draft-ietf-idr-bgp-extended-messages-28.txt   draft-ietf-idr-bgp-extended-messages-29.txt 
Network Working Group R. Bush Network Working Group R. Bush
Internet-Draft Internet Initiative Japan Internet-Draft Internet Initiative Japan
Updates: 4271 (if approved) K. Patel Updates: 4271 (if approved) K. Patel
Intended status: Standards Track Arrcus, Inc. Intended status: Standards Track Arrcus, Inc.
Expires: August 17, 2019 D. Ward Expires: September 11, 2019 D. Ward
Cisco Systems Cisco Systems
February 13, 2019 March 10, 2019
Extended Message support for BGP Extended Message support for BGP
draft-ietf-idr-bgp-extended-messages-28 draft-ietf-idr-bgp-extended-messages-29
Abstract Abstract
The BGP specification mandates a maximum BGP message size of 4096 The BGP specification mandates a maximum BGP message size of 4096
octets. As BGP is extended to support newer AFI/SAFIs and other octets. As BGP is extended to support newer AFI/SAFIs and other
features, there is a need to extend the maximum message size beyond features, there is a need to extend the maximum message size beyond
4096 octets. This document updates the BGP specification RFC4271 by 4096 octets. This document updates the BGP specification RFC4271 by
providing an extension to BGP to extend its current maximum message providing an extension to BGP to extend its current maximum message
size from 4096 octets to 65535 octets for all except the OPEN size from 4096 octets to 65535 octets for all except the OPEN
message. message.
skipping to change at page 1, line 47 skipping to change at page 1, line 47
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 17, 2019. This Internet-Draft will expire on September 11, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 28 skipping to change at page 2, line 28
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGP Extended Message . . . . . . . . . . . . . . . . . . . . 2 2. BGP Extended Message . . . . . . . . . . . . . . . . . . . . 2
3. Extended Message Capability for BGP . . . . . . . . . . . . . 3 3. Extended Message Capability for BGP . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 4 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 4
6. Changes to RFC4271 . . . . . . . . . . . . . . . . . . . . . 4 6. Changes to RFC4271 . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 5 10.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
The BGP specification [RFC4271] mandates a maximum BGP message size The BGP specification [RFC4271] mandates a maximum BGP message size
of 4096 octets. As BGP is extended to support newer AFI/SAFIs and of 4096 octets. As BGP is extended to support newer AFI/SAFIs and
newer capabilities (e.g., BGPsec, [RFC8205], BGP-LS, [RFC7752]), newer capabilities (e.g., BGPsec, [RFC8205], BGP-LS, [RFC7752]),
there is a need to extend the maximum message size beyond 4096 there is a need to extend the maximum message size beyond 4096
octets. This draft provides an extension to BGP to extend its octets. This draft provides an extension to BGP to extend its
current message size limit from 4096 octets to 65535 octets for all current message size limit from 4096 octets to 65535 octets for all
except the OPEN message. except the OPEN message.
skipping to change at page 3, line 13 skipping to change at page 3, line 13
data portion (19 octets). data portion (19 octets).
3. Extended Message Capability for BGP 3. Extended Message Capability for BGP
To advertise the BGP Extended Message Capability to a peer, a BGP To advertise the BGP Extended Message Capability to a peer, a BGP
speaker uses BGP Capabilities Advertisement [RFC5492]. By speaker uses BGP Capabilities Advertisement [RFC5492]. By
advertising the BGP Extended Message Capability to a peer, a BGP advertising the BGP Extended Message Capability to a peer, a BGP
speaker conveys that it is able to send, receive, and properly handle speaker conveys that it is able to send, receive, and properly handle
BGP Extended Messages. BGP Extended Messages.
A peer which does not advertise this capability MUST NOT send BGP
Extended Messages, and BGP Extended Messages MUST NOT be sent to it.
The BGP Extended Message Capability is a new BGP Capability [RFC5492] The BGP Extended Message Capability is a new BGP Capability [RFC5492]
defined with Capability code 6 and Capability length 0. defined with Capability code 6 and Capability length 0.
A peer which does not advertise this capability MUST NOT send BGP
Extended Messages, and BGP Extended Messages MUST NOT be sent to it.
