Network Working Group Enke Chen Internet Draft John Scudder Expiration Date: February 2006 Cisco Systems Extended Optional Parameters for the BGP OPEN Message draft-chen-bgp-ext-opt-param-00.txt 1. Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 2. Abstract In this document we define a new BGP capability termed "Extended Optional Parameters Capability" that would allow the optional parameters for a BGP OPEN message to be carried in a larger size "Extended Optional Parameters" field. Chen & Scudder [Page 1] Internet Draft draft-chen-bgp-ext-opt-param-00.txt August 2005 3. Introduction Currently the size of the Optional Parameters field in the BGP OPEN message [BGP-4] is limited to 255 octets because of the one-octet Optional Parameters Length field. As BGP Capabilities [BGP-CAP] are carried in the Optional Parameters field, and new BGP capabilities continue to be introduced, the limit is becoming a concern for BGP development. In this document we define a new BGP capability termed "Extended Optional Parameters Capability" that would allow the optional parameters for a BGP OPEN message to be carried in a larger size "Extended Optional Parameters" field. 4. Specification of Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-2119]. 5. Extended Optional Parameters in the OPEN Message Except for the larger size of the Parameter Length field, the Extended Optional Parameters field has the same semantics as the Optional Parameters field defined in [BGP-4] for the BGP OPEN message. The Extended Optional Parameters Length field and the Extended Optional Parameters field can be optionally appended to the existing fields of the BGP OPEN message as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+ | Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | My Autonomous System | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Hold Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BGP Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opt Parm Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Chen & Scudder [Page 2] Internet Draft draft-chen-bgp-ext-opt-param-00.txt August 2005 | Optional Parameters (variable) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ext Opt Parm Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Extended Optional Parameters (variable) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Extended Optional Parameters Length: This 2-octet unsigned integer indicates the total length of the Extended Optional Parameters field in octets. If the value of this field is zero, no Extended Optional Parameters are present. Extended Optional Parameters: This field contains a list of optional parameters, where each parameter is encoded as a triplet. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+ | Parm. Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parm. Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Parm. Value (variable) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Parameter Type is an one octet field that unambiguously identifies individual parameters. The Parameter Length is a two octet field that contains the length of the Parameter Value field in octets. The Parameter Value is a variable length field that is interpreted according to the value of the Parameter Type field. Chen & Scudder [Page 3] Internet Draft draft-chen-bgp-ext-opt-param-00.txt August 2005 An Optional Parameter Type defined for the Optional Parameters field is automatically valid for the Extended Optional Parameter field. One example is the Capabilities Optional Parameters defined in [BGP- CAP]. Whether the Extended Optional Parameters field is present in an OPEN message is determined by the Extended Optional Parameters Capability (defined in the next section) in the OPEN message. 6. Extended Optional Parameters Capability The Extended Optional Parameters Capability is a new BGP capability [BGP-CAP]. The Capability Code for this capability is specified in the "IANA Considerations" section of this document. The length of the Capability Value field is one octet. The Capability Value field indicates whether the Extended Optional Parameters Length field, and thus the Extended Optional Parameters field, are included in the OPEN message, and whether the BGP speaker intends to send another OPEN message with the Extended Optional Parameters field. The values and semantics for the Capability Value field are as follows: Value Ext. Opt. Parm Len Included Second OPEN Intended ----- --------------------------- -------------------- 0 NO NO 1 NO YES 2 YES NO By advertising the Extended Optional Parameters Capability in an OPEN message to a peer, a BGP speaker also conveys to the peer that the speaker is capable of receiving and properly handling an OPEN message that carries the Extended Optional Parameters field from the peer. The Extended Optional Parameters Capability carried in the Extended Optional Parameters field is meaningless, and SHALL be ignored by the receiver. In this document we are only concerned with the capability in the Optional Parameters field of an OPEN message. Chen & Scudder [Page 4] Internet Draft draft-chen-bgp-ext-opt-param-00.txt August 2005 7. Operation A BGP speaker that can receive and properly handle an OPEN message carrying the Extended Optional Parameters field from its peer SHOULD use the BGP Capabilities Advertisement [BGP-CAP] to advertise the Extended Optional Parameters Capability to the peer. The Capability Value field SHALL be 0 when the BGP speaker does not include the Extended Optional Parameters field in its OPEN message. A BGP speaker MUST advertise the Extended Optional Parameters Capability with the capability value of 2 in an OPEN message when the Extended Optional Parameters field is carried in the same OPEN message. A BGP speaker MAY send an OPEN message carrying the Extended Optional Parameters field to a peer ONLY after the speaker has received the Extended Optional Parameters Capability from the peer, or has the knowledge (via administrative means) that the capability is supported by the peer. Before receiving an OPEN message from a peer and without knowing (via administrative means) whether the peer supports the capability, a BGP speaker SHALL perform the "double open" procedure if the speaker wishes to carry the Extended Optional Parameters field in an OPEN message. That is, the speaker SHALL first advertise the Extended Optional Parameters Capability with the capability value of 1 in an OPEN message, and then wait for the OPEN message from the peer to determine its next action. If the OPEN message from the peer carries the Extended Optional Parameters Capability, then the speaker MUST send another OPEN message carrying the Extended Optional Parameters Capability (with a capability value of 2) and the Extended Optional Parameters field. Otherwise the speaker MUST NOT send the second OPEN message, and should either proceed with the session establishment based on the first OPEN message sent, or terminate the session until the "capability incompatibility" issue is resolved via administrative means. In processing an OPEN message from a peer, a BGP speaker SHALL consider the Extended Optional Parameters Length field and the Extended Optional Parameters field to be present in the OPEN message ONLY if the Optional Parameters field of the OPEN message carries the Extended Optional Parameters Capability, and the capability value is 2. After advertising the Extended Optional Parameters Capability to a peer, and receiving the capability with a capability value of 1 from the peer, the speaker SHALL use the information in the initial OPEN message received from the peer for the purpose of BGP connection Chen & Scudder [Page 5] Internet Draft draft-chen-bgp-ext-opt-param-00.txt August 2005 collision resolution. However, the speaker MUST wait for the second OPEN message from the peer before transitioning the session to the "Established State" [BGP-4], and the properties of the session SHALL be solely determined by the information in the second OPEN message. 8. IANA Considerations This document uses a BGP capability code to indicate that a BGP speaker supports the Extended Optional Parameters Capability. The capability code needs to be assigned by IANA per RFC 2842. 9. Security Considerations This extension to BGP does not change the underlying security issues. 10. Acknowledgments The authors would like to thank Yakov Rekhter and Srihari Sangli for discussing various options to enlarge the Optional Parameters field. 11. Normative References [BGP-4] Rekhter, Y., T. Li, and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", draft-ietf-idr-bgp4-26.txt, October 2004. [BGP-CAP] R. Chandra, J. Scudder, "Capabilities Advertisement with BGP-4", RFC 3392, November 2002. [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 12. Author Information Enke Chen Cisco Systems, Inc. 170 W. Tasman Dr. San Jose, CA 95134 Email: enkechen@cisco.com John Scudder Cisco Systems, Inc. 170 W. Tasman Dr. Chen & Scudder [Page 6] Internet Draft draft-chen-bgp-ext-opt-param-00.txt August 2005 San Jose, CA 95134 Email: jgs@cisco.com 13. Intellectual Property Considerations The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. 14. Full Copyright Notice Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Chen & Scudder [Page 7]