IDR Workgroup A. Retana
Internet-Draft Y. Qu
Intended status: Standards Track Futurewei Technologies, Inc.
Expires: May 12, 2022 J. Tantsura
Microsoft
November 8, 2021
Use of Streams in BGP over QUIC
draft-retana-idr-bgp-quic-stream-01
Abstract
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
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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 . . . . . . . . 3
3. MultiStream Capability . . . . . . . . . . . . . . . . . . . 4
4. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 5
5. BGP Session Establishment and Collision Avoidance . . . . . . 5
6. Modifications to FSM . . . . . . . . . . . . . . . . . . . . 7
7. Operational Considerations . . . . . . . . . . . . . . . . . 7
7.1. Backward Compatibility . . . . . . . . . . . . . . . . . 7
7.2. Session Prioritization . . . . . . . . . . . . . . . . . 7
7.3. Other Considerations . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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
communication.
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
streams.
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
sessions.
1.1. 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. 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.
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
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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.
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
session.
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
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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.
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
one.
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
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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
[RFC6286].
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
procedure:
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).
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)
[RFC4486].
The remainder of the process is as specified in [RFC4271].
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6. Modifications to FSM
[To be completed.]
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.
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
document.
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.
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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
Capablity (Section 3) as follows:
+-------+----------------------+-----------------+------------------+
| Value | Description | Reference | Change |
| | | | Controller |
+-------+----------------------+-----------------+------------------+
| TBD1 | MultiStream | [This Document] | IETF |
| | Capability | | |
+-------+----------------------+-----------------+------------------+
MultiStream Capability
IANA is asked to assign three values from the OPEN Message Error
subcodes registrty as follows:
+-------+---------------------------------+-----------------+
| Value | Name | Reference |
+-------+---------------------------------+-----------------+
| TBD2 | MultiSession Conflicty | [This Document] |
| TBD3 | Session Capability Mismatch | [This Document] |
| TBD4 | Network Layer Protocol Mismatch | [This Document] |
+-------+---------------------------------+-----------------+
10. Acknowledgement
This document references the text and procedures defined in
[I-D.ietf-idr-bgp-multisession], and we are grateful for their
contributions.
The authors would like to thank xx for review and comments.
11. References
11.1. Normative References
[I-D.chen-idr-bgp-over-quic]
Chen, S., Zhang, Y., Wang, H., and Z. Li, "BGP Over QUIC",
draft-chen-idr-bgp-over-quic-00 (work in progress), June
2021.
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[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>.
[RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease
Notification Message", RFC 4486, DOI 10.17487/RFC4486,
April 2006, <https://www.rfc-editor.org/info/rfc4486>.
[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>.
[RFC6286] Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
Identifier for BGP-4", RFC 6286, DOI 10.17487/RFC6286,
June 2011, <https://www.rfc-editor.org/info/rfc6286>.
[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>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
11.2. Informative References
[I-D.ietf-idr-bgp-multisession]
Scudder, J., Appanna, C., and I. Varlashkin, "Multisession
BGP", draft-ietf-idr-bgp-multisession-07 (work in
progress), September 2012.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006,
<https://www.rfc-editor.org/info/rfc4272>.
[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>.
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[RFC7454] Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
February 2015, <https://www.rfc-editor.org/info/rfc7454>.
Authors' Addresses
Alvaro Retana
Futurewei Technologies, Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: aretana@futurewei.com
Yingzhen Qu
Futurewei Technologies, Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: yingzhen.qu@futurewei.com
Jeff Tantsura
Microsoft
USA
Email: jefftant.ietf@gmail.com
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