Inter-domain Source Address Validation (SAVNET) Architecture
draft-wu-savnet-inter-domain-architecture-05
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| Authors | Jianping Wu , Dan Li , Mingqing(Michael) Huang , Li Chen , Nan Geng , Libin Liu , Lancheng Qin | ||
| Last updated | 2023-10-23 (Latest revision 2023-09-30) | ||
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draft-wu-savnet-inter-domain-architecture-05
Internet Engineering Task Force J. Wu
Internet-Draft D. Li
Intended status: Standards Track Tsinghua University
Expires: 25 April 2024 M. Huang
Huawei
L. Chen
Zhongguancun Laboratory
N. Geng
Huawei
L. Liu
Zhongguancun Laboratory
L. Qin
Tsinghua University
23 October 2023
Inter-domain Source Address Validation (SAVNET) Architecture
draft-wu-savnet-inter-domain-architecture-05
Abstract
This document introduces an inter-domain SAVNET architecture,
providing a comprehensive framework for guiding the design of inter-
domain SAV mechanisms. The proposed architecture empowers ASes to
establish SAV rules by sharing SAV-specific Information between
themselves. During the incremental or partial deployment of SAV-
specific Information, it can rely on general information, such as
routing information from the RIB, to construct the SAV table when
SAV-specific Information for an AS's prefixes is unavailable. Rather
than delving into protocol extensions or implementations, this
document primarily concentrates on proposing SAV-specific and general
information and guiding how to utilize them to generate SAV rules.
It also defines the architectural components and their relations.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on 25 April 2024.
Copyright Notice
Copyright (c) 2023 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Design Goals . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Inter-domain SAVNET Architecture Overview . . . . . . . . . . 6
5. SAV Information Base . . . . . . . . . . . . . . . . . . . . 8
6. SAVNET Communication Channel . . . . . . . . . . . . . . . . 12
6.1. SAV-specific Information Channel . . . . . . . . . . . . 13
6.2. General Information Channel . . . . . . . . . . . . . . . 15
6.3. Management Channel . . . . . . . . . . . . . . . . . . . 15
7. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. SAV at Customer Interfaces . . . . . . . . . . . . . . . 16
7.1.1. Limited Propagation of Prefixes . . . . . . . . . . . 16
7.1.2. Hidden Prefixes . . . . . . . . . . . . . . . . . . . 18
7.1.3. Reflection Attacks . . . . . . . . . . . . . . . . . 19
7.1.4. Direct Attacks . . . . . . . . . . . . . . . . . . . 21
7.2. SAV at Provider/Peer Interfaces . . . . . . . . . . . . . 22
7.2.1. Reflection Attacks . . . . . . . . . . . . . . . . . 22
7.2.2. Direct Attacks . . . . . . . . . . . . . . . . . . . 24
8. Partial/Incremental Deployment Considerations . . . . . . . . 25
9. Convergence Considerations . . . . . . . . . . . . . . . . . 27
10. Manageability Considerations . . . . . . . . . . . . . . . . 27
11. Security Considerations . . . . . . . . . . . . . . . . . . . 28
12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 30
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
14. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
15. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 30
16. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 32
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
17.1. Normative References . . . . . . . . . . . . . . . . . . 32
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17.2. Informative References . . . . . . . . . . . . . . . . . 33
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction
Attacks based on source IP address spoofing, such as reflective DDoS
and flooding attacks, continue to present significant challenges to
Internet security. Mitigating these attacks in inter-domain networks
requires effective source address validation (SAV). While BCP84
[RFC3704] [RFC8704] offers some SAV solutions, such as ACL-based
ingress filtering and uRPF-based mechanisms, existing inter-domain
SAV mechanisms have limitations in terms of validation accuracy and
operational overhead in different scenarios [inter-domain-ps].
To address these issues, the inter-domain SAVNET architecture focuses
on providing a comprehensive framework and guidelines for the design
and implementation of new inter-domain SAV mechanisms. By proposing
the SAV-specific Information which consists of prefixes of ASes and
their corresponding legitimate incoming interfaces and is specialized
for generating SAV rules, the inter-domain SAVNET architecture
empowers ASes to generate accurate SAV rules. Meanwhile, a SAV-
specific communication mechanism is used to define the data structure
or format for communicating the SAV-specific Information, and the
operations and timing for origination, processing, propagation, and
termination of the messages which carry the SAV-specific Information,
to achieve the delivery and automatic update of SAV-specific
Information. Moreover, during the incremental/partial deployment
period of the SAV-specific Information, the inter-domain SAVNET
architecture can leverage the general information, such as the
routing information from the RIB or the {prefix, maximum length,
origin AS} information from the RPKI ROA Objects and the {AS, AS's
Provider} information from the RPKI ASPA Objects, to generate the SAV
rules when the SAV-specific Information is not available. To achieve
this, the inter-domain SAVNET architecture assigns priorities to the
SAV-specific Information and general information and generates the
SAV rules based on priorities of the information in the SAV
Information Base, and the SAV-specific Information has higher
priority compared to the general information.
In addition, by defining the architectural components, relationships,
and the SAV-specific Information and general information used in
inter-domain SAV deployments, this document aims to promote
consistency, interoperability, and collaboration among ASes. This
document primarily describes a high-level architecture for
consolidating SAV-specific Information and general information and
deploying an inter-domain SAV mechanism between ASes. The document
does not specify protocol extensions or implementations. Its purpose
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is to provide a conceptual framework and guidance for the development
of inter-domain SAV mechanisms, allowing implementers to adapt and
implement the architecture based on their specific requirements and
network environments.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Terminology
SAV Rule:
The rule that indicates the validity of a specific source IP
address or source IP prefix.
SAV Table:
The table or data structure that implements the SAV rules and is
used for source address validation on the data plane.
Local Routing Information:
The information is stored in ASBR's local RIB or FIB and can be
used to generate SAV rules in addition to the routing purpose.
SAV-specific Information:
The information is specialized for SAV rule generation, includes
the source prefixes and their legitimate incoming interfaces to
enter an AS, and is communicated between ASes.
General Information:
The information is not specialized for SAV but can be utilized to
generate SAV rules, and is initially utilized for other purposes.
For example, the local routing information is one kind of general
information.
SAV-related Information:
The information is used to be consolidated to generate SAV rules
and can be from SAV-specific Information or general information.
SAV-specific Communication Mechanism:
The mechanism is used to communicate SAV-specific information
between ASes, and it can be a new protocol or an extension to an
existing protocol.
SAV Information Base:
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A table or data structure for storing SAV-related information
collected from SAV-specific Information and general information.
False Positive:
The validation results that the packets with legitimate source
addresses are considered invalid improperly due to inaccurate SAV
rules. False positive may induce improper block problems if
routers block the "invalid" packets.
False Negative:
The validation results that the packets with spoofed source
addresses are considered valid improperly due to inaccurate SAV
rules. False negative may induce improper permit problems if
routers accept the "valid" packets.
3. Design Goals
The inter-domain SAVNET architecture aims to improve SAV accuracy,
facilitate partial deployment with low operational overhead, and
develop a communication approach to communicate SAV-specific
Information between ASes, while achieving efficient convergence and
providing security guarantees to communicated information, which
correspond to the requirements for new inter-domain SAV mechanisms
[inter-domain-ps]. The overall goal can be broken down into the
following aspects:
* G1: The inter-domain SAVNET architecture should learn the real
paths of source prefixes to any destination prefixes or
permissible paths that can cover their real paths, and generate
accurate SAV rules automatically based on the learned information
to avoid false positives and reduce false negatives as much as
possible.
