draft-ietf-idr-bgp-gr-notification-03.txt   draft-ietf-idr-bgp-gr-notification-04.txt 
Network Working Group K. Patel Network Working Group K. Patel
Internet-Draft R. Fernando Internet-Draft R. Fernando
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: December 5, 2014 J. Scudder Expires: October 29, 2015 J. Scudder
J. Haas J. Haas
Juniper Networks Juniper Networks
June 3, 2014 April 27, 2015
Notification Message support for BGP Graceful Restart Notification Message support for BGP Graceful Restart
draft-ietf-idr-bgp-gr-notification-03.txt draft-ietf-idr-bgp-gr-notification-04.txt
Abstract Abstract
The current BGP Graceful Restart mechanism limits the usage of BGP The current BGP Graceful Restart mechanism limits the usage of BGP
Graceful Restart to BGP protocol messages other than a BGP Graceful Restart to BGP protocol messages other than a BGP
NOTIFICATION message. This document defines an extension to the BGP NOTIFICATION message. This document defines an extension to the BGP
Graceful Restart that permits the Graceful Restart procedures to be Graceful Restart that permits the Graceful Restart procedures to be
performed when the BGP speaker receives a BGP NOTIFICATION Message. performed when the BGP speaker receives a BGP NOTIFICATION Message.
This document also defines a new BGP NOTIFICATION Cease Error subcode This document also defines a new BGP NOTIFICATION Cease Error subcode
to prevent BGP speakers supporting the extension defined in this to prevent BGP speakers supporting the extension defined in this
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This Internet-Draft will expire on December 5, 2014. This Internet-Draft will expire on October 29, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Modifications to BGP Graceful Restart Capability . . . . . . 3 2. Modifications to BGP Graceful Restart Capability . . . . . . 3
3. BGP Hard Reset Subcode . . . . . . . . . . . . . . . . . . . 4 3. BGP Hard Reset Subcode . . . . . . . . . . . . . . . . . . . 4
3.1. Sending a Hard Reset . . . . . . . . . . . . . . . . . . 4 3.1. Sending a Hard Reset . . . . . . . . . . . . . . . . . . 4
3.2. Receiving a Hard Reset . . . . . . . . . . . . . . . . . 5 3.2. Sending a Hard Reset . . . . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Rules for the Receiving Speaker . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
For many classes of errors, the BGP protocol must send a NOTIFICATION For many classes of errors, the BGP protocol must send a NOTIFICATION
message and reset the peering session to handle the error condition. message and reset the peering session to handle the error condition.
The BGP Graceful Restart extension defined in [RFC4724] requires that The BGP Graceful Restart extension defined in [RFC4724] requires that
normal BGP procedures defined in [RFC4271] be followed when a normal BGP procedures defined in [RFC4271] be followed when a
NOTIFICATION message is sent or received. This document defines an NOTIFICATION message is sent or received. This document defines an
extension to BGP Graceful Restart that permits the Graceful Restart extension to BGP Graceful Restart that permits the Graceful Restart
procedures to be performed when the BGP speaker receives a procedures to be performed when the BGP speaker receives a
NOTIFICATION message. This permits the BGP speaker to avoid flapping NOTIFICATION message. This permits the BGP speaker to avoid flapping
reachability and continue forwarding while the BGP speaker restarts reachability and continue forwarding while the BGP speaker restarts
the session to handle errors detected in the BGP protocol. the session to handle errors detected in the BGP protocol.
At a high level, this document can be summed up as follows. When a This document defines a BGP NOTIFICATION cease Error subcode for the
BGP session is reset, both speakers operate as "Receiving Speakers" Cease Error code to prevent BGP speakers supporting the extension
according to [RFC4724], meaning they retain each other's routes. defined in this document from performing a Graceful Restart.
This is also true for HOLDTIME expiration. The functionality can be
defeated using a "Hard Reset" subcode for the BGP NOTIFICATION Cease
Error code. If a Hard Reset is used, a full session reset is
performed.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Modifications to BGP Graceful Restart Capability 2. Modifications to BGP Graceful Restart Capability
The BGP Graceful Restart Capability is augmented to signal the The BGP Graceful Restart Capability is augmented to signal the
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Restart Flags: Restart Flags:
This field contains bit flags relating to restart. This field contains bit flags relating to restart.
