



IDR                                                             J. Zhang
Internet-Draft                                                 R. Zhuang
Intended status: Standards Track                            China Mobile
Expires: 16 September 2026                                      Z. Zhang
                                                                 D. Yuan
                                                         ZTE Corporation
                                                           15 March 2026


                          BGP PORT EC for AIDC
                      draft-zhang-idr-portid-ec-01

Abstract

   This document introduces a new BGP extended community attribute for
   use in AI computing, which announces the port ID between Leaf
   switches and servers as preparation for sending large-scale traffic
   before initiating AI tasks.

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 16 September 2026.

Copyright Notice

   Copyright (c) 2026 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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Format  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Specification . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   With the rapid development of Artificial Intelligence (AI) and
   Machine Learning (ML), AI tasks often generate large traffic due to
   the characteristics of large language model computation (LLM).  If
   the link bandwidth is insufficient, packet loss may occur.  AI
   computation has very high reliability requirements and extremely low
   tolerance for packet loss and latency.  When there is link congestion
   in the network that leads to packet loss or excessive latency, it
   will have a significant impact on the computational efficiency of AI
   tasks.

   In data centers used for AI and machine learning, BGP is often used
   as the routing protocol [RFC7938].  In some implementations,
   sufficient bandwidth between the destination server and its connected
   leaf switches must be ensured before sending traffic for AI tasks.
   On the network side, specifically the area comprised of the Leaf and
   Spine switches in Figure 1, there are numerous ECMP links.
   Techniques such as Packet Spray can be used to minimize congestion
   and packet loss.  However, on the computing side, specifically the
   last hop between the Leaf switches and the server, congestion can
   easily lead to packet loss, significantly reducing the efficiency of
   AI tasks.  To minimize or eliminate packet loss on the last hop, BGP
   needs to be extended to include port information on the destination
   leaf switch.  This allows the sender to negotiate based on this
   information before sending traffic, ensuring sufficient bandwidth is



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   available in the last hop and preventing congestion and packet loss
   due to insufficient bandwidth.  To reduce the stress caused by full-
   mesh connections, Leaf switches do not establish neighbors with each
   other.

               +--------+                         +--------+
               | Spine1 |                         | Spine2 |
               +-+-+-+-++                         +-+-+-+-++
                 | | | |                            | | | |
               +------------------------------------+ | | |
               | | | | |    +-------------------------+ | |
               | | | | |    |                   +-------+ |
               | | | | |    |                   |         |
               | | | | +-------------------------------------+
               | | | +-----------------------+  |         |  |
             +---+ +------+ |                |  |         |  |
             | |          | |                |  |         |  |
           +-+-+---+   +--+-+--+           +-+--+--+     ++--+---+
           | Leaf1 |   | Leaf2 |           | Leaf3 |     | Leaf4 |
           +--+-+--+   +---+-+-+           +--+-+--+     +---+-+-+
              | |          | |                | |            | |
              | +--------+ | |                | +----------+ | |
              |          | | |                |            | | |
              | +--------|-+ |                | +----------|-+ |
              | |        |   |                | |          |   |
        +-----+-+-+    +-+-+-+---+        +---+-+---+    +-+---+---+
        | Server1 |    | Server2 |        | Server3 |    | Server4 |
        +---------+    +---------+        +---------+    +---------+

                                  Figure 1

   Figure 1 shows a typical data center used for AI computing.  In this
   network, when Server2, 3, or 4 sends traffic to Server1 through
   leaf1, a common incast congestion problem may occur.  That is, the
   link 1 between Leaf1 switch and Server1 may be congested due to
   insufficient bandwidth, resulting in packet loss.

   Currently, some implementations negotiate before sending traffic from
   devices like Server2 and Server3 to Server1.  The AI task traffic is
   only sent if the link bandwidth between the destination server and
   its connected Leaf switch (referred to as the destination switch) is
   sufficient.  This negotiation method is outside the scope of this
   draft.  However, before negotiation, the port information connecting
   the destination switch to the server needs to be obtained.  This
   information will be sent via the newly added extended community
   "Route Port ID" in BGP.





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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Format

   When announcing the route to the connected server, the BGP protocol
   on the Leaf switch carries the switch's address and the port ID
   information connected to the destination server.

   Transitive IPv4-Address-Specific Extended Community defined in
   [RFC7153] and [I-D.ietf-idr-rfc4360-bis] with new sub-type "Route
   Port ID" is used for carry the IPv4 address of Leaf switch and the
   related port ID to the destination server.

   Transitive IPv6-Address-Specific Extended Community defined in
   [RFC5701] with new sub-type "Route Port ID" is used for carry the
   IPv6 address of the leaf switch and the related port ID to the
   destination server.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | 0x01 or 0x41  |   Sub-Type    |    Global Administrator       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Global Administrator (cont.)  |    Local Administrator        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 2

   Figure 2 shows the format of IPv4-Address-Specific Extended
   Community, where:

   *  Sub-Type: TBD.  This indicates that this is the Route Port ID
      extended community;

   *  Global Administrator: 4 octets, set to the IPv4 address of the
      switch that advertises the server route.  This address can be the
      loopback address for establishing the BGP connection;

   *  Local Administrator: 2 octets, set to the ID of the port
      connecting the switch and the server, with a value range of 1 to
      65535.






