One document matched: draft-ietf-idr-link-bandwidth-01.xml
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<rfc category="std" docName="draft-ietf-idr-link-bandwidth-01.txt"
ipr="pre5378Trust200902">
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<!-- ***** FRONT MATTER ***** -->
<front>
<title abbrev="Link Bandwidth">
BGP Link Bandwidth Extended Community </title>
<!-- add 'role="editor"' below for the editors if appropriate -->
<!-- Another author who claims to be an editor -->
<author fullname="Pradosh Mohapatra" initials="P.M."
surname="Mohapatra">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>170 W. Tasman Drive</street>
<!-- Reorder these if your country does things differently -->
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<phone></phone>
<email>pmohapat@cisco.com</email>
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</address>
</author>
<author fullname="Rex Fernando" initials="R.F."
surname="Fernando">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>170 W. Tasman Drive</street>
<!-- Reorder these if your country does things differently -->
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<phone></phone>
<email>rex@cisco.com</email>
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</address>
</author>
<date month="February" year="2010" />
<!-- Meta-data Declarations -->
<area>General</area>
<workgroup>Network Working Group</workgroup>
<keyword>template</keyword>
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<abstract>
<t>
This document describes an application of BGP extended communities
that allows a router to perform unequal cost load balancing.
</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>
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 might be useful to provide the speaker with information that
would help it distribute the traffic unequally based on the cost of
the external (DMZ) link. This document suggests that the external
link bandwidth be carried in the network using a new extended
community <xref target="RFC4360"></xref> - the link bandwidth
extended community.
</t>
<section title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</section>
</section> <!-- Introduction -->
<section anchor="link_bandwidth"
title="Link Bandwidth Extended Community">
<t>
When a BGP speaker receives a route from a directly connected
external neighbor (the external neighbor that is one IP hop away)
and advertises this route (via IBGP) to internal neighbors, as part
of this advertisement the router may carry the bandwidth of the
link that connects the router with the external neighbor. The
bandwidth of such a link is carried in the Link Bandwidth
Community. The community is optional non-transitive. A border
router MUST strip the link bandwidth community from a route when it
advertises the route to an external neighbor.
The value of the 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 0x04.
The value of the Global Administrator subfield in the Value Field
SHOULD represent the Autonomous System of the router that attaches
the Link Bandwidth Community. If four octet AS numbering scheme is
used <xref target="RFC4893"></xref>, 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 per second. It is carried in the
Local Administrator subfield of the Value Field.
</t>
</section> <!-- Link Bandwidth Extended Community -->
<section title="Deployment Considerations">
<t>
The usage of this community is restricted to the cases where BGP
multipath can be safely deployed. In other words, the IGP distance
between the load balancing router and the exit points should be the
same. Alternatively, the path between the load sharing router and
the exit points could be label switched.
If there are multiple paths to reach a destination and if only some
of them have link bandwidth community, the receiver should not
perform unequal cost load balancing based on link bandwidths.
</t>
</section>
<section title="Acknowledgments">
<t>
The authors would like to thank Yakov Rekhter, Srihari Sangli and
Dan Tappan for proposing unequal cost load balancing as one
possible application of the extended community attribute.
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>
This document defines a specific application of the two-octet AS
specific extended community. IANA is requested to assign a sub-
type value of 0x04 for the link bandwidth extended
community.
<figure align="center">
<artwork align="left"><![CDATA[
Name Value
---- -----
non-transitive Link Bandwidth Ext. Community 0x4004
]]></artwork>
</figure>
</t>
</section>
<section anchor="Security" title="Security Considerations">
<t>
There are no additional security risks introduced by this design.
</t>
</section>
</middle>
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<back>
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