draft-ietf-idr-aigp-07.txt   draft-ietf-idr-aigp-08.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: June 12, 2012 Cisco Systems, Inc. Expires: December 4, 2012 Cisco Systems, Inc.
James Uttaro James Uttaro
ATT ATT
December 12, 2011 June 4, 2012
The Accumulated IGP Metric Attribute for BGP The Accumulated IGP Metric Attribute for BGP
draft-ietf-idr-aigp-07.txt draft-ietf-idr-aigp-08.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
skipping to change at page 2, line 14 skipping to change at page 2, line 14
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) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 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
skipping to change at page 7, line 32 skipping to change at page 7, line 32
- The route is an IGP route that is being redistributed into BGP - The route is an IGP route that is being redistributed into BGP
- The route is an IBGP-learned route whose AS_PATH attribute is - The route is an IBGP-learned route whose AS_PATH attribute is
empty. empty.
- The route is an EBGP-learned route whose AS_PATH contains only - The route is an EBGP-learned route whose AS_PATH contains only
ASes that are in the same AIGP Administrative Domain as the BGP ASes that are in the same AIGP Administrative Domain as the BGP
speaker. speaker.
A BGP speaker MUST NOT add the AIGP attribute to any route for which A BGP speaker R MUST NOT add the AIGP attribute to any route for
it has not set itself as the next hop. which R does not set itself as the next hop.
It SHOULD be possible to set AIGP_ORIGINATE to "enabled for the It SHOULD be possible to set AIGP_ORIGINATE to "enabled for the
routes of a particular IGP that are redistributed into BGP" (where "a routes of a particular IGP that are redistributed into BGP" (where "a
particular IGP" might be "OSPF" or "ISIS"). Other policies particular IGP" might be "OSPF" or "ISIS"). Other policies
determining when and whether to originate an AIGP attribute are also determining when and whether to originate an AIGP attribute are also
possible, depending on the needs of a particular deployment scenario. possible, depending on the needs of a particular deployment scenario.
When originating an AIGP attribute for a BGP route to address prefix When originating an AIGP attribute for a BGP route to address prefix
P, the value of the attribute is set according to policy. There are P, the value of the attribute is set according to policy. There are
a number of useful policies, some of which are in the following list: a number of useful policies, some of which are in the following list:
- When a BGP speaker is redistributing into BGP an IGP route to - When a BGP speaker R is redistributing into BGP an IGP route to
address prefix P, the IGP will have computed a "distance" from R address prefix P, the IGP will have computed a "distance" from R
to P. This distance MAY be assigned as the value of AIGP to P. This distance MAY be assigned as the value of AIGP
attribute. attribute.
- A BGP speaker may be redistributing into BGP a static route to - A BGP speaker R may be redistributing into BGP a static route to
address prefix P, for which a "distance" from R to P has been address prefix P, for which a "distance" from R to P has been
configured. This distance MAY be assigned as the value of AIGP configured. This distance MAY be assigned as the value of AIGP
attribute. attribute.
- A BGP speaker R may have received and installed a BGP-learned - A BGP speaker R may have received and installed a BGP-learned
route to prefix P, with next hop N. Or it may be redistributing route to prefix P, with next hop N. Or it may be redistributing
a static route to P, with next hop N. The "distance" from R to N a static route to P, with next hop N. Then:
MAY be assigned as the value of the AIGP attribute of the route
to P.
* If R has an IGP route to N, the IGP-computed distance from R * If R has an IGP route to N, the IGP-computed distance from R
to N MAY be used. to N MAY be used as the AIGP attribute value of the route to
P.
* If R has a BGP route to N, and an AIGP attribute value has * If R has a BGP route to N, and an AIGP attribute value has
been computed for that route (see section 3.3.3), that value been computed for that route (see section 3.3.3), that value
MAY be used as the AIGP attribute value of the route to P. MAY be used as the AIGP attribute value of the route to P.