* G2: The inter-domain SAVNET architecture should provide sufficient
protection for the source prefixes of ASes that deploy it, even if
only a portion of the Internet implements the architecture.
* G3: The inter-domain SAVNET architecture should adapt to dynamic
networks and asymmetric routing scenarios automatically.
* G4: The inter-domain SAVNET architecture should communicate SAV-
specific Information between ASes automatically with a
communication approach.
* G5: The inter-domain SAVNET architecture should promptly detect
the network changes and launch the convergence process quickly,
while reducing false positives and false negatives during the
convergence process.
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* G6: The inter-domain SAVNET architecture should provide security
guarantees for the communicated SAV-specific Information.
Other design goals, such as low operational overhead and easy
implementation, are also very important and should be considered in
specific protocols or protocol extensions.
4. Inter-domain SAVNET Architecture Overview
+-----------------------------------------------------------+
| Other ASes |
+-----------------------------------------------------------+
| SAV-specific
| Messages
+-----------------------------------------------------------+
| | |
| +-------------------------------------------------------+ |
| | SAV Agent | | |
| | \/ | |
| | +---------------------+ +--------------------------+ | |
| | | General Information | | SAV-specific Information | | |
| | +---------------------+ +--------------------------+ | |
| | | | | |
| | \/ \/ | |
| | +---------------------------------------------------+ | |
| | | +-----------------------------------------------+ | | |
| | | | SAV Information Base | | | |
| | | +-----------------------------------------------+ | | |
| | | SAV Information Base Manager | | |
| | +---------------------------------------------------+ | |
| | |SAV Rules | |
| +-------------------------------------------------------+ |
| | |
| \/ |
| +-------------------------------------------------------+ |
| | SAV Table | |
| +-------------------------------------------------------+ |
+-----------------------------------------------------------+
Figure 1: The inter-domain SAVNET architecture
The inter-domain SAVNET architecture depicted in Figure 1 collects
SAV-specific information from the SAV-specific messages of other
ASes. The SAV-specific information consists of the prefixes and
their legitimate incoming interfaces of the ASes. As a result, the
SAV-specific information can be used to generate SAV rules and build
an accurate SAV table on each AS directly (G1). When the SAV-
specific information is not available due to incremental/partial
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deployment, the inter-domain SAVNET architecture can also leverage
the general information such as the routing information from the RIB
to generate SAV rules (G2).
The inter-domain SAVNET architecture prioritizes the SAV-specific
information and general information. When both SAV-specific
information and general information are available, it guides to adopt
the SAV-specific information to generate SAV rules. The SAV-specific
information can help generate more accurate SAV rules, the rationale
is that the SAV-specific information is designed specifically for
inter-domain SAV to carry the prefixes and their legitimate incoming
interfaces (G1).
The SAV Agent should launch SAV-specific messages to adapt to the
route changes in a timely manner (G3). The SAV-specific
communication mechanism should handle route changes carefully to
avoid false positives. The reasons for leading to false positives
may include late detection of route changes, delayed message
transmission, or packet losses. During the convergence process of
the SAV-specific communication mechanism, the inter-domain SAVNET
architecture can use the information from RPKI ROA Objects and ASPA
objects to generate SAV rules until the convergence process is
finished, since these information is more stable and can help avoid
false positives, and thus avoiding the impact to the legitimate
traffic (G5). However, the detailed design of the SAV-specific
communication mechanism for dealing with route changes is outside the
scope of this document.
A new SAV-specific information communication mechanism is required to
exchange SAV-specific information between ASes. It should define the
data structure or format for communicating the SAV-specific
information and the operations and timing for originating,
processing, propagating, and terminating the messages which carry the
information (G4).
Besides, regarding the security concerns, the inter-domain SAVNET
architecture shares similar security threats with BGP and can
leverage existing BGP security mechanisms to enhance both session and
content security (G6).
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Moreover, the SAV Information Base (SIB) can store SAV-specific and
general information and is maintained by the SAV Information Base
Manager (SIM). The SIM generates SAV rules based on the SIB and
fills out the SAV table in the data plane. The SIB can be managed by
network operators using various methods such as YANG, Command-Line
Interface (CLI), remote triggered black hole (RTBH), and Flowspec.
The detailed collection methods of the SAV-related information depend
on the deployment and implementation of the inter-domain SAV
mechanisms and are out of scope for this document.
It is worth noting that the interfaces in the SIB are logical AS-
level interfaces and need to be mapped to the physical interfaces of
the AS border routers.
5. SAV Information Base
The SIB is managed by the SAV Information Base Manager, which can
consolidate SAV-related information from different sources. The SAV
information sources of SIB include SAV-specific Information and
general information, which are illustrated below:
* SAV-specific Information is the specifically collected information
for SAV and exactly consists of the prefixes and their legitimate
incoming interfaces to enter ASes.
* General information refers to the information that is not directly
related to SAV but can be utilized to generate SAV rules, and
includes routing information from the RIB or FIB, the {prefix,
maximum length, origin AS} information from the RPKI ROA Objects,
and the {AS, AS's Provider} information from the RPKI ASPA
Objects.
In the future, if an information source is created but is not
initially and specially used for SAV, the information can be
categorized into general information. Therefore, the general
information can be considered as the dual-use information.
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+---------------------------------------------------+----------+
| SAV Information Sources |Priorities|
+---------------------------------------------------+----------+
| SAV-specific Information | 1 |
+---------------------+-----------------------------+----------+
| | RPKI ROA Obj. and ASPA Obj. | 2 |
| +-----------------------------+----------+
| General Information | RIB | 3 |
| +-----------------------------+----------+
| | FIB | 4 |
+---------------------+-----------------------------+----------+
Priority ranking from 1 to 4 represents high to low priority.
Figure 2: Priority ranking for the SAV information sources.
Figure 2 presents the priority ranking for the SAV-specific
Information and general information. Priority ranking from 1 to 4
represents high to low priority. Inter-domain SAVNET architecture
should use the SAV information based on the priorities. Once the
SAV-specific Information for a prefix is available within the SIB,
the inter-domain SAVNET generates SAV rules based on the information
from the SAV-specific Information; otherwise, the inter-domain SAVNET
generates SAV rules based on the general information. In other
words, the inter-domain SAVNET architecture assigns priorities to the
information from different SAV information sources, and always
generates the SAV rules using the information with the highest
priority, as long as the information is available.
The priority ranking recommendation for different SAV information
sources in Figure 2 is based on the accuracy of SAV rules generated
based on the information from the different sources. That is
avoiding improper blocks and minimizing improper permits. SAV-
specific Information has higher priority than the general
information, since the SAV-specific Information is specifically
designed to carry more accurate SAV information which comprises ASes'
prefixes and their legitimate incoming interfaces to an AS. The
general information from RPKI ROA Objects and ASPA Objects, RIB, and
FIB has different priorities, ranking 2, 3, and 4, respectively. The
information from RPKI ROA Object and ASPA Object has higher priority
than the one from RIB and FIB, this is because RPKI ROA Object and
ASPA Object can provide authoritative prefixes and topology
information, which can be used to generate more accurate SAV rules.
