RFC 6608 PROPOSED STANDARD ROUTING · BGP
BGP FSM Error Subcodes: Subcodes for BGP Finite State Machine Error
Gives BGP Finite State Machine errors subcodes that say which state saw an unexpected message.
RFC EDITOR
Dong, J., Chen, M., and A. Suryanarayana, "Subcodes for BGP Finite State Machine Error", RFC 6608, DOI 10.17487/RFC6608, May 2012, <https://www.rfc-editor.org/info/rfc6608>.
BIBTEX
@misc{rfc6608,
series = {Request for Comments},
number = 6608,
howpublished = {RFC 6608},
publisher = {RFC Editor},
doi = {10.17487/RFC6608},
url = {https://www.rfc-editor.org/info/rfc6608},
author = {J. Dong and M. Chen and A. Suryanarayana},
title = {{Subcodes for BGP Finite State Machine Error}},
pagetotal = 5,
year = 2012,
month = may,
} LINEAGE · FROM THE RFC INDEXOpen full graph →
RFC text
Contents
Internet Engineering Task Force (IETF) J. Dong
Request for Comments: 6608 M. Chen
Updates: 4271 Huawei Technologies
Category: Standards Track A. Suryanarayana
ISSN: 2070-1721 Cisco Systems
May 2012
Subcodes for BGP Finite State Machine Error
Abstract
This document defines several subcodes for the BGP Finite State
Machine (FSM) Error that could provide more information to help
network operators in diagnosing BGP FSM issues and correlating
network events. This document updates RFC 4271.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 5741.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6608.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2
2. Requirements Language ...........................................2
3. Definition of Finite State Machine Error Subcodes ...............2
4. Usage of FSM Error Subcodes .....................................2
5. Security Considerations .........................................3
6. IANA Considerations .............................................3
7. Contributors ....................................................4
8. Acknowledgements ................................................4
9. References ......................................................4
9.1. Normative References .......................................4
9.2. Informative References .....................................4
1. Introduction
This document defines several subcodes for the BGP [RFC4271] Finite
State Machine (FSM) Error that could provide more information to help
network operators in diagnosing BGP FSM issues and correlating
network events. This information is also helpful to developers in
lab situations. This document updates [RFC4271] by requiring that
BGP implementations insert appropriate FSM Error subcodes in
NOTIFICATION messages for BGP FSM errors.
2. 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 RFC 2119 [RFC2119].
3. Definition of Finite State Machine Error Subcodes
This document defines the following subcodes for the BGP Finite State
Machine Error:
0 - Unspecified Error
1 - Receive Unexpected Message in OpenSent State
2 - Receive Unexpected Message in OpenConfirm State
3 - Receive Unexpected Message in Established State
4. Usage of FSM Error Subcodes
If a BGP speaker receives an unexpected message (e.g., KEEPALIVE/
UPDATE/ROUTE-REFRESH message) on a session in OpenSent state, it MUST
send to the neighbor a NOTIFICATION message with the Error Code
Finite State Machine Error and the Error Subcode "Receive Unexpected
Message in OpenSent State". The Data field is a 1-octet, unsigned
integer that indicates the type of the unexpected message.
If a BGP speaker receives an unexpected message (e.g., OPEN/UPDATE/
ROUTE-REFRESH message) on a session in OpenConfirm state, it MUST
send a NOTIFICATION message with the Error Code Finite State Machine
Error and the Error Subcode "Receive Unexpected Message in
OpenConfirm State" to the neighbor. The Data field is a 1-octet,
unsigned integer that indicates the type of the unexpected message.
If a BGP speaker receives an unexpected message (e.g., OPEN message)
on a session in Established State, it MUST send to the neighbor a
NOTIFICATION message with the Error Code Finite State Machine Error
and the Error Subcode "Receive Unexpected Message in Established
State". The Data field is a 1-octet, unsigned integer that indicates
the type of the unexpected message.