3.3.2. Modifications by the Originator 3.3.2. Modifications by the Originator
If BGP speaker R is the originator of the AIGP attribute of prefix P, If BGP speaker R is the originator of the AIGP attribute of prefix P,
and at some point the "distance" from R to P changes, R SHOULD issue and at some point the "distance" from R to P changes, R SHOULD issue
a new BGP update containing the new value of the AIGP attribute. a new BGP update containing the new value of the AIGP attribute.
skipping to change at page 11, line 18 skipping to change at page 11, line 18
- remove from consideration all routes that are not tied for the - remove from consideration all routes that are not tied for the
lowest value of A. lowest value of A.
4.2. When the Route to the Next Hop has an AIGP attribute 4.2. When the Route to the Next Hop has an AIGP attribute
Suppose that a given router R1 is comparing two BGP-learned routes, Suppose that a given router R1 is comparing two BGP-learned routes,
such that either: such that either:
- the two routes have equal AIGP attribute values, or else - the two routes have equal AIGP attribute values, or else
- neither of the two routes has an AIGP attribute. The BGP - neither of the two routes has an AIGP attribute.
decision process as specified in [BGP] makes use, in its tie
breaker procedures, of "interior cost", defined as follows:
"interior cost of a route is determined by calculating the The BGP decision process as specified in [BGP] makes use, in its tie
metric to the NEXT_HOP for the route using the Routing breaker procedures, of "interior cost", defined as follows:
Table."
Suppose route T has a next hop of N. We modify the notion of the "interior cost of a route is determined by calculating the metric
"interior cost" from node R1 to node N as follows: to the NEXT_HOP for the route using the Routing Table."
- Let R2 be the next hop of the route to N, after all recursive Suppose route T has a next hop of N. We modify the notion of the
"interior cost" from node R1 to node N as follows:
- Let R2 be the BGP next hop of the route to N, after all recursive
resolution of the next hop is done. Let m be the IGP distance resolution of the next hop is done. Let m be the IGP distance
(or in the case of a static route, the configured distance) from (or in the case of a static route, the configured distance) from
R1 to R2. R1 to R2.
- If the installed route to N has an AIGP attribute, set A to the - If the installed route to N has an AIGP attribute, set A to the
AIGP value of the route to N, computing the AIGP value of the AIGP value of the route to N, computing the AIGP value of the
route according to the procedure of section 3.3.3. route according to the procedure of section 3.3.3.
- If the installed route to N does not have an AIGP value, set A to - If the installed route to N does not have an AIGP value, set A to
0. 0.
skipping to change at page 12, line 42 skipping to change at page 12, line 42
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.
8. Acknowledgments 8. Acknowledgments
The authors would like to thank Waqas Alam, Rajiv Asati, Clarence The authors would like to thank Waqas Alam, Rajiv Asati, Clarence
Filsfils, Robert Raszuk, Yakov Rekhter, Samir Saad, John Scudder, and Filsfils, Robert Raszuk, Yakov Rekhter, Eric Rosenberg, Samir Saad,
Shyam Sethuram for their input. John Scudder, and Shyam Sethuram for their input.
9. Authors' Addresses 9. Authors' Addresses
Rex Fernando Rex Fernando
Cisco Systems, Inc. Cisco Systems, Inc.
170 Tasman Drive 170 Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
Email: rex@cisco.com Email: rex@cisco.com
Pradosh Mohapatra Pradosh Mohapatra
skipping to change at page 14, line 13 skipping to change at page 14, line 13
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-02.txt, October 2011. fast-conn-restore-02.txt, October 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, H. Gredler, draft-ietf- Marques, R. Fernando, E. Chen, P. Mohapatra, H. Gredler, draft-ietf-
idr-best-external-04.txt, April 2011. idr-best-external-05.txt, January 2012.
[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.
 End of changes. 15 change blocks. 
24 lines changed or deleted 23 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/