draft-ietf-idr-aigp-04.txt   draft-ietf-idr-aigp-05.txt 
Network Working Group Pradosh Mohapatra Network Working Group Pradosh Mohapatra
Internet Draft Rex Fernando Internet Draft Rex Fernando
Intended Status: Proposed Standard Eric C. Rosen Intended Status: Proposed Standard Eric C. Rosen
Expires: April 8, 2011 Cisco Systems, Inc. Expires: September 29, 2011 Cisco Systems, Inc.
James Uttaro James Uttaro
ATT ATT
October 8, 2010 March 29, 2011
The Accumulated IGP Metric Attribute for BGP The Accumulated IGP Metric Attribute for BGP
draft-ietf-idr-aigp-04.txt draft-ietf-idr-aigp-05.txt
Abstract Abstract
Routing protocols that have been designed to run within a single Routing protocols that have been designed to run within a single
administrative domain ("IGPs") generally do so by assigning a metric administrative domain ("IGPs") generally do so by assigning a metric
to each link, and then choosing as the installed path between two to each link, and then choosing as the installed path between two
nodes the path for which the total distance (sum of the metric of nodes the path for which the total distance (sum of the metric of
each link along the path) is minimized. BGP, designed to provide each link along the path) is minimized. BGP, designed to provide
routing over a large number of independent administrative domains routing over a large number of independent administrative domains
("autonomous systems"), does not make its path selection decisions ("autonomous systems"), does not make its path selection decisions
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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."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Copyright and License Notice Copyright and License Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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out" past an AIGP administrative domain boundary into the Internet. out" past an AIGP administrative domain boundary into the Internet.
The specified procedures also ensure that the value in the AIGP The specified procedures also ensure that the value in the AIGP
attribute has been accumulated all along the path from the attribute has been accumulated all along the path from the
destination, i.e., that the AIGP attribute does not appear when there destination, i.e., that the AIGP attribute does not appear when there
are "gaps" along the path where the IGP metric is unknown. are "gaps" along the path where the IGP metric is unknown.
3. AIGP Attribute 3. AIGP Attribute
The AIGP Attribute is an optional non-transitive BGP Path Attribute. The AIGP Attribute is an optional non-transitive BGP Path Attribute.
The attribute type code for the AIGP Attribute is to be assigned by The attribute type code for the AIGP Attribute is 26. The value
IANA. The value field of the AIGP Attribute is defined here to be a field of the AIGP Attribute is defined here to be a set of TLVs
set of TLVs (elements encoded as "Type/Length/Value"). However, this (elements encoded as "Type/Length/Value"). However, this document
document defines only a single such TLV, the AIGP TLV, that contains defines only a single such TLV, the AIGP TLV, that contains the
the Accumulated IGP Metric. The AIGP TLV is encoded as shown in Accumulated IGP Metric. The AIGP TLV is encoded as shown in Figure
Figure 1. An AIGP Attribute MUST NOT contain more than one AIGP TLV. 1. An AIGP Attribute MUST NOT contain more than one AIGP TLV.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=1 | Length | | | Type=1 | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~ ~ ~
| Accumulated IGP Metric | | Accumulated IGP Metric |
| +-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+
| | | |
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[BESTEXT] and [ADDPATH] be used in conjunction with the AIGP [BESTEXT] and [ADDPATH] be used in conjunction with the AIGP
Attribute. Attribute.
If a Route Reflector does not pass all paths to its clients, then it If a Route Reflector does not pass all paths to its clients, then it
will tend to pass the paths for which the IGP distance from the Route will tend to pass the paths for which the IGP distance from the Route
Reflector itself to the next hop is smallest. This may result in a Reflector itself to the next hop is smallest. This may result in a
non-optimal choice by the clients. non-optimal choice by the clients.
6. IANA Considerations 6. IANA Considerations
IANA shall assign a codepoint for the AIGP attribute. This codepoint IANA has assigned the codepoint 26 in the "BGP Path Attributes"
will come from the "BGP Path Attributes" registry. registry to the AIGP attribute.
IANA shall create a registry for "BGP AIGP Attribute Types". Type 1 IANA shall create a registry for "BGP AIGP Attribute Types". The
should be defined as "AIGP", and should refer to this document. type field consists of a single octet, with possible values from 0 to
255. The allocation policy for this field is to be "Standards Action
with Early Allocation". Type 1 should be defined as "AIGP", and
should refer to this document.
7. Security Considerations 7. Security Considerations
The spurious introduction, though error or malfeasance, of an AIGP The spurious introduction, though error or malfeasance, of an AIGP
attribute, could result in the selection of paths other than those attribute, could result in the selection of paths other than those
desired. desired.
Improper configuration on both ends of an EBGP connection could Improper configuration on both ends of an EBGP connection could
result in an AIGP attribute being passed from one service provider to result in an AIGP attribute being passed from one service provider to
another. This would likely result in an unsound selection of paths. another. This would likely result in an unsound selection of paths.
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10. Normative References 10. Normative References
[BGP], "A Border Gateway Protocol 4 (BGP-4)", Y. Rekhter, T. Li, S. [BGP], "A Border Gateway Protocol 4 (BGP-4)", Y. Rekhter, T. Li, S.
Hares, RFC 4271, January 2006. Hares, RFC 4271, January 2006.
11. Informative References 11. Informative References
[ADDPATH] "Fast Connectivity Restoration Using BGP Add-Path", P. [ADDPATH] "Fast Connectivity Restoration Using BGP Add-Path", P.
Mohapatra, R. Fernando, C. Filsfils, R. Raszuk, draft-pmohapat-idr- Mohapatra, R. Fernando, C. Filsfils, R. Raszuk, draft-pmohapat-idr-
fast-conn-restore-00.txt, September 2008. fast-conn-restore-01.txt, March 2011.
[BESTEXT], " Advertisement of the Best External Route in BGP", P. [BESTEXT], "Advertisement of the Best External Route in BGP", P.
Marques, R. Fernando, E. Chen, P. Mohapatra, draft-ietf-idr-best- Marques, R. Fernando, E. Chen, P. Mohapatra, draft-ietf-idr-best-
external-02.txt, August 2010. external-03.txt, March 2011.
[RFC2119] "Key words for use in RFCs to Indicate Requirement [RFC2119] "Key words for use in RFCs to Indicate Requirement
Levels.", S. Bradner, March 1997 Levels.", S. Bradner, March 1997
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