4. Operation 4. Operation
A BGP speaker that is capable of sending and receiving BGP Extended A BGP speaker that is capable of sending and receiving BGP Extended
Messages SHOULD advertise the BGP Extended Message Capability to the Messages SHOULD advertise the BGP Extended Message Capability to the
peer using BGP Capabilities Advertisement [RFC5492]. A BGP speaker peer using BGP Capabilities Advertisement [RFC5492]. A BGP speaker
MAY send Extended Messages to its peer only if it has sent and MAY send Extended Messages to its peer only if it has fully exchanged
received the Extended Message Capability from that peer. the Extended Message Capability with that peer.
The Extended Message Capability applies to all messages except for The Extended Message Capability applies to all messages except for
the OPEN message. This exception is made to reduce complexity of the OPEN message. This exception is made to reduce complexity of
providing backward compatibility providing backward compatibility
An implementation that advertises support for BGP Extended Messages An implementation that advertises support for BGP Extended Messages
MUST be capable of receiving a message with a length up to and MUST be capable of receiving a message with a length up to and
including 65535 octets. including 65535 octets.
Applications generating information which might be encapsulated Applications generating information which might be encapsulated
skipping to change at page 3, line 47 skipping to change at page 3, line 47
maximum message size into account. maximum message size into account.
If a BGP update with a payload longer than 4096 octets is received by If a BGP update with a payload longer than 4096 octets is received by
a BGP listener who has neither advertised nor agreed to accept BGP a BGP listener who has neither advertised nor agreed to accept BGP
Extended Messages, the listener MUST treat this as a malformed update Extended Messages, the listener MUST treat this as a malformed update
message, and MUST raise an UPDATE Message Error (see [RFC4271] Sec message, and MUST raise an UPDATE Message Error (see [RFC4271] Sec
6.3). 6.3).
A BGP announcement will, in the normal case, propagate throughout the A BGP announcement will, in the normal case, propagate throughout the
BGP speaking Internet; and there will undoubtedly be BGP speakers BGP speaking Internet; and there will undoubtedly be BGP speakers
which do not have the Extended Message capability. Therefore, which do not have the Extended Message capability. Therefore, having
putting an attribute which can not be decomposed to 4096 octets or an attribute set which can not be decomposed to 4096 octets or less
less in an Extended Message is a likely path to routing failure. in an Extended Message will likely raise errors.
A BGP speaker with a mixture of peers some of which have negotiated
BGP Extended Message capability and some which have not, MUST
o support [RFC7606], and
o "treat as withdraw' (see [RFC7606]) a BGP attribue/NLRI pair which
is too large to be sent to a peer which does not support BGP
Extended Messages.
The BGP speaker MAY remove some BGP attributes which are eligible to
use the Attribute discard approach in [RFC7606].
In an iBGP mesh, all peers SHOULD support the BGP Extended Message
Capability and [RFC7606]. Only then is it consistent to deploy with
eBGP peers.
During the incremental deployment of BGP Extended Messages and
[RFC7606] in an iBGP mesh, or with eBGP peers, the operator should
monitor any routes dropped as "treat as withdraw".
It is RECOMMENDED that BGP protocol developers and implementers are It is RECOMMENDED that BGP protocol developers and implementers are
conservative in their application and use of Extended Messages. conservative in their application and use of Extended Messages.
Future protocol specifications will need to describe how to handle Future protocol specifications will need to describe how to handle
peers which can only accommodate 4096 octet messages. peers which can only accommodate 4096 octet messages.
5. Error Handling 5. Error Handling
A BGP speaker that has the ability to use Extended Messages but has A BGP speaker that has the ability to use Extended Messages but has
not advertised the BGP Extended Messages capability, presumably due not advertised the BGP Extended Messages capability, presumably due
to configuration, SHOULD NOT accept an Extended Message. A speaker to configuration, SHOULD NOT accept an Extended Message. A speaker
MAY implement a more liberal policy and accept Extended Messages, SHOULD NOT implement a more liberal policy accepting BGP Extended
even from a peer to which it has not advertised the capability, in Messages.
the interest of preserving the BGP session if at all possible.
