Source Address Validation in Intra-domain Networks Gap Analysis, Problem Statement, and Requirements
draft-ietf-savnet-intra-domain-problem-statement-07

SAVNET                                                             D. Li
Internet-Draft                                                     J. Wu
Intended status: Informational                       Tsinghua University
Expires: 15 May 2025                                              L. Qin
                                                                M. Huang
                                                 Zhongguancun Laboratory
                                                                 N. Geng
                                                                  Huawei
                                                        11 November 2024

Source Address Validation in Intra-domain Networks Gap Analysis, Problem
                      Statement, and Requirements
          draft-ietf-savnet-intra-domain-problem-statement-07

Abstract

   This document provides the gap analysis of existing intra-domain
   source address validation mechanisms, describes the fundamental
   problems, and defines the requirements for technical improvements.

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   This Internet-Draft will expire on 15 May 2025.

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   extracted from this document must include Revised BSD License text as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  Existing Mechanisms . . . . . . . . . . . . . . . . . . . . .   5
   3.  Gap Analysis  . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  SAV on Host-facing or Customer-facing Routers . . . . . .   7
       3.1.1.  Asymmetric Routing  . . . . . . . . . . . . . . . . .   7
       3.1.2.  Hidden Prefix . . . . . . . . . . . . . . . . . . . .   9
     3.2.  SAV on AS Border Routers  . . . . . . . . . . . . . . . .  10
   4.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .  12
   5.  Requirements for New SAV Mechanisms . . . . . . . . . . . . .  12
     5.1.  Automatic Update  . . . . . . . . . . . . . . . . . . . .  12
     5.2.  Accurate Validation . . . . . . . . . . . . . . . . . . .  13
     5.3.  Working in Incremental/Partial Deployment . . . . . . . .  13
     5.4.  Fast Convergence  . . . . . . . . . . . . . . . . . . . .  13
     5.5.  Necessary Security Guarantee  . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Source Address Validation (SAV) is important for defending against
   source address spoofing attacks.  A multi-fence architecture called
   Source Address Validation Architecture (SAVA) [RFC5210] was proposed
   to implement SAV at three levels: access network SAV, intra-domain
   SAV, and inter-domain SAV.  When SAV has not been adopted by every
   source/host, the multi-fence architecture helps enhance the
   effectiveness of SAV across the whole Internet by preventing or
   mitigating source address spoofing.

   Specifically, access network SAV can ensure that a host must use the
   source IP address assigned to the host.  By deploying access network
   SAV, hosts in the corresponding access network cannot forge a source
   address of another host.  There are many mechanisms for SAV in access
   networks.  Static ACL rules can be manually configured for validation
   by specifying which source addresses are acceptable or unacceptable.
   Dynamic ACL is another efficient mechanism which is associated with

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   authentication servers (e.g., RADIUS and DIAMETER).  The servers
   receive access requests and then install or enable ACL rules on the
   device to permit particular users' packets.  SAVI [RFC7039]
   represents a kind of mechanism enforcing that the valid source IP
   address of a host matches the link-layer property of the host's
   network attachment.  For example, SAVI solution for DHCP [RFC7513]
   creates a binding between a DHCPv4/DHCPv6-assigned IP address and a
   link-layer property (like MAC address or switch port) on a SAVI
   device.  IP Source Guard (IPSG) [IPSG] combined with DHCP snooping is
   an implementation of SAVI solution for DHCP.  Cable Source-Verify
   [cable-verify] also shares some features of SAVI and is used in cable
   modem networks.  Cable modem termination system (CMTS) devices with
   Cable Source-Verify maintain the bindings of the CPE's IP address,
   the CPE's MAC address, and the corresponding cable modem identifier.
   When receiving a packet from a host, the device can check the
   validity of source IP address according to the bindings.

   Given numerous access networks managed by different operators
   throughout the world, it is difficult to require all access networks
   to deploy SAV simultaneously.  Therefore, intra-domain SAV and inter-
   domain SAV are needed to block source-spoofed data packets from
   access networks as close to the source as possible.  Intra-domain SAV
   and inter-domain SAV perform SAV at the granularity of IP prefixes,
   which is coarser than the granularity of access network SAV (i.e., IP
   address), as an IP prefix covers a range of IP addresses.

