wdiff draft-ietf-idr-bgp-gr-notification-03.txt draft-ietf-idr-bgp-gr-notification-04.txt

Network Working Group K. Patel
Internet-Draft R. Fernando
Intended status: Standards Track Cisco Systems
Expires: December 5, 2014 October 29, 2015 J. Scudder
J. Haas
Juniper Networks
June 3, 2014
April 27, 2015

Notification Message support for BGP Graceful Restart
draft-ietf-idr-bgp-gr-notification-03.txt
draft-ietf-idr-bgp-gr-notification-04.txt

Abstract

The current BGP Graceful Restart mechanism limits the usage of BGP
Graceful Restart to BGP protocol messages other than a BGP
NOTIFICATION message. This document defines an extension to the BGP
Graceful Restart that permits the Graceful Restart procedures to be
performed when the BGP speaker receives a BGP NOTIFICATION Message.
This document also defines a new BGP NOTIFICATION Cease Error subcode
to prevent BGP speakers supporting the extension defined in this
document from performing a Graceful Restart.

Status of This Memo

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Modifications to BGP Graceful Restart Capability . . . . . . 3
3. BGP Hard Reset Subcode . . . . . . . . . . . . . . . . . . . 4
3.1. Sending a Hard Reset . . . . . . . . . . . . . . . . . . 4
3.2. Receiving Sending a Hard Reset . . . . . . . . . . . . . . . . . 5 . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Rules for the Receiving Speaker
5. Acknowledgements . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6

1. Introduction

For many classes of errors, the BGP protocol must send a NOTIFICATION
message and reset the peering session to handle the error condition.
The BGP Graceful Restart extension defined in [RFC4724] requires that
normal BGP procedures defined in [RFC4271] be followed when a
NOTIFICATION message is sent or received. This document defines an
extension to BGP Graceful Restart that permits the Graceful Restart
procedures to be performed when the BGP speaker receives a
NOTIFICATION message. This permits the BGP speaker to avoid flapping
reachability and continue forwarding while the BGP speaker restarts
the session to handle errors detected in the BGP protocol.

At a high level, this

This document can be summed up as follows. When defines a BGP session is reset, both speakers operate as "Receiving Speakers"
according to [RFC4724], meaning they retain each other's routes.
This is also true for HOLDTIME expiration. The functionality can be
defeated using a "Hard Reset" NOTIFICATION cease Error subcode for the BGP NOTIFICATION
Cease Error code. If a Hard Reset is used, code to prevent BGP speakers supporting the extension
defined in this document from performing a full session reset is
performed. Graceful Restart.

1.1. 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].

2. Modifications to BGP Graceful Restart Capability

The BGP Graceful Restart Capability is augmented to signal the
Graceful Restart support for BGP NOTIFICATION messages. In
particular, the Restart flags field and the Flags field for Address
Family are augmented as follows:

+--------------------------------------------------+
| Restart Flags (4 bits) |
+--------------------------------------------------+
| Restart Time in seconds (12 bits) |
+--------------------------------------------------+
| Address Family Identifier (16 bits) |
+--------------------------------------------------+
| Subsequent Address Family Identifier (8 bits) |
+--------------------------------------------------+
| Flags for Address Family (8 bits) |
+--------------------------------------------------+
| ... |
+--------------------------------------------------+
| Address Family Identifier (16 bits) |
+--------------------------------------------------+
| Subsequent Address Family Identifier (8 bits) |
+--------------------------------------------------+
| Flags for Address Family (8 bits) |
+--------------------------------------------------+

Restart Flags:

This field contains bit flags relating to restart.

0 1 2 3
+-+-+-+-+
|R|N| |
+-+-+-+-+

The second most significant bit ("N") "N" is defined as the a BGP Graceful
Notification bit, which is used to indicate the Graceful Restart
support for BGP NOTIFICATION messages. A BGP speaker indicates support for the procedures of this document, by advertising a
Graceful Restart
Capability with its Graceful NOTIFICATION bit set (value 1). This
also implies support for BGP NOTIFICATION messages and its
ability to handle the new BGP NOTIFICATION Cease message subcode and
the format for a BGP NOTIFICATION Cease message defined in [RFC4486]. [RFC4486]
when the Graceful NOTIFICATION bit is set (value 1).

Flags for Address Family:

This field contains bit flags relating to routes that were
advertised with the given AFI and SAFI.

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F|N| Reserved |
+-+-+-+-+-+-+-+-+

The usage of second most significant bit "N" is deprecated. This bit
MUST
SHOULD be advertised as 0 reserved and MUST be ignored upon receipt. set to 0.

3. BGP Hard Reset Subcode

A new BGP NOTIFICATION Cease message subcode is defined known as the BGP Hard Reset
Subcode. The value of this subcode is discussed in
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. 9.

