



PCE Working Group                                                X. Song
Internet-Draft                                                 ZTE Corp.
Intended status: Standards Track                                W. Cheng
Expires: 26 January 2026                                          S. Yue
                                                            China Mobile
                                                            25 July 2025


   Path Computation Element Communication Protocol for Source Address
                               Validation
                       draft-song-pce-pcep-sav-01

Abstract

   This document presents a method of Path Computation Element (PCE) for
   Source Address Validation (SAV) in networks.  It extends Path
   Computation Element Communication Protocol (PCEP) to support SAV
   policy distribution and synchronization between PCEP speakers for
   threat mitigation for source address spoofing.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 26 January 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.










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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  PCE for SAV Support . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  PCE Integration to SANET Architecture . . . . . . . . . .   3
     3.2.  PCE as SAV Policy Controller  . . . . . . . . . . . . . .   4
     3.3.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   4
   4.  PCEP Extenstions  . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  SAV capability advertisement  . . . . . . . . . . . . . .   5
     4.2.  SAV-POLICY Object . . . . . . . . . . . . . . . . . . . .   5
     4.3.  Mechanism for Updates . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Source Address Validation (SAV) is a critical security mechanism
   designed to mitigate IPv4 and IPv6 source address spoofing attacks by
   validating the legitimacy of source prefixes against their ingress
   interfaces.  Traditional methods like ACL-based ingress filtering,
   strict uRPF and loose uRPF mechanisms [RFC3704] have some issues
   (e.g., high operational overhead, improper block or permit of
   traffic) as described in
   [I-D.ietf-savnet-intra-domain-problem-statement] and
   [I-D.ietf-savnet-inter-domain-problem-statement].  The new inter-
   domain SAV mechanism is required to have accurate source address
   validation to avoid improper block and minimize improper permit of
   traffic, and to support automatic update of SAV rules.

   The PCE architecture, defined in [RFC4655], provides centralized
   control for path computation in networks.  This document presents a
   PCE-based solution for SAVNET to provide dynamic policy enforcement



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   in networks.  By extending the PCEP protocol, PCE can efficiently
   manage SAV policies, validate source prefixes, and enforce traffic
   filtering actions to mitigate the threats of source address spoofing.

2.  Conventions

2.1.  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.

2.2.  Terminology

   This document uses the following terms defined in [RFC5440]: PCC,
   PCE, PCEP Peer, and PCEP speaker.

   This document uses the following terms defined in [RFC8051]: stateful
   PCE.

   This document uses the following terms defined in
   [I-D.ietf-savnet-intra-domain-architecture]: SAV, SAV rule, SAV
   Information Base.

3.  PCE for SAV Support

3.1.  PCE Integration to SANET Architecture

   SAV Information Base (see
   [I-D.ietf-savnet-intra-domain-architecture]) that can be a table or
   data structure in a router which stores SAV-specific information and
   local routing information.  SAV Information Base synchronizes SAV
   rules to PCE via BGP-LS or NETCONF/YANG interfaces, enabling PCE to
   compute validation paths.  The PCE sends requests to PCC, which
   receives the SAV rules distributed by PCE and enforces SAV rules on
   data plane.  For example, in an enterprise AS, PCE collects SAV
   specific routes from edge routers or border routers.  It computes
   that source prefix (for example, 2001:db8:1::/48) is only valid on
   interfaces connected to the data center subnet.  Any traffic with
   this prefix arriving at an AS border router is dropped unless it
   originates from the designated interfaces.

   The PCE-SAVNET integration proposed here supports both single-PCE and
   multi-PCE coorperative environments.  It is applicable to single-
   domain and multi-domain AS scenarios, leveraging PCE for cross-domain
   policy coordination.  For example, if the attacker switches the entry



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   from Eth1/0 of R1 in AS60001 to Eth5/0 of R5 in AS60004, the PCE
   controller needs to synchronize the SAV rules and enforce policies
   for source address validation across domains.

