< draft-ietf-idr-link-bandwidth-05.txt   draft-ietf-idr-link-bandwidth-06.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: May 9, 2013 November 5, 2012 Expires: July 26, 2013 January 22, 2013
BGP Link Bandwidth Extended Community BGP Link Bandwidth Extended Community
draft-ietf-idr-link-bandwidth-05.txt draft-ietf-idr-link-bandwidth-06.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 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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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 9, 2013. This Internet-Draft will expire on July 26, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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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
than English. than English.
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 . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 4 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 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 based on the bandwidth of the external help it distribute the traffic based on the bandwidth of the external
(DMZ) link. This document suggests that the external link bandwidth (DMZ) link. This document suggests that the external link bandwidth
be carried in the network using a new extended community [RFC4360] - be carried in the network using a new extended community [RFC4360] -
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route is received with link bandwidth extended community and the BGP route is received with link bandwidth extended community and the BGP
speaker sets itself as next-hop while announcing that route to other speaker sets itself as next-hop while announcing that route to other
peers, the link bandwidth extended community should be removed. peers, the link bandwidth extended community should be removed.
The extended community is optional non-transitive. The value of the The extended community is optional non-transitive. The value of the
high-order octet of the extended Type Field is 0x40. The value of high-order octet of the extended Type Field is 0x40. The value of
the low-order octet of the extended type field for this community is the low-order octet of the extended type field for this community is
0x04. The value of the Global Administrator subfield in the Value 0x04. The value of the Global Administrator subfield in the Value
Field SHOULD represent the Autonomous System of the router that Field SHOULD represent the Autonomous System of the router that
attaches the Link Bandwidth Community. If four octet AS numbering attaches the Link Bandwidth Community. If four octet AS numbering
scheme is used [RFC4893], AS_TRANS should be used in the Global scheme is used [RFC6793], AS_TRANS should be used in the Global
Administrator subfield. The bandwidth of the link is expressed as 4 Administrator subfield. The bandwidth of the link is expressed as 4
octets in IEEE floating point format, units being bytes (not bits!) octets in IEEE floating point format, units being bytes (not bits!)
per second. It is carried in the Local Administrator subfield of the per second. It is carried in the Local Administrator subfield of the
Value Field. 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. If the path between the load
between the load balancing router and the exit points should be the sharing router and the exit point is not tunneled, then the IGP
same. Alternatively, the path between the load sharing router and distance between the load balancing router and the exit points should
the exit points could be tunneled. If there are multiple paths to be the same.
reach a destination and if only some of them have link bandwidth
community, the receiver should not perform unequal cost load If the path between the load sharing router and the exit point is
balancing based on link bandwidths. tunneled, then the choice to use this community is a purely local
matter to the load sharing router.
In the context of BGP/MPLS VPNs [RFC4364], link bandwidth community
could be used to support inbound load balancing for multihomed sites,
as follows. Consider a site that is connected to PE1 and PE2. Both
PE1 and PE2 would advertise VPN-IP routes associated with the
destinations within the site. One way to enable other PEs to receive
all these routes is to require the RD of the routes advertised by PE1
to be different from the RD of the routes advertised by PE2. The
VPN-IP routes advertised by PE1 should carry the link bandwidth
community; likewise for the VPN-IP routes advertised by PE2. The
bandwidth value carried in the community could be locally determined
by PE1 and PE2. Alternatively CEs of the site, when advertising IP
routes to PE1 and PE2, could add the link bandwith community to these
advertisements, in which case PE1 and PE2, when originating VPN-IP
routes, would use the bandwidth value from the IP routes they
received from the CEs to construct the link bandwidth community
carried by these VPN-IP routes.
An ingress PE, when sending traffic to destinations within the site,
can use the bandwidth value carried in the community of the routes
advertised by PE1 and PE2 to perform load sharing, where some of the
traffic would go via PE1, while other traffic would go via PE2.
If there are multiple paths to reach a destination and if only some
of them have link bandwidth community, the load sharing router should
not perform unequal cost load 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 The authors would like to thank Bruno Decraene, Robert Raszuk, Joel
Halpern, Aleksi Suhonen, and Randy Bush for their useful comments and Halpern, Aleksi Suhonen, Randy Bush, and John Scudder for their
discussions. comments and contributions.
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
6. Security Considerations 6. Security Considerations
There are no additional security risks introduced by this design. There are no additional security risks introduced by this design.
7. Normative References 7. 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.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, February 2006. Communities Attribute", RFC 4360, February 2006.
[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Number Space", RFC 4893, May 2007. Networks (VPNs)", RFC 4364, February 2006.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793,
December 2012.
Authors' Addresses Authors' Addresses
Pradosh Mohapatra Pradosh Mohapatra
Cisco Systems Cisco Systems
170 W. Tasman Drive 170 W. Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Phone: Phone:
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