Open Shortest Path First Z. Zhang Internet-Draft L. Wang Updates: 2328, 5340 (if approved) Juniper Networks, Inc. Intended status: Standards Track D. Dubois Expires: April 5, 2015 General Dynamics C4S V. Julka T. McMillan L3 Communications, Linkabit October 2, 2014 OSPF Two-part Metric draft-zzhang-ospf-two-part-metric-03.txt Abstract This document specifies an optional extension to the OSPF protocol, to represent the metric on a multi-access network as two parts: the metric from a router to the network, and the metric from the network to the router. The router to router metric would be the sum of the two. 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. 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 April 5, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the Zhang, et al. Expires April 5, 2015 [Page 1] Internet-Draft ospf-two-part-metric October 2014 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 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Proposed Enhancement . . . . . . . . . . . . . . . . . . . . . 3 3. Speficications . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Router Interface Parameters . . . . . . . . . . . . . . . . 4 3.2. Advertising Network-to-Router metric in OSPFv2 . . . . . . 5 3.3. Advertising Network-to-Router metric in OSPFv3 . . . . . . 5 3.4. SPF Calculation . . . . . . . . . . . . . . . . . . . . . . 5 3.5. Backward Compatibility . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . . 7 Zhang, et al. Expires April 5, 2015 [Page 2] Internet-Draft ospf-two-part-metric October 2014 1. Introduction For a broadcast network, a Network LSA is advertised to list all routers on the network, and each router on the network includes a link in its Router LSA to describe its connection to the network. The link in the Router LSA includes a metric but the listed routers in the Network LSA does not include a metric. This is based on the assumption that from a particular router, all others on the same network can be reached with the same metric. With some broadcast networks, different routers can be reached with different metrics. RFC 6845 extends the OSPF protocol with a hybrid interface type for that kind of broadcast networks, with which no Network LSA is used and routers simply includes p2p links to all routers on the same network with individual metrics. Broadcast capability is still utilized to optimize database synchronization and adjacency maintenance. That works well for broadcast networks on which metric between different pair of routers are really independent. For example, VPLS networks. With certain types of broadcast networks, further optimization can be made to reduce the size of the Router LSAs and number of updates. Consider a satellite radio network with fixed and mobile ground terminals. All communication go through the satellite. When the mobile terminals move about, their communication capability may change. When OSPF runs over the radio network (routers being or in tandem with the terminals), RFC 6845 hybrid interface can be used, but with the following drawbacks. Consider that one terminal/router moves into an area where communication capability degrades significantly. Through the radio control protocol all other routers determine that the metric to this particular one changed and they all need to update their Router LSAs accordingly. The router in question also determines that its metric to reach all others also changed and it also need to update its Router LSA. Consider that there could be many terminals and many of them can be moving fast and frequently, the number/frequency of updates of those large Router LSAs could become inhibiting. 2. Proposed Enhancement Notice that in the above scenario, when one terminal's communication capability changes, its metric to all other terminals and the metric from all other terminals to it will all change in a similar fashion. Given this, the above problem can be easily addressed by breaking the Zhang, et al. Expires April 5, 2015 [Page 3] Internet-Draft ospf-two-part-metric October 2014 metric into two parts: the metric to the satellite and the metric from the satellite. The metric from terminal R1 to R2 would be the sum of the metric from R1 to the satellite and the metric from the satellite to R2. Now instead of using the RFC6845 hybrid interface type, the network is just treated as a regular broadcast one. A router on the network no longer needs to list individual metrics to each neighbors in its Router LSA. In case of symmetric metric to/from the satellite, it is represented by the transit link's metric in the Router LSA. In case of asymetric metric, it is rerepresented by a special MT Metric (Section 3). With the proposed enhancement, the size of Router LSA will be significantly reduced. In addition, when a router's communication capability changes, only that router needs to update its Router LSA. Note that while the example uses the satellite as the relay point at radio level (layer 2), at layer 3 the satellite does not play any role. It does not need to be running layer 3 protocol at all. Therefore for generality, the metric is abstracted as to/from the "network" rather that specifically to/from the "satellite". 3. Speficications The following protocol specifications are added to or modified from the base OSPF protocol. If an area contains one or more two-part metric networks, then all routers in the area must support the extensions specified here. This document does not currently specify a way to detect a router's capability of supporting this, and relies on operator's due diligence in provisioning. A protocol mechanism may be developer in the future. 