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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 Sproute Networks 4 Intended status: Standards Track R. Fernando 5 Expires: September 6, 2018 Cisco Systems 6 March 5, 2018 8 BGP Link Bandwidth Extended Community 9 draft-ietf-idr-link-bandwidth-07.txt 11 Abstract 13 This document describes an application of BGP extended communities 14 that allows a router to perform unequal cost load balancing. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at https://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on September 6, 2018. 33 Copyright Notice 35 Copyright (c) 2018 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (https://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 This document may contain material from IETF Documents or IETF 49 Contributions published or made publicly available before November 50 10, 2008. The person(s) controlling the copyright in some of this 51 material may not have granted the IETF Trust the right to allow 52 modifications of such material outside the IETF Standards Process. 53 Without obtaining an adequate license from the person(s) controlling 54 the copyright in such materials, this document may not be modified 55 outside the IETF Standards Process, and derivative works of it may 56 not be created outside the IETF Standards Process, except to format 57 it for publication as an RFC or to translate it into languages other 58 than English. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 64 2. Link Bandwidth Extended Community . . . . . . . . . . . . . . 2 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 . . . . . . . . . . . . . . . . . . . . . . . 5 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 based on the bandwidth of the external 78 (DMZ) link. This document suggests that the external link bandwidth 79 be carried in the network using a new extended community [RFC4360] - 80 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 an external neighbor and 91 advertises this route (via IBGP) to internal neighbors, as part of 92 this advertisement the router may carry the cost to reach the 93 external neighbor. The cost can be either configured per neighbor or 94 derived from the bandwidth of the link that connects the router to a 95 directly connected external neighbor. This value is carried in the 96 Link Bandwidth Extended Community. No more than one link bandwidth 97 extended community SHALL be attached to a route. Additionally, if a 98 route is received with link bandwidth extended community and the BGP 99 speaker sets itself as next-hop while announcing that route to other 100 peers, the link bandwidth extended community should be removed. 102 The extended community is optional non-transitive. The value of the 103 high-order octet of the extended Type Field is 0x40. The value of 104 the low-order octet of the extended type field for this community is 105 0x04. The value of the Global Administrator subfield in the Value 106 Field SHOULD represent the Autonomous System of the router that 107 attaches the Link Bandwidth Community. If four octet AS numbering 108 scheme is used [RFC6793], AS_TRANS should be used in the Global 109 Administrator subfield. The bandwidth of the link is expressed as 4 110 octets in IEEE floating point format, units being bytes (not bits!) 111 per second. It is carried in the Local Administrator subfield of the 112 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. If the path between the load 118 sharing router and the exit point is not tunneled, then the IGP 119 distance between the load balancing router and the exit points should 120 be the same. 122 If the path between the load sharing router and the exit point is 123 tunneled, then the choice to use this community is a purely local 124 matter to the load sharing router. 126 In the context of BGP/MPLS VPNs [RFC4364], link bandwidth community 127 could be used to support inbound load balancing for multihomed sites, 128 as follows. Consider a site that is connected to PE1 and PE2. Both 129 PE1 and PE2 would advertise VPN-IP routes associated with the 130 destinations within the site. One way to enable other PEs to receive 131 all these routes is to require the RD of the routes advertised by PE1 132 to be different from the RD of the routes advertised by PE2. The 133 VPN-IP routes advertised by PE1 should carry the link bandwidth 134 community; likewise for the VPN-IP routes advertised by PE2. The 135 bandwidth value carried in the community could be locally determined 136 by PE1 and PE2. Alternatively CEs of the site, when advertising IP 137 routes to PE1 and PE2, could add the link bandwith community to these 138 advertisements, in which case PE1 and PE2, when originating VPN-IP 139 routes, would use the bandwidth value from the IP routes they 140 received from the CEs to construct the link bandwidth community 141 carried by these VPN-IP routes. 143 An ingress PE, when sending traffic to destinations within the site, 144 can use the bandwidth value carried in the community of the routes 145 advertised by PE1 and PE2 to perform load sharing, where some of the 146 traffic would go via PE1, while other traffic would go via PE2. 148 If there are multiple paths to reach a destination and if only some 149 of them have link bandwidth community, the load sharing router should 150 not perform unequal cost load balancing based on link bandwidths. 152 4. Acknowledgments 154 The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan 155 Tappan for proposing unequal cost load balancing as one possible 156 application of the extended community attribute. 158 The authors would like to thank Bruno Decraene, Robert Raszuk, Joel 159 Halpern, Aleksi Suhonen, Randy Bush, and John Scudder for their 160 comments and contributions. 162 5. IANA Considerations 164 This document defines a specific application of the two-octet AS 165 specific extended community. IANA is requested to assign a sub- type 166 value of 0x04 for the link bandwidth extended community. 168 Name Value 169 ---- ----- 170 non-transitive Link Bandwidth Ext. Community 0x4004 172 6. Security Considerations 174 There are no additional security risks introduced by this design. 176 7. Normative References 178 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 179 Requirement Levels", BCP 14, RFC 2119, 180 DOI 10.17487/RFC2119, March 1997, 181 . 183 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 184 Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, 185 February 2006, . 187 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 188 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 189 2006, . 191 [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet 192 Autonomous System (AS) Number Space", RFC 6793, 193 DOI 10.17487/RFC6793, December 2012, 194 . 196 Authors' Addresses 198 Pradosh Mohapatra 199 Sproute Networks 201 Email: pradosh@sproute.com 203 Rex Fernando 204 Cisco Systems 205 170 W. Tasman Drive 206 San Jose, CA 95134 207 USA 209 Email: rex@cisco.com