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Fernando 4 Intended status: Standards Track Cisco Systems 5 Expires: August 28, 2010 February 24, 2010 7 BGP Link Bandwidth Extended Community 8 draft-ietf-idr-link-bandwidth-01.txt 10 Abstract 12 This document describes an application of BGP extended communities 13 that allows a router to perform unequal cost load balancing. 15 Status of this Memo 17 This Internet-Draft is submitted to IETF in full conformance with the 18 provisions of BCP 78 and BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that 22 other groups may also distribute working documents as Internet- 23 Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt. 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html. 36 This Internet-Draft will expire on August 28, 2010. 38 Copyright Notice 40 Copyright (c) 2010 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the BSD License. 53 This document may contain material from IETF Documents or IETF 54 Contributions published or made publicly available before November 55 10, 2008. The person(s) controlling the copyright in some of this 56 material may not have granted the IETF Trust the right to allow 57 modifications of such material outside the IETF Standards Process. 58 Without obtaining an adequate license from the person(s) controlling 59 the copyright in such materials, this document may not be modified 60 outside the IETF Standards Process, and derivative works of it may 61 not be created outside the IETF Standards Process, except to format 62 it for publication as an RFC or to translate it into languages other 63 than English. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 69 2. Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3 70 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 3 71 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4 72 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 73 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 74 7. Normative References . . . . . . . . . . . . . . . . . . . . . 4 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 4 77 1. Introduction 79 When a BGP speaker receives multiple paths from its internal peers, 80 it could select more than one path to send traffic to. In doing so, 81 it might be useful to provide the speaker with information that would 82 help it distribute the traffic unequally based on the cost of the 83 external (DMZ) link. This document suggests that the external link 84 bandwidth be carried in the network using a new extended community 85 [RFC4360] - the link bandwidth extended community. 87 1.1. Requirements Language 89 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 90 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 91 document are to be interpreted as described in RFC 2119 [RFC2119]. 93 2. Link Bandwidth Extended Community 95 When a BGP speaker receives a route from a directly connected 96 external neighbor (the external neighbor that is one IP hop away) and 97 advertises this route (via IBGP) to internal neighbors, as part of 98 this advertisement the router may carry the bandwidth of the link 99 that connects the router with the external neighbor. The bandwidth 100 of such a link is carried in the Link Bandwidth Community. The 101 community is optional non-transitive. A border router MUST strip the 102 link bandwidth community from a route when it advertises the route to 103 an external neighbor. The value of the high-order octet of the 104 extended Type Field is 0x40. The value of the low-order octet of the 105 extended type field for this community is 0x04. The value of the 106 Global Administrator subfield in the Value Field SHOULD represent the 107 Autonomous System of the router that attaches the Link Bandwidth 108 Community. If four octet AS numbering scheme is used [RFC4893], 109 AS_TRANS should be used in the Global Administrator subfield. The 110 bandwidth of the link is expressed as 4 octets in IEEE floating point 111 format, units being bytes per second. It is carried in the Local 112 Administrator subfield of the Value Field. 114 3. Deployment Considerations 116 The usage of this community is restricted to the cases where BGP 117 multipath can be safely deployed. In other words, the IGP distance 118 between the load balancing router and the exit points should be the 119 same. Alternatively, the path between the load sharing router and 120 the exit points could be label switched. If there are multiple paths 121 to reach a destination and if only some of them have link bandwidth 122 community, the receiver should not perform unequal cost load 123 balancing based on link bandwidths. 125 4. Acknowledgments 127 The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan 128 Tappan for proposing unequal cost load balancing as one possible 129 application of the extended community attribute. 131 5. IANA Considerations 133 This document defines a specific application of the two-octet AS 134 specific extended community. IANA is requested to assign a sub- type 135 value of 0x04 for the link bandwidth extended community. 137 Name Value 138 ---- ----- 139 non-transitive Link Bandwidth Ext. Community 0x4004 141 6. Security Considerations 143 There are no additional security risks introduced by this design. 145 7. Normative References 147 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 148 Requirement Levels", BCP 14, RFC 2119, March 1997. 150 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 151 Communities Attribute", RFC 4360, February 2006. 153 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 154 Number Space", RFC 4893, May 2007. 156 Authors' Addresses 158 Pradosh Mohapatra 159 Cisco Systems 160 170 W. Tasman Drive 161 San Jose, CA 95134 162 USA 164 Phone: 165 Email: pmohapat@cisco.com 167 Rex Fernando 168 Cisco Systems 169 170 W. Tasman Drive 170 San Jose, CA 95134 171 USA 173 Phone: 174 Email: rex@cisco.com