Internet Draft Alia Atlas (Avici Systems) Expires: August 2004 Raveendra Torvi (Avici Systems) Gagan Choudhury (AT&T) Christian Martin (Verizon) Brent Imhoff (Wiltel) Don Fedyk (Nortel) OSPFv2 Extensions for Link Capabilities and IP/LDP Local Protection draft-atlas-ospf-local-protect-cap-00.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 This document proposes an extension to OSPF Version 2 for advertising link capabilities using the extensions defined for traffic engineering. The link capabilities are defined there for future extensibility. To support the signaling requirements of IP Local Protection [IP- LOCAL-PROTECT], this document defines two bits in the proposed link capabilities extension. Additionally, this document reserves a bit in the Router Capabilities TLV defined in [OSPF-RTR-CAP]. This document specifies additional information that can inserted in Atlas et al. [Page 1] Internet Draft August 2004 OSPF LSAs to convey link capabilities that may be useful in certain applications. In particular, a router may indicate that zero or more of its links may be used by an upstream router as an alternate, SPT- disjoint path to an arbitrary destination D. Additionally, a router may convey that zero or more of its links are capable of breaking a U-turn, which may be described as a single-hop forwarding loop between two router's. This means that a router can detect the presence of a forwarding loop by recognizing that traffic to a destination is being received from a neighbor to which it has forwarding state pointing back to the same neighbor for that destination. In such a situation, it will switch to a loop-free node-protecting alternate until new primary forwarding state has been installed, thus breaking the U-turn. Therefore, the immediate applicability for these two link capabilities is in support of local protection in the event of a link and/or node failure while the OSPF area is reconverging onto a new topology. Contents 1 Introduction ................................................. 2 2 Link Capabilities sub-TLV .................................... 2 3 IP/LDP Local Protect Router Capability ....................... 3 4 Interpretation for IP/LDP Local Protection ................... 3 5 IANA Considerations .......................................... 4 6 Security Considerations ...................................... 4 7 Full Copyright Statement ..................................... 4 8 References ................................................... 5 9 Authors Information .......................................... 5 1. Introduction The motivations for an extension to OSPF version 2 to allow advertising link capabilities is to both allow the signaling required by [IP-LOCAL-PROTECT] and to provide for future extensibility. [RFC 3630] specifies OSPFv2 Traffic Engineering extensions for carrying link attributes, via a new Link TLV which is carried in the TE LSA. The Link TLV comprises of several sub-TLVs characterizing the links. Among those sub-TLVs are the Link ID and Link Type sub- TLVs, which are the only mandatory sub-TLVs. This is the set of information that is necessary to associated advertised link capabilities to the specific link. To avoid potentially unnecessary redundant advertisement of the Link ID and Link Type, in the event that a router needs to support signaling for both TE and link capabilities, this document proposes adding a Link Capabilities sub- Atlas et al. [Page 2] Internet Draft August 2004 TLV to the Link TLV. The Link Capabilities sub-TLV is defined and two bits are identified to support the signaling required by [IP-LOCAL-PROTECT]. Additionally, this document suggests reserving bit 10 from the Router Capabilities TLV. The interpretation of these bits as they relate to [IP-LOCAL-PROTECT] is explained in Section 4. 2. Link Capabilities sub-TLV A new "Link Capabilities" sub-TLV is defined here to be carried in the "Link" TLV which uses the TE LSA [RFC 3630]. The Link Capabilities field contains 32 flags, each indicating a different link capability. The following flags are defined: Bit Capability 0-3 Reserved 4 Eligible Alternate 5 Eligible U-Turn Recipient 6-31 Future assignments Following is the format for Link-ID sub TLV: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 10 | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Capabilities | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ca 3. IP/LDP Local Protect Router Capability This document reserves bit 10, which is currently unassigned [OSPF- RTR-CAP], to indicate the capability for IP/LDP Local Protection [IP-LOCAL-PROTECT], with an interpretation as described in Section 4. 