0 1 2 3 0 1 2 3
+-+-+-+-+ +-+-+-+-+
|R|N| | |R|N| |
+-+-+-+-+ +-+-+-+-+
The second most significant bit ("N") is defined as the BGP Graceful The second most significant bit "N" is defined as a BGP Graceful
Notification bit, which is used to indicate Graceful Restart support Notification bit, which is used to indicate the Graceful Restart
for BGP NOTIFICATION messages. A BGP speaker indicates support for support for BGP NOTIFICATION messages. BGP speaker indicates the
the procedures of this document, by advertising a Graceful Restart Graceful Restart support for BGP NOTIFICATION messages and its
Capability with its Graceful NOTIFICATION bit set (value 1). This ability to handle the new BGP NOTIFICATION Cease message subcode and
also implies support for the format for a BGP NOTIFICATION Cease the format for a BGP NOTIFICATION Cease message defined in [RFC4486]
message defined in [RFC4486]. when the Graceful NOTIFICATION bit is set (value 1).
Flags for Address Family: Flags for Address Family:
This field contains bit flags relating to routes that were This field contains bit flags relating to routes that were
advertised with the given AFI and SAFI. advertised with the given AFI and SAFI.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|F|N| Reserved | |F|N| Reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
The usage of second most significant bit "N" is deprecated. This bit The usage of second most significant bit "N" is deprecated. This bit
MUST be advertised as 0 and MUST be ignored upon receipt. SHOULD be reserved and set to 0.
3. BGP Hard Reset Subcode 3. BGP Hard Reset Subcode
A new BGP NOTIFICATION Cease message subcode is defined known as the A new BGP Cease message subcode is defined known as BGP Hard Reset
BGP Hard Reset Subcode. The value of this subcode is discussed in Subcode. The value of this subcode is 9.
Section 6. We refer to a BGP NOTIFICATION Cease message with the
Hard Reset subcode as a Hard Reset message, or just a Hard Reset.
3.1. Sending a Hard Reset 3.1. Sending a Hard Reset
A Hard Reset message is used to indicate to a peer with which the A Hard Reset NOTIFICATION Message is used to indicate to a peer with
Graceful Notification flag has been exchanged, that the session is to which the Graceful Notification flag has been exchanged, that the
be fully terminated. session is to be fully terminated.
When sending a Hard Reset, the data portion of the NOTIFICATION is
encoded as follows:
+--------+--------+--------
| ErrCode| Subcode| Data
+--------+--------+--------
ErrCode is a BGP Error Code (as documented in the IANA BGP Error
Codes registry) that indicates the reason for the hard reset.
Subcode is a BGP Error Subcode (as documented in the IANA BGP Error When sending a Hard Reset NOTIFICATION, the data portion of the
Subcodes registry) as appropriate for the ErrCode. Similarly, Data NOTIFICATION message MUST be used to indicate the reason for the hard
is as appropriate for the ErrCode and Subcode. reset. The reason is encoded using a standard BGP Cease error
subcode and MAY also include any relevant data subsequent to the
subcode.
3.2. Receiving a Hard Reset 3.2. Sending a Hard Reset
Whenever a BGP speaker receives a Hard Reset, the speaker MUST Whenever a BGP speaker receives a NOTIFICATION message with the Cease
terminate the BGP session following the standard procedures in Error code and Hard Reset Error subcode, the speaker MUST terminate
[RFC4271]. the BGP session following the standard procedures in [RFC4271].
4. Operation 4. Operation
A BGP speaker that is willing to receive and send BGP NOTIFICATION A BGP speaker that is willing to receive and send BGP NOTIFICATION
messages in Graceful mode MUST advertise the BGP Graceful messages in Graceful mode SHOULD advertise the BGP Graceful
Notification Flag "N" using the Graceful Restart Capability as Notification Flag "N" using the Graceful Restart Capability as
defined in [RFC4724]. defined in [RFC4724].
When such a BGP Speaker receives a BGP NOTIFICATION message other When a BGP Speaker receives a BGP NOTIFICATION message, it SHOULD
than a Hard Reset, it MUST follow the rules for the Receiving Speaker follow the standard rules of the receiving speaker mentioned in
mentioned in Section 4.1. The BGP speaker generating the BGP [RFC4724] for all AFI/SAFIs for which it has announced the BGP
NOTIFICATION message MUST also follow the rules for the Receiving Graceful Notification flag. The BGP speaker generating a BGP
Speaker. NOTIFICATION message SHOULD follow the standard rules of the
receiving Speaker in [RFC4724] for all AFI/SAFIs that were announced
When a BGP speaker resets its session due to a HOLDTIME expiry, it with the BGP Graceful Notification flag.
should generate the relevant BGP NOTIFICATION message as mentioned in
[RFC4271], but subsequently it MUST follow the rules for the
Receiving Speaker mentioned in Section 4.1.
