DOTS T. Reddy
Internet-Draft McAfee
Intended status: Standards Track M. Boucadair
Expires: June 8, 2018 Orange
P. Patil
Cisco
A. Mortensen
Arbor Networks, Inc.
N. Teague
Verisign, Inc.
December 5, 2017
Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal
Channel
draft-ietf-dots-signal-channel-11
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.
Editorial Note (To be removed by RFC Editor)
Please update these statements 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";
o "| 3.00 | Alternate server | [RFCXXXX] |"
o reference: RFC XXXX
o This RFC
Please update TBD statements with the port number to be assigned to
DOTS Signal Channel Protocol.
Reddy, et al. Expires June 8, 2018 [Page 1]
Internet-Draft DOTS Signal Channel December 2017
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 June 8, 2018.
Copyright Notice
Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions and Terminology . . . . . . . . . . . 5
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6
4. DOTS Signal Channel: Messages & Behaviors . . . . . . . . . . 8
4.1. DOTS Server(s) Discovery . . . . . . . . . . . . . . . . 8
4.2. CoAP URIs . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . 8
4.4. DOTS Mitigation Methods . . . . . . . . . . . . . . . . . 10
4.4.1. Request Mitigation . . . . . . . . . . . . . . . . . 10
4.4.2. Retrieve Information Related to a Mitigation . . . . 19
4.4.3. Efficacy Update from DOTS Clients . . . . . . . . . . 27
4.4.4. Withdraw a Mitigation . . . . . . . . . . . . . . . . 29
4.5. DOTS Signal Channel Session Configuration . . . . . . . . 31
4.5.1. Discover Configuration Parameters . . . . . . . . . . 32
Reddy, et al. Expires June 8, 2018 [Page 2]
Internet-Draft DOTS Signal Channel December 2017
4.5.2. Convey DOTS Signal Channel Session Configuration . . 34
4.5.3. Delete DOTS Signal Channel Session Configuration . . 39
4.6. Redirected Signaling . . . . . . . . . . . . . . . . . . 39
4.7. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 41
5. DOTS Signal Channel YANG Module . . . . . . . . . . . . . . . 42
5.1. Tree Structure . . . . . . . . . . . . . . . . . . . . . 42
5.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 44
6. Mapping Parameters to CBOR . . . . . . . . . . . . . . . . . 53
7. (D)TLS Protocol Profile and Performance Considerations . . . 55
7.1. (D)TLS Protocol Profile . . . . . . . . . . . . . . . . . 55
7.2. (D)TLS 1.3 Considerations . . . . . . . . . . . . . . . . 56
7.3. MTU and Fragmentation . . . . . . . . . . . . . . . . . . 57
8. Mutual Authentication of DOTS Agents & Authorization of DOTS
Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59
9.1. DOTS Signal Channel UDP and TCP Port Number . . . . . . . 59
9.2. Well-Known 'dots' URI . . . . . . . . . . . . . . . . . . 59
9.3. CoAP Response Code . . . . . . . . . . . . . . . . . . . 59
9.4. DOTS Signal Channel CBOR Mappings Registry . . . . . . . 60
9.4.1. Registration Template . . . . . . . . . . . . . . . . 60
9.4.2. Initial Registry Contents . . . . . . . . . . . . . . 60
9.5. DOTS Signal Channel YANG Module . . . . . . . . . . . . . 66
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 66
10.1. nttdots . . . . . . . . . . . . . . . . . . . . . . . . 66
11. Security Considerations . . . . . . . . . . . . . . . . . . . 67
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 68
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 68
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 68
14.1. Normative References . . . . . . . . . . . . . . . . . . 68
14.2. Informative References . . . . . . . . . . . . . . . . . 70
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 74
1. Introduction
A distributed denial-of-service (DDoS) attack is an attempt to make
machines or network resources unavailable to their intended users.
In most cases, sufficient scale 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, number of
processes or threads they can create and use, maximum number of
simultaneous connections it can handle, limited resources of the
control plane, etc. When processing network traffic, such
applications are supposed to use these resources to offer the
intended task in the most efficient fashion. However, a DDoS
attacker may be able to prevent an application from performing its
Reddy, et al. Expires June 8, 2018 [Page 3]
Internet-Draft DOTS Signal Channel December 2017
intended task by causing the application to exhaust the finite supply
of a specific resource.
TCP DDoS SYN-flood, for example, is a memory-exhaustion attack on the
victim and ACK-flood is a CPU exhaustion attack on the victim
[RFC4987]. Attacks on the link are carried out by sending enough
traffic such that the link becomes excessively congested, and
legitimate traffic suffers high packet loss. Stateful firewalls can
also be attacked by sending traffic that causes the firewall to hold
excessive state. The firewall then runs out of memory, and can no
longer instantiate the state required to pass legitimate flows.
Other possible DDoS attacks are discussed in [RFC4732].
In many cases, it may not be possible for network administrators to
determine the causes of an attack, but instead just realize that
certain resources seem to be under attack. This document defines a
lightweight protocol permitting 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.
An example of network diagram showing a deployment of DOTS agents is
shown in Figure 1. In this example, the DOTS server is operating on
the access network. The DOTS client is located on the LAN (Local
Area Network), while a DOTS gateway is embedded in the CPE (Customer
Premises Equipment).
Network
Resource CPE router Access network __________
+-----------+ +--------------+ +-------------+ / \
| |____| |_______| |___ | Internet |
|DOTS client| | DOTS gateway | | DOTS server | | |
| | | | | | | |
+-----------+ +--------------+ +-------------+ \__________/
Figure 1: Sample DOTS Deployment (1)
The DOTS server can also be reachable over the Internet, as depicted
in Figure 2.
Reddy, et al. Expires June 8, 2018 [Page 4]
Internet-Draft DOTS Signal Channel December 2017
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 domain, while the DOTS server is owned and operated by
a different domain providing DDoS mitigation services. That domain
providing DDoS mitigation service might, or might not, provide
connectivity service 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 obtained from [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 to the DOTS data channel specification
[I-D.ietf-dots-data-channel] that defines a configuration and bulk
data exchange mechanism supporting the DOTS signal channel.
2. Notational Conventions and 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
[RFC2119].
(D)TLS is used for statements that apply to both Transport Layer
Security [RFC5246] and Datagram Transport Layer Security [RFC6347].
Specific terms will be used for any statement that applies to either
protocol alone.
Reddy, et al. Expires June 8, 2018 [Page 5]
Internet-Draft DOTS Signal Channel December 2017
The reader should be familiar with the terms defined in
[I-D.ietf-dots-architecture].
The meaning of the symbols in YANG tree diagrams is defined in
[I-D.ietf-netmod-yang-tree-diagrams].
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. CoAP's
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 make it a good foundation on which to build the DOTS signaling
mechanism.
The DOTS signal channel is layered on existing standards (Figure 3).
+--------------+
| DOTS |
+--------------+
| CoAP |
+--------------+
| TLS | DTLS |
+--------------+
| TCP | UDP |
+--------------+
| IP |
+--------------+
Figure 3: Abstract Layering of DOTS signal channel over CoAP over
(D)TLS
By default, 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 mutual agreement with its DOTS clients to use a port number other
than TBD for DOTS signal channel, or DOTS clients supports means to
dynamically discover the ports used by their DOTS servers. In order
to use a distinct port number (vs. 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 deployment
contexts where both a DOTS gateway and an IoT gateway (e.g., Figure 3
of [RFC7452]) are present.
The signal channel is initiated by the DOTS client (Section 4.4).
Once the signal channel is established, the DOTS agents periodically
Reddy, et al. Expires June 8, 2018 [Page 6]
Internet-Draft DOTS Signal Channel December 2017
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, due to
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 [RFC6347] over UDP and TLS
[RFC5246] 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], CBOR is a binary
encoding designed for small code and message size. CBOR encoded
payloads are used to convey signal channel specific payload messages
that convey request parameters and response information such as
errors. This specification uses the encoding rules defined in
[I-D.ietf-core-yang-cbor] for representing mitigation scope and DOTS
signal channel session configuration data defined using YANG
(Section 5) as CBOR data.
In order to prevent fragmentation, DOTS agents must follow the
recommendations 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 and 3.xx Response Codes
MUST be of content type "application/cbor" (Section 5.5.1 of
[RFC7252]). 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 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).
Reddy, et al. Expires June 8, 2018 [Page 7]
Internet-Draft DOTS Signal Channel December 2017
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 a variety of
means (e.g., local configuration, or dynamic means such as DHCP).
These means are out of scope of this document.
Likewise, it is out of scope of this document to specify the behavior
to follow by a DOTS client to place its requests (e.g., contact all
servers, select one server among the list) when multiple DOTS servers
are provisioned.
