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Use of Streams in BGP over QUIC

Document Type Active Internet-Draft (individual)
Authors Alvaro Retana , Yingzhen Qu , Jeff Tantsura
Last updated 2022-05-11
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IDR Workgroup                                                  A. Retana
Internet-Draft                                                     Y. Qu
Intended status: Standards Track            Futurewei Technologies, Inc.
Expires: 12 November 2022                                    J. Tantsura
                                                             11 May 2022

                    Use of Streams in BGP over QUIC


   This document specifies the use of QUIC Streams to support multiple
   BGP sessions over one connection in order to achieve high resiliency.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 12 November 2022.

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   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Multiple BGP Sessions . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Multiple QUIC Streams . . . . . . . . . . . . . . . . . .   3
     2.2.  Multiple BGP Sessions Using QUIC Streams  . . . . . . . .   4
   3.  MultiStream Capability  . . . . . . . . . . . . . . . . . . .   4
   4.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  BGP Session Establishment and Collision Avoidance . . . . . .   6
   6.  Modifications to FSM  . . . . . . . . . . . . . . . . . . . .   7
   7.  Operational Considerations  . . . . . . . . . . . . . . . . .   7
     7.1.  Backward Compatibility  . . . . . . . . . . . . . . . . .   7
     7.2.  Session Prioritization  . . . . . . . . . . . . . . . . .   7
     7.3.  Other Considerations  . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     11.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The Border Gateway Protocol (BGP) [RFC4271] uses TCP as its transport
   protocol.  BGP establishes peer relationships between routers using a
   TCP session on port 179.  TCP also provides reliable packet

   Multiprotocol Extensions for BGP-4 (MP-BGP) [RFC4760] allow BGP to
   carry information for multiple Network Layer protocols.  However,
   only a single TCP connection can reach the Established state between
   a pair of peers [RFC4271].

   As pointed out by [I-D.ietf-idr-bgp-multisession], there are some
   disadvantages of using a single BGP session:

      A common criticism of BGP is the fact that most malformed messages
      cause the session to be terminated.  While this behavior is
      necessary for protocol correctness, one may observe that the
      protocol machinery of a given implementation may only be defective
      with respect to a given AFI/SAFI.  Thus, it would be desirable to
      allow the session related to that family to be terminated while
      leaving other AFI/SAFI unaffected.  As BGP is commonly deployed,
      this is not possible.

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      A second criticism of BGP is that it is difficult or in some cases
      impossible to manage control plane resource contention when BGP is
      used to support diverse services over a single session.  In
      contrast, if a single BGP session carries only information for a
      single service (or related set of services) it may be easier to
      manage such contention.

   QUIC [RFC9000] is a UDP-based multiplexed and secure transport
   protocol.  QUIC can provide low latency and encrypted transport with
   resilient connections.  [I-D.chen-idr-bgp-over-quic] specifies the
   procedure to use BGP over QUIC.  Complementary to it, this document
   specifies a mechanism to support multiple BGP sessions using QUIC

   Each BGP session operates independently.  Thus, an error on one
   session has no impact on any other session.  The Network Layer
   protocol(s) negotiated in the BGP OPEN message distinguish the

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.  Multiple BGP Sessions

2.1.  Multiple QUIC Streams

   QUIC [RFC9000] is a UDP-based secure transport protocol that provides
   connection-oriented and stateful interaction between a client and
   server.  It integrates TLS and allows the exchange of application
   data as soon as possible.

   In QUIC, application protocols exchange information via streams, and
   multiple streams can be multiplexed onto an underlying connection.
   Each stream is a separate unidirectional or bidirectional channel of
   "order stream of bytes."  Moreover, each stream has flow control
   which limits bytes sent on a stream, together with flow control of
   the connection.

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2.2.  Multiple BGP Sessions Using QUIC Streams

   BGP over QUIC [I-D.chen-idr-bgp-over-quic] proposes different options
   to map streams.  This document specifies a complementary and backward
   compatible mechanism to establish multiple BGP sessions using QUIC
   streams.  An implementation can assign one or more Network Layer
   protocols to a BGP session.

   A QUIC stream is created by sending a BGP OPEN message, and each
   stream MUST be bidirectional as described in Section 2.1 of
   [RFC9000].  In addition, the corresponding stream MUST end (clean
   termination) as described in Section 2.4 of [RFC9000] when a BGP
   session is terminated.

   Section 5 describes the Connection Collision Detection procedure to
   be used with streams.  Each BGP session operates independently, which
   means critical conditions (such as a malformed message) in one
   session won't affect others.

3.  MultiStream Capability

   The MultiStream Capability (MSC) is defined to indicate that a BGP
   speaker supports multiple sessions as specified in this document.
   The capability [RFC5492] is defined as follows:

      Capability code (1 octet): TBD1

      Capability length (1 octet): 1

      Capability value (1 octet): flag field reserved.

