draft-ietf-idr-aigp-02.txt   draft-ietf-idr-aigp-03.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: October 2, 2010 Cisco Systems, Inc. Expires: October 16, 2010 Cisco Systems, Inc.
James Uttaro James Uttaro
ATT ATT
April 2, 2010 April 16, 2010
The Accumulated IGP Metric Attribute for BGP The Accumulated IGP Metric Attribute for BGP
draft-ietf-idr-aigp-02.txt draft-ietf-idr-aigp-03.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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1 Specification of requirements ......................... 3 1 Specification of requirements ......................... 3
2 Introduction .......................................... 3 2 Introduction .......................................... 3
3 AIGP Attribute ........................................ 5 3 AIGP Attribute ........................................ 5
3.1 Applicability Restrictions and Cautions ............... 6 3.1 Applicability Restrictions and Cautions ............... 6
3.2 Restrictions on Sending/Receiving ..................... 6 3.2 Restrictions on Sending/Receiving ..................... 6
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 .................... 10
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 ....................................... 11 8 Acknowledgments ....................................... 12
9 Authors' Addresses .................................... 12 9 Authors' Addresses .................................... 12
10 Normative References .................................. 12 10 Normative References .................................. 13
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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some IS-IS), or if the meaning of the metrics is different in the some IS-IS), or if the meaning of the metrics is different in the
different IGPs (e.g., if the metric represents bandwidth in some IGP different IGPs (e.g., if the metric represents bandwidth in some IGP
domains but represents latency in others). These procedures also are domains but represents latency in others). These procedures also are
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
Support for the AIGP attribute involves several modifications to the
tie breaking procedures of the BGP "phase 2" decision described in
[BGP], section 9.1.2.2. These modifications are described below in
sections 4.1 and 4.2.
In some cases, the BGP decision process may install a route without
executing any tie breaking procedures. This may happen, e.g., if
only one route to a given prefix has the highest degree of preference
(as defined in [BGP] section 9.1.1). In this case, the AIGP
attribute is not considered.
In other cases, some routes may be eliminated before the tie breaking
procedures are invoked, e.g., routes with AS-PATH attributes
indicating a loop, or routes with unresolvable next hops. In these
cases, the AIGP attributes of the eliminated routes are not
considered.
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 Assuming that the BGP decision process invokes the tie breaking
"phase 2" decision process as described in [BGP], section 9.1.2.2. procedures, the procedures in this section MUST be executed BEFORE
The procedures defined in this section MUST be executed BEFORE any of any of the tie breaking procedures described in [BGP] section 9.1.2.2
the tie breaking procedures described therein are executed. are executed.
If any routes have an AIGP attribute, remove from consideration all If any routes have an AIGP attribute, remove from consideration all
routes that do not have an AIGP attribute. routes that do not have an AIGP attribute.
If router R is considering route T, where T has an AIGP attribute, If router R is considering route T, where T has an AIGP attribute,
- then R must compute the value A, defined as follows: set A to the - 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 sum of (a) T's AIGP attribute value and (b) the IGP distance from
R to T's next hop. R to T's next hop.
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8. Acknowledgments 8. Acknowledgments
The authors would like to thank Rajiv Asati, Clarence Filsfils, The authors would like to thank Rajiv Asati, Clarence Filsfils,
Robert Raszuk, Yakov Rekhter, Samir Saad, and John Scudder for their Robert Raszuk, Yakov Rekhter, Samir Saad, and John Scudder for their
input. input.
9. Authors' Addresses 9. Authors' Addresses
Rex Fernando Rex Fernando
Juniper Networks Cisco Systems, Inc.
1194 N. Mathilda Ave 170 Tasman Drive
Sunnyvale, CA 94089 San Jose, CA 95134
USA Email: rex@cisco.com
Email: rex@juniper.net
Pradosh Mohapatra Pradosh Mohapatra
Cisco Systems, Inc. Cisco Systems, Inc.
170 Tasman Drive 170 Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
Email: pmohapat@cisco.com Email: pmohapat@cisco.com
Eric C. Rosen Eric C. Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Avenue 1414 Massachusetts Avenue
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