   This document focuses on the analysis of intra-domain SAV.  In
   contrast to inter-domain SAV, intra-domain SAV does not require
   collaboration between different ASes.  Intra-domain SAV rules can be
   generated by the AS itself.  Consider an AS X which provides its host
   networks or customer networks with the connectivity to the rest of
   the Internet.  Intra-domain SAV for AS X aims at achieving two goals
   without collaboration with other ASes: i) blocking source-spoofed
   packets originated from its host networks or customer networks using
   a source address of other networks; and ii) blocking source-spoofed
   packets coming from other ASes using a source address of AS X.

   Figure 1 illustrates the goals and function of intra-domain SAV with
   two cases.  Case i shows that the host network or customer network of
   AS X originates source-spoofed packets using a source address of
   other networks.  If AS X deploys intra-domain SAV, the spoofed
   packets can be blocked by host-facing routers or customer-facing
   routers of AS X (i.e., Goal i).  Case ii shows that AS X receives
   source-spoofed packets using a source address of AS X from other ASes
   (e.g., AS Y).  If AS X deploys intra-domain SAV, the spoofed packets
   from AS Y can be blocked by AS border routers of AS X (i.e., Goal
   ii).

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   Case i: The host network or customer network of AS X originates
           packets spoofing source addresses of other networks
   Goal i: If AS X deploys intra-domain SAV,
           the spoofed packets can be blocked by AS X

                                       Spoofed packets
                                       using source addresses
     +-------------------------------+ of other networks     +------+
     | Host/Customer Network of AS X |---------------------->| AS X |
     +-------------------------------+                       +------+

   Case ii: AS X receives packets spoofing source addresses of AS X
            from other ASes (e.g., AS Y)
   Goal ii: If AS X deploys intra-domain SAV,
            the spoofed packets can be blocked by AS X

              Spoofed packets
              using source addresses
     +------+ of AS X               +------+
     | AS X |<----------------------| AS Y |
     +------+                       +------+

           Figure 1: An example for illustrating intra-domain SAV

   The scope of intra-domain SAV includes all IP-encapsulated scenarios:

   *  Native IP forwarding: including both forwarding based on global
      routing table and CE site forwarding of VPN.

   *  IP-encapsulated Tunnel (IPsec, GRE, SRv6, etc.): focusing on the
      validation of the outer layer IP address.

   *  Validating both IPv4 and IPv6 addresses.

   Scope does not include:

   *  Non-IP packets: including MPLS label-based forwarding and other
      non-IP-based forwarding.

   There are many mechanisms for intra-domain SAV.  This document
   provides the gap analysis of existing intra-domain SAV mechanisms.
   According to the gap analysis, the document concludes the main
   problems of existing intra-domain SAV mechanisms and describes the
   requirements for future ones.

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1.1.  Terminology

   SAV Rule: The rule in a router that describes the mapping
   relationship between a source address (prefix) and the valid incoming
   interface(s).  It is used by a router to make SAV decisions and is
   inferred from the SAV Information Base.

   Host-facing Router: An intra-domain router facing an intra-domain
   host network.

   Customer-facing Router: An intra-domain router facing an intra-domain
   customer network.

   AS Border Router: An intra-domain router facing an external AS.

   Improper Block: The validation results that the packets with
   legitimate source addresses are blocked improperly due to inaccurate
   SAV rules.

   Improper Permit: The validation results that the packets with spoofed
   source addresses are permitted improperly due to inaccurate SAV
   rules.

1.2.  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.  Existing Mechanisms

   This section briefly introduces existing intra-domain SAV mechanisms.
   Particularly, ingress filtering (i.e., BCP38 [RFC2827] and BCP84
   [RFC3704]) is the best current practice for intra-domain SAV.