Once the session is re-established, both BGP speakers SHOULD set
their "Forwarding State" bit to 1. If the "Forwarding State" bit is
not set, then according to the procedures of [RFC4724] S. 4.2, the
relevant routes will be flushed, defeating the goals of this
specification.
4.1. Rules for the Receiving Speaker
[RFC4724] S. 4.2 defines rules for the Receiving Speaker. These are A BGP speaker MAY continue to operate in the Graceful Restart mode
modified as follows. even if it receives a Graceful Restart capability without a Graceful
Notification Flag.
As part of this extension, routes from the peer previously marked as When a BGP speaker resets its session due to a HOLDTIME expiry, it
stale MUST NOT be deleted, until and unless the timer mentioned in SHOULD follow the standard rules of the receiving speaker mentioned
the final paragraph of [RFC4724] S. 4.2 expires, or unless a Hard in [RFC4724] aside from generating a BGP NOTIFICATION message as
Reset is performed. This supersedes the "consecutive restarts" mentioned in [RFC4271].
requirement of [RFC4724] S. 4.2.
In addition to the rules already specified in [RFC4724] S. 4.2 for Once the session is re-established, both BGP speakers MUST set their
how variations in the received Graceful Restart Capability should be "Forwarding State" bit to 1 if they want to apply planned graceful
interpreted (the paragraph that begins "Once the session is re- restart. The handling of the "Forwarding State" bit should be done
established..."), if the Graceful Notification ("N") bit is not set as specified by the procedures of the Receiving speaker in [RFC4724]
in the newly received Graceful Restart Capability, no new actions are are applied.
triggered on the Receiving Speaker -- in particular, a clear "N" bit
does not trigger deletion of stale routes.
Other than these modifications, the rules for the Receiving Speaker As part of this extension, any possible consecutive restarts SHOULD
are as specified in [RFC4724] S. 4.2. NOT delete a route (from the peer) previously marked as stale, until
required by rules mentioned in [RFC4724].
5. Acknowledgements 5. Acknowledgements
The authors would like to thank Jim Uttaro for the suggestion, and The authors would like to thank Robert Raszuk for the review and
Chris Hall, Paul Mattes and Robert Raszuk for the review and
comments. comments.
6. IANA Considerations 6. IANA Considerations
IANA is requested to assign a new subcode in the "BGP Cease This document defines a new BGP Cease message subcode known as BGP
NOTIFICATION message subcodes" registry. The suggested name for the Hard Reset Subcode. IANA mantains the list of existing BGP Cease
code point is "Hard Reset". The suggested value is 9. message subcodes. This document proposes defining a new BGP Cease
message subcode known as BGP Hard Reset Subcode with the value 9.
7. Security Considerations 7. Security Considerations
This extension to BGP does not change the underlying security issues This extension to BGP does not change the underlying security issues
inherent in the existing [RFC4724] and [RFC4271]. inherent in the existing [RFC4724] and [RFC4271]
8. Normative References 8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2842] Chandra, R. and J. Scudder, "Capabilities Advertisement
with BGP-4", RFC 2842, May 2000.
[RFC3392] Chandra, R. and J. Scudder, "Capabilities Advertisement [RFC3392] Chandra, R. and J. Scudder, "Capabilities Advertisement
with BGP-4", RFC 3392, November 2002. with BGP-4", RFC 3392, November 2002.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease
Notification Message", RFC 4486, April 2006. Notification Message", RFC 4486, April 2006.
[RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y. [RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724, Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
January 2007. January 2007.
8.2. Informative References
[RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
"Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.
Authors' Addresses Authors' Addresses
Keyur Patel Keyur Patel
Cisco Systems Cisco Systems
170 W. Tasman Drive 170 W. Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: keyupate@cisco.com Email: keyupate@cisco.com
Rex Fernando Rex Fernando
Cisco Systems Cisco Systems
170 W. Tasman Drive 170 W. Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: rex@cisco.com Email: rex@cisco.com
John Scudder John Scudder
Juniper Networks Juniper Networks
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