The information from RPKI ROA Object and ASPA Object is more stable
and can be used to reduce the risk of improper blocks during the
convergence process of the network. Although the fundamental
information source for RIB and FIB is the same, the RIB consists of
more back path information than the FIB, which can reduce improper
blocks.
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+------------------+
| AS 3(P3) |
+-+/\------+/\+----+
/ \
/ \
/ \
Itf.1 / (C2P) \
+------------------+ \
| AS 4(P4) | \
++/\+---+/\+---+/\++ \
Itf.2 / | Itf.3 \ Itf.4 \
P6[AS 1, AS 2] / | \ \
P2[AS 2] / | \ \
/ (C2P) | \ \
+----------------+ | \ \
| AS 2(P2) | | P1[AS 1] \ P5[AS 5] \ P5[AS 5]
+----------+/\+--+ | P6[AS 1] \ \
\ | NO_EXPORT \ \
P6[AS 1] \ | \ \
P1[AS 1] \ | \ \
NO_EXPORT \ (C2P) | (C2P) (C2P) \ (C2P) \
+----------------+ +----------------+
| AS 1(P1, P6) | | AS 5(P5) |
+----------------+ +----------------+
Both AS 1 and AS 4 deploy the inter-domain SAVNET architecture
and can exchange the SAV-specific information with each other,
while other ASes do not deploy it.
Figure 3: An example of AS topology
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+-----+------+------------------+---------+------------------------+
|Index|Prefix|AS-level Interface|Direction| SAV Information Source |
+-----+------+------------------+---------+------------------------+
| 0 | P1 | Itf.2 |Customer |SAV-specific Information|
+-----+------+------------------+---------+------------------------+
| 1 | P1 | Itf.3 |Customer | General Information |
+-----+------+------------------+---------+------------------------+
| 2 | P2 | Itf.2 |Customer | General Information |
+-----+------+------------------+---------+------------------------+
| 3 | P3 | Itf.1 |Provider | General Information |
+-----+------+------------------+---------+------------------------+
| 4 | P5 | Itf.1 |Provider | General Information |
+-----+------+------------------+---------+------------------------+
| 5 | P5 | Itf.4 |Customer | General Information |
+-----+------+------------------+---------+------------------------+
| 6 | P6 | Itf.2 |Customer | General Information |
| | | | |SAV-specific Information|
+-----+------+------------------+---------+------------------------+
| 7 | P6 | Itf.3 |Customer | General Information |
+-----+------+------------------+---------+------------------------+
Figure 4: An example for the SAV information base in AS 4
We use the examples shown in Figure 3 and Figure 4 to introduce SIB
and illustrate how to generate SAV rules based on the SIB. Figure 3
shows an example of AS topology and Figure 4 depicts an example of
the SIB established in AS 4. As shown in Figure 3, AS 4 has four AS-
level interfaces, each connected to a different AS. Specifically,
Itf.1 is connected to AS 3, Itf.2 to AS 2, Itf.3 to AS 1, and Itf.4
to AS 5. The arrows in the figure represent the commercial
relationships between ASes. AS 3 is the provider of AS 4 and AS 5,
while AS 4 is the provider of AS 1, AS 2, and AS 5, and AS 2 is the
provider of AS 1. Assuming prefixes P1, P2, P3, P4, P5, and P6 are
all the prefixes in the network.
Each row of the SIB contains an index, prefix, AS-level incoming
interface for the prefix, incoming direction, and the corresponding
sources of this information. The incoming direction consists of
customer, provider, and peer. For example, in Figure 4, the row with
index 0 indicates prefix P1's valid incoming interface is Itf.2, the
ingress direction of P1 is AS 4's customer AS (AS 2), and this
information is from the RIB. Note that the same SAV-related
information may have multiple sources and the SIB records them all,
such as the row indexed 6 in Figure 4. Moreover, the SIB should be
carefully implemented in the specific protocol or protocol extensions
to avoid becoming a heavy burden of the router, and the similar
optimization approaches used for the RIB may be applied.
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Recall that the inter-domain SAVNET architecture generates SAV rules
based on the SAV-related information in the SIB and their priorities.
In addition, in the case of an AS's provider/peer interfaces where
loose SAV rules are applicable, the inter-domain SAVNET architecture
recommends to use blocklist at such interfaces to only block the
prefixes that are sure not to come at these interfaces, while in the
case of an AS's customer interfaces that necessitate stricter SAV
rules, the inter-domain SAVNET architecture recommends to use
allowlist to only permit the prefixes that are allowed to come at
these interfaces.
Based on the above rules, take the SIB in Figure 4 as an example to
illustrate how the inter-domain SAVNET architecture generates the SAV
table to perform SAV in the data plane. AS 4 can conduct SAV at its
interfaces as follows: SAV at the interface Itf.1 blocks P1, P2, and
P6 according to the rows indexed 0, 2, and 6 in the SIB, SAV at the
interface Itf.2 permits P1, P2, and P6 according to the rows indexed
0, 2, and 6 in the SIB, SAV at the interface Itf.3 does not permit
any prefixes according to the row indexed 0, 1, 6, and 7 in the SIB,
and SAV at the interface Itf.4 permits P5 according to the row
indexed 6 in the SIB.
6. SAVNET Communication Channel
+------+
| | SAV-specific Information Channel +-----------------------------+
| |<===================================| SAV Agent in AS 2 |
| | +-----------------------------+
| |
| | General Information Channel +-----------------------------+
| |<-----------------------------------| RPKI ROA Obj. and ASPA Obj. |
| | +-----------------------------+
| SAV |
|Agent | General Information Channel +-----------------------------+
| in |<-----------------------------------| RIB |
| AS 1 | +-----------------------------+
| |
| | General Information Channel +-----------------------------+
| |<-----------------------------------| FIB |
| | +-----------------------------+
| |
| | Management Channel +-----------------------------+
| |<-----------------------------------| Network Operators |
| | +-----------------------------+
+------+
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Figure 5: The management channel and information channel for
collecting SAV- related information from different SAV
information sources
The SAV-specific Information relies on the communication between SAV
Agents within ASes and the general information can be from multiple
sources, such as RPKI ROA objects and ASPA objects, RIB, and FIB.
Therefore, as illustrated in Figure 5, the SAV Agent needs to receive
the SAV-related information from these SAV information sources.
Besides, the SAV Agent also needs to accept the configurations from
network operators for the management operations. The connections for
collecting these types of information are abstracted as SAVNET
communication channel, which includes SAV-specific information
channel, general information channel, and management channel.
6.1. SAV-specific Information Channel
+----------------------+ +----------------------+
| AS 1 (P1) | SAV-specific Messages | AS 2 (P2) |
| +-----------------+ | (P1, Itf.2) Itf.2 | +-----------------+ |
| | SAV |--|--------------------------|->| SAV | |
| | Agent |<-|--------------------------|--| Agent | |
| +-----------------+ | Itf.1 (P2, Itf.1) | +-----------------+ |
+----------------------+ SAV-specific Messages +----------------------+
Figure 6: An example for Exchanging SAV-specific Information with
SAV-specific Messages between AS1 and AS 2
The SAV-specific information channel is the abstraction of the
connections between ASes for communicating SAV-specific information.