   *  ACL-based ingress filtering [RFC2827] is a typical mechanism for
      intra-domain SAV.  It requires that network operators manually
      configure ACL rules on intra-domain routers to block or permit
      data packets using specific source addresses.  This mechanism can
      be used on interfaces of host-facing or customer-facing routers
      facing an intra-domain host/customer network to prevent the
      corresponding host/customer network from spoofing source prefixes
      of other networks [manrs-antispoofing].  In addition, it is also
      usually used on interfaces of AS border routers facing an external
      AS to block data packets using disallowed source addresses, such
      as internal source addresses owned by the local AS [nist-rec].  In

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      any application scenario, ACL rules must be updated in time to be
      consistent with the latest filtering criteria when the network
      changes.

   *  Strict uRPF [RFC3704] is another typical intra-domain SAV
      mechanism.  It is typically used on interfaces of host-facing or
      customer-facing routers facing an intra-domain host/customer
      network.  Routers deploying strict uRPF accept a data packet only
      when i) the local FIB contains a prefix covering the packet's
      source address and ii) the corresponding outgoing interface for
      the prefix in the FIB matches the packet's incoming interface.
      Otherwise, the packet will be blocked.

   *  Loose uRPF [RFC3704] uses a pretty looser validation method which
      loses the directionality.  A packet will be accepted if the
      router's local FIB contains a prefix covering the packet's source
      address regardless of the interface from which the packet is
      received.  In fact, interfaces of AS border routers facing an
      external AS may use loose uRPF to block incoming data packets
      using non-global addresses [nist-rec].

   *  Carrier Grade NAT has some operations on the source addresses of
      packets, but it is not an anti-spoofing tool, as described in
      [manrs-antispoofing].  If the source address of a packet is in the
      INSIDE access list, the NAT rule can translate the source address
      to an address in the pool OUTSIDE.  The NAT rule cannot determine
      whether the source address is spoofed or not.  In addition, the
      packet using a spoofed source address will still be forwarded if
      the spoofed source address is not included in the INSIDE access
      list.  Therefore, Carrier Grade NAT cannot help identify and block
      source-spoofed data packets.

3.  Gap Analysis

   Towards the two goals of intra-domain SAV in Figure 1, intra-domain
   SAV is commonly deployed on host-facing routers, customer-facing
   routers, and AS border routers.  This section elaborates the key
   problems of SAV on host-facing or customer-facing routers and SAV on
   AS border routers, respectively.  Since existing intra-domain SAV
   mechanisms either require high operational overhead or have
   limitations in accuracy, they will improperly block data packets
   using a legitimate source address (i.e., improper block) or
   improperly permit data packets using a spoofed source address (i.e.,
   improper permit).

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3.1.  SAV on Host-facing or Customer-facing Routers

   Towards Goal i in Figure 1, intra-domain SAV is typically deployed on
   interfaces of host-facing or customer-facing routers facing an intra-
   domain host/customer network to validate data packets originated from
   that network, since SAV is more effective when deployed closer to the
   source.

   As described previously, ACL rules can be configured on such
   interfaces for ingress filtering.  These ACL rules must be manually
   updated according to prefix changes or topology changes in a timely
   manner.  Otherwise, if ACL rules are not updated in time, improper
   block or improper permit problems may occur.  To ensure the accuracy
   of ACL rules in dynamic networks, high operational overhead will be
   induced to achieve timely updates for ACL configurations.

   Strict uRPF can also be used for SAV on host-facing or customer-
   facing routers.  It can generate and update SAV rules in an automatic
   way but it will cause improper blocks in the scenario of asymmetric
   routing or hidden prefix.