4. Interpretation for IP/LDP Local Protection The OSPFv2 extensions described in this document define three bits which are relevant for determining the capabilities of a link in reference to IP/LDP Local Protection. The Link Capabilities advertised in the TE LSA and the Router Capabilities in "Router Information" LSA are independent, i.e. a router may send Link Atlas et al. [Page 3] Internet Draft August 2004 Capabilities without including Router Capabilities and vice versa. They are to be interpreted as follows: +------------------+-----------------+------------+ |IP/LDP Local | Eligible | Usable | |Protect Router | Alternate | as | |Capability | Link Capability | Alternate? | +------------------+-----------------+------------+ | 0 or Not Present | 0 or Not Present| NO | +------------------+-----------------+------------+ | 0 or Not Present | 1 | YES | +------------------+-----------------+------------+ | 1 | 0 or Not Present| NO | +------------------+-----------------+------------+ | 1 | 1 | YES | +------------------+-----------------+------------+ If a link is usable as an alternate, then the router's neighbors can assume that the router will have considered that link as an alternate next-hop. +------------------+-----------------+------------+ |IP/LDP Local | Eligible U-Turn | Usable | |Protect Router | Recipient | as U-Turn | |Capability | Link Capability | Recipient? | +------------------+-----------------+------------+ | 0 or Not Present | 0 or Not Present| NO | +------------------+-----------------+------------+ | 0 or Not Present | 1 | YES | +------------------+-----------------+------------+ | 1 | 0 or Not Present| NO | +------------------+-----------------+------------+ | 1 | 1 | YES | +------------------+-----------------+------------+ If a router's link is usable as a U-Turn recipient, then the router can determine if traffic received on that link is from the router's primary neighbor for that traffic and, if so, redirect it to the router's alternate next-hop. If a router's link is usable as a U- Turn recipient, then the router's neighbor can use select for an alternate a U-Turn alternate which goes across that link to that router. The following picture may clarify this. If B indicates that it can be a U-Turn Recipient on the link from A to B, then if A can use the link from A to B as an alternate, A can use the link as a U- Turn alternate, if appropriate. Atlas et al. [Page 4] Internet Draft August 2004 Usable as a Usable as an U-Turn Recipient Alternate / / +----------- +--------- +---+ +---+ | A |-------------------------------------| B | +---+ +---+ --------+ -----------+ / / Usable as an Usable as a Alternate U-Turn Recipient 5. IANA Considerations A new sub-TLV in the Link TLV will need to be assigned by IANA; this is requested to be type 10, which is to be assigned via Standards Action [RFC 3630]. A new bit in the Capabilities field specified in the OSPF Router Capabilities TLV will need to be assigned; this is requested to be bit 10. The remaining bits in the Link Capabilities sub-TLV will need to be assigned by IANA. 6. Security Considerations This document does not introduce any new security issues. 7. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. Atlas et al. [Page 5] Internet Draft August 2004 The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. 8. References [IP-LOCAL-PROTECT] A. Atlas, R. Torvi, G. Choudhury, C. Martin, B. Imhoff, and D. Fedyk, "IP/LDP Local Protection", draft-atlas-ip- local-protection-00.txt, February 2004, work-in-progress [RFC 3630] D. Katz, K. Kompella, and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003 [OSPF-RTR-CAP] A. Lindem, N. Shen, R. Aggarwal, S. Shaffer, JP Vasseur, "Extensions to OSPF for Advertising Optional Router Capabilities", draft-ietf-ospf-cap-01.txt, April 2004, work-in- progress [RFC3137] Retana, A., Nguyen, L., White, R., Zinin, A., and McPherson, D., "OSPF Stub Router Advertisement", RFC 3137, June 2001 9. Authors Information Alia Atlas Avici Systems 101 Billerica Avenue N. Billerica, MA 01862 USA email: aatlas@avici.com phone: +1 978 964 2070 Raveendra Torvi Avici Systems 101 Billerica Avenue N. Billerica, MA 01862 USA email: rtorvi@avici.com phone: +1 978 964 2026 Gagan Choudhury AT&T Room D5-3C21 Atlas et al. [Page 6] Internet Draft August 2004 200 Laurel Avenue Middletown, NJ 07748 USA email: gchoudhury@att.com phone: +1 732 420-3721 Christian Martin Verizon 1880 Campus Commons Drive Reston, VA 20191 email: cmartin@verizon.com Brent Imhoff WilTel Communications 3180 Rider Trail South Bridgeton, MO 63045 USA email: brent.imhoff@wcg.com phone: +1 314 595 6853 Don Fedyk Nortel Networks 600 Technology Park Billerica, MA 01450 email: dwfedyk@nortelnetworks.com phone: +1 978 288 3041 Atlas et al. [Page 7]