OSPF K. Patel Internet-Draft P. Pillay-Esnault Intended status: Standards Track M. Bhardwaj Expires: November 7, 2015 S. Bayraktar Cisco Systems May 6, 2015 H-bit Support for OSPFv2 draft-keyupate-ospf-ospfv2-hbit-00 Abstract OSPFv3 [RFC5340] defines an option field for router-LSAs known as a R-bit. 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 November 7, 2015. Copyright Notice Copyright (c) 2015 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Patel, et al. Expires November 7, 2015 [Page 1] Internet-Draft May 2015 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 . . . . . . . . . . . . . . . . . . . . . . 4 5. Auto Discovery and Backwards Compatibility . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 5 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 10.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 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-orr], 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" are to be interpreted as described in [RFC2119] only when they appear in all upper case. They may also appear in lower or mixed case as English words, without any normative meaning. Patel, et al. Expires November 7, 2015 [Page 2] Internet-Draft May 2015 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 forwarder router. When set, the OSPFv2 router indicates that the forwarding 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: 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. Patel, et al. Expires November 7, 2015 [Page 3] Internet-Draft May 2015 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 MUST 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. 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 immediatately. 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 [I-D.ietf-ospf-rfc4970bis]. Patel, et al. Expires November 7, 2015 [Page 4] Internet-Draft May 2015 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 gurantees 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 Fucntional 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, and Burjiz Pithawala for their comments. 9. Change Log Initial Version: April 23 2015 10. References 10.1. Normative References [I-D.ietf-ospf-rfc4970bis] Lindem, A., Shen, N., Vasseur, J., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", draft-ietf-ospf-rfc4970bis-00 (work in progress), January 2015. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Patel, et al. Expires November 7, 2015 [Page 5] Internet-Draft May 2015 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, July 2008. [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. McPherson, "OSPF Stub Router Advertisement", RFC 6987, September 2013. 10.2. Informative References [I-D.ietf-idr-bgp-optimal-route-reflection] Raszuk, R., Cassar, C., Aman, E., Decraene, B., and S. Litkowski, "BGP Optimal Route Reflection (BGP-ORR)", draft-ietf-idr-bgp-optimal-route-reflection-09 (work in progress), April 2015. Authors' Addresses Keyur Patel Cisco Systems 170 W. Tasman Drive San Jose, CA 95124 95134 USA Email: keyupate@cisco.com Padma Pillay-Esnault Cisco Systems 170 W. Tasman Drive San Jose, CA 95124 95134 USA Email: ppe@cisco.com Manish Bhardwaj Cisco Systems 170 W. Tasman Drive San Jose, CA 95124 95134 USA Email: manbhard@cisco.com Patel, et al. Expires November 7, 2015 [Page 6] Internet-Draft May 2015 Serpil Bayraktar Cisco Systems 170 W. Tasman Drive San Jose, CA 95124 95134 USA Email: serpil@cisco.com Patel, et al. Expires November 7, 2015 [Page 7]