3.1.1.  Asymmetric Routing

   Figure 2 shows asymmetric routing in a multi-homing scenario.  In the
   figure, Network 1 is a host/customer network of the AS.  It owns
   prefix 192.0.2.0/24 [RFC6890] and is attached to two intra-domain
   routers, i.e., Router 1 and Router 2.  For the load balance purpose
   of traffic flowing to Network 1, Network 1 expects the incoming
   traffic destined for the sub-prefix 192.0.2.128/25 to come only from
   Router 1 and the incoming traffic destined for the other sub-prefix
   192.0.2.0/25 to come only from Router 2.  To this end, Router 1 only
   learns the route to sub-prefix 192.0.2.128/25 from Network 1, while
   Router 2 only learns the route to the other sub-prefix 192.0.2.0/25
   from Network 1.  Then, Router 1 and Router 2 distribute the sub-
   prefix information to routers in the AS through intra-domain routing
   protocols such as OSPF or IS-IS.  Finally, Router 1 learns the route
   to 192.0.2.0/25 from Router 3, and Router 2 learns the route to
   192.0.2.128/25 from Router 3.  The FIBs of Router 1 and Router 2 are
   shown in the figure.  Although Network 1 does not expect traffic
   destined for 192.0.2.0/25 to come from Router 1, it may send traffic
   with source addresses of prefix 192.0.2.0/25 to Router 1 for load
   balance of traffic originated from Network 1.  As a result, there is
   asymmetric routing of data packets between Network 1 and Router 1.
   Arrows in the figure indicate the flowing direction of traffic.
   Similarly, Network 1 may also send traffic with source addresses of
   prefix 192.0.2.128/25 to Router 2, resulting in asymmetric routing
   between Network 1 and Router 2.  In addition to the traffic
   engineering mentioned above, other factors may also cause similar

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   asymmetric routing between host-facing/customer-facing routers and
   host/customer networks.

    +---------------------------------------------------------------+
    |                                                           AS  |
    |                         +----------+                          |
    |                         | Router 3 |                          |
    |FIB of Router 1          +----------+  FIB of Router 2         |
    |Dest           Next_hop    /      \    Dest           Next_hop |
    |192.0.2.128/25 Network 1  /        \   192.0.2.0/25   Network 1|
    |192.0.2.0/25   Router 3  /          \  192.0.2.128/25 Router 3 |
    |                  +----------+     +----------+                |
    |                  | Router 1 |     | Router 2 |                |
    |                  +-----+#+--+     +-+#+------+                |
    |                        /\           /                         |
    |     Traffic with        \          / Traffic with             |
    |     source IP addresses  \        /  destination IP addresses |
    |     of 192.0.2.0/25       \      \/  of 192.0.2.0/25          |
    |                      +----------------+                       |
    |                      |  Host/Customer |                       |
    |                      |    Network 1   |                       |
    |                      | (192.0.2.0/24) |                       |
    |                      +----------------+                       |
    |                                                               |
    +---------------------------------------------------------------+

    The legitimate traffic originated from Network 1 with source IP
    addresses of 192.0.2.0/25 will be improperly blocked by Router 1
    if Router 1 uses strict uRPF.

           Figure 2: Asymmetric routing in multi-homing scenario

   Strict uRPF takes the entries in FIB for SAV.  It will improperly
   block data packets which use legitimate source addresses when
   asymmetric routing exists.  In the figure, if Router 1 uses strict
   uRPF on interface '#', the SAV rule is that Router 1 only accepts
   packets with source addresses of 192.0.2.128/25 from Network 1.
   Therefore, when Network 1 sends packets with source addresses of
   192.0.2.0/25 to Router 1, strict uRPF at Router 1 will improperly
   block these legitimate packets.  Similarly, when Router 2 uses strict
   uRPF on its interface '#' and receives packets with source addresses
   of prefix 192.0.2.128/25 from Network 1, it will also improperly
   block these legitimate packets because strict uRPF at Router 2 will
   only accept packets from Network 1 using source addresses of prefix
   192.0.2.0/25.

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3.1.2.  Hidden Prefix

   For special business purposes, a host/customer network will originate
   data packets using a source address that is not distributed through
   intra-domain routing protocol.  In other words, the IP address/prefix
   is hidden from intra-domain routing protocol and intra-domain
   routers.  In this scenario, strict uRPF on host-facing or customer-
   facing routers will improperly block data packets from the host/
   customer network using source addresses in a hidden prefix.

