Internet Engineering Task Force T. Scholl
Internet-Draft AT&T
Intended status: Standards Track J. Scudder
Expires: September 5, 2009 Juniper Networks
March 4, 2009
BGP Advisory Message
draft-scholl-idr-advisory-00.txt
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Abstract
The BGP routing protocol is used with external as well as internal
neighbors to propagate route advertisements. In the case of external
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BGP sessions, there is typically a demarcation of administrative
responsibility between the two entities. Provisioning, maintenance
and administrative actions are communicated via off-line methods such
as email or telephone calls. While these methods have been used for
many years, it can be troublesome for an operator to correlate a BGP-
related event in the network with a notice that was transmitted in
email.
This document proposes a new BGP message type, the Advisory message,
which can be used to convey advisory information to a BGP speaker's
peer. A capability is used to ensure that the recipient of the
Advisory message is capable of supporting it.
1. Introduction
The BGP routing protocol is used with external as well as internal
neighbors to propagate route advertisements. In the case of external
BGP sessions, there is typically a demarcation of administrative
responsibility between the two entities. Provisioning, maintenance
and administrative actions are communicated via off-line methods such
as email or telephone calls. While these methods have been used for
many years, it can be troublesome for an operator to correlate a BGP-
related event in the network with a notice that was transmitted in
email.
There are several events that require communication between the
administrators of peering routers. When a router is shut down for
maintenance resulting in BGP sessions to many neighbors being reset,
operators may be unable to correlate the event to an already notified
maintenance action. In addition, maintenance actions via email may
contain outdated trouble ticket information, incorrect router names
or incomplete time zones specified. Another complication is that
email based notifications are not always sent to the correct parties.
It is common in the settlement-free peering world for the
administrative/policy contacts to be separate from the technical/
troubleshooting contacts.
This draft outlines a method to provide within BGP the ability to
transmit a text message to a BGP neighbor. This capability can speed
up operator reaction and resolution time by providing a direct
correlation between a BGP event and the root cause. This eliminates
the possibility for an operator to be "out of the loop" to any off-
line notifications of events.
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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. Capability
A new BGP capability [RFC5492] called Advisory is introduced, with
type code TBD. This capability indicates that the router advertising
it is capable of receiving and parsing Advisory messages. The
capability is of variable length. The data portion of the capability
lists the Advisory message subtypes which are supported. The String
subtype MUST be supported, which implies that the length MUST be at
least 2 if the capability is advertised.
3. Advisory Message
The Advisory message is a BGP message of type TBD. It consists of a
BGP fixed header followed by a two-byte subtype and a data portion of
variable length, calculated according to the Length field in the
fixed header. The format of the data portion is dependent on the
subtype. This document defines the following subtypes:
0 - Reserved:
MUST NOT be sent, MUST be ignored (other than optionally
logging an error) on receipt.
1 - String:
A message comprised of a string of ASCII characters. The
string's length is given by the length of the message, there is
no null termination. Upon reception, the string SHOULD be
reported to the router's administrator. The means of reporting
the string are implementation-specific but could include
methods such as syslog.
While this document mandates no particular events for which advisory
messages should be generated, one suggested application is if a peer
is approaching a configured prefix limit. It is also likely that an
implementation will want to provide a way for an arbitrary, user-
specified string to be sent. Implementations MUST limit the rate at
which advisory messages are sent for any particular type of event.
As its name implies the Advisory message is intended to be used to
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advise a peer of some condition which may be of interest to that peer
(or its administrator). It MUST NOT be used as a replacement for the
Notification message in fatal error situations (i.e., situations
where the integrity of the BGP peering is violated or suspect),
although an Advisory message MAY precede a Notification message.
4. Error Handling
An Advisory message MUST NOT be sent to any peer which has not
advertised the Advisory capability indicating support for the
relevant subtype. If a router which has advertised the Advisory
capability receives an Advisory message with a subtype for which it
has not advertised support, it MUST accept and discard that message.
It MAY locally log an error when this occurs.
5. IANA Considerations
IANA is requested to allocate a type code for the Advisory message
from the BGP Message Types registry, to allocate a type code for the
Advisory Capability from the Capability Codes registry, and to
establish and maintain a registry for BGP Advisory message subtypes,
to be allocated according to the First Come First Served policy
defined in [RFC5226].
6. Security Considerations
No new security issues are introduced to the BGP protocol by this
specification.
7. 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.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, February 2009.
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Authors' Addresses
Tom Scholl
AT&T
Email: ts3127@att.com
John Scudder
Juniper Networks
Email: jgs@juniper.net
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