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 | /v1/mitigate | Section 4.4 |
+-----------------------+----------------+-------------+
| Session configuration | /v1/config | Section 4.5 |
+-----------------------+----------------+-------------+
Table 1: Operations and their corresponding URIs
4.3. Happy Eyeballs for DOTS Signal Channel
DOTS signaling can happen with DTLS over UDP and TLS over TCP. A
DOTS client can use DNS to determine the IP address(es) of a DOTS
server or a DOTS client may be provided with the list of DOTS server
IP addresses. The DOTS client MUST know a DOTS server's domain name;
hard-coding the domain name of the DOTS server into software is NOT
RECOMMENDED in case the domain name is not valid or needs to change
for legal or other reasons. The DOTS client performs A and/or AAAA
record lookup of the domain name and the result will be a list of IP
addresses, each of which can be used to contact the DOTS server using
UDP and TCP.
If an IPv4 path to reach a DOTS server is found, but the DOTS
server's IPv6 path is not working, a dual-stack DOTS client can
Reddy, et al. Expires June 8, 2018 [Page 8]
Internet-Draft DOTS Signal Channel December 2017
experience a significant connection delay compared to an IPv4-only
DOTS client. The other problem is that if a middlebox between the
DOTS client and DOTS server is configured to block UDP, the DOTS
client will fail to establish a DTLS session with the DOTS server and
will, then, have to fall back to TLS over TCP incurring significant
connection delays. [I-D.ietf-dots-requirements] discusses that DOTS
agents will have to support both connectionless and connection-
oriented protocols.
To overcome these connection setup problems, the DOTS client can try
connecting to the DOTS server using both IPv6 and IPv4, and try both
DTLS over UDP and TLS over TCP in a fashion similar to the Happy
Eyeballs mechanism [RFC6555]. These connection attempts are
performed by the DOTS client when its initializes, and the client
uses that information for its subsequent alert to the DOTS server.
In order of preference (most preferred first), it is UDP over IPv6,
UDP over IPv4, TCP over IPv6, and finally TCP over IPv4, which
adheres to address preference order [RFC6724] and the DOTS preference
that UDP be used over TCP (to avoid TCP's head of line blocking).
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
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 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 repeats the mechanism to discover if DOTS signaling with DTLS
over UDP becomes available from the DOTS server, so the DOTS client
can migrate the DOTS signal channel from TCP to UDP, but 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 June 8, 2018 [Page 9]
Internet-Draft DOTS Signal Channel December 2017
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 convey 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 on average more than one UDP datagram per RTT to the peer
DOTS agent.
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 when possible
(case 2 in Section 3.1.3 of [RFC8085]).
4.4.1. Request Mitigation
When a DOTS client requires mitigation for any reason, the DOTS
client uses CoAP PUT method to send a mitigation request to its DOTS
server(s) (Figure 5, illustrated in JSON diagnostic notation). If
this DOTS client is entitled to solicit the DOTS service, the DOTS
server can enable mitigation on behalf of the DOTS client by
communicating the DOTS client's request to the mitigator and relaying
selected mitigator feedback to the requesting DOTS client.
Reddy, et al. Expires June 8, 2018 [Page 10]
Internet-Draft DOTS Signal Channel December 2017
Header: PUT (Code=0.03)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Content-Type: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer,
"target-ip": [
"string"
],
"target-prefix": [
"string"
],
"target-port-range": [
{
"lower-port": integer,
"upper-port": integer
}
],
"target-protocol": [
integer
],
"target-fqdn": [
"string"
],
"target-uri": [
"string"
],
"alias-name": [
"string"
],
"lifetime": integer
}
]
}
}
Figure 5: PUT to convey DOTS signals
The parameters are described below:
Reddy, et al. Expires June 8, 2018 [Page 11]
Internet-Draft DOTS Signal Channel December 2017
client-identifier: The client identifier MAY be conveyed by the DOTS
gateway to propagate the DOTS client identity from the gateway's
client-side to the gateway's server-side, and from the gateway's
server-side to the DOTS server. This allows the final DOTS server
to accept mitigation requests with scopes which the DOTS client is
authorized to manage.
The 'client-identifier' value MUST be assigned by the DOTS gateway
in a manner that ensures that there is no probability that the
same value will be assigned to a different DOTS client. The DOTS
gateway MUST obscure potentially sensitive DOTS client identity
information. The client-identifier attribute SHOULD NOT to be
generated and included by the DOTS client.
This is an optional attribute.
mitigation-id: Identifier for the mitigation request represented
using an integer. This identifier MUST be unique for each
mitigation request bound to the DOTS client, i.e., the mitigation-
id parameter value in the mitigation request needs to be unique
relative to the mitigation-id parameter values of active
mitigation requests conveyed from the DOTS client to the DOTS
server. This identifier MUST be generated by the DOTS client.
This document does not make any assumption about how this
identifier is generated.
This is a mandatory attribute.
target-ip: A list of IP addresses identifying resources under
attack. This is an optional attribute.
target-prefix: A list of prefixes identifying resources under
attack. Prefixes are represented using Classless Inter-domain
Routing (CIDR) notation [RFC4632].
This is an optional attribute.
target-port-range: A list of port numbers bound to resources under
attack.
The 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], the
range of ports can be, for example, 1024-65535.
This is an optional attribute.
Reddy, et al. Expires June 8, 2018 [Page 12]
Internet-Draft DOTS Signal Channel December 2017
target-protocol: A list of protocols involved in an attack. Values
are taken from the IANA protocol registry [proto_numbers].
The value 0 has a special meaning for 'all protocols'.
This is an optional attribute.
target-fqdn: A list of Fully Qualified Domain Names (FQDNs)
identifying resources under attack. An FQDN is the full name of a
resource, rather than just its hostname. For example, "venera" is
a hostname, and "venera.isi.edu" is an FQDN.
This is an optional attribute.
target-uri: A list of Uniform Resource Identifiers (URIs) [RFC3986]
identifying resources under attack.
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 (60
minutes) -- this value was chosen to be long enough so that
refreshing is not typically a burden on the DOTS client, while
expiring the request where the client has unexpectedly quit in a
timely manner. 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.
Reddy, et al. Expires June 8, 2018 [Page 13]
Internet-Draft DOTS Signal Channel December 2017
The DOTS server MUST always indicate the actual lifetime in the
response and the remaining lifetime in status messages sent to the
DOTS client.
This is a mandatory attribute.
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 'scope' parameters in the same PUT request.
The CBOR key values for the parameters are defined in Section 6.
Section 9 defines how the CBOR key values can be allocated to
standards bodies and vendors.
FQDN and URI mitigation scopes may be thought of as a form of scope
alias, in which the addresses to which the domain name or URI resolve
represent the full scope of the mitigation.
In the PUT request at least one of the attributes 'target-ip' or
'target-prefix' or 'target-fqdn' or 'target-uri 'or 'alias-name' MUST
be present. If the attribute value is empty, then the attribute MUST
NOT be present in the request.
The relative order of two mitigation requests from a DOTS client is
determined by comparing their respective 'mitigation-id' values. If
two mitigation requests have overlapping mitigation scopes, the
mitigation request with higher numeric 'mitigation-id' value will
override the mitigation request with a lower numeric 'mitigation-id'
value. Two mitigation-ids from a DOTS client are overlapping if
there is a common IP address, IP prefix, FQDN, URI, or alias-name.
To avoid maintaining a long list of overlapping mitigation requests
from a DOTS client and avoid error-prone provisioning of mitigation
requests from a DOTS client, the overlapped lower numeric
'mitigation-id' MUST be automatically deleted and no longer available
at the DOTS server.
The Uri-Path option carries a major and minor version nomenclature to
manage versioning and DOTS signal channel in this specification uses
v1 major version.
Figure 6 shows a PUT request example to signal that ports 80, 8080,
and 443 on the servers 2001:db8:6401::1 and 2001:db8:6401::2 are
being attacked (illustrated in JSON diagnostic notation).
Reddy, et al. Expires June 8, 2018 [Page 14]
Internet-Draft DOTS Signal Channel December 2017
Header: PUT (Code=0.03)
Uri-Host: "www.example.com"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "v1"
Uri-Path: "mitigate"
Content-Format: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"dz6pHjaADkaFTbjr0JGBpw"
],
"scope": [
{
"mitigation-id": 12332,
"target-ip": [
"2001:db8:6401::1",
"2001:db8:6401::2"
],
"target-port-range": [
{
"lower-port": 80
},
{
"lower-port": 443
},
{
"lower-port": 8080
}
],
"target-protocol": [
6
]
}
]
}
}
Figure 6: PUT for DOTS signal
The corresponding CBOR encoding format is shown in Figure 7.
