Network Working Group Gargi Nalawade Internet Draft Ruchi Kapoor Expires: April 2004 Dan Tappan Cisco Systems Tunnel SAFI draft-nalawade-kapoor-tunnel-safi-01.txt 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. Abstract There is a need for Tunnel end-point discovery within and across Autonomous Systems. BGP is the only protocol that is widely-spoken across Autonomous Systems and can carry this information. This document defines how BGP speakers can convey Tunnel end-point reachability information. 1. Introduction Two end-points of a Tunnel need to know the end-point information and its binding to a network address at the remote point. Normally, this can be statically shared and configured. But in case of a large draft-nalawade-kapoor-tunnel-safi-01.txt [Page 1] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 network where there may be a need for a large number of tunnels, the number of tunnel end-points that need to be exchanged and maintained, grows. It then needs to be exchanged and maintained using an inter-AS protocol. 2. The Tunnel SAFI This document defines a new SAFI called the Tunnel SAFI. The [IANA-AFI] [IANA-SAFI] value pair used to identify this SAFI is (AFI=1, SAFI=TBD) for the IPv4 AFI and (AFI=2, SAFI=TBD) for the IPv6 AFI. For BGP Speakers supporting [BGP-4], the tunnel end point address will be carried as an NLRI in the MP_REACH attribute for this SAFI. For BGP Speakers suppprting [BGP-UPDATEv2], the tunnel end point address will be carried as an NLRI in the NLRI section of the BGP Updatev2 message. The NLRI will be encoded as a 2-octet Identifier followed by the NLRI format as specified by the respective AFI. The Identifier will contain a 2-octet Identifier that identifies the Tunnel end point being advertised. This Identifier enables multiple Tunnel end-points to share the same network address, thus conserving the number of addresses needed to be configured by the operator on each of the Tunnel-endpoints. 3. BGP Attribute The BGP SSA Attribute [BGP-SSA] will be used to carry the Tunnel end-point information. The Value Field of the BGP SSA Attribute, MUST contain at least one of the following valid Type codes for this SAFI. It MAY contain one or more TLVs with these Type codes. Type 1: L2TPv3 Tunnel information Type 2: mGRE Tunnel information Type 3: IPSec Tunnel information Type 4: MPLS Tunnel information 3.1. L2TPv3 Tunnel information TLV The L2TPv3 Tunnel Information TLV has a type of 1. The value part of the L2TPv3 Tunnel Information Type contains the following : draft-nalawade-kapoor-tunnel-safi-01.txt [Page 2] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 - Preference (2 Octets) - Flags (1 Octet) - Cookie Length (1 Octet) - Session ID (4 Octets) - Cookie (Variable) The L2TPv3 Tunnel Information TLV looks as follows : 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 0x01 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length (2 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preference (2 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Flags | Cookie Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Session ID (4 Octets) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Cookie (Variable) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where Length A 2 Octet field that specifies the length of the L2TPv3 attribute in octets. The value contained in this Length field MUST not exceed the total length of the BGP SSA [SSA] Attribute minus the total length of any prior TLVs. Preference A 2 Octet field containing a Preference associated with the TLV. The Preference value indicates a preferred ordering of tunneling encapsulations according to the sender. The recipient of the information SHOULD take the sender's preference into account in selecting which encapsulation it will use. A higher value indicates a higher preference. Flags A 1 Octet field containing flag-bits. The leftmost bit indicates whether Sequence numbering is to be used or not. The draft-nalawade-kapoor-tunnel-safi-01.txt [Page 3] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 remaining bits are reserved for future use. Cookie Length Cookie Length is a 1 Octet field that contains the length of the Variable length Cookie. Session ID A 4 Octet field containing a non-zero identifier for a session. Cookie Cookie is a variable length (maximum 64 bits), value used by L2TPv3 to check the association of a received data message with the session identified by the Session ID. The default value of the Length Field for the L2TPv3 Tunnel information TLV is between 8 and 16 bytes, depending on the length of the Cookie field specified in Cookie length. If the length of the TLV is greater than that value, the subsequent portion of the Value field contains one or more sub-TLVs. A Sub-TLV when present is of the following format : 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where Sub-Type & Length are of 1-Octet each & the Value field is variable as specified by the Length. 