      0 1 2 3 4 5 6 7
     |   Reserved    |

   Flags: bitfield - MUST be set to zero and ignored by the receiver.

   The MSC only applies when using BGP over QUIC
   [I-D.chen-idr-bgp-over-quic].  It MUST be included in all OPEN
   messages.  It MUST be ignored otherwise.

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   This specification applies only if both peers advertise the MSC
   during the establishment of the "initial session."  Otherwise, the
   processes specified in [I-D.chen-idr-bgp-over-quic] MUST be followed.
   In particular, if a peer that advertises the MSC doesn't receive an
   OPEN message with the MSC from its peer, it SHOULD NOT terminate the

   Using the MSC allows peers to establish multiple BGP sessions, one
   per QUIC stream.  Each new BGP session is established using a
   separate OPEN message [RFC4271] and MUST include the MSC.  If both
   peers exchange the MSC in the "initial session," they MUST include it
   when establishing other sessions.  Otherwise, the new session MUST be
   terminated, and the Error Subcode MUST be set to MultiStream Conflict
   (TBD2), defined in Section 4.

   Once a BGP session is established, it follows the procedures
   specified in [RFC4271].

4.  Error Handling

   OPEN message error handling is defined in section 6.2 of [RFC4271].
   This document introduces the following OPEN Message Error subcodes:

      TBD2 - MultiSession Conflict - Used if the MSC is exchanged by
      both peers in the "initial session" but is not present when
      establishing a new session.

      TBD3 - Session Capability Mismatch - Used if a BGP speaker
      terminates a session in the case where it sends an OPEN message
      with the MSC but receives an OPEN message without it.

      TBD4 - Network Layer Protocol Mismatch - Used if a BGP session has
      already been established for a signaled Network Layer Protocol,
      either individually or as part of a set.

   Section 3 recommends not terminating a session when only one peer
   supports the MSC.  If such a BGP speaker does terminate the session,
   the Error Subcode MUST be set to Session Capability Mismatch (TBD3).

   Any individual BGP session can be terminated as specified in
   [RFC4486].  If multiple sessions are to be terminated, then the
   procedure MUST be followed for each one.

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5.  BGP Session Establishment and Collision Avoidance

   Before creating a new session, a BGP speaker should check that no
   session exists for the same Network Layer protocol(s).  If a session
   already exists, the BGP speaker SHOULD NOT attempt to create a new

   If a pair of BGP speakers try to establish a BGP session with each
   other simultaneously, then two parallel sessions will be formed.  In
   the case of BGP over QUIC, the IP addresses of the connection cannot
   be used to resolve collisions when using multiple streams.

   To avoid connection collisions, a session is identified by the My
   Autonomous System and BGP Identifier fields pair in the OPEN message.
   In this context, a connection collision is the attempt to open a BGP
   session for which the set of Network Layer protocols is the same.
   One of the connections MUST be closed.

   The connection collision is resolved using the extension specified in
   [RFC6286].  In other words, the session with the higher-valued BGP
   Identifier is preserved [RFC4271].  If the BGP Identifiers are
   identical, then the session with the larger ASN is preserved

   Upon receiving an OPEN message, the local system MUST examine all of
   its sessions in the OpenConfirm state.  A BGP speaker MAY also
   examine sessions in an OpenSent state if it knows the BGP Identifier
   of the peer by means outside of the protocol.  If among these
   sessions, there is one to a remote BGP speaker whose BGP Identifier
   and ASN pair equals the one in the OPEN message, and this session
   collides with the connection over which the OPEN message is received,
   then the local system performs the following collision resolution

      1) The BGP Identifier of the local system is compared to the BGP
      Identifier of the remote system (as specified in the OPEN
      message).  Comparing BGP Identifiers is done by converting them to
      host byte order and treating them as 4-octet unsigned integers.

      2) If the value of the local BGP Identifier is less than the
      remote one, the local system closes the BGP connection that
      already exists (the one that is already in the OpenConfirm state)
      and accepts the BGP connection initiated by the remote system.

      2a) Otherwise, the local system closes the newly created BGP
      connection (the one associated with the recently received OPEN
      message) and continues to use the existing one (the one that is
      already in the OpenConfirm state).

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      3) If the BGP Identifiers of the peers involved in the connection
      collision are identical, then the session initiated by the BGP
      speaker with the larger AS number is preserved.

   Unless allowed via configuration, a connection collision with an
   existing BGP session in the Established state causes the closing of
   the newly created session.

   Closing the BGP session (that results from the collision resolution
   procedure) is accomplished by sending the NOTIFICATION message with
   the Error Code Cease, Subcode Connection Collision Resolution (7)

   The remainder of the process is as specified in [RFC4271].

