draft-ietf-idr-aigp-00.txt		draft-ietf-idr-aigp-01.txt
	Network Working Group Pradosh Mohapatra		Network Working Group Pradosh Mohapatra
	Internet Draft Cisco Systems, Inc.		Internet Draft Cisco Systems, Inc.
	Intended Status: Proposed Standard		Intended Status: Proposed Standard
	Expires: November 8, 2009 Rex Fernando		Expires: April 7, 2010 Rex Fernando
	Juniper Networks, Inc.		Juniper Networks, Inc.
	Eric C. Rosen		Eric C. Rosen
	Cisco Systems, Inc.		Cisco Systems, Inc.
	James Uttaro		James Uttaro
	ATT		ATT
	May 8, 2009		October 7, 2009
	The Accumulated IGP Metric Attribute for BGP		The Accumulated IGP Metric Attribute for BGP
	draft-ietf-idr-aigp-00.txt		draft-ietf-idr-aigp-01.txt
	Status of this Memo		Status of this Memo
	This Internet-Draft is submitted to IETF in full conformance with the		This Internet-Draft is submitted to IETF in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	other groups may also distribute working documents as Internet-		other groups may also distribute working documents as Internet-
	Drafts.		Drafts.
	skipping to change at page 3, line 22		skipping to change at page 3, line 22
	3.3 Creating and Modifying the AIGP Attribute ............. 7		3.3 Creating and Modifying the AIGP Attribute ............. 7
	3.3.1 Originating the AIGP Attribute ........................ 7		3.3.1 Originating the AIGP Attribute ........................ 7
	3.3.2 Modifications by the Originator ....................... 7		3.3.2 Modifications by the Originator ....................... 7
	3.3.3 Modifications by a Non-Originator ..................... 8		3.3.3 Modifications by a Non-Originator ..................... 8
	4 Decision Process ...................................... 9		4 Decision Process ...................................... 9
	4.1 When a Route has an AIGP Attribute .................... 9		4.1 When a Route has an AIGP Attribute .................... 9
	4.2 When the Route to the Next Hop has an AIGP attribute .. 10		4.2 When the Route to the Next Hop has an AIGP attribute .. 10
	5 Deployment Considerations ............................. 11		5 Deployment Considerations ............................. 11
	6 IANA Considerations ................................... 11		6 IANA Considerations ................................... 11
	7 Security Considerations ............................... 11		7 Security Considerations ............................... 11
	8 Acknowledgments ....................................... 12		8 Acknowledgments ....................................... 11
	9 Authors' Addresses .................................... 12		9 Authors' Addresses .................................... 12
	10 Normative References .................................. 13		10 Normative References .................................. 12
	11 Informative References ................................ 13		11 Informative References ................................ 13
	1. Specification of requirements		1. Specification of requirements
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Introduction		2. Introduction
	skipping to change at page 9, line 44		skipping to change at page 9, line 44
	unlikely to give a sensible result if the metric assigned to inter-AS		unlikely to give a sensible result if the metric assigned to inter-AS
	BGP links (on which no IGP is running) or to static routes is not		BGP links (on which no IGP is running) or to static routes is not
	comparable to the IGP metrics. All such cases are outside the scope		comparable to the IGP metrics. All such cases are outside the scope
	of the current document.		of the current document.
	4. Decision Process		4. Decision Process
	4.1. When a Route has an AIGP Attribute		4.1. When a Route has an AIGP Attribute
	Use of the AIGP attribute involves several modifications to the BGP		Use of the AIGP attribute involves several modifications to the BGP
	decision process.		"phase 2" decision process as described in [BGP], section 9.1.2.2.
			The procedures defined in this section MUST be executed BEFORE any of
	The procedures defined in this section MUST be executed BEFORE the		the tie breaking procedures described therein are executed.
	LOCAL_PREF comparison step in the BGP decision process.
	When comparing two routes, one of which has an AIGP attribute and one
	of which does not, the route with the AIGP attribute MUST be
	considered to be the preferable route.
	When a given router R is comparing two routes, T1 and T2, each of
	which has an AIGP attribute, the preferred route is selected
	according to the following rule:
	- Set A1 to the sum of (a) T1's AIGP attribute value and (b) the
	IGP distance from R to T1's next hop.
	- Set A2 to the sum of (a) T2's AIGP attribute value and (b) the
	IGP distance from R to T2's next hop.
	- If A1 is less than A2, select T1.		If any routes have an AIGP attribute, remove from consideration all
			routes that do not have an AIGP attribute.
	- If A2 is less than A1, select T2.		If router R is considering route T, where T has an AIGP attribute,
	- If A1 is equal to A2, T1 and T2 are equally preferable.		- then R must compute the value A, defined as follows: set A to the
			sum of (a) T's AIGP attribute value and (b) the IGP distance from
			R to T's next hop.
	In all other respects, the decision process is unchanged. In		- remove from consideration all routes that are not tied for the
	particular, the tie-breaking rules for equally preferable paths		lowest value of A.
	remain unchanged, and the AS_PATH continues to be used to prevent
	consideration of routes that traverse an AS more than once.
	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 routes, neither of		Suppose that a given router R1 is comparing two routes, neither of
	which has an AIGP attribute. The BGP decision process as specified		which has an AIGP attribute. The BGP decision process as specified
	in [BGP] makes use, in its tie breaker procedures, of "interior		in [BGP] makes use, in its tie breaker procedures, of "interior
	cost", defined as follows:		cost", defined as follows:
	"interior cost of a route is determined by calculating the metric		"interior cost of a route is determined by calculating the metric
	to the NEXT_HOP for the route using the Routing Table."		to the NEXT_HOP for the route using the Routing Table."
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