5. Security Considerations
Specification, implementation, and deployment of the proposed BGP FSM
Error subcodes could make BGP implementation fingerprinting easier
and probably more accurate. Operators using BGP need to consider
this as an operational security consideration of their BGP deployment
decisions.
[BFMR2010] discusses a number of BGP security issues and potential
solutions that might be relevant both to BGP implementers and BGP
operators.
6. IANA Considerations
IANA has created the registry "BGP Finite State Machine Error
Subcodes", within the "BGP Error Subcodes" registry, with a
Registration Procedure of "Standards Action" as defined in [RFC5226]
(early allocation of such subcodes is allowed, in accordance with
[RFC4020]).
The registry has been populated with the following values:
Value Name
0 Unspecified Error
1 Receive Unexpected Message in OpenSent State
2 Receive Unexpected Message in OpenConfirm State
3 Receive Unexpected Message in Established State
7. Contributors
The following individuals contributed to this document:
Xiaoming Gu
EMail: guxiaoming@huawei.com
Chong Wang
EMail: chongwang@huawei.com
8. Acknowledgements
The authors would like to thank John Scudder, Jeffrey Haas, Susan
Hares, Keyur Patel, Enke Chen, Ruediger Volk, and Ran Atkinson for
their valuable suggestions and comments to this document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4020] Kompella, K. and A. Zinin, "Early IANA Allocation of
Standards Track Code Points", BCP 100, RFC 4020, February
2005.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, January
2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
9.2. Informative References
[BFMR2010] Butler, K., Farley, T., Mcdaniel, P., and J. Rexford, "A
Survey of BGP Security Issues and Solutions", January
2010.
Authors' Addresses
Jie Dong
Huawei Technologies
Huawei Building, No.156 Beiqing Rd
Beijing 100095
China
EMail: jie.dong@huawei.com
Mach Chen
Huawei Technologies
Huawei Building, No.156 Beiqing Rd
Beijing 100095
China
EMail: mach.chen@huawei.com
Anantharamu Suryanarayana
Cisco Systems
USA
EMail: asuryana@cisco.com
AI ELI5
On this page
PROBLEMThe BGP Finite State Machine Error code gave operators little detail for diagnosing problems.
MECHANISMSubcodes 0 to 3 are defined, and a speaker that gets an unexpected message in OpenSent, OpenConfirm or Established MUST send a NOTIFICATION with the matching subcode.
WHY IT MATTERSOperators get more information, though the RFC warns it could make BGP implementation fingerprinting easier. It updates RFC 4271.
§1Why FSM Subcodes
The subcodes help network operators diagnose BGP finite state machine (FSM) problems and correlate network events, and help developers in lab situations. The RFC updates RFC 4271 by requiring BGP implementations to insert appropriate FSM Error subcodes in NOTIFICATION messages.
Extra detail on the error message helps people find the cause faster.
§2The Subcodes
Four subcodes are defined for the Finite State Machine Error:
0: Unspecified Error1: Receive Unexpected Message in OpenSent State2: Receive Unexpected Message in OpenConfirm State3: Receive Unexpected Message in Established State
Each number names a different step where the surprise happened.
§3How Speakers Use Them
If a speaker receives an unexpected message in OpenSent (for example KEEPALIVE, UPDATE or ROUTE-REFRESH), OpenConfirm (OPEN, UPDATE or ROUTE-REFRESH) or Established (for example OPEN), it MUST send a NOTIFICATION with the Finite State Machine Error code and the matching subcode.
The Data field is a 1-octet, unsigned integer indicating the type of the unexpected message.
When a router gets a message at the wrong time, it tells its neighbor which step it was in and what message surprised it.
§4Security and IANA
The subcodes could make BGP implementation fingerprinting easier and probably more accurate, which operators should consider as an operational security matter. IANA created the registry "BGP Finite State Machine Error Subcodes" with a Registration Procedure of "Standards Action", populated with values 0 to 3.
More detail helps repairs, but it could also help someone guess which brand of router you use.