Internet Engineering Task Force T. Scholl
Internet-Draft ATT
Intended status: Standards Track J. Scudder
Expires: April 20, 2010 Juniper Networks
R. Steenbergen
Server Central / nLayer
D. Freedman
Claranet Limited
October 17, 2009
BGP Advisory Message
draft-ietf-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
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. While initial configuration
and troubleshooting of these sessions is handled via offline means
such as email or telephone calls, there is gap when it comes to
advising a BGP neighbor of a behavior that is occurring or will occur
momentarily. There is a need for operators to transmit a message to
a BGP neighbor to notify them of a variety of types of messages.
These messages typically would include those related to a planned or
unplanned maintenance action. These advisory messages could then be
interpreted by the remote party and either parsed via logging
mechanisms or viewed by a human on the remote end via the CLI. This
capability will improve operator NOC-to-NOC communication by
providing a communications medium on an established and trusted BGP
session between two autonomous systems.
The reason that this method is preferred for NOC-to-NOC
communications is that other offline methods do fail for a variety of
reasons. Emails to NOC aliases ahead of a planned maintanance may
have ignored the mail or may have not of recorded it properly within
an internal tracking system. Even if the message was recorded
properly, the staff that is on-duty at the time of the maintenance
event typically was not the same staff who received the maintenance
notice several days prior. In addition, the staff on duty at the
time of the event may not even be able to find the recorded event in
their internal tracking systems. The end result is that during a
planned event, some subset of eBGP peers will respond to a session/
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peer down event with additional communications to the operator who is
initiating the maintenance action. This can be via telephone or via
email, but either way, it may result in a sizable amount of replies
inquiring as to why the session is down. The result of this is that
the NOC responsible for initiating the maintenance can be innundated
with calls/emails from a variety of parties inquiring as to the
status of the BGP session. The NOC initating the maintenance may
have to further inquire with engineering staff (if they are not
already aware) to find out the extent of the maintenance and
communicate this back to all of the NOCs calling for additional
information. The above scenario outlines what is typical in a
planned maintenance event. In an unplanned maintenance event (the
need for and immediate router upgrade/reload), the number of calls
and emails will dramatically increase as more parties are unaware of
the event.
With the BGP advisory capability, an operator can transmit an
advisory message just prior to initiating the maintenance specifying
what event will happen, what ticket number this event is associated
with and the expected duration of the event. This message would be
received by BGP peers and stored in their router syslog as well as
any monitoring system if they have this capability. Now, all of the
BGP peers have immediate access to the information about this
session, why it went down, what ticket number this is being tracked
under and how long they should wait before assuming there is an
actual problem. Even smaller networks without the network management
capabilities to corrolate BGP events and advisory messages would
typically have an operator login to a router and examine the logs via
the CLI.
There are several problems with e-mail only notifications:
Up-to-date contact information is fairly difficult to maintain.
Some networks who have very open peering policies may peer with
up to 1,000 unique ASNs.
A NOC e-mail address does not always reach its way to the
proper individuals at the NOC. A large amount of e-mail
received at NOC aliases are typically spam or issues not
appropriate for a typical NOC queue.
E-mail is not real time. In some environments, e-mail
processing can be delayed and when looking at unplanned
maintenances, some operators do not have the time to draft an
e-mail as well as the distribution list.
There are several advantages to the advisory capability to operators:
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There is no requirement for an external contact database.
Contact databases are important, but this capability provides a
way for an operator to transmit a message about a specific BGP
session with no external contact information being required.
The very existance of the BGP session itself has inherent
authentication and message routing properties. An operator
immediately knows for every advisory message that it is coming
from someone you are directly connected to (and thus have a
relationship with) and which particular BGP session this is
regarding. This is all completed without any additional human
parsing required.
Because there is a BGP session that exists, an operator already
has an authenticated session. There is no requirement for
further authentication of the BGP session (key exchange).
The advisory message provides for real-time delivery of a
message to a BGP neighbor. This will provide a rapid option in
comparison to drafting an email to all BGP peers and waiting
for the receipt before commencing with an unplanned maintenance
event.
This draft aims to provide operators with the capability to transmit
an advisory message to BGP peers to assist with daily network
operations.
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
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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 - Advisory 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.
2 - Static 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
stored in a BGP neighbor statistics field within the router.
This string would then be accessable to the operator by
executing CLI commands or any other remote method to obtain BGP
neighbor statistics (NETCONF, SNMP). The expectation is that
the last static message received from a BGP neighbor will be
the message visible to the operator (the most current static
message).
While this document mandates no particular events for which advisory
messages should be generated, there are a variety of applications
where the advisory message may be used. Implementations SHOULD
provide its users the ability to transmit a free form text message
generated by user input.
Implementations MAY choose to define a standard set of advisory
messages that are automatically driven rather than requiring a human
to enter specific reasons. These messages may be automatically
transmitted based upon specific router functions such as a router
reload, administrative action (neighbor shutdown) or reconfiguration
(new BGP address-family support).
Implementations SHOULD provide router administrators with the ability
to filter out specific BGP Advisory message types on a per neighbor
or per peer-group basis. This interface should be provided to the
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operator to clearly define if they want advisory, static or both
types of messages.
Implementations MUST rate-limit the rate in which they transmit and
receieve advisory messages. Specifically, an implementation MUST NOT
allow the handling of advisory messages to negatively impact any
other functions on a router such as regular BGP message handling or
other routing protocols.
As its name implies the Advisory message is intended to be used to
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.
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[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.
Authors' Addresses
Tom Scholl
ATT
Email: tom.scholl@att.com
John Scudder
Juniper Networks
Email: jgs@juniper.net
Richard Steenbergen
Server Central / nLayer
Email: ras@e-gerbil.net
David Freedman
Claranet Limited
Email: david.freedman@uk.clara.net
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