             +-------------------------+
             |          AS Y           | AS Y announces the route
             |   (where the anycast    | for anycast prefix P3
             |    server is located)   | in BGP
             +-----------+-------------+
                         |
                         |
             +-----------+-------------+
             |       Other ASes        |
             +-------------------------+
                /                    \
               /                      \
              /                        \
   +------------------+   +---------------------------------------+
   |      AS Z        |   |         +----------+             AS X |
   | (where the user  |   |         | Router 4 |                  |
   |    is located)   |   |         +----------+                  |
   +------------------+   |              |                        |
                          |              |                        |
                          |         +----+-----+                  |
                          |         | Router 5 |                  |
                          |         +----#-----+                  |
                          |              /\    DSR responses with |
                          |              |     source IP addresses|
                          |              |     of P3              |
                          |       +---------------+               |
                          |       | Host/Customer |               |
                          |       |   Network 2   |               |
                          |       |     (P2)      |               |
                          |       +---------------+               |
                          | (where the edge server is located)    |
                          +---------------------------------------+
   DSR response packets from edge server in Network 2 with
   source IP addresses of P3 (i.e., the anycast prefix) will
   be improperly blocked by Router 5 if Router 5 uses strict uRPF.

              Figure 3: Hidden prefix in CDN and DSR scenario

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   The Content Delivery Networks (CDN) and Direct Server Return (DSR)
   scenario is a representative example of hidden prefix.  In this
   scenario, the edge server in an AS will send DSR response packets
   using a source address of the anycast server which is located in
   another remote AS.  However, the source address of anycast server is
   hidden from intra-domain routing protocol and intra-domain routers in
   the local AS.  While this is an inter-domain scenario, we note that
   DSR response packets may also be improperly blocked by strict uRPF
   when edge server is located in the host/customer network.  For
   example, in Figure 3, assume edge server is located in Host/Customer
   Network 2 and Router 5 only learns the route to P2 from Network 2.
   When edge server receives the request from the remote anycast server,
   it will directly return DSR response packets using the source address
   of anycast server (i.e., P3).  If Router 5 uses strict uRPF on
   interface '#', the SAV rule is that Router 5 only accepts packets
   with source addresses of P2 from Network 2.  As a result, DSR
   response packets will be blocked by strict uRPF on interface '#'.  In
   addition, loose uRPF on this interface will also improperly block DSR
   response packets if prefix P3 is not in the FIB of Router 5.

3.2.  SAV on AS Border Routers

   Towards Goal ii in Figure 1, intra-domain SAV is typically deployed
   on interfaces of AS border routers facing an external AS to validate
   packets arriving from other ASes.  Figure 4 shows an example of SAV
   on AS border routers.  In the figure, Router 3 and Router 4 deploy
   intra-domain SAV on interface '#' for validating data packets coming
   from external ASes.

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    Packets with +              Packets with +
    spoofed P1/P2|              spoofed P1/P2|
   +-------------|---------------------------|---------+
   |   AS        \/                          \/        |
   |         +--+#+-----+               +---+#+----+   |
   |         | Router 3 +---------------+ Router 4 |   |
   |         +----------+               +----+-----+   |
   |          /        \                     |         |
   |         /          \                    |         |
   |        /            \                   |         |
   | +----------+     +----------+      +----+-----+   |
   | | Router 1 |     | Router 2 |      | Router 5 |   |
   | +----------+     +----------+      +----+-----+   |
   |        \             /                  |         |
   |         \           /                   |         |
   |          \         /                    |         |
   |       +---------------+         +-------+-------+ |
   |       |   Customer    |         |     Host      | |
   |       |   Network     |         |   Network     | |
   |       |     (P1)      |         |     (P2)      | |
   |       +---------------+         +---------------+ |
   |                                                   |
   +---------------------------------------------------+

              Figure 4: An example of SAV on AS border routers

   ACL-based ingress filtering is usually used for this purpose.  By
   configuring specified ACL rules, data packets that use disallowed
   source addresses (e.g., non-global addresses or internal source
   addresses) can be blocked at AS border routers.  As mentioned above,
   ACL-based ingress filtering requires manual updates when internal
   source prefixes change dynamically.  If ACL rules are not updated in
   time, there may be improper block or improper permit problems.  The
   operational overhead of maintaining updated ACL rules will be
   extremely high when there are multiple AS border routers adopting SAV
   as shown in Figure 4.

