--- 1/draft-ietf-idr-aigp-00.txt 2009-10-07 19:12:09.000000000 +0200 +++ 2/draft-ietf-idr-aigp-01.txt 2009-10-07 19:12:09.000000000 +0200 @@ -1,28 +1,28 @@ Network Working Group Pradosh Mohapatra Internet Draft Cisco Systems, Inc. Intended Status: Proposed Standard -Expires: November 8, 2009 Rex Fernando +Expires: April 7, 2010 Rex Fernando Juniper Networks, Inc. Eric C. Rosen Cisco Systems, Inc. James Uttaro ATT - May 8, 2009 + October 7, 2009 The Accumulated IGP Metric Attribute for BGP - draft-ietf-idr-aigp-00.txt + draft-ietf-idr-aigp-01.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. @@ -77,23 +77,23 @@ 3.3 Creating and Modifying the AIGP Attribute ............. 7 3.3.1 Originating the AIGP Attribute ........................ 7 3.3.2 Modifications by the Originator ....................... 7 3.3.3 Modifications by a Non-Originator ..................... 8 4 Decision Process ...................................... 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 5 Deployment Considerations ............................. 11 6 IANA Considerations ................................... 11 7 Security Considerations ............................... 11 - 8 Acknowledgments ....................................... 12 + 8 Acknowledgments ....................................... 11 9 Authors' Addresses .................................... 12 -10 Normative References .................................. 13 +10 Normative References .................................. 12 11 Informative References ................................ 13 1. Specification of requirements 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 [RFC2119]. 2. Introduction @@ -357,49 +357,35 @@ 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 comparable to the IGP metrics. All such cases are outside the scope of the current document. 4. Decision Process 4.1. When a Route has an AIGP Attribute Use of the AIGP attribute involves several modifications to the BGP - decision process. - - The procedures defined in this section MUST be executed BEFORE the - 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. + "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 tie breaking procedures described therein are executed. - - 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 - particular, the tie-breaking rules for equally preferable paths - remain unchanged, and the AS_PATH continues to be used to prevent - consideration of routes that traverse an AS more than once. + - remove from consideration all routes that are not tied for the + lowest value of A. 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 which has an AIGP attribute. The BGP 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 metric to the NEXT_HOP for the route using the Routing Table."