal Channel Protocol January 2019
[I-D.ietf-dots-data-channel]
Boucadair, M., K, R., Nishizuka, K., Xia, L., Patil, P.,
Mortensen, A., and N. Teague, "Distributed Denial-of-
Service Open Threat Signaling (DOTS) Data Channel
Specification", draft-ietf-dots-data-channel-24 (work in
progress), December 2018.
[I-D.ietf-dots-requirements]
Mortensen, A., Moskowitz, R., and R. K, "Distributed
Denial of Service (DDoS) Open Threat Signaling
Requirements", draft-ietf-dots-requirements-16 (work in
progress), October 2018.
[I-D.ietf-dots-use-cases]
Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
Open Threat Signaling", draft-ietf-dots-use-cases-17 (work
in progress), January 2019.
[I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-30 (work in progress),
November 2018.
[IANA.CBOR.Tags]
IANA, "Concise Binary Object Representation (CBOR) Tags",
<http://www.iana.org/assignments/cbor-tags/
cbor-tags.xhtml>.
[IANA.CoAP.Content-Formats]
IANA, "CoAP Content-Formats",
<http://www.iana.org/assignments/core-parameters/
core-parameters.xhtml#content-formats>.
[IANA.MediaTypes]
IANA, "Media Types",
<http://www.iana.org/assignments/media-types>.
[proto_numbers]
"IANA, "Protocol Numbers"", 2011,
<http://www.iana.org/assignments/protocol-numbers>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
Reddy, et al. Expires July 22, 2019 [Page 94]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<https://www.rfc-editor.org/info/rfc3022>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340,
DOI 10.17487/RFC4340, March 2006,
<https://www.rfc-editor.org/info/rfc4340>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006,
<https://www.rfc-editor.org/info/rfc4732>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>.
[RFC4987] Eddy, W., "TCP SYN Flooding Attacks and Common
Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007,
<https://www.rfc-editor.org/info/rfc4987>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008,
<https://www.rfc-editor.org/info/rfc5389>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
Reddy, et al. Expires July 22, 2019 [Page 95]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/info/rfc6146>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011,
<https://www.rfc-editor.org/info/rfc6296>.
[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
<https://www.rfc-editor.org/info/rfc6724>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <https://www.rfc-editor.org/info/rfc6888>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
<https://www.rfc-editor.org/info/rfc7413>.
Reddy, et al. Expires July 22, 2019 [Page 96]
Internet-Draft DOTS Signal Channel Protocol January 2019
[RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
"Architectural Considerations in Smart Object Networking",
RFC 7452, DOI 10.17487/RFC7452, March 2015,
<https://www.rfc-editor.org/info/rfc7452>.
[RFC7589] Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
NETCONF Protocol over Transport Layer Security (TLS) with
Mutual X.509 Authentication", RFC 7589,
DOI 10.17487/RFC7589, June 2015,
<https://www.rfc-editor.org/info/rfc7589>.
[RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport
Layer Security (TLS) False Start", RFC 7918,
DOI 10.17487/RFC7918, August 2016,
<https://www.rfc-editor.org/info/rfc7918>.
[RFC7924] Santesson, S. and H. Tschofenig, "Transport Layer Security
(TLS) Cached Information Extension", RFC 7924,
DOI 10.17487/RFC7924, July 2016,
<https://www.rfc-editor.org/info/rfc7924>.
[RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 8305,
DOI 10.17487/RFC8305, December 2017,
<https://www.rfc-editor.org/info/rfc8305>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
Authors' Addresses
Tirumaleswar Reddy (editor)
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
Reddy, et al. Expires July 22, 2019 [Page 97]
Internet-Draft DOTS Signal Channel Protocol January 2019
Mohamed Boucadair (editor)
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Prashanth Patil
Cisco Systems, Inc.
Email: praspati@cisco.com
Andrew Mortensen
Arbor Networks, Inc.
2727 S. State St
Ann Arbor, MI 48104
United States
Email: andrew@moretension.com
Nik Teague
Verisign, Inc.
United States
Email: nteague@verisign.com
Reddy, et al. Expires July 22, 2019 [Page 98]