BGP Extension for Secure Session State Synchronization
draft-xu-idr-bgp-sec-sync-00

Network Working Group                                              H. Xu
Internet-Draft                                                 S. Zhuang
Intended status: Standards Track                                 H. Wang
Expires: 6 January 2027                              Huawei Technologies
                                                             5 July 2026

         BGP Extension for Secure Session State Synchronization
                      draft-xu-idr-bgp-sec-sync-00

Abstract

   This document defines a new BGP Address Family, termed the Secure
   Session Synchronization Address Family, allowing BGP speakers to
   exchange stateful firewall, NAT, and IPSec session information across
   distributed nodes.  This architecture facilitates zero-packet-loss
   failover and seamless path protection for Secure SD-WAN, SASE, and
   SSE multi-POP deployments, entirely bypassing the scalability limits
   of traditional layer-2 synchronization protocols.

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.

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
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   This Internet-Draft will expire on 6 January 2027.

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Copyright Notice

   Copyright (c) 2026 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/
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   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.  Protocol Extensions: AFI and SAFI Definitions . . . . . . . .   3
   3.  The Secure Session NLRI Format  . . . . . . . . . . . . . . .   3
   4.  Session State Path Attributes (TLV Structure) . . . . . . . .   4
     4.1.  TCP State TLV (Type 1)  . . . . . . . . . . . . . . . . .   4
     4.2.  NAT Binding TLV (Type 2)  . . . . . . . . . . . . . . . .   5
     4.3.  Session Expiry TLV (Type 3) . . . . . . . . . . . . . . .   5
   5.  Operational Procedures & Flood Dampening Mechanics  . . . . .   5
     5.1.  State-Driven Triggering Window  . . . . . . . . . . . . .   5
     5.2.  Batching and Coalescing Regimes . . . . . . . . . . . . .   6
     5.3.  Session Teardown and Graceful Withdrawal  . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Modern Secure SD-WAN and Secure Access Service Edge (SASE/SSE)
   architectures rely heavily on dynamic, stateful packet inspection
   deployed on edge Customer Premises Equipment (CPE) and distributed
   Cloud Points of Presence (POPs).  When link failures or node outages
   trigger a data-plane switchover, traffic is rerouted to an alternate
   gateway node.

   However, traditional routing protocols only synchronize Layer 3
   reachability.  The underlying stateful security contexts—such as TCP
   sequence numbers, NAT translation bindings, and IPSec anti-replay

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   windows—are lost during the transition.  This mismatch forces edge
   clients to re-establish hundreds of thousands of concurrent active
   sessions, leading to substantial packet drops, broken flows, and
   severe application degradation.

   Existing state synchronization mechanisms (e.g., dedicated single-hop
   sync links) are bounded by proprietary protocols and cannot scale
   across multi-hop wide area networks (WANs) or mesh topologies.

   This document leverages BGP's proven database scalability by
   introducing a novel Address Family dedicated to carrying session
   states as control-plane attributes.  Using BGP Route Reflectors (RRs)
   and Route Target (RT) filtering constraints, session states can be
   selectively and efficiently broadcasted to eligible backup peers,
   enabling hitless stateful cross-POP/site failovers.

2.  Protocol Extensions: AFI and SAFI Definitions

   To transport secure session states without interfering with existing
   unicast routing structures, this document requests a new Address
   Family Identifier (AFI) and Subsequent Address Family Identifier
   (SAFI) from IANA:

   *  AFI: Secure Session Space (TBD1)

   *  SAFI: Session State Synchronization (TBD2)

   BGP speakers MUST negotiate Capability Advertisements [RFC5492] for
   AFI=TBD1 / SAFI=TBD2 during the BGP session initialization phase.

3.  The Secure Session NLRI Format

   The Secure Session Network Layer Reachability Information (NLRI) is
   carried inside BGP UPDATE messages using MP_REACH_NLRI and
   MP_UNREACH_NLRI attributes [RFC4760].  The unique "key" that
   identifies a discrete network session is structured within the NLRI
   as follows:

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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Length (2 octets)                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Route Distinguisher                       |
      |                          (8 octets)                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   IP Version  |   Protocol    |           Reserved            |
      | (1=IPv4,2=IPv6|  (TCP, UDP)   |            0x00               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Source Port        |        Destination Port       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Source IP Address                       |
      |                    (4 octets or 16 octets)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Destination IP Address                     |
      |                    (4 octets or 16 octets)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   *  Route Distinguisher (RD): An 8-octet identifier used to isolate
      overlapping IP spaces belonging to distinct VRFs or enterprise
      tenants sharing the same multi-tenant SASE fabric.

