draft-ietf-idr-link-bandwidth-01.txt   draft-ietf-idr-link-bandwidth-02.txt 
Network Working Group P. Mohapatra Network Working Group P. Mohapatra
Internet-Draft R. Fernando Internet-Draft R. Fernando
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: August 28, 2010 February 24, 2010 Expires: September 10, 2011 March 9, 2011
BGP Link Bandwidth Extended Community BGP Link Bandwidth Extended Community
draft-ietf-idr-link-bandwidth-01.txt draft-ietf-idr-link-bandwidth-02.txt
Abstract Abstract
This document describes an application of BGP extended communities This document describes an application of BGP extended communities
that allows a router to perform unequal cost load balancing. that allows a router to perform unequal cost load balancing.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
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skipping to change at page 2, line 30 skipping to change at page 2, line 24
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3 2. Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3
3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 3 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 3
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . . 4 7. Normative References . . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
When a BGP speaker receives multiple paths from its internal peers, When a BGP speaker receives multiple paths from its internal peers,
it could select more than one path to send traffic to. In doing so, it could select more than one path to send traffic to. In doing so,
it might be useful to provide the speaker with information that would it might be useful to provide the speaker with information that would
help it distribute the traffic unequally based on the cost of the help it distribute the traffic unequally based on the bandwidth of
external (DMZ) link. This document suggests that the external link the external (DMZ) link. This document suggests that the external
bandwidth be carried in the network using a new extended community link bandwidth be carried in the network using a new extended
[RFC4360] - the link bandwidth extended community. community [RFC4360] - the link bandwidth extended community.
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. Link Bandwidth Extended Community 2. Link Bandwidth Extended Community
When a BGP speaker receives a route from a directly connected When a BGP speaker receives a route from an external neighbor and
external neighbor (the external neighbor that is one IP hop away) and
advertises this route (via IBGP) to internal neighbors, as part of advertises this route (via IBGP) to internal neighbors, as part of
this advertisement the router may carry the bandwidth of the link this advertisement the router may carry the cost to reach the
that connects the router with the external neighbor. The bandwidth neighbor. The cost can be either configured per neighbor or derived
of such a link is carried in the Link Bandwidth Community. The from the bandwidth of the link that connects the router to a directly
community is optional non-transitive. A border router MUST strip the connected external neighbor. This value is carried in the Link
link bandwidth community from a route when it advertises the route to Bandwidth Extended Community. No more than one link bandwidth
an external neighbor. The value of the high-order octet of the extended community SHALL be attached to a route. Additionally, if a
extended Type Field is 0x40. The value of the low-order octet of the route is received with link bandwidth extended community and the BGP
extended type field for this community is 0x04. The value of the speaker sets itself as next-hop while announcing that route to other
Global Administrator subfield in the Value Field SHOULD represent the peers, the link bandwidth extended community should be removed.
Autonomous System of the router that attaches the Link Bandwidth
Community. If four octet AS numbering scheme is used [RFC4893], The extended community is optional non-transitive. The value of the
AS_TRANS should be used in the Global Administrator subfield. The high-order octet of the extended Type Field is 0x40. The value of
bandwidth of the link is expressed as 4 octets in IEEE floating point the low-order octet of the extended type field for this community is
format, units being bytes per second. It is carried in the Local 0x04. The value of the Global Administrator subfield in the Value
Administrator subfield of the Value Field. Field SHOULD represent the Autonomous System of the router that
attaches the Link Bandwidth Community. If four octet AS numbering
scheme is used [RFC4893], AS_TRANS should be used in the Global
Administrator subfield. The bandwidth of the link is expressed as 4
octets in IEEE floating point format, units being bytes (not bits!)
per second. It is carried in the Local Administrator subfield of the
Value Field.
3. Deployment Considerations 3. Deployment Considerations
The usage of this community is restricted to the cases where BGP The usage of this community is restricted to the cases where BGP
multipath can be safely deployed. In other words, the IGP distance multipath can be safely deployed. In other words, the IGP distance
between the load balancing router and the exit points should be the between the load balancing router and the exit points should be the
same. Alternatively, the path between the load sharing router and same. Alternatively, the path between the load sharing router and
the exit points could be label switched. If there are multiple paths the exit points could be tunneled. If there are multiple paths to
to reach a destination and if only some of them have link bandwidth reach a destination and if only some of them have link bandwidth
community, the receiver should not perform unequal cost load community, the receiver should not perform unequal cost load
balancing based on link bandwidths. balancing based on link bandwidths.
4. Acknowledgments 4. Acknowledgments
The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan
Tappan for proposing unequal cost load balancing as one possible Tappan for proposing unequal cost load balancing as one possible
application of the extended community attribute. application of the extended community attribute.
The authors would like to thank Bruno Decraene, Robert Raszuk, Joel
Halpern, and Aleksi Suhonen for their useful comments and
discussions.
5. IANA Considerations 5. IANA Considerations
This document defines a specific application of the two-octet AS This document defines a specific application of the two-octet AS
specific extended community. IANA is requested to assign a sub- type specific extended community. IANA is requested to assign a sub- type
value of 0x04 for the link bandwidth extended community. value of 0x04 for the link bandwidth extended community.
Name Value Name Value
---- ----- ---- -----
non-transitive Link Bandwidth Ext. Community 0x4004 non-transitive Link Bandwidth Ext. Community 0x4004
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