Reddy, et al. Expires June 8, 2018 [Page 15]
Internet-Draft DOTS Signal Channel December 2017
A1 # map(1)
01 # unsigned(1)
A2 # map(2)
18 20 # unsigned(32)
81 # array(1)
76 # text(22)
647A3670486A6141446B614654626A72304A47427077 # "dz6pHjaADkaFTbjr0JGBpw"
02 # unsigned(2)
81 # array(1)
A4 # map(4)
03 # unsigned(3)
19 302C # unsigned(12332)
04 # unsigned(4)
82 # array(2)
70 # text(16)
323030313A6462383A363430313A3A31 # "2001:db8:6401::1"
70 # text(16)
323030313A6462383A363430313A3A32 # "2001:db8:6401::2"
05 # unsigned(5)
83 # array(3)
A1 # map(1)
06 # unsigned(6)
18 50 # unsigned(80)
A1 # map(1)
06 # unsigned(6)
19 01BB # unsigned(443)
A1 # map(1)
06 # unsigned(6)
19 1F90 # unsigned(8080)
08 # unsigned(8)
81 # array(1)
06 # unsigned(6)
Figure 7: PUT for DOTS signal (CBOR)
If the DOTS client is using the certificate provisioned by the
Enrollment over Secure Transport (EST) server [RFC7030] in the DOTS
gateway-domain to authenticate itself to the DOTS gateway, then the
'client-identifier' value can be the output of a cryptographic hash
algorithm whose input is the DER-encoded ASN.1 representation of the
Subject Public Key Info (SPKI) of an X.509 certificate. In this
version of the specification, the cryptographic hash algorithm used
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. If the
'client-identifier' value is already present in the mitigation
request received from the DOTS client, the DOTS gateway MAY compute
the 'client-identifier' value, as discussed above, and add the
Reddy, et al. Expires June 8, 2018 [Page 16]
Internet-Draft DOTS Signal Channel December 2017
computed 'client-identifier' value to the end of the 'client-
identifier' list. The DOTS server MUST NOT use the 'client-
identifier' for the DOTS client authentication process.
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 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 which the DOTS client is authorized to manage. The DOTS
server couples the DOTS signal and data channel sessions using the
DOTS client identity and the 'client-identifier' 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 returns 4.00 (Bad Request) in the
response.
The DOTS server uses 'mitigation-id' parameter value to detect
duplicate mitigation requests. If the mitigation request contains
both alias-name and other parameters identifying the target resources
(such as, 'target-ip', 'target-prefix', 'target-port-range', 'target-
fqdn', or 'target-uri'), then the DOTS server appends the parameter
values in 'alias-name' with the corresponding parameter values in
'target-ip', '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 has erred or is currently
unavailable to provide mitigation in response to the mitigation
request from the DOTS client.
Figure 8 shows an example of a PUT request that is successfully
processed (i.e., CoAP 2.xx response codes).
Reddy, et al. Expires June 8, 2018 [Page 17]
Internet-Draft DOTS Signal Channel December 2017
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer,
"lifetime": integer
}
]
}
}
Figure 8: 2.xx response body
If the request is missing one or more mandatory attributes, includes
multiple 'scope' parameters, or contains invalid or unknown
parameters, the DOTS server replies with 4.00 (Bad Request). DOTS
agents can safely ignore Vendor-Specific 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 'mitigation-id' 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.
If the DOTS server finds the 'mitigation-id' parameter value conveyed
in the PUT request in its configuration data, it MAY update the
mitigation request, and a 2.04 (Changed) response is returned to
indicate a successful update of the mitigation request.
If the request is conflicting with an existing mitigation request
from a different DOTS client, and the DOTS server decides to maintain
the conflicting mitigation request, the DOTS server returns 4.09
(Conflict) [RFC8132] to the requesting DOTS client. The response
includes enough information for a DOTS client to recognize the source
of the conflict (refer to 'conflict-information' specified in
Section 4.4.2).
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 'mitigation-id' value, and MUST repeat all the other parameters
Reddy, et al. Expires June 8, 2018 [Page 18]
Internet-Draft DOTS Signal Channel December 2017
as sent in the original mitigation request apart from a possible
change to the lifetime parameter value.
A DOTS gateway MUST update the 'client-identifier' list in the
response to remove the 'client-identifier' value it had added in the
corresponding request before forwarding the response to the DOTS
client.
4.4.2. Retrieve Information Related to a Mitigation
A GET request is used to retrieve information (including status) of a
DOTS mitigation from a DOTS server. If the DOTS server does not find
the 'mitigation-id' parameter value conveyed in the GET request in
its configuration data, it responds with a 4.04 (Not Found) error
response code.
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) or configuration data or both. The DOTS
server SHOULD support this optional filtering capability but can
safely ignore it if not supported.
The following examples illustrate how a DOTS client retrieves active
mitigation requests from a DOTS server. In particular:
o Figure 9 shows the example of a GET request to retrieve all DOTS
mitigation requests signaled by a DOTS client.
o Figure 10 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 it was processed at the DOTS server.
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.
Reddy, et al. Expires June 8, 2018 [Page 19]
Internet-Draft DOTS Signal Channel December 2017
Header: GET (Code=0.01)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Observe : 0
{
"mitigation-scope": {
"client-identifier": [
"string"
]
}
}
Figure 9: GET to retrieve all DOTS mitigation requests
Header: GET (Code=0.01)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Observe : 0
Content-Format: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer
}
]
}
}
Figure 10: GET to retrieve a specific DOTS mitigation request
Figure 11 shows a response example of all active mitigation requests
associated with the DOTS client on the DOTS server and the mitigation
status of each mitigation request.
Reddy, et al. Expires June 8, 2018 [Page 20]
Internet-Draft DOTS Signal Channel December 2017
{
"mitigation-scope": {
"scope": [
{
"mitigation-id": 12332,
"mitigation-start": 1507818434.00,
"target-protocol": [
17
],
"lifetime":1800,
"status":2,
"bytes-dropped": 134334555,
"bps-dropped": 43344,
"pkts-dropped": 333334444,
"pps-dropped": 432432
},
{
"mitigation-id": 12333,
"mitigation-start": 1507818393.00,
"target-protocol": [
6
],
"lifetime":1800,
"status":3
"bytes-dropped": 0,
"bps-dropped": 0,
"pkts-dropped": 0,
"pps-dropped": 0
}
]
}
}
Figure 11: Response body
The mitigation status parameters are described below:
mitigation-start: Mitigation start time is represented in seconds
relative to 1970-01-01T00:00Z in UTC time (Section 2.4.1 of
[RFC7049]). The encoding is modified so that the leading tag 1
(epoch-based date/time) MUST be omitted.
lifetime: The remaining lifetime of the mitigation request, in
seconds.
status: Status of attack mitigation. The 'status' parameter is a
mandatory attribute. The various possible values of 'status'
parameter are explained in Table 2.
Reddy, et al. Expires June 8, 2018 [Page 21]
Internet-Draft DOTS Signal Channel December 2017
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.
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 white list. This code is
returned when the DDoS mitigation detects source addresses/
prefixes in the white-listed ACLs are attacking the target.
conflict-scope Indicates the 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, or a list of alias-names.
retry-timer Indicates, in seconds, the time upon 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
Reddy, et al. Expires June 8, 2018 [Page 22]
Internet-Draft DOTS Signal Channel December 2017
mitigation request after retry-timer seconds before expiry of
lifetime and check if the conflict is resolved.
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 integer.
This is an optional attribute.
bps-dropped: The average dropped bytes per second for the mitigation
request since the attack mitigation is triggered. This SHOULD be
a five-minute average. This is an optional attribute.
pkts-dropped: The total dropped packet count for the mitigation
request since the attack mitigation is triggered. This is an
optional attribute.
pps-dropped: The average dropped packets per second for the
mitigation request since the attack mitigation is triggered. This
SHOULD be a five-minute average. This is an optional attribute.
Reddy, et al. Expires June 8, 2018 [Page 23]
Internet-Draft DOTS Signal Channel December 2017
+-----------+-------------------------------------------------------+
| Parameter | Description |
| value | |
+-----------+-------------------------------------------------------+
| 1 | Attack mitigation is in progress (e.g., changing the |
| | network path to re-route the inbound traffic to DOTS |
| | mitigator). |
+-----------+-------------------------------------------------------+
| 2 | Attack is 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. |
+-----------+-------------------------------------------------------+
| 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. |
+-----------+-------------------------------------------------------+
| 8 | Attack mitigation is rejected. |
+-----------+-------------------------------------------------------+
Table 2: Values of 'status' parameter
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
resource and requests this representation be updated by the server as
long as the client is interested in the resource. A DOTS client
conveys the observe option set to '0' in the GET request to receive
unsolicited notifications of attack mitigation status from the DOTS
server. Unidirectional notifications within the bidirectional signal
channel allows unsolicited message delivery, enabling asynchronous
notifications between the agents. Due to the higher likelihood of
packet loss during a DDoS attack, 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 a RTT estimate, it SHOULD NOT send
more than one unsolicited notification every 3 seconds, and SHOULD
use an even less aggressive rate when possible (case 2 in
Section 3.1.3 of [RFC8085]).