3.2.  PCE as SAV Policy Controller

   The example of process for PCE using PCEP to install SAV policies on
   edge routers (i.e., PCC role) in inter-domain networks is showed
   below:

   PCE as SAV controller collects SAV-specific information for SAV
   policy generation of mapping valid interfaces with prefix (e.g.,
   2001:db8::/32) to have the capability of global SAV policy visibility
   for single or multiple domains policy enforcement and coordination.

   PCE sends PCEP protocol messages (see [RFC8231]) to instal SAV
   policies, dynamic SAV policy updates.

   PCC deploys SAV policies which stores in SAV Information Database for
   mapping of source address prefix with valid ingress interfaces for
   ingress traffic filtering.

3.3.  Requirements

   When the PCE speakers supporting SAV, the PCEP is required to support
   the following functionalities.

   The PCEP MUST support SAV-specific information and local routing
   information collection for cross-domain coordination and policy
   enforcement.

   The PCEP MUST support SAV capability advertisement in single and
   multi-domains.

   The PCEP MUST support dynamic updates of SAV policies for network
   changes (e.g., link failures, prefix additions).

   The PCEP MUST support backward compatibility with existing SAVNET
   mechanisms (e.g., BAR-SAV).

   The PCEP sessions for SAV MUST be secured against tampering and
   unauthorized access.

4.  PCEP Extenstions







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4.1.  SAV capability advertisement

   The open message is used to establish a PCEP session between PCEP
   speakers.  To support SAV functionality, a new flag is required for
   SAV capability advertisement which is introduced in this document.

   The SAV-CAPABILITY TLV is an optional TLV for use in the OPEN object
   for SAV capability advertisement.  The format for SAV-CAPABILITY TLV
   refers to figure 9 in [RFC8231].  A new value for Flags field is TBD
   for the SAV capability advertisement.

4.2.  SAV-POLICY Object

   To support SAV functions, a new optional SAV object (class=TBD) for
   SAV information and its related object body formatted as TLV
   introduced in this document.  A SAV-POLICY object is used to carry
   information of SAV policy within a PCEP update message, which may
   carry a set of SAV policies delivery and updates.


     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Object-class            |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //                      Object Body                            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: SAV-POLICY Object Format

   SAV-POLICY object class value is TBD.

   The TLV format for SAV-POLICY object consists of IPv4/IPv6 prefix and
   incoming-interface list (legitimate or illegitimate interfaces).  The
   information for SAV-POLICY object is carried as TLV format, showed as
   the following figure:













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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|     Type    |      Flag     |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length |       IP Source Prefix (variable)             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |InterfaceLength|         Interface List (variable)             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 2: SAV-CAPABILITY TLV Format

   The type (8 bits) of the TLV is TBD.

   The length field is 16 bits long, indicates the total length of the
   TLV in octects.

   The value contains the following fields:

   L: 1 bit long, identifies IP source prefix types, including IPv4 and
   IPv6 types.

   Flag: 8 bits long, identifies the validation modes used in network
   nodes.  The validation modes include 4 modes: interface-based prefix
   allowlist, interface-based prefix blocklist, prefix-based interface
   allowlist, prefix-based interface blocklist.  By selecting modes in
   different scenarios, the network can be secured to mitigate spoofing
   attacks, as introduced in [I-D.ietf-savnet-general-sav-capabilities].

   Interface List: contains a list of interfaces.  If it is a whitelist,
   it represents a list of interfaces allowed to access; if it is a
   blacklist, it represents a list of interfaces not allowed to access.
   The interface list can be expressed in the form of interface ID,
   interface name, or index.

   IP source prefix: contains the source address prefix information.

4.3.  Mechanism for Updates

   The PCE needs send PCUpd message for triggering mechanism when PCE
   makes actively update to the SAV policies, the possible trigger
   conditions may involve: topology changes (e.g., interface status
   modified), policy updates (e.g., the new added IP source prefix
   affiliated interfaces), and attack response from external threats.