A BGP speaker that does not advertise the BGP Extended Messages A BGP speaker that does not advertise the BGP Extended Messages
capability might also genuinely not support Extended Messages. Such capability might also genuinely not support Extended Messages. Such
a speaker MUST follow the error handling procedures of [RFC4271] if a speaker will follow the error handling procedures of [RFC4271] if
it receives an Extended Message. Similarly, any speaker that treats it receives an Extended Message. Similarly, any speaker that treats
an improper Extended Message as a fatal error, MUST treat it an improper Extended Message as a fatal error, MUST treat it
similarly. similarly.
The inconsistency between the local and remote BGP speakers MUST be The inconsistency between the local and remote BGP speakers MUST be
flagged to the network operator through standard operational flagged to the network operator through standard operational
interfaces. The information should include the NLRI and as much interfaces. The information should include the NLRI and as much
relevant information as reasonably possible. relevant information as reasonably possible.
6. Changes to RFC4271 6. Changes to RFC4271
skipping to change at page 5, line 10 skipping to change at page 5, line 26
Value Description Document Value Description Document
----- ----------------------------------- ------------- ----- ----------------------------------- -------------
6 BGP-Extended Message [this draft] 6 BGP-Extended Message [this draft]
8. Security Considerations 8. Security Considerations
This extension to BGP does not change BGP's underlying security This extension to BGP does not change BGP's underlying security
issues; see [RFC4272]. issues; see [RFC4272].
Section 5 allowed a receiver to accept an Extended Message even Section 5 allows a receiver to accept an Extended Message even though
though it had not advertised the capability. This slippery slope it had not advertised the capability. This slippery slope could lead
could lead to sloppy implementations sending Extended Messages when to sloppy implementations sending Extended Messages when the receiver
the receiver is not prepared to deal with them, e.g. to peer groups. is not prepared to deal with them, e.g. to peer groups. At best,
At best, this will result in errors; at worst, buffer overflows. this will result in errors; at worst, buffer overflows.
Due to increased memory requirements for buffering, there may be Due to increased memory requirements for buffering, there may be
increased exposure to resource exhaustion, intentional or increased exposure to resource exhaustion, intentional or
unintentional. unintentional.
As this draft requires support for [RFC7606] update error handling,
it inherits the security considerations of [RFC7606]. BGP peers may
avoid such issues by using Authenticated Encryption with additional
Data (AEAD) ciphers [RFC5116] and discard messages that do not
verify.
If a remote attacker is able to craft a large BGP Extended Message to
send on a path where one or more peers do not support BGP Extended
Messages, peers which support BGP Extended Messages may incur
resource load (processing, message resizing, etc.) reformatting the
large messages. Worse, ([RFC7606] "treat as withdraw" may
consistently withdraw announcements causing inconsistent routing.
BGP routes are filtered by policies set by the operators.
Implementations may provide policies to filter routes that would
cause the "treat as withdraw" from being pass by an extended message
speaker.
9. Acknowledgments 9. Acknowledgments
The authors thank Alvaro Retana, Enke Chen, Susan Hares, John The authors thank Alvaro Retana, Enke Chen, Susan Hares, John
Scudder, John Levine, and Job Snijders for their input; and Oliver Scudder, John Levine, and Job Snijders for their input; and Oliver
Borchert and Kyehwan Lee for their implementations and testing. Borchert and Kyehwan Lee for their implementations and testing.
10. References 10. References
10.1. Normative References 10.1. Normative References
skipping to change at page 5, line 44 skipping to change at page 6, line 29
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>. <http://www.rfc-editor.org/info/rfc4271>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006, RFC 4272, DOI 10.17487/RFC4272, January 2006,
<http://www.rfc-editor.org/info/rfc4272>. <http://www.rfc-editor.org/info/rfc4272>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<http://www.rfc-editor.org/info/rfc5116>.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
2009, <http://www.rfc-editor.org/info/rfc5492>. 2009, <http://www.rfc-editor.org/info/rfc5492>.
[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
Patel, "Revised Error Handling for BGP UPDATE Messages",
RFC 7606, DOI 10.17487/RFC7606, August 2015,
<http://www.rfc-editor.org/info/rfc7606>.
10.2. Informative References 10.2. Informative References
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<http://www.rfc-editor.org/info/rfc7752>. <http://www.rfc-editor.org/info/rfc7752>.
[RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol [RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
Specification", RFC 8205, DOI 10.17487/RFC8205, September Specification", RFC 8205, DOI 10.17487/RFC8205, September
 End of changes. 17 change blocks. 
28 lines changed or deleted 71 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/