Reddy, et al. Expires June 8, 2018 [Page 24]
Internet-Draft DOTS Signal Channel December 2017
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. 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 '8 (Attack
mitigation is rejected)' and 'conflict-status' set to '1' is sent
to a DOTS client to indicate that this mitigation request is
rejected because a conflict is detected.
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.
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 then 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 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).
Figure 12 shows an example of a DOTS client requesting a DOTS server
to send notifications related a given mitigation request.
Reddy, et al. Expires June 8, 2018 [Page 25]
Internet-Draft DOTS Signal Channel December 2017
DOTS Client DOTS Server
| |
| GET /<mitigation-id number> |
| Token: 0x4a | Registration
| Observe: 0 |
+------------------------------>|
| |
| 2.05 Content |
| Token: 0x4a | Notification of
| Observe: 12 | the current state
| status: "mitigation |
| in progress" |
|<------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 44 | a state change
| status: "mitigation |
| complete" |
|<------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 60 | a state change
| status: "attack stopped" |
|<------------------------------+
| |
Figure 12: Notifications of attack mitigation status
4.4.2.1. 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 given 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, and the DOTS client recalls the
mitigation request by issuing a DELETE request for the mitigation-id.
A DOTS client SHOULD react to the status of the attack from the DOTS
server and not the fact that it has recognized, using its own means,
that the attack has been mitigated. This ensures that the DOTS
client does not recall a mitigation request in a premature fashion
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 and the attack is not completely averted.
Reddy, et al. Expires June 8, 2018 [Page 26]
Internet-Draft DOTS Signal Channel December 2017
4.4.3. Efficacy Update from DOTS Clients
While DDoS mitigation is active, 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.
The PUT request MUST include all the parameters used in the PUT
request to convey the DOTS signal (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 'mitigation-id' in
the request matches a mitigation request from that DOTS client, then
the request is processed. If no match is found, the PUT request is
silently ignored.
An example of an efficacy update message, which includes an If-Match
option with an empty value, is depicted in Figure 13.
Reddy, et al. Expires June 8, 2018 [Page 27]
Internet-Draft DOTS Signal Channel December 2017
Header: PUT (Code=0.03)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Content-Format: "application/cbor"
If-Match:
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer,
"target-ip": [
"string"
],
"target-port-range": [
{
"lower-port": integer,
"upper-port": integer
}
],
"target-protocol": [
integer
],
"target-fqdn": [
"string"
],
"target-uri": [
"string"
],
"alias-name": [
"string"
],
"lifetime": integer,
"attack-status": integer
}
]
}
}
Figure 13: Efficacy Update
Reddy, et al. Expires June 8, 2018 [Page 28]
Internet-Draft DOTS Signal Channel December 2017
The 'attack-status' parameter is a mandatory attribute when doing an
efficacy update. The various possible values contained in the
'attack-status' parameter are described in Table 3.
+-----------+-------------------------------------------------------+
| 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.
4.4.4. Withdraw a Mitigation
A DELETE request is used to withdraw a DOTS mitigation request from a
DOTS server (Figure 14).
Reddy, et al. Expires June 8, 2018 [Page 29]
Internet-Draft DOTS Signal Channel December 2017
Header: DELETE (Code=0.04)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "mitigate"
Content-Format: "application/cbor"
{
"mitigation-scope": {
"client-identifier": [
"string"
],
"scope": [
{
"mitigation-id": integer
}
]
}
}
Figure 14: Withdraw DOTS signal
If the request does not include a 'mitigation-id', the DOTS server
MUST reply with a 4.00 (Bad Request).
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 'mitigation-id'
parameter value conveyed in the DELETE request does not exist in its
configuration data before the request.
If the DOTS server finds the 'mitigation-id' parameter value conveyed
in the DELETE request in its configuration data, then to protect
against route or DNS flapping caused by a DOTS client rapidly
toggling 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 active-but- terminating period up to a maximum of 300
seconds (5 minutes).
Reddy, et al. Expires June 8, 2018 [Page 30]
Internet-Draft DOTS Signal Channel December 2017
After 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 ceases incurring cost at this point.
4.5. DOTS Signal Channel Session Configuration
The DOTS client can negotiate, configure, and retrieve the DOTS
signal channel session behavior. The DOTS signal channel can be
used, for example, to configure the following:
a. Heartbeat interval: DOTS agents regularly send heartbeats (CoAP
Ping/Pong) to each other after mutual authentication in order to
keep the DOTS signal channel open, heartbeat messages are
exchanged between the DOTS agents every heartbeat-interval
seconds to detect the current status of the DOTS signal channel
session.
b. Missing heartbeats 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.
Reliability is provided to requests and responses by marking them as
Confirmable (CON) 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 is not
able to 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 message is explained in Section 2.2 of [RFC7252].
When the response is ready, the server sends it in a new Confirmable
message which then 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 June 8, 2018 [Page 31]
Internet-Draft DOTS Signal Channel December 2017
Implementation Note: A DOTS client that receives a response in a
CON 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 CON, the DOTS client may no longer have any state
to which to correlate this response, making the retransmission an
unexpected message; 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 and current configuration
parameters on the DOTS server for DOTS signal channel session
configuration. Figure 15 shows how to obtain acceptable
configuration parameters for the DOTS server.
Header: GET (Code=0.01)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "config"
Figure 15: 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.
Reddy, et al. Expires June 8, 2018 [Page 32]
Internet-Draft DOTS Signal Channel December 2017
Content-Format: "application/cbor"
{
"heartbeat-interval": {
"CurrentValue": integer,
"MinValue": integer,
"MaxValue" : integer,
},
"missing-hb-allowed": {
"CurrentValue": integer,
"MinValue": integer,
"MaxValue" : integer,
},
"max-retransmit": {
"CurrentValue": integer,
"MinValue": integer,
"MaxValue" : integer,
},
"ack-timeout": {
"CurrentValue": integer,
"MinValue": integer,
"MaxValue" : integer,
},
"ack-random-factor": {
"CurrentValue": number,
"MinValue": number,
"MaxValue" : number,
},
"trigger-mitigation": {
"CurrentValue": boolean,
}
}
Figure 16: GET response body
Figure 17 shows an example of acceptable and current configuration
parameters on the DOTS server for DOTS signal channel session
configuration.
Reddy, et al. Expires June 8, 2018 [Page 33]
Internet-Draft DOTS Signal Channel December 2017
Content-Format: "application/cbor"
{
"heartbeat-interval": {
"CurrentValue": 30,
"MinValue": 15,
"MaxValue" : 240,
},
"missing-hb-allowed": {
"CurrentValue": 5,
"MinValue": 3,
"MaxValue" : 9,
},
"max-retransmit": {
"CurrentValue": 3,
"MinValue": 2,
"MaxValue" : 15,
},
"ack-timeout": {
"CurrentValue": 2,
"MinValue": 1,
"MaxValue" : 30,
},
"ack-random-factor": {
"CurrentValue": 1.5,
"MinValue": 1.1,
"MaxValue" : 4.0,
},
"trigger-mitigation": {
"CurrentValue": true,
}
}
Figure 17: Configuration response body
4.5.2. Convey DOTS Signal Channel Session Configuration
A PUT request 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-010 of
[I-D.ietf-dots-requirements]). According to [RFC8085], keepalive
Reddy, et al. Expires June 8, 2018 [Page 34]
Internet-Draft DOTS Signal Channel December 2017
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 second may be seen as too chatty in
some deployments. For such deployments, DOTS agents may negotiate
longer heartbeat-interval values to avoid overloading the network
with too frequent keepalives.
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, then 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 the DOTS agents.
Reddy, et al. Expires June 8, 2018 [Page 35]
Internet-Draft DOTS Signal Channel December 2017
Header: PUT (Code=0.03)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "config"
Content-Format: "application/cbor"
{
"signal-config": {
"session-id": integer,
"heartbeat-interval": integer,
"missing-hb-allowed": integer,
"max-retransmit": integer,
"ack-timeout": integer,
"ack-random-factor": number
"trigger-mitigation": boolean
}
}
Figure 18: PUT to convey the DOTS signal channel session
configuration data.
The parameters are described below:
session-id: Identifier for the DOTS signal channel session
configuration data represented as an integer. This identifier
MUST be generated by the DOTS client. This document does not make
any assumption about how this identifier is generated.
This is a mandatory attribute.
heartbeat-interval: Time interval in seconds between two
consecutive heartbeat messages.
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.
Reddy, et al. Expires June 8, 2018 [Page 36]
Internet-Draft DOTS Signal Channel December 2017
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.
trigger-mitigation: If the parameter value is set to 'false', then
DDoS mitigation is triggered only when the DOTS signal channel
session is lost. Automated mitigation on loss of signal is
discussed in Section 3.3.3 of [I-D.ietf-dots-architecture].
