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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4893 (Obsoleted by RFC 6793) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Mohapatra 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track R. Fernando 5 Expires: September 4, 2009 Juniper Networks 6 March 3, 2009 8 BGP Link Bandwidth Extended Community 9 draft-rfernando-idr-link-bandwidth-00.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. This document may contain material 15 from IETF Documents or IETF Contributions published or made publicly 16 available before November 10, 2008. The person(s) controlling the 17 copyright in some of this material may not have granted the IETF 18 Trust the right to allow modifications of such material outside the 19 IETF Standards Process. Without obtaining an adequate license from 20 the person(s) controlling the copyright in such materials, this 21 document may not be modified outside the IETF Standards Process, and 22 derivative works of it may not be created outside the IETF Standards 23 Process, except to format it for publication as an RFC or to 24 translate it into languages other than English. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF), its areas, and its working groups. Note that 28 other groups may also distribute working documents as Internet- 29 Drafts. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 The list of current Internet-Drafts can be accessed at 37 http://www.ietf.org/ietf/1id-abstracts.txt. 39 The list of Internet-Draft Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 This Internet-Draft will expire on September 4, 2009. 44 Copyright Notice 46 Copyright (c) 2009 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents in effect on the date of 51 publication of this document (http://trustee.ietf.org/license-info). 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. 55 Abstract 57 This document describes an application of BGP extended communities 58 that allows a router to perform unequal cost load balancing. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 64 2. Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3 65 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 3 66 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4 67 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 68 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 69 7. Normative References . . . . . . . . . . . . . . . . . . . . . 4 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 4 72 1. Introduction 74 When a BGP speaker receives multiple paths from its internal peers, 75 it could select more than one path to send traffic to. In doing so, 76 it might be useful to provide the speaker with information that would 77 help it distribute the traffic unequally based on the cost of the 78 external (DMZ) link. This document suggests that the external link 79 bandwidth be carried in the network using a new extended community 80 [RFC4360] - the link bandwidth extended community. 82 1.1. Requirements Language 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 86 document are to be interpreted as described in RFC 2119 [RFC2119]. 88 2. Link Bandwidth Extended Community 90 When a BGP speaker receives a route from a directly connected 91 external neighbor (the external neighbor that is one IP hop away) and 92 advertises this route (via IBGP) to internal neighbors, as part of 93 this advertisement the router may carry the bandwidth of the link 94 that connects the router with the external neighbor. The bandwidth 95 of such a link is carried in the Link Bandwidth Community. The 96 community is optional non-transitive. A border router MUST strip the 97 link bandwidth community from a route when it advertises the route to 98 an external neighbor. The value of the high-order octet of the 99 extended Type Field is 0x40. The value of the low-order octet of the 100 extended type field for this community is 0x04. The value of the 101 Global Administrator subfield in the Value Field SHOULD represent the 102 Autonomous System of the router that attaches the Link Bandwidth 103 Community. If four octet AS numbering scheme is used [RFC4893], 104 AS_TRANS should be used in the Global Administrator subfield. The 105 bandwidth of the link is expressed as 4 octets in IEEE floating point 106 format, units being bytes per second. It is carried in the Local 107 Administrator subfield of the Value Field. 109 3. Deployment Considerations 111 The usage of this community is restricted to the cases where BGP 112 multipath can be safely deployed. In other words, the IGP distance 113 between the load balancing router and the exit points should be the 114 same. Alternatively, the path between the load sharing router and 115 the exit points could be label switched. If there are multiple paths 116 to reach a destination and if only some of them have link bandwidth 117 community, the receiver should not perform unequal cost load 118 balancing based on link bandwidths. 120 4. Acknowledgments 122 The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan 123 Tappan for proposing unequal cost load balancing as one possible 124 application of the extended community attribute. 126 5. IANA Considerations 128 This document defines a specific application of the two-octet AS 129 specific extended community. IANA is requested to assign a sub- type 130 value of 0x04 for the link bandwidth extended community. 132 Name Value 133 ---- ----- 134 non-transitive Link Bandwidth Ext. Community 0x4004 136 6. Security Considerations 138 There are no additional security risks introduced by this design. 140 7. Normative References 142 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 143 Requirement Levels", BCP 14, RFC 2119, March 1997. 145 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 146 Communities Attribute", RFC 4360, February 2006. 148 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 149 Number Space", RFC 4893, May 2007. 151 Authors' Addresses 153 Pradosh Mohapatra 154 Cisco Systems 155 170 W. Tasman Drive 156 San Jose, CA 95134 157 USA 159 Phone: 160 Email: pmohapat@cisco.com 162 Rex Fernando 163 Juniper Networks 164 1194 N. Mathilda Ave 165 Sunnyvale, CA 94089 166 USA 168 Phone: 169 Email: rex@juniper.net