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.
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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
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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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