If the DOTS client ceases to respond to heartbeat messages, the
DOTS server can detect that the DOTS session is lost.
The default value of the parameter is 'true'.
This is an optional attribute.
In the PUT request at least one of the attributes 'heartbeat-
interval', 'missing-hb-allowed', 'max-retransmit', 'ack-timeout',
'ack-random-factor', and 'trigger-mitigation' MUST be present. The
PUT request with higher numeric 'session-id' value over-rides the
DOTS signal channel session configuration data installed by a PUT
request with a lower numeric 'session-id' value.
Figure 19 shows a PUT request example to convey the configuration
parameters for the DOTS signal channel.
Reddy, et al. Expires June 8, 2018 [Page 37]
Internet-Draft DOTS Signal Channel December 2017
Header: PUT (Code=0.03)
Uri-Host: "www.example.com"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "v1"
Uri-Path: "config"
Content-Format: "application/cbor"
{
"signal-config": {
"session-id": 1234534333242,
"heartbeat-interval": 91,
"missing-hb-allowed": 3,
"max-retransmit": 7,
"ack-timeout": 5,
"ack-random-factor": 1.5,
"trigger-mitigation": false
}
}
Figure 19: PUT to convey the configuration parameters
The DOTS server indicates the result of processing the PUT request
using CoAP response codes:
o If the DOTS server finds the 'session-id' parameter value conveyed
in the PUT request in its configuration data and if the DOTS
server has accepted the updated configuration parameters, then
2.04 (Changed) code is returned in the response.
o If the DOTS server does not find the 'session-id' 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) is returned in the response.
o If the request is missing one or more mandatory attributes or it
contains one or more invalid or unknown parameters, then 4.00 (Bad
Request) is returned in the response.
o Response code 4.22 (Unprocessable Entity) is returned in the
response, 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.
Upon receipt of the 4.22 error response code, the DOTS client
should request 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.
Reddy, et al. Expires June 8, 2018 [Page 38]
Internet-Draft DOTS Signal Channel December 2017
4.5.3. Delete DOTS Signal Channel Session Configuration
A DELETE request is used to delete the installed DOTS signal channel
session configuration data (Figure 20).
Header: DELETE (Code=0.04)
Uri-Host: "host"
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "version"
Uri-Path: "config"
Content-Format: "application/cbor"
Figure 20: 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.
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 3.00
(alternate server) will be returned in the response to the client.
The DOTS server can return the error response code 3.00 in response
to a PUT request from the DOTS client or convey the error response
code 3.00 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 IP address(es) and time
to live values in the CBOR body.
Reddy, et al. Expires June 8, 2018 [Page 39]
Internet-Draft DOTS Signal Channel December 2017
{
"alt-server": "string",
"alt-server-record": [
{
"addr": "string",
"ttl" : integer,
}
]
}
Figure 21: Error response body
The parameters are described below:
alt-server: FQDN of an alternate DOTS server.
addr: IP address of an alternate DOTS server.
ttl: Time to live (TTL) represented as an integer number of seconds.
Figure 22 shows a 3.00 response example to convey the DOTS alternate
server 'alt-server.example', its IP addresses 2001:db8:6401::1 and
2001:db8:6401::2, and TTL values 3600 and 1800.
{
"alt-server": "alt-server.example",
"alt-server-record": [
{
"ttl" : 3600,
"addr": "2001:db8:6401::1"
},
{
"ttl" : 1800,
"addr": "2001:db8:6401::2"
}
]
}
Figure 22: Example of error response body
When the DOTS client receives 3.00 response, it considers the current
request as having failed, but SHOULD try the request with the
alternate DOTS server. During a DDOS attack, the DNS server may be
subjected to DDOS attack, alternate DOTS server IP addresses conveyed
in the 3.00 response help the DOTS client to skip DNS lookup of the
alternate DOTS server and can try to establish UDP or TCP session
with the alternate DOTS server IP addresses. The DOTS client SHOULD
Reddy, et al. Expires June 8, 2018 [Page 40]
Internet-Draft DOTS Signal Channel December 2017
implement DNS64 function to handle the scenario where IPv6-only DOTS
client communicates with IPv4-only alternate DOTS server.
4.7. Heartbeat Mechanism
To provide a metric 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 extended
absence of a peer agent heartbeat.
While the communication between the DOTS agents is quiescent, the
DOTS client will probe the DOTS server to ensure it has maintained
cryptographic state and vice versa. Such probes can also keep alive
firewall and/or NAT bindings. This probing reduces the frequency of
establishing a new handshake when a DOTS signal needs to be conveyed
to the DOTS server.
In case of a volumetric DDoS attack saturating the incoming link 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 and DOTS messages from the DOTS client. In this scenario,
the DOTS agents MUST behave differently to handle message
transmission and DOTS session liveliness during link saturation:
o The DOTS client MUST NOT consider the DOTS session terminated even
after maximum 'missing-hb-allowed' threshold is reached. The DOTS
client SHOULD continue to use the current DOTS session, and send
heartbeat requests over the current DOTS session, so the DOTS
server knows the DOTS client has not disconnected the DOTS
session.
After the maximum 'missing-hb-allowed' threshold is reached, the
DOTS client SHOULD try (D)TLS session resumption. The DOTS client
SHOULD send mitigation requests over the current DOTS session, and
in parallel, try (D)TLS session resumption or 0-RTT mode in DTLS
1.3 to piggyback the mitigation request in the ClientHello
message.
Once the link is no longer saturated, if traffic from the DOTS
server reaches the DOTS client over the current DOTS session, the
DOTS client can stop (D)TLS session resumption or if (D)TLS
session resumption is successful then disconnect the current DOTS
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
Reddy, et al. Expires June 8, 2018 [Page 41]
Internet-Draft DOTS Signal Channel December 2017
client and after maximum 'missing-hb-allowed' threshold is
reached, the DOTS server concludes the session is disconnected.
In DOTS over UDP, heartbeat messages may 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 an Reset
message.
In DOTS over TCP, heartbeat messages can be exchanged between the
DOTS agents using the Ping and Pong messages specified in Section 4.4
of [I-D.ietf-core-coap-tcp-tls]. 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 Module
This document defines a YANG [RFC7950] module for mitigation scope
and DOTS signal channel session configuration data.
5.1. Tree Structure
This document defines the YANG module "ietf-dots-signal"
(Section 5.2), which has the following tree structure. A DOTS signal
message can either be a mitigation or a configuration message.
Reddy, et al. Expires June 8, 2018 [Page 42]
Internet-Draft DOTS Signal Channel December 2017
module: ietf-dots-signal
+--rw dots-signal
+--rw (message-type)?
+--:(mitigation-scope)
| +--rw client-identifier* binary
| +--rw scope* [mitigation-id]
| +--rw mitigation-id int32
| +--rw target-ip* inet:ip-address
| +--rw target-prefix* inet:ip-prefix
| +--rw target-port-range* [lower-port upper-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 mitigation-start? int64
| +--ro status? enumeration
| +--ro conflict-information
| | +--ro conflict-status? enumeration
| | +--ro conflict-cause? enumeration
| | +--ro retry-timer? int32
| | +--ro conflict-scope
| | +--ro target-ip* inet:ip-address
| | +--ro target-prefix* inet:ip-prefix
| | +--ro target-port-range* [lower-port upper-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 pkts-dropped? yang:zero-based-counter64
| +--ro bps-dropped? yang:zero-based-counter64
| +--ro bytes-dropped? yang:zero-based-counter64
| +--ro pps-dropped? yang:zero-based-counter64
+--:(configuration)
+--rw session-id int32
+--rw heartbeat-interval? int16
+--rw missing-hb-allowed? int16
+--rw max-retransmit? int16
+--rw ack-timeout? int16
+--rw ack-random-factor? decimal64
+--rw trigger-mitigation? boolean
Reddy, et al. Expires June 8, 2018 [Page 43]
Internet-Draft DOTS Signal Channel December 2017
5.2. YANG Module
<CODE BEGINS> file "ietf-dots-signal@2017-12-05.yang"
module ietf-dots-signal {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal";
prefix "signal";
import ietf-inet-types {prefix "inet";}
import ietf-yang-types {prefix yang; }
organization "IETF DOTS Working Group";
contact
"Konda, Tirumaleswar Reddy <TirumaleswarReddy_Konda@McAfee.com>
Mohamed Boucadair <mohamed.boucadair@orange.com>
Prashanth Patil <praspati@cisco.com>
Andrew Mortensen <amortensen@arbor.net>
Nik Teague <nteague@verisign.com>";
description
"This module contains YANG definition for the signaling
messages exchanegd between the DOTS client to the DOTS server.
