Network working group J. Dong
Internet Draft M. Chen
Intended status: Standards Track Huawei Technologies
Expires: September 1, 2010 A. Suryanarayana
Juniper Networks
March 1, 2010
Subcodes for BGP Finite State Machine Error
draft-dong-idr-fsm-subcode-00.txt
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Abstract
This document defines several subcodes for BGP Finite State Machine
Error that could provide more information to help network operators
in diagnosing BGP FSM issues and correlating network events. It also
provides a mechanism for BGP speaker to notify its peer the reason
for last time session flap after the session comes up again.
Table of Contents
1. Introduction.................................................2
2. Conventions used in this document............................2
3. Definition of Finite State Machine Error Subcodes............3
4. Usage of FSM Error Subcodes..................................3
5. BGP Session Information Capability...........................4
6. Operation of BGP Session Information Capability..............5
7. Security Considerations......................................6
8. IANA Considerations..........................................6
9. Contributors.................................................6
10. Acknowledgements............................................7
11. References..................................................7
11.1. Normative References...................................7
11.2. Informative References.................................7
12. Authors' Addresses..........................................8
1. Introduction
This document defines several subcodes for BGP Finite State Machine
Error that could provide more information to help network operators
in diagnosing BGP FSM issues and correlating network events. It also
provides a general mechanism for BGP speaker to notify its peer
additional information about the session. This document defines two
kinds of BGP Session Information: reason for last time session flap
and BGP speaker description.
2. Conventions used in this document
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 [RFC2119].
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3. Definition of Finite State Machine Error Subcodes
This document defines following subcodes for BGP Finite State Machine
Error:
0 - Unspecific Error
1 - Receive Unexpected Message in OpenSent State
2 - Receive Unexpected Message in OpenConfirm State
3 - Receive Unexpected Message in Established State
4 - Error Caused by TCP connection problem
4. Usage of FSM Error Subcodes
If a BGP speaker receives an unexpected message
(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 which indicates type of the unexpected message.
If a BGP speaker receives an unexpected message (OPEN/UPDATE/ROUTE-
REFRESH message) on a session in OpenConfirm 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
OpenConfirm State". The Data field is a 1-octet unsigned integer
which indicates type of the unexpected message.
If a BGP speaker receives an unexpected message (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 which indicates
type of the unexpected message.
If there is some problem in the underlying TCP connection, such as
connection closed, connection reset or connection timeout, the BGP
speaker SHOULD generate a Notification message with the Error Code
Finite State Machine Error and the Error Subcode "Error Caused by TCP
connection problem". This message MUST be recorded locally and SHOULD
be prepared to be sent to Network Management System (NMS) and BMP
monitoring station.
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In response to any other Finite State Machine error, the BGP speaker
SHOULD generate a Notification message with the Error Code Finite
State Machine Error and the Error Subcode "Unspecific Error".
5. BGP Session Information Capability
When there is some problem in underlying TCP connection, the Error
Code and Error Subcode cannot be advertised to peer because the
transmission is interrupted. Thus a mechanism is needed to send TCP
related Error information to peer when the session comes up again.
This document proposes to use a new BGP Capability to carry this
information, called BGP Session Information Capability.
A BGP speaker that is willing to announce additional information
about the session can use this capability as described below.
[RFC5492]
BGP Open message Parameter: 2 (Capability)
BGP Open message Parameter Length: Variable (Minimum: 2, Maximum: 255)
Capability Code: <Session Information Capability - TBA> (1 octet)
Capability Length: Variable (1 octet)
Capability Value: One or more informational entries as shown in
Figure 1.
+-----------------------------------+
| Information Type (1 octet) |
+-----------------------------------+
| Information Len (1 octet, Min: 2) |
+-----------------------------------+
| Information Value (Var length) |
+-----------------------------------+
Figure 1
This document defines following types of BGP Session Information:
Information Type: 1 (BGP Session Last Flap Cause)
Information Len: 4 (1 Octet)
Information Value: (2 Octets)
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Notification "Code" value of last session flap event followed by
Notification "Sub-Code" value of last session flap event.