3.1. Router Interface Parameters The "Router interface parameters" have the following additions: o Two-part metric: TRUE if the interface connects to a multi-access network that uses two-part metric. o Interface input cost: Link state metric from the network to this router. Defaulted to "Interface output cost". May be configured or dynamically adjusted to a value different from the "Interface output cost". If different from the output cost, it MUST be advertised in addition to the link (output) cost for this interface in the router's Router LSA. Zhang, et al. Expires April 5, 2015 [Page 4] Internet-Draft ospf-two-part-metric October 2014 3.2. Advertising Network-to-Router metric in OSPFv2 For OSPFv2, the Network-to-Router metric is encoded in an OSPF Extended Link TLV Sub-TLV [ietf-ospf-lsa-extend], defined in this document as Network-to-Router Metric Sub-TLV. The type of the Sub- TLV is TBD. The length of the Sub-TLV is 4 (for the value part only). The value part of the Sub-TLV is defined as the following: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MT | 0 | MT metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Multiple such Sub-TLV can exist in a single OSPF Extended Link TLV, one for each topology. The OSPF Extended Link TLV identifies the transit link to the network, and is part of a OSPFv2 Extended Link Opaque LSA. 3.3. Advertising Network-to-Router metric in OSPFv3 For OSPFv3, the same Network-to-Router Metric Sub-TLV definition is used, though it is part of the Router-Link TLV of E-Router-LSA [ietf- ospf-ospfv3-lsa-extend]. Currently OSPFv3 Multi-Toplogy is not defined so the only valid value for the MT field is 0 and only one such Sub-TLV exist in the Router-Link TLV. 3.4. SPF Calculation During the first stage of shortest-path tree calculation for an area, when a vertex V corresponding to a Network LSA is added to the shortest-path tree and its adjacent vertex W (joined by a link in V's corresponding Network LSA), the cost from V to W, which is W's network-to-router cost, is determined the following way: o For OSPFv2, if vertex W has a corresponding Extended Link Opaque LSA with an Extended Link TLV for the link from W to V, and the Extended Link TLV has a Network-to-Router Metric Sub-TLV for the corresponding topology, then the cost from V to W is the metric in the Sub-TLV. Otherwise, the cost is 0. o For OSPFv3, if vertex W has a corresponding E-Router-LSA with a Router-Link TLV for the link from W to V, and the Router-Link TLV has a Network-to-Router Metric Sub-TLV, then the cost from V to W is the metric in the Sub-TLV. If not, the cost is 0. Zhang, et al. Expires April 5, 2015 [Page 5] Internet-Draft ospf-two-part-metric October 2014 3.5. Backward Compatibility Due to the change of procedures in the SPF calculation, all routers in an area that includes one or more two-part metric networks must support the changes specified in this document. To ensure that, if an area is provisioned to support two-part metric networks, all routers supporting this capability must advertise Router Information (RI) LSA with a newly assigned bit set in Router Informational Capabilities TLV: Bit Capabilities 0-5 Various alreay assigned bits 6 OSPF Two-part Metric [TPM] Upon detecting the presence of a reachable Router LSA without a companion RI LSA that has the bit set, all routers MUST disable the two-part metric functionalities and take the following actions: o If this router advertised network-to-router costs before, remove the stub links in OSPFv2 or secondary prefix entries in OSPFv3 that are used for that purpose, and update the metric in the primary prefix entry to 0. o Recalculate routes w/o considering any network-to-router costs. 4. IANA Considerations This document requests IANA to assigna a new bit in the Router Informational Capabilities TLV to indicate the capability of supporting two-part metric. 5. Security Considerations This document does not introduce new security risks. 6. Acknowledgements The authors would like to thank Acee Lindem, Abhay Roy, Hannes Gredler, Peter Psenak and Eric Wu for their comments and suggestions. 7. References 7.1. Normative References [I-D.ietf-ospf-lsa-extend] Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and Zhang, et al. Expires April 5, 2015 [Page 6] Internet-Draft ospf-two-part-metric October 2014 A. Lindem, "OSPFv2 LSA Extendibility", draft-ietf-ospf-lsa-extend-00 (work in progress), August 2014. [I-D.ietf-ospf-ospfv3-lsa-extend] Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf- ospfv3-lsa-extend-04 (work in progress), September 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. Pillay- Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, June 2007. [RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 4970, July 2007. [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, July 2008. [RFC5613] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D. Yeung, "OSPF Link-Local Signaling", RFC 5613, August 2009. 7.2. Informative References [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast and Point- to-Multipoint Interface Type", RFC 6845, January 2013. Zhang, et al. Expires April 5, 2015 [Page 7] Internet-Draft ospf-two-part-metric October 2014 Authors' Addresses Jeffrey Zhang Juniper Networks, Inc. 10 Technology Park Drive Westford, MA 01886 EMail: zzhang@juniper.net Lili Wang Juniper Networks, Inc. 10 Technology Park Drive Westford, MA 01886 EMail: liliw@juniper.net David Dubois General Dynamics C4S 400 John Quincy Adams Road Taunton, MA 02780 EMail: dave.dubois@gdc4s.com Vibhor Julka L3 Communications, Linkabit 9890 Towne Centre Drive San Diego, CA 92121 EMail: vibhor.julka@l-3Com.com Tom McMillan L3 Communications, Linkabit 9890 Towne Centre Drive San Diego, CA 92121 EMail: tom.mcmillan@l-3com.com Zhang, et al. Expires April 5, 2015 [Page 8]