OSPF K. Patel Internet-Draft Cisco Systems Intended status: Standards Track P. Pillay-Esnault Expires: January 6, 2017 Huawei Technologies M. Bhardwaj S. Bayraktar Cisco Systems July 5, 2016 H-bit Support for OSPFv2 draft-ietf-ospf-ospfv2-hbit-01 Abstract OSPFv3 defines an option field for router-LSAs known as a R-bit in RFC5340. If the R-bit is clear, an OSPFv3 router can participate in OSPF topology distribution without acting as a forwarder to forward the transit traffic. In such cases, an OSPF router would only accept traffic intended for local delivery. This draft defines R-bit functionality for OSPFv2 defined in RFC2328. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 6, 2017. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Patel, et al. Expires January 6, 2017 [Page 1] Internet-Draft July 2016 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 3. H-bit Support . . . . . . . . . . . . . . . . . . . . . . . . 3 4. SPF Modifications . . . . . . . . . . . . . . . . . . . . . . 5 5. Auto Discovery and Backwards Compatibility . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction OSPFv3 [RFC5340] defines an option field for router-LSAs known as a R-bit. If the R-bit is clear, an OSPF router can participate in OSPFv3 topology distribution without acting as a forwarder to forward the transit traffic. In such cases, an OSPF router would only accept traffic intended for local delivery. This functionality is particularly useful for BGP Route Reflectors known as virtual Route Reflectors (vRRs) that are not in the forwarding path but are in central location such as data centers. Such Route Reflectors typically are used for route distribution and are not capable of forwarding data traffic. However, they need to participate in the IGP routing for: 1) computing SPFs for Optimal Route Reflection functionality defined in [I-D.ietf-idr-bgp-optimal-route-reflection], and 2) resolving reachability for its Route Reflector Clients. This draft defines R-bit functionality for OSPFv2 defined in [RFC2328] by introducing a new Router LSA bit known as a "H-bit". 2. Requirements Language 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 [RFC2119] only when Patel, et al. Expires January 6, 2017 [Page 2] Internet-Draft July 2016 they appear in all upper case. They may also appear in lower or mixed case as English words, without any normative meaning. 3. H-bit Support This draft defines a new Router-LSA bit known as a Host Bit or a H-bit. The H-bit indicates the OSPFv2's capability of acting as a transit router. When set, the OSPFv2 router indicates that the transit capability is disabled. The bit value usage of the H-bit is reversed as opposed to the R-bit value defined in OSPFv3 [RFC5340] to support backward compatibility. The OSPFv2 Router LSA format is defined as: Patel, et al. Expires January 6, 2017 [Page 3] Internet-Draft July 2016 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age | Options | 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |H|0|0|N|W|V|E|B| 0 | # links | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | # TOS | metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TOS | 0 | TOS metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | bit H When set, an OSPFv2 router is a non-transit router and is incapable of acting as a forwarder. When H-bit is set, an OSPFv2 router is a non-transit router and is incapable of acting as a forwarder. In this mode, the other OSPFv2 routers SHOULD NOT use the originating OSPFv2 router for the transit traffic, but they will use the OSPFv2 router for data traffic destined to that OSPFv2 router. An OSPFv2 router originating a Router LSA with the H-bit set SHOULD advertise its LINKS with MAX Link cost as defined in Section 3 of [RFC6987]. This is to increase the applicability of the H-bit in partial deployments where it is the responsibility of the operator to ensure that the H-bit does not result in routing loops. Patel, et al. Expires January 6, 2017 [Page 4] Internet-Draft July 2016 When H-bit is set, IPv4 prefixes associated with local interfaces MAY be advertised in summary LSAs. Non-local IPv4 prefixes, e.g., those advertised by other routers and installed during the SPF computation, MAY be advertised in summary-LSAs if configured by policy. Likewise, when H-bit is set, only IPv4 prefixes associated with local interfaces MAY be advertised in AS-external LSAs. Non-local IPv4 prefixes, e.g., those exported from other routing protocols, MUST NOT be advertised in AS-external-LSAs. Finally, when H-bit is set, an ABR MUST advertise a consistent H-bit setting in its self-originated router-LSAs for all attached areas. 4. SPF Modifications The SPF calculation described in section 16.1 [RFC2328] will be modified to assure that the routers originating router-LSAs with the H-bit set will not be used for transit traffic. Step 2 is modified as follows: 2) Call the vertex just added to the tree vertex V. Examine the LSA associated with vertex V. This is a lookup in the Area A's link state database based on the Vertex ID. If this is a router-LSA, and the H-bit of the router-LSA is set, and vertex V is not the root, then the router should not be used for transit and step (3) should be executed immediately. If this is a router-LSA, and bit V of the router-LSA (see Section A.4.2) is set, set Area A's TransitCapability to TRUE. In any case, each link described by the LSA gives the cost to an adjacent vertex. For each described link, (say it joins vertex V to vertex W): 5. Auto Discovery and Backwards Compatibility To avoid the possibility of any routing loops due to partial deployments, this draft defines a new OSPF Router Functional Capability known as a Host Support Capability. The value of this capability is a bit value to be assigned by IANA from OSPF Router Functional Capability Bits registry [RFC7770] . Patel, et al. Expires January 6, 2017 [Page 5] Internet-Draft July 2016 The Auto Discovery via announcement of the Host Support Functional Capability ensures that the H-bit functionality and its associated SPF changes SHOULD only take effect if all the routers in a given OSPF area support this functionality. Implementations are encouraged to provide a knob to manually override enforcement of the H-bit functionality in partial deployment scenarios for cases where the topology guarantees that the router supporting the H-bit will not cause routing loops. 6. IANA Considerations This draft defines a new Router LSA bit known as a H-bit. This draft requests IANA to 1) Create a new OSPF Router LSA bits registry and 2) assign a H-bit code type from the newly allocated OSPF Router LSA bit registry. This draft defines a new Router Functional Capability known as a Host Support Functional Capability. This draft requests IANA to allocate the value of this capability from the Router Functional Capability Bits TLV. 7. Security Considerations This document introduces no new security considerations above and beyond those already specified in [RFC2328] and [RFC5340]. 8. Acknowledgements The authors would like to acknowledge Acee Lindem, Abhay Roy, David Ward, Burjiz Pithawala and Michael Barnes for their comments. 9. Change Log Initial Version: April 23 2015 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . Patel, et al. Expires January 6, 2017 [Page 6] Internet-Draft July 2016 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, February 2016, . 10.2. Informative References [I-D.ietf-idr-bgp-optimal-route-reflection] Raszuk, R., Cassar, C., Aman, E., Decraene, B., Litkowski, S., and K. Wang, "BGP Optimal Route Reflection (BGP-ORR)", draft-ietf-idr-bgp-optimal-route-reflection-11 (work in progress), January 2016. [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. McPherson, "OSPF Stub Router Advertisement", RFC 6987, DOI 10.17487/RFC6987, September 2013, . Authors' Addresses Keyur Patel Cisco Systems 170 W. Tasman Drive San Jose CA 95134, USA Email: keyupate@cisco.com Padma Pillay-Esnault Huawei Technologies 2330 Central Expressway Santa Clara, CA 95050 USA Email: padma@huawei.com Patel, et al. Expires January 6, 2017 [Page 7] Internet-Draft July 2016 Manish Bhardwaj Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 USA Email: manbhard@cisco.com Serpil Bayraktar Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 USA Email: serpil@cisco.com Patel, et al. Expires January 6, 2017 [Page 8]