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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Mohapatra 3 Internet-Draft R. Fernando 4 Intended status: Standards Track Cisco Systems 5 Expires: July 26, 2013 January 22, 2013 7 BGP Link Bandwidth Extended Community 8 draft-ietf-idr-link-bandwidth-06.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 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). Note that other groups may also distribute 22 working documents as Internet-Drafts. The list of current Internet- 23 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on July 26, 2013. 32 Copyright Notice 34 Copyright (c) 2013 IETF Trust and the persons identified as the 35 document authors. All rights reserved. 37 This document is subject to BCP 78 and the IETF Trust's Legal 38 Provisions Relating to IETF Documents 39 (http://trustee.ietf.org/license-info) in effect on the date of 40 publication of this document. Please review these documents 41 carefully, as they describe your rights and restrictions with respect 42 to this document. Code Components extracted from this document must 43 include Simplified BSD License text as described in Section 4.e of 44 the Trust Legal Provisions and are provided without warranty as 45 described in the Simplified BSD License. 47 This document may contain material from IETF Documents or IETF 48 Contributions published or made publicly available before November 49 10, 2008. The person(s) controlling the copyright in some of this 50 material may not have granted the IETF Trust the right to allow 51 modifications of such material outside the IETF Standards Process. 52 Without obtaining an adequate license from the person(s) controlling 53 the copyright in such materials, this document may not be modified 54 outside the IETF Standards Process, and derivative works of it may 55 not be created outside the IETF Standards Process, except to format 56 it for publication as an RFC or to translate it into languages other 57 than English. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 63 2. Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3 64 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 3 65 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4 66 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 67 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 68 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 71 1. Introduction 73 When a BGP speaker receives multiple paths from its internal peers, 74 it could select more than one path to send traffic to. In doing so, 75 it might be useful to provide the speaker with information that would 76 help it distribute the traffic based on the bandwidth of the external 77 (DMZ) link. This document suggests that the external link bandwidth 78 be carried in the network using a new extended community [RFC4360] - 79 the link bandwidth extended community. 81 1.1. Requirements Language 83 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 84 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 85 document are to be interpreted as described in RFC 2119 [RFC2119]. 87 2. Link Bandwidth Extended Community 89 When a BGP speaker receives a route from an external neighbor and 90 advertises this route (via IBGP) to internal neighbors, as part of 91 this advertisement the router may carry the cost to reach the 92 external neighbor. The cost can be either configured per neighbor or 93 derived from the bandwidth of the link that connects the router to a 94 directly connected external neighbor. This value is carried in the 95 Link Bandwidth Extended Community. No more than one link bandwidth 96 extended community SHALL be attached to a route. Additionally, if a 97 route is received with link bandwidth extended community and the BGP 98 speaker sets itself as next-hop while announcing that route to other 99 peers, the link bandwidth extended community should be removed. 101 The extended community is optional non-transitive. The value of the 102 high-order octet of the extended Type Field is 0x40. The value of 103 the low-order octet of the extended type field for this community is 104 0x04. The value of the Global Administrator subfield in the Value 105 Field SHOULD represent the Autonomous System of the router that 106 attaches the Link Bandwidth Community. If four octet AS numbering 107 scheme is used [RFC6793], AS_TRANS should be used in the Global 108 Administrator subfield. The bandwidth of the link is expressed as 4 109 octets in IEEE floating point format, units being bytes (not bits!) 110 per second. It is carried in the Local Administrator subfield of the 111 Value Field. 113 3. Deployment Considerations 115 The usage of this community is restricted to the cases where BGP 116 multipath can be safely deployed. If the path between the load 117 sharing router and the exit point is not tunneled, then the IGP 118 distance between the load balancing router and the exit points should 119 be the same. 121 If the path between the load sharing router and the exit point is 122 tunneled, then the choice to use this community is a purely local 123 matter to the load sharing router. 125 In the context of BGP/MPLS VPNs [RFC4364], link bandwidth community 126 could be used to support inbound load balancing for multihomed sites, 127 as follows. Consider a site that is connected to PE1 and PE2. Both 128 PE1 and PE2 would advertise VPN-IP routes associated with the 129 destinations within the site. One way to enable other PEs to receive 130 all these routes is to require the RD of the routes advertised by PE1 131 to be different from the RD of the routes advertised by PE2. The 132 VPN-IP routes advertised by PE1 should carry the link bandwidth 133 community; likewise for the VPN-IP routes advertised by PE2. The 134 bandwidth value carried in the community could be locally determined 135 by PE1 and PE2. Alternatively CEs of the site, when advertising IP 136 routes to PE1 and PE2, could add the link bandwith community to these 137 advertisements, in which case PE1 and PE2, when originating VPN-IP 138 routes, would use the bandwidth value from the IP routes they 139 received from the CEs to construct the link bandwidth community 140 carried by these VPN-IP routes. 142 An ingress PE, when sending traffic to destinations within the site, 143 can use the bandwidth value carried in the community of the routes 144 advertised by PE1 and PE2 to perform load sharing, where some of the 145 traffic would go via PE1, while other traffic would go via PE2. 147 If there are multiple paths to reach a destination and if only some 148 of them have link bandwidth community, the load sharing router should 149 not perform unequal cost load balancing based on link bandwidths. 151 4. Acknowledgments 153 The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan 154 Tappan for proposing unequal cost load balancing as one possible 155 application of the extended community attribute. 157 The authors would like to thank Bruno Decraene, Robert Raszuk, Joel 158 Halpern, Aleksi Suhonen, Randy Bush, and John Scudder for their 159 comments and contributions. 161 5. IANA Considerations 163 This document defines a specific application of the two-octet AS 164 specific extended community. IANA is requested to assign a sub- type 165 value of 0x04 for the link bandwidth extended community. 167 Name Value 168 ---- ----- 169 non-transitive Link Bandwidth Ext. Community 0x4004 171 6. Security Considerations 173 There are no additional security risks introduced by this design. 175 7. Normative References 177 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 178 Requirement Levels", BCP 14, RFC 2119, March 1997. 180 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 181 Communities Attribute", RFC 4360, February 2006. 183 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 184 Networks (VPNs)", RFC 4364, February 2006. 186 [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet 187 Autonomous System (AS) Number Space", RFC 6793, 188 December 2012. 190 Authors' Addresses 192 Pradosh Mohapatra 193 Cisco Systems 194 170 W. Tasman Drive 195 San Jose, CA 95134 196 USA 198 Phone: 199 Email: pmohapat@cisco.com 200 Rex Fernando 201 Cisco Systems 202 170 W. Tasman Drive 203 San Jose, CA 95134 204 USA 206 Phone: 207 Email: rex@cisco.com