Each AS pair which deploys inter-domain SAVNET architecture has a
SAV-specific information channel between. An AS can have multiple
SAV-specific information channels with others. Within the SAV-
specific information channel, the SAV-specific message is used to
carry the SAV-specific information.
Figure 6 uses an example for exchanging SAV-specific information with
SAV-specific messages between AS1 and AS 2. The SAV-specific
Information is the information consisting of source prefixes and
their legitimate incoming interfaces entering an AS, and the
legitimate incoming interfaces are the interfaces where the packets
whose source addresses are encompassed in the source prefixes come.
Therefore, the SAV-specific Information can be expressed as <Prefix,
Interface> pairs, e.g., (P1, Itf.2) and (P2, Itf.1) in Figure 6. It
is noted that the same prefix may have different legitimate incoming
interfaces for an AS, since the dataplane packets with the source
addresses encompassed in the source prefixes may have different
destination addresses.
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The SAV-specific Information can be exchanged between ASes by the
SAV-specific messages. As shown in Figure 6, the SAV-specific
messages are used to propagate or originate the SAV-specific
Information between ASes by the SAV Agent. For an AS which initiates
its own SAV-specific messages, the SAV Agent within the AS can obtain
the next hop of the corresponding prefixes based on the local RIB and
use SAV-specific messages to carry the AS's prefixes to the next hops
for the corresponding destinations. This is achieved by setting the
SAV-specific messages' destination addresses as the destination
addresses in the local RIB. When the SAV Agents of other ASes
receive the SAV-specific messages, they parse the messages to obtain
the carried source prefixes, as well as the corresponding legitimate
incoming interfaces by checking the interfaces which the SAV-specific
messages arrive at. Meanwhile, the SAV Agents also check the
destination addresses of the SAV-specific messages, if their
destination addresses are ASes themselves, they will terminate the
message; otherwise, they will forward them based on the local RIB.
Following this, the SAV-specific messages can propagate the SAV-
specific Information between ASes.
Moreover, if SAV-specific messages are used to exchange SAV-specific
Information between ASes, a new SAV-specific communication mechanism
would need to be developed to communicate the SAV-specific messages.
The SAV-specific communication mechanism needs to define the data
structure or format to communicate the SAV-specific messages and the
operations and timing for originating, processing, propagating, and
terminating the messages. If an extension to an existing protocol is
used to exchange SAV-specific Information, the corresponding existing
protocol should not be affected. The SAV Agent is the entity to
support the SAV-specific communication mechanism. By parsing the
SAV-specific messages, it obtains the ASN, the prefixes, the AS-level
interfaces to receive the messages, and their incoming AS direction
for maintaining the SIB. It is important to note that the SAV Agent
within an AS has the capability to establish connections with
multiple SAV Agents within different ASes, relying on either manual
configurations by operators or an automatic mechanism.
The need for a SAV-specific communication mechanism arises from the
facts that the SAV-specific Information needs to be obtained and
communicated between ASes. Different from the general information
such as routing information from the RIB, there are no existing
mechanisms which can support the perception and communication of SAV-
specific Information between ASes. Hence, a SAV-specific
communication mechanism is needed to provide a medium and set of
rules to establish communication between different ASes for the
exchange of SAV-specific Information.
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Furthermore, an AS which initiates an SAV-specific message needs to
assemble its source prefixes into the SAV-specific messages. In
order to obtain all the source prefixes of an AS, the inter-domain
SAVNET architecture can communicate with the intra-domain SAVNET
architecture [intra-domain-arch] to obtain all the prefixes belonging
to the AS.
Additionally, the preferred AS paths of an AS may change over time
due to route changes or network failures. The SAV Agent should
launch SAV-specific messages to adapt to the route changes in a
timely manner. The SAV-specific communication mechanism should
handle route changes carefully to avoid false positives. The reasons
for leading to false positives may include late detection of route
changes, delayed message transmission, or packet losses. However,
the detailed design of the SAV-specific communication mechanism for
dealing with route changes is outside the scope of this document.
6.2. General Information Channel
The general information channel is the abstraction of the connections
between ASes for communicating routing information or the connections
between AS and RPKI cache servers for obtaining {prefix, maximum
length, origin AS} and {AS, AS's Provider} information. The
communication of the general information within the general
information channel can rely on existing protocols, such as BGP and
RTR [RFC8210].
6.3. Management Channel
The management channel is the abstraction of the connections between
SAV Agent and network operators. The primary purpose of the
management channel is to deliver manual configurations of network
operators. Examples of the management configurations include, but
are not limited to:
* SAV configurations using YANG, CLI, RTBH, or Flowspec.
* SAVNET operation and management.
* Inter-domain SAVNET provisioning.
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Note that the configuration information can be delivered at any time
and requires reliable delivery for the management channel
implementation. Additionally, the management channel can carry
telemetry information, such as metrics pertaining to forwarding
performance, the count of spoofing packets and discarded packets,
provided that the inter-domain SAVNET has access to such data. It
can include information regarding the prefixes associated with the
spoofing traffic, as observed until the most recent time.
7. Use Cases
This section utilizes the sample use cases to showcase that the
inter-domain SAVNET architecture can improve the validation accuracy
in the scenarios of limited propagation of prefixes, hidden prefixes,
reflection attacks, and direct attacks, compared to existing SAV
mechanisms, which are also utilized for the gap analysis of existing
inter-domain SAV mechanisms in [inter-domain-ps]. In the following,
these use cases are discussed for SAV at customer interfaces and SAV
at provider/peer interfaces, respectively.
7.1. SAV at Customer Interfaces
In order to prevent the source address spoofing, operators can enable
ACL-based ingress filtering, source-based RTBH filtering, and/or
uRPF-based mechanisms at customer interfaces, namely Strict uRPF, FP-
uRPF, VRF uRPF, or EFP-uRPF [manrs] [nist]. However, as analyzed in
[inter-domain-ps], uRPF-based mechanisms may lead to false positives
in two inter-domain scenarios: limited propagation of prefixes and
hidden prefixes, or may lead to false negatives in the scenarios of
source address spoofing attacks within a customer cone, while ACL-
based ingress filtering and source-based RTBH filtering need to
update SAV rules in a timely manner and lead to high operational
overhead. The following showcases that the inter-domain SAVNET
architecture can avoid false positives and false negatives in these
scenarios.
7.1.1. Limited Propagation of Prefixes
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+----------------+
| AS 3(P3) |
+-+/\----+/\+----+
/ \
/ \
/ \
/ (C2P) \
+----------------+ \
| AS 4(P4) | \
++/\+--+/\+--+/\++ \
/ | \ \
P2[AS 2] / | \ \
/ | \ \
/ (C2P) | \ P5[AS 5] \ P5[AS 5]
+----------------+ | \ \
| AS 2(P2) | | P1[AS 1] \ \
+----------+/\+--+ | P6[AS 1] \ \
\ | NO_EXPORT \ \
P1[AS 1] \ | \ \
NO_EXPORT \ | \ \
\ (C2P) | (C2P/P2P)(C2P) \ (C2P) \
+----------------+ +----------------+
| AS 1(P1, P6) | | AS 5(P5) |
+----------------+ +----------------+
Figure 7: Limited propagation of prefixes caused by NO_EXPORT.
