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
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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) 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.
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	- 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.
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