Information Type: 2 (BGP Speaker Description)
Information Len: Variable (Min: 2)
Information value: Brief description of the BGP speaker in English
ASCII format.
Additional information types can be added to this TLV on a need basis.
6. Operation of BGP Session Information Capability
A BGP speaker that is willing to announce additional information
about the session should advertise the BGP Session Information
Capability to the peer using BGP Capability advertisement as
described in Section 5. [RFC5492]
A BGP speaker that receives Session Information Capability must
process and take necessary actions as appropriate. Since this
capability is mainly informational, contents must be stored and
presented to NMS. If unknown information type is found inside
information capability, it must be ignored.
"BGP Session Last Flap Cause" information is used to convey to the
peer, the reason for last session flap. A session is considered
"flapped" only if the session state ever moves out of the
"Established" state.
"BGP Speaker Description" information is used to convey additional
description type information to the peer. Typically this is useful
during BGP sessions trouble-shooting. This information can also be
used for "description - IP address mapping" to reduce manual
configuration of peer's description.
It is possible for one to fill up entire capability with just
information capability. Keeping this in mind, "Information Len" field
has been intentionally limited to a single byte. It is recommended
that implementations should take necessary precaution and encode
information capability only if there is enough room in the capability
area. It should also be given lower priority when there is contention
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for encoding capabilities in the limited open message capability
parameter space.
However, this problem is not applicable after [I-D.chen-bgp-ext-opt-
param] draft standardization is complete.
7. Security Considerations
This document does not change the security properties of BGP.
8. IANA Considerations
This document defines Error Subcodes 0 - 4 for BGP Finite State
Machine Error.
0 - Unspecific Error
1 - Receive Unexpected Message in OpenSent State
2 - Receive Unexpected Message in OpenConfirm State
3 - Receive Unexpected Message in Established State
4 - Error Caused by TCP connection problem
This document defines a new BGP Capability called BGP Session
Information Capability (TBA). This document defines following types
of BGP Session Information:
Name Type Value
---- ----------
BGP Session Last Flap Cause 1
BGP Speaker Description 2
9. Contributors
Xiaoming Gu
Huawei Technologies Co.,Ltd
HuaWei Bld., No.3 Xinxi Rd.,
Shang-Di Information Industry Base,
Hai-Dian District Beijing P.R. China
EMail: guxiaoming@huawei.com
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Chong Wang
Huawei Technologies Co.,Ltd
HuaWei Bld., No.3 Xinxi Rd.,
Shang-Di Information Industry Base,
Hai-Dian District Beijing P.R. China
EMail: chongwang@huawei.com
10. Acknowledgements
The authors would like to thank John Scudder for his valuable
comments to this document.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, May
2008.
[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5492] Scudder, J. and Chandra, R., "Capabilities Advertisement
with BGP-4" RFC 5492, February 2009.
11.2. Informative References
[I-D.chen-bgp-ext-opt-param] Chen, E. and Scudder, J., "Extended
Optional Parameters Length for BGP OPEN Message", draft-
chen-bgp-ext-opt-param-02 (work in progress), February 2010.
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12. Authors' Addresses
Jie Dong
Huawei Technologies Co.,Ltd.
KuiKe Building, No.9 Xinxi Rd.,
Hai-Dian District
Beijing, 100085
P.R. China
EMail: dongjie_dj@huawei.com
Mach(Guoyi) Chen
Huawei Technologies Co.,Ltd.
KuiKe Building, No.9 Xinxi Rd.,
Hai-Dian District
Beijing, 100085
P.R. China
EMail: mach@huawei.com
Anantharamu Suryanarayana
Juniper Networks
EMail: anantha@juniper.net
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