Internet DRAFT - draft-spaghetti-grow-bcp-ext-comms
draft-spaghetti-grow-bcp-ext-comms
Global Routing Operations J. Snijders
Internet-Draft Fastly
Intended status: Best Current Practice S. Konstantaras
Expires: 12 August 2024 AMS-IX
M. Shivji
LINX
9 February 2024
Recommendation to avoid use of BGP Extended Communities at Internet
Exchange Route Servers
draft-spaghetti-grow-bcp-ext-comms-00
Abstract
This document outlines a recommendation to the Internet operational
community to avoid the use of BGP Extended Communities in BGP
announcements. It includes guidance for both Internet Service
Provider networks and Internet Exchange Points (IXPs). This approach
aims to help the global Internet routing system's performance and
help protect Route Server participants against misconfigurations.
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 12 August 2024.
Copyright Notice
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 3
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
This document outlines a recommendation to the Internet operational
community to avoid the use of BGP Extended Communities [RFC4360] in
BGP announcements. It includes guidance for both Internet Service
Provider networks and Internet Exchange Points (IXPs). This approach
aims to help the global Internet routing system's performance and
help protect Route Server participants against misconfigurations.
2. 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.
3. Background
The main use-case for Extended Communities are as Route Targets
within VPN [RFC4364] deployments, but Extended Communities
historically also have been used as an operational utility to signal
requests to IXP Route-servers [RFC7947], [RFC7948] such as
functionality to reduce propagation scope or AS_PATH prepending.
Use of Extended Communities arose from a lack of support to fit
4-octet Autonomous System Numbers (ASNs) [RFC4893] in Classic BGP
communities [RFC1997], thus operators improvised a method that could
allow BGP signaling from IXP participants with 4-octet ASN. The
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6-octet space for the Global and Local administrator part of the BGP
Extended Community provides sufficient space for a single 4-octet
ASN. However, the 6-octet space is not sufficient enough should a
4-octet ASN participant of an IXP want to send a signal to a 4-octet
ASN Route Server or to another 4-octet ASN participant. Moreover,
the flexibility to insert a 4-octet ASN either in the Global or the
Local Administrator part, proved to bring extra complexity both in
the BGP implementations and in the route propagation functions that
are being triggered through BGP Extended Communities. Although, this
method was widely considered to be an acceptable workaround for a
period of time, a more robust and future proof solution was needed
that could overcome the aforementioned obstacles.
BGP Large communities [RFC8092] addressed the operational
requirements for working with 4-octet ASNs in a variety of scenarios.
With a total space of 12 octets divided into 3 separate fields,
signalling between 2-octet ASNs and 4-octet ASNs, or 4-octet ASNs and
4-octet ASNs, making the use of BGP Extended Communities redundant.
Since the introduction of BGP Large communities in 2017 - by now -
virtually all BGP implementations have adopted this standard, making
this feature usable in all public Internet deployments.
At the moment of writing, there are still IP Network and IXP
operators that support BGP Extended Communities for IXP Route Server
signalling purposes. However, supporting three flavors of BGP
Communities (Classic, Large, and Extended) contribute to increased
memory consumption, increased complexity in Routing Policies, and
reduced stability of the Internet ecosystem as BGP speakers need to
send a BGP UPDATE message every time any type of BGP Community is
added, removed or modified. As each and every BGP UPDATE message
propagated and received requires CPU cycles for processing, any
efforts that mimize the number of BGP UPDATE messages are
advantageous for the routing system. The authors of this document
posit that Extended Communities are superfluous in context of the
existence of Large Communities.
4. Recommendation
Operators that tag or match on route announcements on the public
Internet with Extended Communities for 4-octet ASNs are RECOMMENDED
to replace these configurations with equivalent functionality
implemented using Large Communities [RFC8092].
Operators of Internet Exchange Route Servers are RECOMMENDED to scrub
Extended Communities in both inbound and outbound directions.
5. Acknowledgments
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6. Security Considerations
There are no security considerations accompanying this document.
7. IANA Considerations
This document has no actions for IANA.
8. References
8.1. 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>.
[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>.
8.2. Informative References
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
<https://www.rfc-editor.org/info/rfc1997>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <https://www.rfc-editor.org/info/rfc4360>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
Number Space", RFC 4893, DOI 10.17487/RFC4893, May 2007,
<https://www.rfc-editor.org/info/rfc4893>.
[RFC7947] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
"Internet Exchange BGP Route Server", RFC 7947,
DOI 10.17487/RFC7947, September 2016,
<https://www.rfc-editor.org/info/rfc7947>.
[RFC7948] Hilliard, N., Jasinska, E., Raszuk, R., and N. Bakker,
"Internet Exchange BGP Route Server Operations", RFC 7948,
DOI 10.17487/RFC7948, September 2016,
<https://www.rfc-editor.org/info/rfc7948>.
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[RFC8092] Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas,
I., and N. Hilliard, "BGP Large Communities Attribute",
RFC 8092, DOI 10.17487/RFC8092, February 2017,
<https://www.rfc-editor.org/info/rfc8092>.
Authors' Addresses
Job Snijders
Fastly, Inc.
Amsterdam
Netherlands
Email: job@fastly.com
Stavros Konstantaras
Amsterdam Internet Exchange
Amsterdam
Netherlands
Email: stavros.konstantaras@ams-ix.net
Mo Shivji
London Internet Exchange Ltd
London
United Kingdom
Email: moyaze@linx.net
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