3.2. mGRE Tunnel Information TLV The mGRE Tunnel Information Type has a Type 2. The value part of the mGRE Tunnel Information Type contains the following : - Preference (2 Octets) - Flags (1 Octet) - mGRE Key (0 or 4 Octets) The mGRE Tunnel Information TLV looks as follows : 0 1 draft-nalawade-kapoor-tunnel-safi-01.txt [Page 4] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 0x02 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length (2 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preference (2 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S|K| Flags | | +-+-+-+-+-+-+-+-+ | | mGRE Key (4 Octets) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Length A 2 Octet field that specifies the length of the mGRE information in octets. The value contained in this Length field MUST not exceed the total length of the BGP SSA [SSA] Attribute minus the total length of any prior TLVs. Preference A 2 Octet field containing a Preference associated with the TLV. The Preference value indicates a preferred ordering of tunneling encapsulations according to the sender. The recipient of the information SHOULD take the sender's preference into account in selecting which encapsulation it will use. A higher value indicates a higher preference. Flags A 1 Octet field containing flag-bits. The leftmost bit indicates whether Sequence numbering is to be used or not. The 2nd bit indicates whether an mGRE Key is present or not. The remaining bits are reserved for future use. mGRE Key A 4 Octet field containing an optional mGRE Key. If the Length field of the TLV contains a value greater than 3 Octets plus the value specified in the Key Length, the subsequent portion of the Value field contains one or more sub-TLVs. A Sub-TLV when present is of the following format : 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Type | Length | draft-nalawade-kapoor-tunnel-safi-01.txt [Page 5] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where Sub-Type & Length are of 1-Octet each & the Value field is variable as specified by the Length. 3.3. IPSec Tunnel Information TLV The IPSec Tunnel Information Type has a Type 3. The format of the IPSec Tunnel Information TLV is TBD. 3.4. MPLS TLV The MPLS TLV has a Type 4. The format of the MPLS TLV is TBD. 4. Capability Advertisement A BGP speaker that wishes to exchange the IPv4-Tunnel SAFI, MUST use the MP_EXT Capability Code as defined in [BGP-MP], to advertise the corresponding (AFI, SAFI) pair. A BGP speaker MAY participate in the distribution of IPv4-Tunnel information. 5. Operation A BGP Speaker that receives the Capability for the IPv4-Tunnel or IPv6-Tunnel SAFI, MAY advertise the IPv4-Tunnel or IPv6-Tunnel prefixes to that peer respectively. In the UPDATE message for this SAFI sent to a peer, a BGP speaker MUST only advertise the SAFI-specific attribute [SSA] TLVs that are defined as valid for this SAFI. If a BGP Speaker receives an SSA TLV that it does not recognize, it will accept it and propagate it to other peers. 6. Deployment Considerations In order for the Tunnels to come up between two end-points, the BGP Speakers advertising the Tunnel end-points using the Ipv4 Tunnel SAFI, MUST exchange at least one common encapsulation option. 7. Security Considerations draft-nalawade-kapoor-tunnel-safi-01.txt [Page 6] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 This extension to BGP does not change the underlying security issues. 8. Acknowledgements We would like to thank Jim Guichard, Arjun Sreekantiah, Shyam Suri, Chandrashekhar Appanna, John Scudder and Mark Townsley for their comments and suggestions. 9. References [IANA-AFI] http://www.iana.org/assignments/address-family-numbers [IANA-SAFI] http://www.iana.org/assignments/safi-namespace [BGP-4] Rekhter, Y. and T. Li (editors), "A Border Gateway Protocol 4 (BGP-4)", Internet Draft draft-ietf-idr-bgp4-22.txt, February 2004. [BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with BGP-4", draft-ietf-idr-rfc2842bis-02.txt, April 2002. [BGP-SSA] Kapoor R., Nalawade G., "BGPv4 SAFI-Specific Attribute", draft-nalawade-kapoor-bgp-ssa-00.txt, work in progress. [MULTI-BGP] Bates et al, "Multiprotocol Extensions for BGP-4", draft- ietf-idr-rfc2858bis-02.txt, work in progress. [BGP_UPDATEv2] Nalawade G.et al, "BGPv4 Update-v2 Message", draft- nalawade-bgp-update-v2-01.txt, work in progress. [IPSEC-ARCH] Kent, S., and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. 10. Authors' Addresses Gargi Nalawade Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95134 mailto:gargi@cisco.com Ruchi Kapoor Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95134 mailto:ruchi@cisco.com Dan Tappan Cisco Systems, Inc draft-nalawade-kapoor-tunnel-safi-01.txt [Page 7] Internet Draft draft-nalawade-kapoor-tunnel-safi-01.txt October 2003 170 West Tasman Drive San Jose, CA 95134 mailto:tappan@cisco.com 11. Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. 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