   In addition to ACL-based ingress filtering, loose uRPF is also often
   used for SAV on AS border routers and is more adaptive than ACL-based
   rules.  But it sacrifices the directionality of SAV and has limited
   blocking capability, because it allows packets with source addresses
   that exist in the FIB table on all router interfaces.

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4.  Problem Statement

   Accurate validation and low operational overhead are two important
   design goals of intra-domain SAV mechanisms.  However, as analyzed
   above, existing intra-domain SAV mechanisms have problems of
   inaccurate validation or high operational overhead.

   ACL-based ingress filtering relies on manual configurations and thus
   requires high operational overhead in dynamic networks.  To guarantee
   accuracy of ACL-based SAV, network operators have to manually update
   the ACL-based filtering rules in time when the prefix or topology
   changes.  Otherwise, improper block or improper permit problems may
   appear.

   Strict uRPF can automatically update SAV rules, but may improperly
   block legitimate traffic under asymmetric routing scenario or hidden
   prefix scenario.  The root cause is that strict uRPF uses the
   router's local FIB to determine the valid incoming interface for a
   specific source address, which may not match the real incoming
   direction from the source, due to the existence of asymmetric routes.
   Hence, it may mistakenly consider a valid incoming interface as
   invalid, resulting in improper block problems; or it may mistakenly
   consider an invalid incoming interface as valid, resulting in
   improper permit problems.

   Loose uRPF is also an automated SAV mechanism but its SAV rules are
   overly loose.  Most spoofed packets will be improperly permitted by
   loose uRPF.

5.  Requirements for New SAV Mechanisms

   This section lists the requirements which can be a guidance for
   narrowing the gaps of existing intra-domain SAV mechanisms.  The
   requirements can be fully or partially fulfilled when designing new
   intra-domain SAV mechanisms.  The new intra-domain SAV mechanisms
   SHOULD avoid data-plane packet modification.  Existing architectures
   or protocols or mechanisms can be used in the new SAV mechanisms to
   achieve better SAV function.

5.1.  Automatic Update

   The new intra-domain SAV mechanism MUST be able to automatically
   adapt to network dynamics such as routing changes or prefix changes,
   instead of purely relying on manual update.

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5.2.  Accurate Validation

   The new intra-domain SAV mechanism need to improve the validation
   accuracy upon existing intra-domain SAV mechanisms.  In a static
   network, improper block MUST be avoided to guarantee that legitimate
   traffic will not be blocked.  Improper permit SHOULD be reduced as
   much as possible so that the malicious packets with forged source
   addresses can be efficiently filtered.  When there are network
   changes, the new mechanisms MUST update SAV rules efficiently for
   keeping the high accuracy of validation.

5.3.  Working in Incremental/Partial Deployment

   The new intra-domain SAV mechanism SHOULD NOT assume pervasive
   adoption, and some routers that intend to adopt the new mechanism may
   not be able to be upgraded immediately.  The new intra-domain SAV
   mechanism SHOULD be able to provide incremental protection when it is
   incrementally deployed.  The effectiveness of the new intra-domain
   SAV mechanism under incremental deployment SHOULD be no worse than
   existing ones.

5.4.  Fast Convergence

   The new intra-domain SAV mechanism MUST adapt to prefix changes,
   route changes, and topology changes in an intra-domain network, and
   update SAV rules in a timely manner.  In addition, it MUST consider
   how to update SAV rules proactively or reactively so as to minimize
   improper blocks during convergence.

5.5.  Necessary Security Guarantee

   Necessary security tools SHOULD be considered in the new intra-domain
   SAV mechanism.  These security tools can help protect the SAV rule
   generation process.  Section 6 details the security scope and
   considerations for the new intra-domain SAV mechanism.