Figure 7 presents a scenario where the limited propagation of
prefixes occurs due to the NO_EXPORT community attribute. In this
scenario, AS 1 is a customer of AS 2, AS 2 is a customer of AS 4, AS
4 is a customer of AS 3, and AS 5 is a customer of both AS 3 and AS
4. The relationship between AS 1 and AS 4 can be either customer-to-
provider (C2P) or peer-to-peer (P2P). AS 1 advertises prefixes P1 to
AS 2 and adds the NO_EXPORT community attribute to the BGP
advertisement sent to AS 2, preventing AS 2 from further propagating
the route for prefix P1 to AS 4. Similarly, AS 1 adds the NO_EXPORT
community attribute to the BGP advertisement sent to AS 4, resulting
in AS 4 not propagating the route for prefix P6 to AS 3.
Consequently, AS 4 only learns the route for prefix P1 from AS 1 in
this scenario. Suppose AS 1 and AS 4 have deployed inter-domain SAV
while other ASes have not, and AS 4 has deployed EFP-uRPF at its
customer interfaces.
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In this scenario, existing uRPF-based SAV mechanisms would block the
traffic with P1 as source addresses improperly, and thus suffer from
the problem of false positives [inter-domain-ps]. If the inter-
domain SAVNET architecture is deployed, AS 1 can communicate the SAV-
specific information to AS 4 and AS 4 will be aware that the traffic
with P1 as source addresses can arrive at the interfaces facing AS 1
and AS 2. As a result, the false positive problem can be avoided.
7.1.2. Hidden Prefixes
+----------------+
Anycast Server+-+ AS 3(P3) |
+-+/\----+/\+----+
/ \
P3[AS 3] / \ P3[AS 3]
/ \
/ (C2P) \
+----------------+ \
| AS 4(P4) | \
++/\+--+/\+--+/\++ \
P6[AS 1, AS 2] / | \ \
P2[AS 2] / | \ \
/ | \ \
/ (C2P) | \ P5[AS 5] \ P5[AS 5]
+----------------+ | \ \
User+-+ AS 2(P2) | | P1[AS 1] \ \
+----------+/\+--+ | P6[AS 1] \ \
P6[AS 1] \ | NO_EXPORT \ \
P1[AS 1] \ | \ \
NO_EXPORT \ | \ \
\ (C2P) | (C2P) (C2P) \ (C2P) \
+----------------+ +----------------+
Edge Server+-+ AS 1(P1, P6) | | AS 5(P5) |
+----------------+ +----------------+
P3 is the anycast prefix and is only advertised by AS 3 through BGP.
Figure 8: A Direct Server Return (DSR) scenario.
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Figure 8 illustrates a direct server return (DSR) scenario where the
anycast IP prefix P3 is only advertised by AS 3 through BGP. In this
example, AS 3 is the provider of AS 4 and AS 5, AS 4 is the provider
of AS 1, AS 2, and AS 5, and AS 2 is the provider of AS 1. AS 1 and
AS 4 have deployed inter-domain SAV, while other ASes have not. When
users in AS 2 send requests to the anycast destination IP, the
forwarding path is AS 2->AS 4->AS 3. The anycast servers in AS 3
receive the requests and tunnel them to the edge servers in AS 1.
Finally, the edge servers send the content to the users with source
addresses in prefix P3. The reverse forwarding path is AS 1->AS
4->AS 2.
In this scenario, existing uRPF-based mechanisms will improperly
block the legitimate response packets from AS 1 at the customer
interface of AS 4 facing AS 1 [inter-domain-ps]. In contrast, if the
inter-domain SAVNET architecture is deployed, AS 1 can communicate
the SAV-specific information to AS 4 and AS 4 will be aware that the
traffic with P3 as source addresses can arrive at the interfaces
facing AS 1 and AS 3. As a result, the legitimate response packets
with P3 as source addresses from AS 1 can be allowed and the false
positive problem can be avoided.
7.1.3. Reflection Attacks
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+----------------+
| AS 3(P3) |
+-+/\----+/\+----+
/ \
/ \
/ \
/ (C2P) \
+----------------+ \
| AS 4(P4) | \
++/\+--+/\+--+/\++ \
P6[AS 1, AS 2] / | \ \
P2[AS 2] / | \ \
/ | \ \
/ (C2P) | \ P5[AS 5] \ P5[AS 5]
+----------------+ | \ \
Attacker(P1')-+ AS 2(P2) | | P1[AS 1] \ \
+----------+/\+--+ | P6[AS 1] \ \
P6[AS 1] \ | NO_EXPORT \ \
P1[AS 1] \ | \ \
NO_EXPORT \ | \ \
\ (C2P) | (C2P) (C2P) \ (C2P) \
+----------------+ +----------------+
Victim+-+ AS 1(P1, P6) | Server+-+ AS 5(P5) |
+----------------+ +----------------+
P1' is the spoofed source prefix P1 by the attacker which is inside of
AS 2 or connected to AS 2 through other ASes.
Figure 9: A scenario of reflection attacks by source address
spoofing within a customer cone.
Figure 9 depicts the scenario of reflection attacks by source address
spoofing within a customer cone. The reflection attack by source
address spoofing takes place within AS 4's customer cone, where the
attacker spoofs the victim's IP address (P1) and sends requests to
servers' IP address (P5) that are designed to respond to such
requests. As a result, the server sends overwhelming responses back
to the victim, thereby exhausting its network resources. The arrows
in Figure 9 illustrate the commercial relationships between ASes. AS
3 serves as the provider for AS 4 and AS 5, while AS 4 acts as the
provider for AS 1, AS 2, and AS 5. Additionally, AS 2 is the
provider for AS 1. Suppose AS 1 and AS 4 have deployed inter-domain
SAV, while the other ASes have not.
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In this scenario, EFP-uRPF with algorithm A/B will improperly permit
the spoofing attacks originating from AS 2 [inter-domain-ps]. If the
inter-domain SAVNET architecture is deployed, AS 1 can communicate
the SAV-specific information to AS 4 and AS 4 will be aware that the
traffic with P1 as source addresses can only arrive at the interface
facing AS 1. Therefore, at the interface of AS 4 facing AS 2, the
spoofing traffic can be blocked.
7.1.4. Direct Attacks
+----------------+
| AS 3(P3) |
+-+/\----+/\+----+
/ \
/ \
/ \
/ (C2P) \
+----------------+ \
| AS 4(P4) | \
++/\+--+/\+--+/\++ \
P6[AS 1, AS 2] / | \ \
P2[AS 2] / | \ \
/ | \ \
/ (C2P) | \ P5[AS 5] \ P5[AS 5]
+----------------+ | \ \
Attacker(P5')-+ AS 2(P2) | | P1[AS 1] \ \
+----------+/\+--+ | P6[AS 1] \ \
P6[AS 1] \ | NO_EXPORT \ \
P1[AS 1] \ | \ \
NO_EXPORT \ | \ \
\ (C2P) | (C2P) (C2P) \ (C2P) \
+----------------+ +----------------+
Victim+-+ AS 1(P1, P6) | | AS 5(P5) |
+----------------+ +----------------+
P5' is the spoofed source prefix P5 by the attacker which is inside of
AS 2 or connected to AS 2 through other ASes.
Figure 10: A scenario of the direct attacks by source address
spoofing within a customer cone.