   *  Protocol: Matches the IP packet header protocol field (e.g., 6 for
      TCP, 17 for UDP).

   *  Source / Destination IPs and Ports: Defines the strict 5-tuple
      identifying the communication flow.

4.  Session State Path Attributes (TLV Structure)

   Dynamic session parameters that fluctuate over time MUST NOT be
   encoded inside the static NLRI key.  Instead, they MUST be advertised
   via a new optional, non-transitive BGP attribute named the **Secure
   Session Attribute**. This attribute is composed of individual TLVs:

4.1.  TCP State TLV (Type 1)

   *  Type: 1

   *  Length: 8 octets

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   *  Value: Contains the localized TCP state engine classification
      (e.g., 0x03 for ESTABLISHED) along with synchronized forward and
      reverse TCP Sequence and Acknowledgment Numbers.

4.2.  NAT Binding TLV (Type 2)

   *  Type: 2

   *  Length: Variable (Depends on IPv4/IPv6)

   *  Value: Carries the Post-NAT translated Source IP and translated
      Source Port.  This ensures that a backup CPE or POP can maintain
      identical NAT bindings for the tenant upon hot-standby takeover.

4.3.  Session Expiry TLV (Type 3)

   *  Type: 3

   *  Length: 4 octets

   *  Value: A 32-bit integer indicating the remaining lifetime of the
      session in seconds.

5.  Operational Procedures & Flood Dampening Mechanics

   Because data-plane session allocations happen at scales multiple
   orders of magnitude higher than standard infrastructure routing
   updates, implementations MUST strictly comply with the following
   control-plane dampening rules to maintain BGP process stability:

5.1.  State-Driven Triggering Window

   *  A BGP speaker MUST NOT generate a BGP UPDATE message for every
      individual TCP packet or state transition (e.g., handshaking
      phase).

   *  The generation of an MP_REACH_NLRI for a TCP session MUST be
      deferred until the local security engine verifies the session has
      successfully entered the `ESTABLISHED` state.

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5.2.  Batching and Coalescing Regimes

   *  BGP speakers running this address family MUST implement a
      mandatory coalescing timer (suggested default: 200 milliseconds).

   *  Newly established sessions captured within this window MUST be
      aggregated and transmitted in bulk within a single BGP UPDATE
      message, effectively dampening packet processing stress on the BGP
      peer.

5.3.  Session Teardown and Graceful Withdrawal

   *  When an active session naturally times out or intercepts an
      explicit teardown sequence (TCP FIN or RST), the originating node
      MUST queue an MP_UNREACH_NLRI to withdraw the session key from the
      network.

   *  Backup nodes receiving this withdrawal MUST purge the matching
      entry from their shadow forwarding tables.

6.  Security Considerations

   Transporting exact firewall session tables over BGP means that if an
   unauthorized entity eavesdrops on the control-plane data, they gain
   access to the entire active topology and session matrix of the
   network.  Therefore, sessions utilizing this address family MUST
   enforce transport-layer encryption mechanisms such as TLS [RFC8205]
   or IPsec protection for the BGP peering sessions.

7.  IANA Considerations

   This document requests IANA to allocate an AFI value of TBD1 for the
   "Secure Session Space" and a SAFI value of TBD2 for "Session State
   Synchronization".

8.  Contributors

   The following people made significant contributions to this document:

   To be added.

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9.  Acknowledgements

   The authors would like to acknowledge the review and inputs from xxx.

10.  References

10.1.  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>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
              <https://www.rfc-editor.org/info/rfc4456>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <https://www.rfc-editor.org/info/rfc5492>.

   [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>.

   [RFC8205]  Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
              Specification", RFC 8205, DOI 10.17487/RFC8205, September
              2017, <https://www.rfc-editor.org/info/rfc8205>.

10.2.  Informative References

Authors' Addresses

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   Haijun Xu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: xuhaijun@huawei.com

   Shunwan Zhuang
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: zhuangshunwan@huawei.com

   Haibo Wang
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: rainsword.wang@huawei.com

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