6.  Security Considerations

   The new intra-domain SAV mechanisms should not introduce additional
   security vulnerabilities or confusion to the existing intra-domain
   architectures or control or management plane protocols.

   Similar to the security scope of intra-domain routing protocols,
   intra-domain SAV mechanisms should ensure integrity and
   authentication of protocol messages that deliver the required SAV
   information, and consider avoiding unintentional misconfiguration.
   It is not necessary to provide protection against compromised or
   malicious intra-domain routers which poison existing control or

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   management plane protocols.  Compromised or malicious intra-domain
   routers may not only affect SAV, but also disrupt the whole intra-
   domain routing domain.  Security solutions to prevent these attacks
   are beyond the capability of intra-domain SAV.

7.  IANA Considerations

   This document does not request any IANA allocations.

8.  Acknowledgements

   Many thanks to the valuable comments from: Jared Mauch, Barry Greene,
   Fang Gao, Kotikalapudi Sriram, Anthony Somerset, Yuanyuan Zhang, Igor
   Lubashev, Alvaro Retana, Joel Halpern, Aijun Wang, Michael
   Richardson, Li Chen, Gert Doering, Mingxing Liu, Libin Liu, John
   O'Brien, Roland Dobbins, Xiangqing Chang, Tony Przygienda, Yingzhen
   Qu, Changwang Lin, etc.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <https://www.rfc-editor.org/info/rfc2827>.

   [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/info/rfc3704>.

   [RFC5210]  Wu, J., Bi, J., Li, X., Ren, G., Xu, K., and M. Williams,
              "A Source Address Validation Architecture (SAVA) Testbed
              and Deployment Experience", RFC 5210,
              DOI 10.17487/RFC5210, June 2008,
              <https://www.rfc-editor.org/info/rfc5210>.

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   [cable-verify]
              "Cable Source-Verify and IP Address Security", January
              2021, <https://www.cisco.com/c/en/us/support/docs/
              broadband-cable/cable-security/20691-source-verify.html>.

   [IPSG]     "Configuring DHCP Features and IP Source Guard", January
              2016, <https://www.cisco.com/c/en/us/td/docs/switches/lan/
              catalyst2960/software/release/12-
              2_53_se/configuration/guide/2960scg/swdhcp82.html>.

   [RFC7039]  Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
              "Source Address Validation Improvement (SAVI) Framework",
              RFC 7039, DOI 10.17487/RFC7039, October 2013,
              <https://www.rfc-editor.org/info/rfc7039>.

   [RFC7513]  Bi, J., Wu, J., Yao, G., and F. Baker, "Source Address
              Validation Improvement (SAVI) Solution for DHCP",
              RFC 7513, DOI 10.17487/RFC7513, May 2015,
              <https://www.rfc-editor.org/info/rfc7513>.

   [RFC6890]  Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
              "Special-Purpose IP Address Registries", BCP 153,
              RFC 6890, DOI 10.17487/RFC6890, April 2013,
              <https://www.rfc-editor.org/info/rfc6890>.

   [manrs-antispoofing]
              "MANRS Implementation Guide", January 2023,
              <https://www.manrs.org/netops/guide/antispoofing>.

   [nist-rec] "Resilient Interdomain Traffic Exchange - BGP Security and
              DDoS Mitigation", January 2019,
              <https://www.nist.gov/publications/resilient-interdomain-
              traffic-exchange-bgp-security-and-ddos-mitigation">.

Authors' Addresses

   Dan Li
   Tsinghua University
   Beijing
   China
   Email: tolidan@tsinghua.edu.cn

   Jianping Wu
   Tsinghua University
   Beijing
   China
   Email: jianping@cernet.edu.cn

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   Lancheng Qin
   Zhongguancun Laboratory
   Beijing
   China
   Email: qinlc@mail.zgclab.edu.cn

   Mingqing Huang
   Zhongguancun Laboratory
   Beijing
   China
   Email: huangmq@mail.zgclab.edu.cn

   Nan Geng
   Huawei
   Beijing
   China
   Email: gengnan@huawei.com

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