Figure 10 portrays a scenario of direct attacks by source address
spoofing within a customer cone and is used to analyze the gaps of
uRPF-based mechanisms below. The direct attack by source address
spoofing takes place within AS 4's customer cone, where the attacker
spoofs a source address (P5) and directly targets the victim's IP
address (P1), overwhelming its network resources. The arrows in
Figure 10 illustrate the commercial relationships between ASes. AS 3
serves as the provider for AS 4 and AS 5, while AS 4 acts as the
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provider for AS 1, AS 2, and AS 5. Additionally, AS 2 is the
provider for AS 1. Suppose AS 1 and AS 4 have deployed inter-domain
SAV, while the other ASes have not.
In this scenario, EFP-uRPF with algorithm A/B will improperly permit
the spoofing attacks [inter-domain-ps]. If the inter-domain SAVNET
architecture is deployed, AS 5 can communicate the SAV-specific
information to AS 4 and AS 4 will be aware that the traffic with P5
as source addresses can arrive at the interface facing AS 3 and AS 5.
Therefore, at the interface of AS 4 facing AS 2, the spoofing traffic
can be blocked.
7.2. SAV at Provider/Peer Interfaces
In order to prevent packets with spoofed source addresses from the
provider/peer AS, ACL-based ingress filtering, Loose uRPF, and/or
source-based RTBH filtering can be deployed [nist]. [inter-domain-ps]
exposes the limitations of ACL-based ingress filtering, source-based
RTBH filtering, and Loose uRPF for SAV at provider/peer interfaces in
scenarios of source address spoofing attacks from provider/peer AS.
The source address spoofing attacks from provider/peer AS include
reflection attacks from provider/peer AS and direct attacks from
provider/peer AS. The following showcases that the inter-domain
SAVNET architecture can avoid false negatives in these scenarios.
7.2.1. Reflection Attacks
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+----------------+
Attacker(P1')+-+ AS 3(P3) |
+-+/\----+/\+----+
/ \
/ \
/ \
/ (C2P/P2P) \
+----------------+ \
| AS 4(P4) | \
++/\+--+/\+--+/\++ \
P6[AS 1, AS 2] / | \ \
P2[AS 2] / | \ \
/ | \ \
/ (C2P) | \ P5[AS 5] \ P5[AS 5]
+----------------+ | \ \
Server+-+ AS 2(P2) | | P1[AS 1] \ \
+----------+/\+--+ | P6[AS 1] \ \
P6[AS 1] \ | NO_EXPORT \ \
P1[AS 1] \ | \ \
NO_EXPORT \ | \ \
\ (C2P) | (C2P) (C2P) \ (C2P) \
+----------------+ +----------------+
Victim+-+ AS 1(P1, P6) | | AS 5(P5) |
+----------------+ +----------------+
P1' is the spoofed source prefix P1 by the attacker which is inside of
AS 3 or connected to AS 3 through other ASes.
Figure 11: A scenario of reflection attacks by source address
spoofing from provider/peer AS.
Figure 11 depicts the scenario of reflection attacks by source
address spoofing from provider/peer AS. In this case, the attacker
spoofs the victim's IP address (P1) and sends requests to servers' IP
address (P2) that respond to such requests. The servers then send
overwhelming responses back to the victim, exhausting its network
resources. The arrows in Figure 11 represent the commercial
relationships between ASes. AS 3 acts as the provider or lateral
peer of AS 4 and the provider for AS 5, while AS 4 serves as the
provider for AS 1, AS 2, and AS 5. Additionally, AS 2 is the
provider for AS 1. Suppose AS 1 and AS 4 have deployed inter-domain
SAV, while the other ASes have not.
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Both ACL-based ingress filtering and source-based RTBH filtering will
induce additional operational overhead, and Loose uRPF may improperly
permit spoofed packets [inter-domain-ps]. If the inter-domain SAVNET
architecture is deployed, AS 1 can communicate the SAV-specific
information to AS 4 and AS 4 will be aware that the traffic with P1
as source addresses can arrive at the interface facing AS 1 and AS 2.
Therefore, at the interface of AS 4 facing AS 3, the spoofing traffic
can be blocked.
7.2.2. Direct Attacks
+----------------+
Attacker(P2')+-+ AS 3(P3) |
+-+/\----+/\+----+
/ \
/ \
/ \
/ (C2P/P2P) \
+----------------+ \
| AS 4(P4) | \
++/\+--+/\+--+/\++ \
P6[AS 1, AS 2] / | \ \
P2[AS 2] / | \ \
/ | \ \
/ (C2P) | \ P5[AS 5] \ P5[AS 5]
+----------------+ | \ \
| AS 2(P2) | | P1[AS 1] \ \
+----------+/\+--+ | P6[AS 1] \ \
P6[AS 1] \ | NO_EXPORT \ \
P1[AS 1] \ | \ \
NO_EXPORT \ | \ \
\ (C2P) | (C2P) (C2P) \ (C2P) \
+----------------+ +----------------+
Victim+-+ AS 1(P1, P6) | | AS 5(P5) |
+----------------+ +----------------+
P2' is the spoofed source prefix P2 by the attacker which is inside of
AS 3 or connected to AS 3 through other ASes.
Figure 12: A scenario of direct attacks by source address
spoofing from provider/peer AS.
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Figure 12 showcases a scenario of direct attack by source address
spoofing from provider/peer AS. In this case, the attacker spoofs
another source address (P2) and directly targets the victim's IP
address (P1), overwhelming its network resources. The arrows in
Figure 12 represent the commercial relationships between ASes. AS 3
acts as the provider or lateral peer of AS 4 and the provider for AS
5, while AS 4 serves as the provider for AS 1, AS 2, and AS 5.
Additionally, AS 2 is the provider for AS 1. Suppose AS 1 and AS 4
have deployed inter-domain SAV, while the other ASes have not.
Also, in this scenario, Both ACL-based ingress filtering and source-
based RTBH filtering will induce additional operational overhead, and
Loose uRPF may improperly permit spoofed packets [inter-domain-ps].
If the inter-domain SAVNET architecture is deployed, AS 2 can
communicate the SAV-specific information to AS 4 and AS 4 will be
aware that the traffic with P2 as source addresses can only arrive at
the interface facing AS 2. Therefore, at the interface of AS 4
facing AS 3, the spoofing traffic can be blocked.
8. Partial/Incremental Deployment Considerations
The inter-domain SAVNET architecture MUST ensure support for partial/
incremental deployment as it is not feasible to deploy it
simultaneously in all ASes. The partial/incremental deployment of
the inter-domain SAVNET architecture consists of different aspects,
which include the partial/incremental deployment of the architecture
and the partial/incremental deployment of the information sources.
Within the architecture, the general information like the prefixes
and topological information from RPKI ROA Objects and ASPA Objects
and the routing information from the RIB can be obtained locally when
the corresponding sources are available. Even when both SAV-specific
Information and the information from RPKI ROA Objects and ASPA
Objects are not available, the routing information from the RIB can
be used to generate SAV rules.