Copyright (c) 2017 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 2017-12-05 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
grouping target {
description
Reddy, et al. Expires June 8, 2018 [Page 44]
Internet-Draft DOTS Signal Channel December 2017
"Specifies the scope of the mitigation request.";
leaf-list target-ip {
type inet:ip-address;
description
"IPv4 or IPv6 address identifying the target.";
}
leaf-list target-prefix {
type inet:ip-prefix;
description
"IPv4 or IPv6 prefix identifying the target.";
}
list target-port-range {
key "lower-port upper-port";
description
"Port range. When only lower-port is
present, it represents a single port.";
leaf lower-port {
type inet:port-number;
mandatory true;
description "Lower port number.";
}
leaf upper-port {
type inet:port-number;
must ". >= ../lower-port" {
error-message
"The upper port number must be greater than
or equal to lower port number.";
}
description "Upper port number.";
}
}
leaf-list target-protocol {
type uint8;
description
"Identifies the target protocol number.
The value '0' means 'all protocols'.
Values are taken from the IANA protocol registry:
https://www.iana.org/assignments/protocol-numbers/
protocol-numbers.xhtml
Reddy, et al. Expires June 8, 2018 [Page 45]
Internet-Draft DOTS Signal Channel December 2017
For example, 6 for a TCP or 17 for UDP.";
}
leaf-list target-fqdn {
type inet:domain-name;
description "FQDN identifying the target.";
}
leaf-list target-uri {
type inet:uri;
description "URI identifying the target.";
}
leaf-list alias-name {
type string;
description "alias name";
}
}
grouping mitigation-scope {
description
"Specifies the scope of the mitigation request.";
leaf-list client-identifier {
type binary;
description
"The client identifier may be conveyed by
the DOTS gateway to propagate the DOTS client
identity from the gateway's client-side to the
gateway's server-side, and from the gateway's
server-side to the DOTS server.
It allows the final DOTS server to accept
mitigation requests with scopes which the DOTS
client is authorized to manage.";
}
list scope {
key mitigation-id;
description
"The scope of the request.";
leaf mitigation-id {
type int32;
description
"Mitigation request identifier.
This identifier must be unique for each mitigation
Reddy, et al. Expires June 8, 2018 [Page 46]
Internet-Draft DOTS Signal Channel December 2017
request bound to the DOTS client.";
}
uses target;
leaf lifetime {
type int32;
units "seconds";
default 3600;
description
"Indicates the lifetime of the mitigation request.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf mitigation-start {
type int64;
units "seconds";
description
"Mitigation start time is represented in seconds
relative to 1970-01-01T00:00Z in UTC time.";
}
leaf status {
type enumeration {
enum "1" {
description
"Attack mitigation is in progress (e.g., changing
the network path to re-route the inbound traffic
to DOTS mitigator).";
}
enum "2" {
description
"Attack is successfully mitigated (e.g., traffic
is redirected to a DDOS mitigator and attack
traffic is dropped).";
}
enum "3" {
description
"Attack has stopped and the DOTS client can
withdraw the mitigation request.";
}
enum "4" {
Reddy, et al. Expires June 8, 2018 [Page 47]
Internet-Draft DOTS Signal Channel December 2017
description
"Attack has exceeded the mitigation provider
capability.";
}
enum "5" {
description
"DOTS client has withdrawn the mitigation
request and the mitigation is active but
terminating.";
}
enum "6" {
description
"Attack mitigation is now terminated.";
}
enum "7" {
description
"Attack mitigation is withdrawn.";
}
enum "8" {
description
"Attack mitigation is rejected.";
}
}
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.
Must only be used for responses.";
leaf conflict-status {
type enumeration {
enum "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.";
Reddy, et al. Expires June 8, 2018 [Page 48]
Internet-Draft DOTS Signal Channel December 2017
}
enum "2" {
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
This mitigation request is currently active.";
}
enum "3" {
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients. All
conflicting mitigation requests are inactive.";
}
}
description
"Indicates the conflict status.
It must be included in responses, only.";
}
leaf conflict-cause {
type enumeration {
enum "1" {
description
"Overlapping targets. conflict-scope provides
more details about the exact conflict.";
}
enum "2" {
description
"Conflicts with an existing white list.
This code is returned when the DDoS mitigation
detects source addresses/prefixes in the
white-listed ACLs are attacking the target.";
}
}
description
"Indicates the cause of the conflict.
It must be included in responses, only.";
}
leaf retry-timer {
type int32;
units "seconds";
description
"The DOTS client must not re-send the
Reddy, et al. Expires June 8, 2018 [Page 49]
Internet-Draft DOTS Signal Channel December 2017
same request before the expiry of this timer.
It must be included in responses, only.";
}
container conflict-scope {
description
"Provides more information about the conflict scope.";
uses target;
}
}
leaf pkts-dropped {
type yang:zero-based-counter64;
config false;
description
"Number of dropped packets";
}
leaf bps-dropped {
type yang:zero-based-counter64;
config false;
description
"The average dropped bytes per second for
the mitigation request since the attack
mitigation is triggered.";
}
leaf bytes-dropped {
type yang:zero-based-counter64;
units 'bytes';
config false;
description
"Counter for dropped pacckets; in bytes.";
}
leaf pps-dropped {
type yang:zero-based-counter64;
config false;
description
"The average dropped packets per second
for the mitigation request since the attack
mitigation is triggered.";
}
}
}
grouping signal-config {
description
Reddy, et al. Expires June 8, 2018 [Page 50]
Internet-Draft DOTS Signal Channel December 2017
"DOTS signal channel session configuration.";
leaf session-id {
type int32;
mandatory true;
description
"An identifier for the DOTS signal channel
session configuration data.";
}
leaf heartbeat-interval {
type int16;
units "seconds";
default 30;
description
"DOTS agents regularly send heartbeats to each other
after mutual authentication in order to keep
the DOTS signal channel open.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf missing-hb-allowed {
type int16;
default 5;
description
"Maximum number of missing heartbeats allowed.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf max-retransmit {
type int16;
default 3;
description
"Maximum number of retransmissions of a
Confirmable message.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
leaf ack-timeout {
type int16;
units "seconds";
default 2;
Reddy, et al. Expires June 8, 2018 [Page 51]
Internet-Draft DOTS Signal Channel December 2017
description
"Initial retransmission timeout value.";
reference
"Section 4.8 of RFC 7552.";
}
leaf ack-random-factor {
type decimal64 {
fraction-digits 2;
}
default 1.5;
description
"Random factor used to influence the timing of
retransmissions.";
reference
"Section 4.8 of RFC 7552.";
}
leaf trigger-mitigation {
type boolean;
default true;
description
"If false, then mitigation is triggered
only when the DOTS server channel session is lost";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel";
}
}
container dots-signal {
description
"Main contaner for DOTS signal message.
A DOTS signal message can be a mitigation messages or
a configuration message.";
choice message-type {
description
"Either a mitigation or a configuration message.";
case mitigation-scope {
description
"Mitigation scope of a mitigation message.";
uses mitigation-scope;
}
case configuration {
description
Reddy, et al. Expires June 8, 2018 [Page 52]
Internet-Draft DOTS Signal Channel December 2017
"Configuration message.";
uses signal-config;
}
}
}
}
<CODE ENDS>
6. Mapping Parameters to CBOR
All parameters in the payload in the DOTS signal channel MUST be
mapped to CBOR types as shown in Table 4 and are given an integer key
to save space. The recipient of the payload MAY reject the
information if it is not suitably mapped.
Reddy, et al. Expires June 8, 2018 [Page 53]
Internet-Draft DOTS Signal Channel December 2017
/----------------------+----------------+--------------------------\
| Parameter name | CBOR key | CBOR major type of value |
+----------------------+----------------+--------------------------+
| mitigation-scope | 1 | 5 (map) |
| scope | 2 | 5 (map) |
| mitigation-id | 3 | 0 (unsigned) |
| target-ip | 4 | 4 (array) |
| target-port-range | 5 | 4 |
| lower-port | 6 | 0 |
| upper-port | 7 | 0 |
| target-protocol | 8 | 4 |
| target-fqdn | 9 | 4 |
| target-uri | 10 | 4 |
| alias-name | 11 | 4 |
| lifetime | 12 | 0 |
| attack-status | 13 | 0 |
| signal-config | 14 | 5 |
| heartbeat-interval | 15 | 0 |
| max-retransmit | 16 | 0 |
| ack-timeout | 17 | 0 |
| ack-random-factor | 18 | 7 |
| MinValue | 19 | 0 |
| MaxValue | 20 | 0 |
| status | 21 | 0 |
| conflict-information | 22 | 5 (map) |
| conflict-status | 23 | 0 |
| conflict-cause | 24 | 0 |
| retry-timer | 25 | 0 |
| bytes-dropped | 26 | 0 |
| bps-dropped | 27 | 0 |
| pkts-dropped | 28 | 0 |
| pps-dropped | 29 | 0 |
| session-id | 30 | 0 |
| trigger-mitigation | 31 | 7 (simple types) |
| missing-hb-allowed | 32 | 0 |
| CurrentValue | 33 | 0 |
| mitigation-start | 34 | 7 (floating-point) |
| target-prefix | 35 | 4 (array) |
| client-identifier | 36 | 2 (byte string) |
| alt-server | 37 | 2 |
| alt-server-record | 38 | 4 |
| addr | 39 | 2 |
| ttl | 40 | 0 |
\----------------------+----------------+--------------------------/
Table 4: CBOR mappings used in DOTS signal channel message
Reddy, et al. Expires June 8, 2018 [Page 54]
Internet-Draft DOTS Signal Channel December 2017
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 machine-in-the-middle and
protocol downgrade. These are general attacks on (D)TLS and not
specific to DOTS over (D)TLS; please 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 encryption of
DOTS using (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, DOTS client MUST verify the entire certification path
per [RFC5280]. The DOTS client additionaly uses [RFC6125] validation
techniques to compare the domain name to the certificate provided.