6.  Modifications to FSM

   The modifications to BGP FSM is described in section 4.4 of
   [I-D.chen-idr-bgp-over-quic].  For simplicity and security reason, it
   is suggested that 1-RTT is used.

   This specification does not modify BGP FSM, but the collision
   handling procedure should be replaced with the procedure described in
   this document.

7.  Operational Considerations

7.1.  Backward Compatibility

   A BGP speaker that doesn't understand the MSC will ignore it
   [RFC5492].  Section 3 recommends not terminating a session when only
   one peer supports the MSC.  Instead, the operation will continue as
   specified in [I-D.chen-idr-bgp-over-quic].

7.2.  Session Prioritization

   One of the drawbacks of a single BGP session is that control plane
   messages for all supported Network Layer protocols use the same
   connection, which may cause resource contention.

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   QUIC [RFC9000] does not provide a mechanism for exchanging
   prioritization information.  Instead, it recommends that
   implementations provide ways for an application to indicate the
   relative priority of streams, in this case, mapped to BGP sessions.
   An operator should prioritize BGP sessions (streams) that carry
   critical control plane information if the functionality is available.
   The definition of this functionality and the determination of the
   importance of a BGP session are both outside the scope of this

   An example implementation is to have four priority (0-3) defined, and
   smaller number means higher priority.  Each AFI/SAFI should be
   assigned a default priority and optional configuration to modify the
   default value.  For example, IPv4 and IPv6 unicast AFI/SAFI (1/1 and
   2/1) may have priority of 1, while BGP-LS (16388/71 and 16388/72) may
   have a priority of 3, and BGP FlowSpec (1/133 and 1/134) may have a
   priority of 4.

7.3.  Other Considerations

   A configuration command SHOULD be implemented to allow grouping of
   some AFI/SAFIs into one session.

8.  Security Considerations

   This document specifies how to establish multiple BGP sessions over a
   single QUIC connection.  The general operation of BGP is not changed,
   nor is its security model.  The security considerations of
   [I-D.chen-idr-bgp-over-quic] apply.  Also, the non-TCP-related
   considerations of [RFC4271], [RFC4272], and [RFC7454] apply to the
   specification in this document.

   By separating the control plane traffic over multiple sessions, the
   effect of a session-based vulnerability is reduced; only a single
   session is affected and not the whole connection.  The result is
   increased resiliency.

   On the other hand, a high number of BGP sessions may result in higher
   resource utilization and the risk of depletion.  Also, more sessions
   may imply additional configuration and operational complexity.
   However, this risk is mitigated by the fact that BGP sessions
   typically require explicit configuration by the operator.

9.  IANA Considerations

   IANA is asked to assign a new Capability Code for the MultiStream
   Capability (Section 3) as follows:

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    | Value | Description            | Reference | Change Controller |
    | TBD1  | MultiStream Capability | [This     | IETF              |
    |       |                        | Document] |                   |

                     Table 1: MultiStream Capability

   IANA is asked to assign three values from the OPEN Message Error
   subcodes registry as follows:

       | Value | Name                            | Reference       |
       | TBD2  | MultiSession Conflicty          | [This Document] |
       | TBD3  | Session Capability Mismatch     | [This Document] |
       | TBD4  | Network Layer Protocol Mismatch | [This Document] |

                                  Table 2

10.  Acknowledgement

   This document references the text and procedures defined in
   [I-D.ietf-idr-bgp-multisession], and we are grateful for their

   The authors would like to thank xx for review and comments.

11.  References

11.1.  Normative References

              Chen, S., Zhang, Y., Wang, H., and Z. Li, "BGP Over QUIC",
              Work in Progress, Internet-Draft, draft-chen-idr-bgp-over-
              quic-00, 3 June 2021, <

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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   [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,

   [RFC4486]  Chen, E. and V. Gillet, "Subcodes for BGP Cease
              Notification Message", RFC 4486, DOI 10.17487/RFC4486,
              April 2006, <>.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <>.

   [RFC6286]  Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
              Identifier for BGP-4", RFC 6286, DOI 10.17487/RFC6286,
              June 2011, <>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,

11.2.  Informative References

              Scudder, J., Appanna, C., and I. Varlashkin, "Multisession
              BGP", Work in Progress, Internet-Draft, draft-ietf-idr-
              bgp-multisession-07, 13 September 2012,

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,

   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
              February 2015, <>.

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Authors' Addresses

   Alvaro Retana
   Futurewei Technologies, Inc.
   2330 Central Expressway
   Santa Clara, CA 95050
   United States of America

   Yingzhen Qu
   Futurewei Technologies, Inc.
   2330 Central Expressway
   Santa Clara, CA 95050
   United States of America

   Jeff Tantsura
   United States of America

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