Furthermore, it is not mandatory for all ASes to deploy SAV Agents
for SAV-specific Information. Instead, a SAV Agent should be able to
effortlessly establish a logical neighboring relationship with
another AS that has deployed a SAV Agent. The connections for
communicating SAV-specific Information can be achieved by manual
configurations set by operators or an automatic neighbor discovery
mechanism. This flexibility enables the architecture to accommodate
varying degrees of deployment, promoting interoperability and
collaboration among participating ASes. During the partial/
incremental deployment of SAV Agent, the SAV-specific Information for
the ASes which do not deploy SAV Agent can not be obtained. To
protect the prefixes of these ASes, inter-domain SAVNET architecture
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can use the SAV-related information from the general information in
the SIB to generate SAV rules. At least, the routing information
from the RIB can be always available in the SIB.
As more ASes adopt the inter-domain SAVNET architecture, the
"deployed area" expands, thereby increasing the collective defense
capability against source address spoofing. Furthermore, if multiple
"deployed areas" can be logically interconnected across "non-deployed
areas", these interconnected "deployed areas" can form a logical
alliance, providing enhanced protection against address spoofing.
Especially, along with more ASes deploy SAV Agent and support the
communication of SAV-specific Information, the generated SAV rules of
the inter-domain SAVNET architecture to protect these ASes will
become more accurate, as well as enhancing the protection capability
against source address spoofing for the inter-domain SAVNET
architecture.
In addition, releasing the SAV functions of the inter-domain SAVNET
architecture incrementally is one potential way to reduce the
deployment risks and can be considered in its deployment by network
operators:
* First, the inter-domain SAVNET can only do the measurement in the
data plane and do not take any other actions. Based on the
measurement data, the operators can evaluate the effect of the
inter-domain SAVNET on the legitimate traffic, including
validation accuracy and forwarding performance, as well as the
operational overhead.
* Second, the inter-domain SAVNET can open the function to limit the
rate of the traffic that is justified as spoofing traffic. The
operators can further evaluate the effect of the inter-domain
SAVNET on the legitimate traffic and spoofing traffic, such as
limiting the rate of all the spoofing traffic without hurting the
legitimate traffic.
* Third, when the validation accuracy, forwarding performance, and
operational overhead have been verified on a large scale by the
live network, the inter-domain SAVNET can open the function to
directly block the spoofing traffic that is justified by the SAV
table in the data plane.
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9. Convergence Considerations
Convergence issues SHOULD be carefully considered in inter-domain SAV
mechanisms due to the dynamic nature of the Internet. Internet
routes undergo continuous changes, and SAV rules MUST proactively
adapt to these changes, such as prefix and topology changes, in order
to prevent false positives and reduce false negatives. To
effectively track these changes, the SIM should promptly collect SAV-
related information from various SAV information sources and
consolidate them in a timely manner.
In particular, it is essential for the SAV Agents to proactively
communicate the changes of the SAV-specific Information between ASes
and adapt to route changes promptly. However, during the routing
convergence process, the traffic paths of the source prefixes can
undergo rapid changes within a short period. The changes of the SAV-
specific Information may not be communicated in time between ASes to
update SAV rules, false positives or false negatives may happen.
Such inaccurate validation is caused by the delays in communicating
SAV-specific Information between ASes, which occur due to the factors
like packet losses, unpredictable network latencies, or message
processing latencies. The design of the SAV-specific communication
mechanism should consider these issues to reduce the inaccurate
validation.
Besides, for the inter-domain SAVNET architecture, the potential ways
to deal with the inaccurate validation issues during the convergence
of the SAV-specific communication mechanism is to consider using the
information from RPKI ROA Objects and ASPA objects to generate SAV
rules until the convergence process of the SAV-specific communication
mechanism is finished, since these information is more stable and can
help avoid false positives, and thus avoiding the impact to the
legitimate traffic.
10. Manageability Considerations
It is crucial to consider the operations and management aspects of
SAV information sources, the SAV-specific communication mechanism,
SIB, SIM, and SAV table in the inter-domain SAVNET architecture. The
following guidelines should be followed for their effective
management:
First, management interoperability should be supported across devices
from different vendors or different releases of the same product,
based on a unified data model such as YANG [RFC6020]. This is
essential because the Internet comprises devices from various vendors
and different product releases that coexist simultaneously.
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Second, scalable operation and management methods such as NETCONF
[RFC6241] and syslog protocol [RFC5424] should be supported. This is
important as an AS may have hundreds or thousands of border routers
that require efficient operation and management.
Third, management operations, including default initial
configuration, alarm and exception reporting, logging, performance
monitoring and reporting for the control plane and data plane, as
well as debugging, should be designed and implemented in the
protocols or protocol extensions. These operations can be performed
either locally or remotely, based on the operational requirements.
By adhering to these rules, the management of SAV information sources
and related components can be effectively carried out, ensuring
interoperability, scalability, and efficient operations and
management of the inter-domain SAVNET architecture.
11. Security Considerations
In the inter-domain SAVNET architecture, the SAV Agent plays a
crucial role in generating and disseminating SAV-specific Messages
across different ASes. To safeguard against the potential risks
posed by a malicious AS generating incorrect or forged SAV-specific
Messages, it is important for the SAV Agents to employ security
authentication measures for each received SAV-specific Message. The
majour security threats faced by inter-domain SAVNET can be
categorized into two aspects: session security and content security.
Session security pertains to verifying the identities of both parties
involved in a session and ensuring the integrity of the session
content. Content security, on the other hand, focuses on verifying
the authenticity and reliability of the session content, thereby
enabling the identification of forged SAV-specific Messages.
The threats to session security include:
* Session identity impersonation: This occurs when a malicious
router deceitfully poses as a legitimate peer router to establish
a session with the targeted router. By impersonating another
router, the malicious entity can gain unauthorized access and
potentially manipulate or disrupt the communication between the
legitimate routers.
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* Session integrity destruction: In this scenario, a malicious
intermediate router situated between two peering routers
intentionally tampers with or destroys the content of the relayed
SAV-specific Message. By interfering with the integrity of the
session content, the attacker can disrupt the reliable
transmission of information, potentially leading to
miscommunication or inaccurate SAV-related data being propagated.
The threats to content security include:
* Message alteration: A malicious router has the ability to
manipulate or forge any portion of a SAV-specific Message. For
example, the attacker may employ techniques such as using a
spoofed Autonomous System Number (ASN) or modifying the AS Path
information within the message. By tampering with the content,
the attacker can potentially introduce inaccuracies or deceive the
receiving ASes, compromising the integrity and reliability of the
SAV-related information.
* Message injection: A malicious router injects a seemingly
"legitimate" SAV-specific Message into the communication stream
and directs it to the corresponding next-hop AS. This type of
attack can be likened to a replay attack, where the attacker
attempts to retransmit previously captured or fabricated messages
to manipulate the behavior or decisions of the receiving ASes.
The injected message may contain malicious instructions or false
information, leading to incorrect SAV rule generation or improper
validation.
* Path deviation: A malicious router intentionally diverts a SAV-
specific Message to an incorrect next-hop AS, contrary to the
expected path defined by the AS Path. By deviating from the
intended routing path, the attacker can disrupt the proper
dissemination of SAV-related information and introduce
inconsistencies or conflicts in the validation process. This can
undermine the effectiveness and accuracy of source address
validation within the inter-domain SAVNET architecture.