A key challenge to deploying DOTS is provisioning DOTS clients,
including the distribution of keying material to DOTS clients to make
possible the required mutual authentication of DOTS agents. EST
defines a method of certificate enrollment by which domains operating
DOTS servers may provision DOTS clients with all necessary
cryptographic keying material, including a private key and
certificate with which to authenticate itself. One deployment option
is DOTS clients to behave as EST clients for certificate enrollment
from an EST server provisioned by the mitigation provider. This
document does not specify which EST mechanism the DOTS client uses to
achieve initial enrollment.
Implementations compliant with this profile MUST implement all of the
following items:
o DTLS record replay detection (Section 3.3 of [RFC6347]) to protect
against replay attacks.
o (D)TLS session resumption without server-side state [RFC5077] to
resume session and convey the DOTS signal.
o Raw public keys [RFC7250] or PSK handshake [RFC4279] which reduce
the size of the ServerHello, and can be used by DOTS agents that
cannot obtain certificates (e.g., DOTS clients and DOTS gateways
on private networks).
Reddy, et al. Expires June 8, 2018 [Page 55]
Internet-Draft DOTS Signal Channel December 2017
Implementations compliant with this profile SHOULD implement all of
the following items to reduce the delay required to deliver a DOTS
signal:
o TLS False Start [RFC7918] which reduces round-trips by allowing
the TLS 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.
7.2. (D)TLS 1.3 Considerations
TLS 1.3 [I-D.ietf-tls-tls13] provides critical latency improvements
for connection establishment over TLS 1.2. The DTLS 1.3 protocol
[I-D.ietf-tls-dtls13] is based on the TLS 1.3 protocol and provides
equivalent security guarantees. (D)TLS 1.3 provides two basic
handshake modes of interest to DOTS signal channel:
o Absent packet loss, a full handshake in which the DOTS client is
able to send the DOTS signal message after one round trip and the
DOTS server immediately after receiving the first DOTS signal
message from the client.
o 0-RTT mode in which the DOTS client can authenticate itself and
send DOTS signal message on its first flight, 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 SHOULD
establish a (D)TLS session with the DOTS server during peacetime
and share a PSK. During DDOS attack, the DOTS client can use the
(D)TLS session to convey the DOTS signal message and if there is
no response from the server after multiple re-tries then the DOTS
client can resume the (D)TLS session in 0-RTT mode using PSK. A
simplified TLS 1.3 handshake with 0-RTT DOTS signal message
exchange is shown in Figure 23.
Reddy, et al. Expires June 8, 2018 [Page 56]
Internet-Draft DOTS Signal Channel December 2017
DOTS Client DOTS Server
ClientHello
(Finished)
(0-RTT DOTS signal message)
(end_of_early_data) -------->
ServerHello
{EncryptedExtensions}
{ServerConfiguration}
{Certificate}
{CertificateVerify}
{Finished}
<-------- [DOTS signal message]
{Finished} -------->
[DOTS signal message] <-------> [DOTS signal message]
Figure 23: TLS 1.3 handshake with 0-RTT
7.3. MTU and Fragmentation
To avoid DOTS signal message fragmentation and the consequently
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 length of the URL MUST NOT exceed 256 bytes. If UDP
is used to convey the DOTS signal messages then 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 overhead of 13 octets + authentication overhead
of the negotiated DTLS cipher suite + block padding (Section 4.1.1.1
of [RFC6347]). If the request size exceeds the path MTU then the
DOTS client MUST split the DOTS signal into separate messages, for
example the list of addresses in the 'target-ip' 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 absolutely ensure that there is no IP
fragmentation. If IPv4 support on unusual networks is a
consideration and 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 up to 576 bytes should never need
to be fragmented, thus sending a maximum of 500 bytes of DOTS signal
over a UDP datagram will generally avoid IP fragmentation.
Reddy, et al. Expires June 8, 2018 [Page 57]
Internet-Draft DOTS Signal Channel December 2017
8. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients
(D)TLS based on client certificate can be used for mutual
authentication between DOTS agents. If a DOTS gateway is involved,
DOTS clients and DOTS gateway MUST perform mutual authentication;
only authorized DOTS clients are allowed to send DOTS signals to a
DOTS gateway. DOTS gateway and DOTS server MUST perform mutual
authentication; DOTS server only allows DOTS signals from authorized
DOTS gateway, creating a two-link chain of transitive authentication
between the DOTS client and the DOTS server.
+-----------------------------------------------+
| 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 24: Example of Authentication and Authorization of DOTS Agents
In the example depicted in Figure 24, the DOTS gateway and DOTS
clients within the 'example.com' domain mutually authenticate with
each other. 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 detector to request DDOS mitigation, but does not permit the
user of type 'guest' to request DDOS mitigation.
Reddy, et al. Expires June 8, 2018 [Page 58]
Internet-Draft DOTS Signal Channel December 2017
Also, DOTS gateway and DOTS server 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 24, the DOTS server only allows the DOTS gateway
to request mitigation for 'example.com' domain and not for other
domains.
9. IANA Considerations
This specification registers a service port (Section 9.1), an URI
suffix in the Well-Known URIs registry (Section 9.2), a CoAP response
code (Section 9.3), a YANG module (Section 9.5). It also creates a
registry for mappings to CBOR (Section 9.4).
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.
It is strongly suggested that the port number 4646 is to be assigned.
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 in
the Well-Known URIs registry (https://www.iana.org/assignments/well-
known-uris/well-known-uris.xhtml) as defined by [RFC5785].
URI suffix: dots
Change controller: IETF
Specification document(s): This RFC
Related information: None
9.3. CoAP Response Code
IANA is requested to add the following entry to the "CoAP Response
Codes" sub-registry available at https://www.iana.org/assignments/
core-parameters/core-parameters.xhtml#response-codes:
Reddy, et al. Expires June 8, 2018 [Page 59]
Internet-Draft DOTS Signal Channel December 2017
+------+------------------+-----------+
| Code | Description | Reference |
+------+------------------+-----------+
| 3.00 | Alternate server | [RFCXXXX] |
+------+------------------+-----------+
Table 4: CoAP Response Code
9.4. DOTS Signal Channel CBOR Mappings Registry
The document requests IANA to create a new registry, entitled "DOTS
Signal Channel CBOR Mappings Registry". The structrue of this
registry is provided in Section 9.4.1.
The registry is initially populated with the values in Section 9.4.2.
Values from that registry MUST be assigned via Expert Review
[RFC8126].
9.4.1. Registration Template
Parameter name:
Parameter names (e.g., "target_ip") in the DOTS signal channel.
CBOR Key Value:
Key value for the parameter. The key value MUST be an integer in
the range of 1 to 65536. The key values in the range of 32768 to
65536 are assigned for Vendor-Specific parameters.
CBOR Major Type:
CBOR Major type and optional tag for the claim.
Change Controller:
For Standards Track RFCs, list the "IESG". For others, give the
name of the responsible party. Other details (e.g., postal
address, email address, home page URI) 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.