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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | 0x00 or 0x40  |    Sub-Type   |    Global Administrator       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Global Administrator (cont.)                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Global Administrator (cont.)                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Global Administrator (cont.)                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Global Administrator (cont.)  |    Local Administrator        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 3

   Figure 3 shows the format of IPv6-Address-Specific Extended
   Community, where:

   *  Sub-Type: TBD.  This indicates that this is the Route Port ID
      extended community;

   *  Global Administrator: 16 octets, set to the IPv6 address of the
      switch that advertises the server route.  This address can be the
      loopback address for establishing the BGP connection;

   *  Local Administrator: 2 octets, set to the ID of the port
      connecting the switch and the server, with a value range of 1 to
      65535.

3.  Specification

   When the Leaf switch advertises routes to the server, the
   advertisement includes the Route Port ID extended community, which is
   transmitted along with the route advertisement.

   In the example shown in Figure 1, Leaf1, when advertising routes to
   the Spine switch, includes the Route Port ID extended community,
   which contains the Loopback address used to establish the BGP
   connection and the port ID connected to the server.  The Leaf2 is the
   same.

   Upon receiving the route carrying the Route Port ID extended
   community, the leaf switch checks if the address is reachable.  If
   unreachable, the extended community is ignored.  If reachable, the
   address and port information are stored locally or sent to the
   server.  This storing or sending process is outside the scope of this
   draft.



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   Because data centers used for AI computing have a large number of
   ECMP paths, deploying this feature requires enabling the ADD-PATH
   advertisement function defined in [RFC7911], to ensure the
   propagation of extended community attributes.  Spine or higher-level
   switches do not need to generate entries based on this extended
   community attribute.  To avoid a large number of route advertisements
   that may result from enabling the ADD-PATH function, this
   advertisement SHOULD be limited to a single PoD.

   When a server wants to send large traffic for AI tasks, it will
   negotiate bandwidth based on the destination switch and port
   information obtained from BGP.  Traffic will only be sent after
   successful negotiation, thus avoiding packet loss caused by
   congestion.  Traffic will be sent to the server via the successfully
   negotiated Leaf switch.  This negotiation process is outside the
   scope of this draft.

   In the example shown in Figure 1, the routes advertised by Leaf1 and
   Leaf2 to Server1 will carry the Route Port ID extended community.
   When Server3 wants to send AI task traffic to Server1, it can first
   negotiate with Leaf1.  If the negotiation fails, it may negotiate
   with Leaf2.  Only after the negotiation succeeds will the traffic be
   sent.  In this example, assuming Leaf1 is successfully negotiated,
   traffic will be sent to Server1 through Leaf1.

4.  IANA Considerations

   IANA is requested to allocate two new code points from the
   "Transitive IPv4-Address-Specific Extended Community Sub-Types" and
   the "Transitive IPv6-Address-Specific Extended Community Sub-Types"
   registry.

                 +======+===============+===============+
                 | Type |  Description  |   Reference   |
                 +======+===============+===============+
                 | TBD  | Route Port ID | This Document |
                 +------+---------------+---------------+

                             Table 1: TABLE_1

5.  Security Considerations

   This extension to BGP has similar security implications as BGP
   Extended Communities [RFC7153], [RFC5701] and
   [I-D.ietf-idr-rfc4360-bis].

6.  References




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6.1.  Normative References

   [I-D.ietf-idr-rfc4360-bis]
              Sangli, S. R. and N. Kao, "BGP Extended Communities
              Attribute", Work in Progress, Internet-Draft, draft-ietf-
              idr-rfc4360-bis-02, 6 December 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              rfc4360-bis-02>.

   [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>.

   [RFC5701]  Rekhter, Y., "IPv6 Address Specific BGP Extended Community
              Attribute", RFC 5701, DOI 10.17487/RFC5701, November 2009,
              <https://www.rfc-editor.org/info/rfc5701>.

   [RFC7153]  Rosen, E. and Y. Rekhter, "IANA Registries for BGP
              Extended Communities", RFC 7153, DOI 10.17487/RFC7153,
              March 2014, <https://www.rfc-editor.org/info/rfc7153>.

6.2.  Informative References

   [RFC7911]  Walton, D., Retana, A., Chen, E., and J. Scudder,
              "Advertisement of Multiple Paths in BGP", RFC 7911,
              DOI 10.17487/RFC7911, July 2016,
              <https://www.rfc-editor.org/info/rfc7911>.

   [RFC7938]  Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of
              BGP for Routing in Large-Scale Data Centers", RFC 7938,
              DOI 10.17487/RFC7938, August 2016,
              <https://www.rfc-editor.org/info/rfc7938>.

Authors' Addresses

   Junye Zhang
   China Mobile
   China
   Email: zhangjunye@chinamobile.com


   Rui Zhuang
   China Mobile
   China
   Email: zhuangruiyjy@chinamobile.com





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   Zheng Zhang
   ZTE Corporation
   China
   Email: zhang.zheng@zte.com.cn


   Dongyu Yuan
   ZTE Corporation
   China
   Email: yuan.dongyu@zte.com.cn









































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