Overall, inter-domain SAVNET shares similar security threats with BGP
and can leverage existing BGP security mechanisms to enhance both
session and content security. Session security can be enhanced by
employing session authentication mechanisms used in BGP, such as MD5,
TCP-AO, or Keychain. Similarly, content security can benefit from
the deployment of existing BGP security mechanisms like RPKI, BGPsec,
and ASPA. While these mechanisms can address content security
threats, their widespread deployment is crucial. Until then, it is
necessary to develop an independent security mechanism specifically
designed for inter-domain SAVNET. One potential approach is for each
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origin AS to calculate a digital signature for each AS path and
include these digital signatures within the SAV-specific Messages.
Upon receiving a SAV-specific Message, the SAV Agent can verify the
digital signature to ascertain the message's authenticity.
Furthermore, it is worth noting that the information channel of the
inter-domain SAVNET architecture may need to operate over a network
link that is currently under a source address spoofing attack. As a
result, it may experience severe packet loss and high latency due to
the ongoing attack, and the implementation of the information channel
should ensure uninterrupted communication. Detailed security designs
and considerations will be addressed in a separate draft, ensuring
the robust security of inter-domain SAVNET.
12. Privacy Considerations
TBD
13. IANA Considerations
This document has no IANA requirements.
14. Scope
In this architecture, the choice of protocols used for communication
between the SIM and different SAV information sources is not limited.
The inter-domain SAVNET architecture presents considerations on how
to consolidate SAV-related information from various sources to
generate SAV rules and perform SAV using the SAV table in the
dataplane. The detailed design and implementation for SAV rule
generation and SAV execution depend on the specific inter-domain SAV
mechanisms employed.
This document does not cover administrative or business agreements
that may be established between the involved inter-domain SAVNET
parties. These considerations are beyond the scope of this document.
However, it is assumed that authentication and authorization
mechanisms can be implemented to ensure that only authorized ASes can
communicate SAV-related information.
15. Assumptions
This document makes the following assumptions:
* All ASes where the inter-domain SAVNET is deployed are assumed to
provide the necessary connectivity between SAV Agent and any
intermediate network elements. However, the architecture does not
impose any specific limitations on the form or nature of this
connectivity.
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* Congestion and resource exhaustion can occur at various points in
the inter-domain networks. Hence, in general, network conditions
should be assumed to be hostile. The inter-domain SAVNET
architecture must be capable of functioning reliably under all
circumstances, including scenarios where the paths for delivering
SAV-related information are severely impaired. It is crucial to
design the inter-domain SAVNET system with a high level of
resilience, particularly under extremely hostile network
conditions. The architecture should ensure uninterrupted
communication between inter-domain SAV Agents, even when data-
plane traffic saturates the link.
* The inter-domain SAVNET architecture does not impose rigid
requirements for the SAV information sources that can be used to
generate SAV rules. Similarly, it does not dictate strict rules
on how to utilize the SAV-related information from diverse sources
or perform SAV in the dataplane. Network operators have the
flexibility to choose their approaches to generate SAV rules and
perform SAV based on their specific requirements and preferences.
Operators can either follow the recommendations outlined in the
inter-domain SAVNET architecture or manually specify the rules for
governing the use of SAV-related information, the generation of
SAV rules, and the execution of SAV in the dataplane.
* The inter-domain SAVNET architecture does not impose restrictions
on the selection of the local AS with which AS to communicate SAV-
specific Information. The ASes have the flexibility to establish
connections for SAV-specific communication based on the manual
configurations set by operators or other automatic mechanisms.
* The inter-domain SAVNET architecture provides the flexibility to
accommodate Quality-of-Service (QoS) policy agreements between
SAVNET-enabled ASes or local QoS prioritization measures, but it
does not make assumptions about their presence. These agreements
or prioritization efforts are aimed at ensuring the reliable
delivery of SAV-specific Information between SAV Agents. It is
important to note that QoS is considered as an operational
consideration rather than a functional component of the inter-
domain SAVNET architecture.
* The information and management channels are loosely coupled and
are used for collecting SAV-related information from different
sources, and how the inter-domain SAVNET synchronize the
management and operation configurations is out of scope of this
document.
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16. Contributors
Igor Lubashev
Akamai Technologies
145 Broadway
Cambridge, MA, 02142
United States of America
Email: ilubashe@akamai.com
Many thanks to Igor Lubashev for the significantly helpful revision
suggestions.
17. References
17.1. Normative References
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March
2004, <https://www.rfc-editor.org/rfc/rfc3704>.
[RFC8704] Sriram, K., Montgomery, D., and J. Haas, "Enhanced
Feasible-Path Unicast Reverse Path Forwarding", BCP 84,
RFC 8704, DOI 10.17487/RFC8704, February 2020,
<https://www.rfc-editor.org/rfc/rfc8704>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/rfc/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/rfc/rfc6241>.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,
DOI 10.17487/RFC5424, March 2009,
<https://www.rfc-editor.org/rfc/rfc5424>.
[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/rfc/rfc2119>.
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17.2. Informative References
[inter-domain-ps]
"Source Address Validation in Inter-domain Networks Gap
Analysis, Problem Statement, and Requirements", 2023,
<https://datatracker.ietf.org/doc/draft-ietf-savnet-inter-
domain-problem-statement/>.
[intra-domain-arch]
"Intra-domain Source Address Validation (SAVNET)
Architecture", 2023, <https://datatracker.ietf.org/doc/
draft-li-savnet-intra-domain-architecture/>.
[RFC5635] Kumari, W. and D. McPherson, "Remote Triggered Black Hole
Filtering with Unicast Reverse Path Forwarding (uRPF)",
RFC 5635, DOI 10.17487/RFC5635, August 2009,
<https://www.rfc-editor.org/rfc/rfc5635>.
[RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules",
RFC 8955, DOI 10.17487/RFC8955, December 2020,
<https://www.rfc-editor.org/rfc/rfc8955>.
[RFC8210] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol, Version 1",
RFC 8210, DOI 10.17487/RFC8210, September 2017,
<https://www.rfc-editor.org/rfc/rfc8210>.
[manrs] MANRS, "MANRS Implementation Guide", 2023,
<https://www.manrs.org/netops/guide/antispoofing/>.
[nist] NIST, "Resilient Interdomain Traffic Exchange: BGP
Security and DDos Mitigation", 2019,
<https://www.nist.gov/publications/resilient-interdomain-
traffic-exchange-bgp-security-and-ddos-mitigation>.
Acknowledgements
Many thanks to Alvaro Retana, Kotikalapudi Sriram, Rüdiger Volk,
Xueyan Song, Ben Maddison, Jared Mauch, Joel Halpern, Aijun Wang,
Jeffrey Haas, Xiangqing Chang, Changwang Lin, Mingxing Liu, Zhen Tan,
Yuanyuan Zhang, Yangyang Wang, etc. for their valuable comments on
this document.
Authors' Addresses
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Jianping Wu
Tsinghua University
Beijing
China
Email: jianping@cernet.edu.cn
Dan Li
Tsinghua University
Beijing
China
Email: tolidan@tsinghua.edu.cn
Mingqing Huang
Huawei
Beijing
China
Email: huangmingqing@huawei.com
Li Chen
Zhongguancun Laboratory
Beijing
China
Email: lichen@zgclab.edu.cn
Nan Geng
Huawei
Beijing
China
Email: gengnan@huawei.com
Libin Liu
Zhongguancun Laboratory
Beijing
China
Email: liulb@zgclab.edu.cn
Lancheng Qin
Tsinghua University
Beijing
China
Email: qlc19@mails.tsinghua.edu.cn
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