9.4.2. Initial Registry Contents
o Parameter Name: "mitigation-scope"
o CBOR Key Value: 1
o CBOR Major Type: 5
Reddy, et al. Expires June 8, 2018 [Page 60]
Internet-Draft DOTS Signal Channel December 2017
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "scope"
o CBOR Key Value: 2
o CBOR Major Type: 5
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "mitigation-id"
o CBOR Key Value: 3
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:target-ip
o CBOR Key Value: 4
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-port-range
o CBOR Key Value: 5
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "lower-port"
o CBOR Key Value: 6
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "upper-port"
o CBOR Key Value: 7
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: target-protocol
o CBOR Key Value: 8
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "target-fqdn"
o CBOR Key Value: 9
o CBOR Major Type: 4
Reddy, et al. Expires June 8, 2018 [Page 61]
Internet-Draft DOTS Signal Channel December 2017
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "target-uri"
o CBOR Key Value: 10
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: alias-name
o CBOR Key Value: 11
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: "lifetime"
o CBOR Key Value: 12
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: attack-status
o CBOR Key Value: 13
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: signal-config
o CBOR Key Value: 14
o CBOR Major Type: 5
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: heartbeat-interval
o CBOR Key Value: 15
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: max-retransmit
o CBOR Key Value: 16
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: ack-timeout
o CBOR Key Value: 17
o CBOR Major Type: 0
Reddy, et al. Expires June 8, 2018 [Page 62]
Internet-Draft DOTS Signal Channel December 2017
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: ack-random-factor
o CBOR Key Value: 18
o CBOR Major Type: 7
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: MinValue
o CBOR Key Value: 19
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: MaxValue
o CBOR Key Value: 20
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: status
o CBOR Key Value: 21
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-information
o CBOR Key Value: 22
o CBOR Major Type: 5
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-status
o CBOR Key Value: 23
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: conflict-cause
o CBOR Key Value: 24
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: retry-timer
o CBOR Key Value: 25
o CBOR Major Type: 0
Reddy, et al. Expires June 8, 2018 [Page 63]
Internet-Draft DOTS Signal Channel December 2017
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: bytes-dropped
o CBOR Key Value: 26
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: bps-dropped
o CBOR Key Value: 27
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: pkts-dropped
o CBOR Key Value: 28
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: pps-dropped
o CBOR Key Value: 29
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: session-id
o CBOR Key Value: 30
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: trigger-mitigation
o CBOR Key Value: 31
o CBOR Major Type: 7
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: missing-hb-allowed
o CBOR Key Value: 32
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name: CurrentValue
o CBOR Key Value: 33
o CBOR Major Type: 0
Reddy, et al. Expires June 8, 2018 [Page 64]
Internet-Draft DOTS Signal Channel December 2017
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:mitigation-start
o CBOR Key Value: 34
o CBOR Major Type: 7
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:target-prefix
o CBOR Key Value: 35
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:client-identifier
o CBOR Key Value: 36
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:alt-server
o CBOR Key Value: 37
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:alt-server-record
o CBOR Key Value: 38
o CBOR Major Type: 4
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:addr
o CBOR Key Value: 39
o CBOR Major Type: 2
o Change Controller: IESG
o Specification Document(s): this document
o Parameter Name:ttl
o CBOR Key Value: 40
o CBOR Major Type: 0
o Change Controller: IESG
o Specification Document(s): this document
Reddy, et al. Expires June 8, 2018 [Page 65]
Internet-Draft DOTS Signal Channel December 2017
9.5. DOTS Signal Channel YANG Module
This document requests IANA to register the following URI in the
"IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-dots-signal
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document requests IANA to register the following YANG module in
the "YANG Module Names" registry [RFC7950].
name: ietf-signal
namespace: urn:ietf:params:xml:ns:yang:ietf-dots-signal
prefix: signal
reference: RFC XXXX
10. Implementation Status
[Note to RFC Editor: Please remove this section and reference to
[RFC7942] prior to publication.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
10.1. nttdots
Organization: NTT Communication is developing a DOTS client and
DOTS server software based on DOTS signal channel specified in
this draft. It will be open-sourced.
Reddy, et al. Expires June 8, 2018 [Page 66]
Internet-Draft DOTS Signal Channel December 2017
Description: Early implementation of DOTS protocol. It is aimed to
implement a full DOTS protocol spec in accordance with maturing of
DOTS protocol itself.
Implementation: https://github.com/nttdots/go-dots
Level of maturity: It is a early implementation of DOTS protocol.
Messaging between DOTS clients and DOTS servers has been tested.
Level of maturity will increase in accordance with maturing of
DOTS protocol itself.
Coverage: Capability of DOTS client: sending DOTS messages to the
DOTS server in CoAP over DTLS as dots-signal. Capability of DOTS
server: receiving dots-signal, validating received dots-signal,
starting mitigation by handing over the dots-signal to DDOS
mitigator.
Licensing: It will be open-sourced with BSD 3-clause license.
Implementation experience: It is implemented in Go-lang. Core
specification of signaling is mature to be implemented, however,
finding good libraries(like DTLS, CoAP) is rather difficult.
Contact: Kaname Nishizuka <kaname@nttv6.jp>
11. Security Considerations
Authenticated encryption MUST be used for data confidentiality and
message integrity. The interaction between the DOTS agents requires
Datagram Transport Layer Security (DTLS) and Transport Layer Security
(TLS) with a cipher suite offering confidentiality protection and the
guidance given in [RFC7525] MUST be followed to avoid attacks on
(D)TLS.
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 client SHOULD re-use the (D)TLS session.
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.
In order to prevent leaking internal information outside a client-
domain, DOTS gateways located in the client-domain SHOULD NOT reveal
the identity of internal DOTS clients (client-identifier) unless
explicitly configured to do so.
Special care should be taken in order to ensure that the activation
of the proposed mechanism won't have an impact on the stability of
Reddy, et al. Expires June 8, 2018 [Page 67]
Internet-Draft DOTS Signal Channel December 2017
the network (including connectivity and services delivered over that
network).
Involved functional elements in the cooperation system must establish
exchange instructions and notification over a secure and
authenticated channel. Adequate filters can be enforced to avoid
that nodes outside a trusted domain can inject request such as
deleting filtering rules. Nevertheless, attacks can be initiated
from within the trusted domain if an entity has been corrupted.
Adequate means to monitor trusted nodes should also be enabled.
12. Contributors
The following individuals have contributed to this document:
Mike Geller Cisco Systems, Inc. 3250 Florida 33309 USA Email:
mgeller@cisco.com
Robert Moskowitz HTT Consulting Oak Park, MI 42837 United States
Email: rgm@htt-consult.com
Dan Wing Email: dwing-ietf@fuggles.com
13. Acknowledgements
Thanks to Christian Jacquenet, Roland Dobbins, Roman D. Danyliw,
Michael Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang
Xia, Jon Shallow, Gilbert Clark, and Nesredien Suleiman for the
discussion and comments.
14. References
14.1. Normative References
[I-D.ietf-core-coap-tcp-tls]
Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets",
draft-ietf-core-coap-tcp-tls-10 (work in progress),
October 2017.
[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>.
Reddy, et al. Expires June 8, 2018 [Page 68]
Internet-Draft DOTS Signal Channel December 2017
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
Reddy, et al. Expires June 8, 2018 [Page 69]
Internet-Draft DOTS Signal Channel December 2017
[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>.
[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>.
[RFC8132] van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
FETCH Methods for the Constrained Application Protocol
(CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
<https://www.rfc-editor.org/info/rfc8132>.
14.2. Informative References
[I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
Management Interface", draft-ietf-core-comi-01 (work in
progress), July 2017.
[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-05 (work in progress), August
2017.
Reddy, et al. Expires June 8, 2018 [Page 70]
Internet-Draft DOTS Signal Channel December 2017
[I-D.ietf-dots-architecture]
Mortensen, A., Andreasen, F., Reddy, T.,
christopher_gray3@cable.comcast.com, c., Compton, R., and
N. Teague, "Distributed-Denial-of-Service Open Threat
Signaling (DOTS) Architecture", draft-ietf-dots-
architecture-05 (work in progress), October 2017.
[I-D.ietf-dots-data-channel]
Reddy, T., Boucadair, M., Nishizuka, K., Xia, L., Patil,
P., Mortensen, A., and N. Teague, "Distributed Denial-of-
Service Open Threat Signaling (DOTS) Data Channel", draft-
ietf-dots-data-channel-08 (work in progress), November
2017.
[I-D.ietf-dots-requirements]
Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed
Denial of Service (DDoS) Open Threat Signaling
Requirements", draft-ietf-dots-requirements-07 (work in
progress), October 2017.
[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-09 (work
in progress), November 2017.
[I-D.ietf-netmod-yang-tree-diagrams]
Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
ietf-netmod-yang-tree-diagrams-02 (work in progress),
October 2017.
[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-dtls13-22 (work in progress),
November 2017.
[I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-21 (work in progress),
July 2017.
[proto_numbers]
"IANA, "Protocol Numbers"", 2011,
<http://www.iana.org/assignments/protocol-numbers>.
Reddy, et al. Expires June 8, 2018 [Page 71]
Internet-Draft DOTS Signal Channel December 2017
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[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>.
[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>.
[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>.
[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>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April
2012, <https://www.rfc-editor.org/info/rfc6555>.
Reddy, et al. Expires June 8, 2018 [Page 72]
Internet-Draft DOTS Signal Channel December 2017
[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>.
[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>.
[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>.
[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>.
[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>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[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>.
Reddy, et al. Expires June 8, 2018 [Page 73]
Internet-Draft DOTS Signal Channel December 2017
Authors' Addresses
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
Mohamed Boucadair
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: amortensen@arbor.net
Nik Teague
Verisign, Inc.
United States
Email: nteague@verisign.com
Reddy, et al. Expires June 8, 2018 [Page 74]