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'BGP-CAP' Summary: 6 errors (**), 0 flaws (~~), 3 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Enke Chen 2 Internet Draft Siara Systems 3 Expiration Date: August 2000 5 Route Refresh Capability for BGP-4 7 draft-ietf-idr-bgp-route-refresh-01.txt 9 1. Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as ``work in progress.'' 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 2. Abstract 32 This document defines a new BGP capability termed 'Route Refresh 33 Capability', which would allow the dynamic exchange of route refresh 34 request between BGP speakers and subsequent re-advertisement of the 35 respective Adj-RIB-Out. One possible application of this capability 36 is to facilitate non-disruptive routing policy changes. 38 3. Introduction 40 Currently there does not exist a mechanism in BGP-4 [BGP-4] to 41 dynamically request a re-advertisement of the Adj-RIB-Out from a BGP 42 peer. When the inbound routing policy for a peer changes, all 43 prefixes from that peer must be somehow made available and then re- 44 examined against the new policy. To accomplish this, a commonly used 45 approach, known as 'soft-reconfiguration', is to store an unmodified 46 copy of all routes from that peer at all times, even though routing 47 policies do not change frequently (typically no more than a couple 48 times a day). Additional memory and CPU are required to maintain 49 these routes. 51 This document proposes an alternative solution that avoids the 52 additional maintenance cost. More specifically, it defines a new BGP 53 capability termed 'Route Refresh Capability', which would allow the 54 dynamic exchange of route refresh request between BGP speakers and 55 subsequent re-advertisement of the respective Adj-RIB-Out. 57 4. Route Refresh Capability 59 To advertise the Route Refresh Capability to a peer, a BGP speaker 60 uses BGP Capabilities Advertisement [BGP-CAP]. This capability is 61 advertised using the Capability code 2 and Capability length 0. 63 By advertising the Route Refresh Capability to a peer, a BGP speaker 64 conveys to the peer that the speaker is capable of receiving and 65 properly handling the ROUTE-REFRESH message (as defined in Section 5) 66 from the peer. 68 5. Route-REFRESH Message 70 The ROUTE-REFRESH message is a new BGP message type defined as 71 follows: 73 Type: 5 - ROUTE-REFRESH 75 Message Format: One encoded as 77 0 7 15 23 31 78 +-------+-------+-------+-------+ 79 | AFI | Res. | SAFI | 80 +-------+-------+-------+-------+ 82 The meaning, use and encoding of this field is the 83 same as defined in [BGP-MP, sect. 8]. More specifically, 84 AFI - Address Family Identifier (16 bit). 86 Res. - Reserved (8 bit) field. Should be set to 0 by the 87 sender and ignored by the receiver. 89 SAFI - Subsequent Address Family Identifier (8 bit). 91 6. Operation 93 A BGP speaker that is willing to receive the ROUTE-REFRESH message 94 from its peer should advertise the Route Refresh Capability to the 95 peer using BGP Capabilities advertisement [BGP-CAP]. 97 A BGP speaker may send a ROUTE-REFRESH message to its peer only if it 98 has received the Route Refresh Capability from its peer. The carried in such a message should be one of the that 100 the peer has advertised to the speaker at the session establishment 101 time via capability advertisement. 103 If a BGP speaker receives from its peer a ROUTE-REFRESH message with 104 the that the speaker didn't advertise to the peer at the 105 session establishment time via capability advertisement, the speaker 106 shall ignore such a message. Otherwise, the BGP speaker shall re- 107 advertise to that peer the Adj-RIB-Out of the carried in 108 the message, based on its outbound route filtering policy. 110 7. Security Considerations 112 This extension to BGP does not change the underlying security issues. 114 8. Acknowledgments 116 The concept of Route Refresh proposed is similar to the one used in 117 IDRP. 119 The author would like to thank Yakov Rekhter, Ravi Chandra, Srihari 120 Ramachandra and Bruce Cole for their review and comments. 122 9. References 124 [BGP-4] Rekhter, Y., and T. Li, 'A Border Gateway Protocol 4 (BGP- 125 4)', RFC 1771, March 1995. 127 [BGP-MP] Bates, T., Chandra, R., Katz, D., and Rekhter, Y., 128 'Multiprotocol Extensions for BGP-4', work in progress 130 [BGP-CAP] Chandra, R., Scudder, J., 'Capabilities Advertisement with 131 BGP-4', work in progress 133 10. Author Information 135 Enke Chen 136 Siara Systems Incorporated 137 1195 Borregas Ave. 138 Sunnyvale, Ca. 94089 139 e-mail: enkechen@siara.com