Network Working Group Ruchi Kapoor Internet Draft Gargi Nalawade Expires: December 2003 Chandra Appanna Cisco Systems BGPv4 SAFI-Specific Attribute draft-kapoor-nalawade-idr-bgp-ssa-00.txt 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 This document defines a new BGP attribute called the "SAFI [IANA-SAFI] Specific Attribute" (SSA). This attribute consists of a set of TLVs (it MUST contain atleast one TLV; it MAY contain more than one TLV). Each Subsequent Address Family Identifier (SAFI) that uses this attribute MUST define the Typecodes that are valid for the respective SAFI. 3. Introduction draft-kapoor-nalawade-idr-bgp-ssa-00.txt [Page 1] Internet Draft draft-kapoor-nalawade-idr-bgp-ssa-00.txt June 2003 This document defines a new BGP attribute called the "SAFI Specific Attribute" (SSA). The value part of the SSA consists of a set of TLVs (it MUST contain atleast one TLV; it MAY contain more than one TLVs). The intent behind SSA is to introduce an attribute, which is flexible enough so that it has utility for multiple applications. The SSA provides a general way of encoding application (AFI/SAFI) specific data. AFI/SAFIs may encode data in the form of TLVs. The AFI/SAFI specific data does not necessarily have global meaning across all AFI/SAFIs, i.e. some typecodes of the TLVs could be relevant to only one AFI/SAFI. Each AFI/SAFI MUST specify the Typecodes that are valid for the respective AFI/SAFI. The SSA TLV is a variable length entity. 4. Format of the SAFI-Specific Attribute The format of the BGP SSA attribute will be as follows: | Attr. Flags | Attr.Type Code| 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|1|0|?|UNUSED | Type = TBD | Length (2 Octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Attribute Value | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The BGP SSA is a variable length, optional transitive attribute. The Value field of the attribute may contain one or more SSA TLVs. The Value field of the SSA Attribute is encoded as follows and may contain one or more tuples of the following: - Type Field : 2 octets - Length Field: 2 octets - Value Field : Variable 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 draft-kapoor-nalawade-idr-bgp-ssa-00.txt [Page 2] Internet Draft draft-kapoor-nalawade-idr-bgp-ssa-00.txt June 2003 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type Field: The format of the Type Field is as shown below: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |T| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ T - Transitive bit Value 1: The SSA type is transitive across ASes Value 0: The SSA type is non-transitive across ASes Remaining 15 bits: Indicate the type of the SSA TLV. Length Field: The Length is 2 octets long and indicates the length of the Value field. The value contained in this Length field MUST not exceed the total length of the BGP SSA Attribute minus the total length of any prior TLVs. Value Field: The Value Field contains a TLV where the Types of the TLV are defined by the respective SAFIs. The TLV in the Value field of this Attribute will be of the form : - Type Field : 2 octets - Length Field: 2 octets - Value Field : Variable The Value field will have a fixed part as specified by the respective SAFI-Specific Types and may have a variable part in the form of Sub-TLVs encoded as follows : - Sub-Type Field : 1 octets - Length Field: 1 octets - Value Field : Variable 5. Operation draft-kapoor-nalawade-idr-bgp-ssa-00.txt [Page 3] Internet Draft draft-kapoor-nalawade-idr-bgp-ssa-00.txt June 2003 A BGP speaker that supports a SAFI, MUST accept any SSA TLVs that are defined as valid for the SAFI. If the SSA TLV is transitive, the BGP speaker MUST forward it even if it does not understand it. Operation rules are governed by those for the SAFI. This attribute only requires that it be forwarded even when it is not understood. When sending an UPDATE message for this SAFI to a peer, a BGP speaker MUST only advertise the SSA TLVs that are defined and are valid for that SAFI. A Capability has not been defined for this attribute intentionally. For newer SAFIs, it is concieved that presence of the SAFI would imply understanding the SSA attribute and the SSA TLVs. If existing SAFIs make use of this Attribute, a capability may be defined depending on the operational rules defined when the valid Typecodes for this attribute are defined for that SAFI. 6. Security Considerations This extension to BGP does not change the underlying security issues. 7. Acknowledgements We would like to thank Dan Tappan, Arjun Sreekantiah, Jim Guichard, Shyam Suri and John Scudder for their comments and suggestions. 8. Normative References [BGP-4] Rekhter, Y. and T. Li (editors), "A Border Gateway Protocol 4 (BGP-4)", Internet Draft draft-ietf-idr-bgp4-17.txt, January 2002. [BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with BGP-4", draft-ietf-idr-rfc2842bis-02.txt, April 2002. [IANA-AFI] http://www.iana.org/assignments/address-family-numbers. [IANA-SAFI] http://www.iana.org/assignments/safi-namespace. 9. Authors' Addresses Ruchi Kapoor Cisco Systems, Inc 170 West Tasman Drive draft-kapoor-nalawade-idr-bgp-ssa-00.txt [Page 4] Internet Draft draft-kapoor-nalawade-idr-bgp-ssa-00.txt June 2003 San Jose, CA 95134 Email:ruchi@cisco.com Gargi Nalawade Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95134 Email:gargi@cisco.com Chandra Appanna Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95134 Email: achandra@cisco.com 10. 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Expiration Date This memo is filed as , and expires Dec, 2003. draft-kapoor-nalawade-idr-bgp-ssa-00.txt [Page 6]