3.1. Sending a Hard Reset

A Hard Reset message NOTIFICATION Message is used to indicate to a peer with
which the Graceful Notification flag has been exchanged, that the
session is to be fully terminated.

When sending a Hard Reset, Reset NOTIFICATION, 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 message MUST be used to indicate the reason for the hard
reset.

Subcode The reason is encoded using a standard BGP Error Subcode (as documented in the IANA BGP Error
Subcodes registry) as appropriate for the ErrCode. Similarly, Data
is as appropriate for the ErrCode Cease error
subcode and Subcode. MAY also include any relevant data subsequent to the
subcode.

3.2. Receiving Sending a Hard Reset

Whenever a BGP speaker receives a NOTIFICATION message with the Cease
Error code and Hard Reset, Reset Error subcode, the speaker MUST terminate
the BGP session following the standard procedures in [RFC4271].

4. Operation

A BGP speaker that is willing to receive and send BGP NOTIFICATION
messages in Graceful mode MUST SHOULD advertise the BGP Graceful
Notification Flag "N" using the Graceful Restart Capability as
defined in [RFC4724].

When such a BGP Speaker receives a BGP NOTIFICATION message other
than a Hard Reset, message, it MUST SHOULD
follow the standard rules for of the Receiving Speaker receiving speaker mentioned in Section 4.1.
[RFC4724] for all AFI/SAFIs for which it has announced the BGP
Graceful Notification flag. The BGP speaker generating the a BGP
NOTIFICATION message MUST also SHOULD follow the standard rules of the
receiving Speaker in [RFC4724] for all AFI/SAFIs that were announced
with the Receiving
Speaker. BGP Graceful Notification flag.

A BGP speaker MAY continue to operate in the Graceful Restart mode
even if it receives a Graceful Restart capability without a Graceful
Notification Flag.

When a BGP speaker resets its session due to a HOLDTIME expiry, it
should generate
SHOULD follow the relevant standard rules of the receiving speaker mentioned
in [RFC4724] aside from generating a BGP NOTIFICATION message as
mentioned in
[RFC4271], but subsequently it MUST follow the rules for the
Receiving Speaker mentioned in Section 4.1. [RFC4271].

Once the session is re-established, both BGP speakers SHOULD MUST set their
"Forwarding State" bit to 1. If 1 if they want to apply planned graceful
restart. The handling of the "Forwarding State" bit is
not set, then according to the procedures of [RFC4724] S. 4.2, the
relevant routes will should be flushed, defeating done
as specified by the goals procedures of this
specification.

4.1. Rules for the Receiving Speaker speaker in [RFC4724] S. 4.2 defines rules for the Receiving Speaker. These
are
modified as follows. applied.

As part of this extension, routes from any possible consecutive restarts SHOULD
NOT delete a route (from the peer peer) previously marked as
stale MUST NOT be deleted, stale, until and unless the timer mentioned in
the final paragraph of [RFC4724] S. 4.2 expires, or unless a Hard
Reset is performed. This supersedes the "consecutive restarts"
requirement of [RFC4724] S. 4.2.

In addition to the rules already specified in [RFC4724] S. 4.2 for
how variations in the received Graceful Restart Capability should be
interpreted (the paragraph that begins "Once the session is re-
established..."), if the Graceful Notification ("N") bit is not set
in the newly received Graceful Restart Capability, no new actions are
triggered on the Receiving Speaker -- in particular, a clear "N" bit
does not trigger deletion of stale routes.

Other than these modifications, the
required by rules for the Receiving Speaker
are as specified mentioned in [RFC4724] S. 4.2. [RFC4724].

5. Acknowledgements

The authors would like to thank Jim Uttaro for the suggestion, and
Chris Hall, Paul Mattes and Robert Raszuk for the review and
comments.

6. IANA Considerations

IANA is requested to assign

This document defines a new BGP Cease message subcode in known as BGP
Hard Reset Subcode. IANA mantains the "BGP list of existing BGP Cease
NOTIFICATION
message subcodes" registry. The suggested name for subcodes. This document proposes defining a new BGP Cease
message subcode known as BGP Hard Reset Subcode with the
code point is "Hard Reset". The suggested value is 9.

7. Security Considerations

This extension to BGP does not change the underlying security issues
inherent in the existing [RFC4724] and [RFC4271]. [RFC4271]

8. References

8.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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
with BGP-4", RFC 3392, November 2002.

[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.

[RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease
Notification Message", RFC 4486, April 2006.

[RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
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

Keyur Patel
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
USA

Email: keyupate@cisco.com
Rex Fernando
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
USA

Email: rex@cisco.com

John Scudder
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
USA

Email: jgs@juniper.net

Jeff Haas
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
USA

Email: jhaas@juniper.net