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5.  IANA Considerations

   This document requests one new value for SAV capability
   advertisement, one new value for class of SAV policy object
   introduced in this document.  IANA is requested to allocate TLV
   values for SAV-CAPABILITY TLV.

6.  Security Considerations

   Security considerations for PCE are covered in the PCE Architecture
   [RFC5394], PCEP [RFC5440] and stateful PCE [RFC8231].  PCEP sessions
   for SAV policy distribution MUST use TLS 1.3 [RFC8346] to prevent
   tampering.  SAVNET security considerations covered in
   [I-D.ietf-savnet-intra-domain-architecture] and
   [I-D.ietf-savnet-inter-domain-architecture] are also applicable to
   the SAVNET procedures through PCEP defined in this document.

7.  Acknowledgements

   The authors would like to acknowledge Haisheng Wu and Zhenghai Wang
   for their helpful comments.

8.  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>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [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>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

9.  Informative References






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   [I-D.ietf-savnet-general-sav-capabilities]
              Huang, M., Cheng, W., Li, D., Geng, N., and L. Chen,
              "General Source Address Validation Capabilities", Work in
              Progress, Internet-Draft, draft-ietf-savnet-general-sav-
              capabilities-01, 24 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-savnet-
              general-sav-capabilities-01>.

   [I-D.ietf-savnet-inter-domain-architecture]
              Li, D., Chen, L., Geng, N., Liu, L., and L. Qin, "Inter-
              domain Source Address Validation (SAVNET) Architecture",
              Work in Progress, Internet-Draft, draft-ietf-savnet-inter-
              domain-architecture-01, 3 March 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-savnet-
              inter-domain-architecture-01>.

   [I-D.ietf-savnet-inter-domain-problem-statement]
              Li, D., Wu, J., Liu, L., Huang, M., and K. Sriram, "Source
              Address Validation in Inter-domain Networks Gap Analysis,
              Problem Statement, and Requirements", Work in Progress,
              Internet-Draft, draft-ietf-savnet-inter-domain-problem-
              statement-09, 4 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-savnet-
              inter-domain-problem-statement-09>.

   [I-D.ietf-savnet-intra-domain-architecture]
              Li, D., Wu, J., Qin, L., Geng, N., and L. Chen, "Intra-
              domain Source Address Validation (SAVNET) Architecture",
              Work in Progress, Internet-Draft, draft-ietf-savnet-intra-
              domain-architecture-02, 13 April 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-savnet-
              intra-domain-architecture-02>.

   [I-D.ietf-savnet-intra-domain-problem-statement]
              Li, D., Wu, J., Qin, L., Huang, M., and N. Geng, "Source
              Address Validation in Intra-domain Networks Gap Analysis,
              Problem Statement, and Requirements", Work in Progress,
              Internet-Draft, draft-ietf-savnet-intra-domain-problem-
              statement-17, 7 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-savnet-
              intra-domain-problem-statement-17>.

   [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>.






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   [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
              Computation Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC5394]  Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
              "Policy-Enabled Path Computation Framework", RFC 5394,
              DOI 10.17487/RFC5394, December 2008,
              <https://www.rfc-editor.org/info/rfc5394>.

   [RFC8051]  Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
              Stateful Path Computation Element (PCE)", RFC 8051,
              DOI 10.17487/RFC8051, January 2017,
              <https://www.rfc-editor.org/info/rfc8051>.

   [RFC8346]  Clemm, A., Medved, J., Varga, R., Liu, X.,
              Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model
              for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346,
              March 2018, <https://www.rfc-editor.org/info/rfc8346>.

Authors' Addresses

   Xueyan Song
   ZTE Corp.
   China
   Email: song.xueyan2@zte.com.cn


   Weiqiang Cheng
   China Mobile
   China
   Email: chengweiqiang@chinamobile.com


   Shengna Yue
   China Mobile
   China
   Email: yueshengnan@chinamobile.com













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