Network Working Group Z. Zhang Internet-Draft L. Wang Updates: 2328, 5340 (if approved) Juniper Networks, Inc. Intended status: Standards Track A. Lindem Expires: March 2, 2017 Cisco Systems August 29, 2016 OSPF Two-part Metric draft-ietf-ospf-two-part-metric-09.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. This document updates RFC 2328. 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 March 2, 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 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 Zhang, et al. Expires March 2, 2017 [Page 1] Internet-Draft ospf-two-part-metric August 2016 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Proposed Enhancement . . . . . . . . . . . . . . . . . . . . 3 3. Speficications . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Router Interface Parameters . . . . . . . . . . . . . . . 4 3.2. Advertising Network-to-Router Metric in OSPFv2 . . . . . 4 3.3. Advertising Network-to-Router TE Metric . . . . . . . . . 5 3.4. Advertising Network-to-Router Metric in OSPFv3 . . . . . 5 3.5. OSPF Stub Router Behavior . . . . . . . . . . . . . . . . 5 3.6. SPF Calculation . . . . . . . . . . . . . . . . . . . . . 5 3.7. Backward Compatibility . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8 Appendix B. Contributors' Addreses . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction With Open Shortest Path First (OSPF, [RFC2328], [RFC5340]) protocol, 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 do 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. [RFC6845] extends the OSPF protocol with a hybrid interface type for that kind of broadcast network, where no Network LSA is advertised and Router-LSAs simply include 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 where the metric between different pair of routers are really independent. For example, VPLS networks. Zhang, et al. Expires March 2, 2017 [Page 2] Internet-Draft ospf-two-part-metric August 2016 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 goes 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), [RFC6845] hybrid interface can be used, but with the following drawbacks. Consider that one terminal/router moves into an area where its communication capability degrades significantly. Through the radio control protocol, all other routers determine that the metric to this particular router 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 needs 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 inhibit network scaling. 1.1. 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]. 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 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 network. A router on the network no longer lists individual metrics to each neighbor in its Router-LSA. Instead, each router advertises the metric from the network to itself in addition to the normal metric for the network. With the normal Router-to-Network and additional Network-to-Router metrics advertised for each router, individual router-to-router metric can be calculated. Zhang, et al. Expires March 2, 2017 [Page 3] Internet-Draft ospf-two-part-metric August 2016 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 the radio level (layer-2), at layer-3, the satellite does not participate in packet forwarding. In fact, the satellite does not need to be running any layer-3 protocol. 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 herein. This is ensured by procedures described in Section 3.7. 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. All routers connected to the same network SHOULD have the same configuration for their corresponding interfaces. o Interface input cost: Link state metric from the two-part-metric network to this router. Defaulted to "Interface output cost" but not valid for normal networks using a single metric. May be configured or dynamically adjusted to a value different from the "Interface output cost". 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 [RFC7684], defined in this document as the Network-to-Router Metric Sub-TLV. The type of the Sub-TLV is TBD2. The length of the Sub-TLV is 4 (for the value part only). The value part of the Sub-TLV is defined as follows: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Zhang, et al. Expires March 2, 2017 [Page 4] Internet-Draft ospf-two-part-metric August 2016 Multiple such Sub-TLVs can exist in a single OSPF Extended Link TLV, one for each topology [RFC4915]. The OSPF Extended Link TLV identifies the transit link to the network, and is part of an OSPFv2 Extended-Link Opaque LSA. The Sub-TLV MUST ONLY appear in Extended- Link TLVs for Link Type 2 (link to transit network), and MUST be ignored if received for other link types. 3.3. Advertising Network-to-Router TE Metric A Traffic Engineering Network-to-Router Metric Sub-TLV is defined, similar to the Traffic Engineering Metric Sub-TLV defined in Section 2.5.5 of [RFC3630]. The only difference is the TLV type, which is TBD3. The Sub-TLV MUST only appear in type 2 Link TLVs (Multi-access) of Traffic Engineer LSAs (OSPF2) or Intra-Area-TE-LSAs (OSPFv3) [RFC5329], and MUST appear at most once in one such Link TLV. 3.4. Advertising Network-to-Router Metric in OSPFv3 Network-to-Router metric advertisement in OSPFv3 Extended-Router-LSA [I-D.ietf-ospf-ospfv3-lsa-extend] will be described in a separate document. 3.5. OSPF Stub Router Behavior When an OSPF router with interfaces including two-part metric is advertising itself as a stub router [RFC6987], only the Router-to- Network metric in the stub router's OSPF Router-LSA links is set to the MaxLinkMetric. This is fully backward compatible and will result in the same behavior as [RFC6987]. 3.6. SPF Calculation The first stage of the shortest-path tree calculation is described in section 16.1 of [RFC2328]. With two-part metric, when a vertex V corresponding to a Network-LSA has just been added to the Shortest Path Tree (SPT) and an adjacent vertex W (joined by a link in V's corresponding Network-LSA) is being added to the candidate list, the cost from V to W (W's network-to-router cost) is determined as follows: 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. Zhang, et al. Expires March 2, 2017 [Page 5] Internet-Draft ospf-two-part-metric August 2016 o OSPFv3 [RFC5340] SPF changes will be described in a separate document. 3.7. 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 a Router Information (RI) LSA with a Router Functional Capabilities TLV [RFC7770] that includes the following Router Functional Capability Bit: Bit Capabilities TBD1 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 recalculate routes without considering any network-to-router costs. 4. IANA Considerations This document requests the following IANA assignments: o A new bit (TBD1) in Registry for OSPF Router Informational Capability Bits, to indicate the capability of supporting two-part metric. o A new Sub-TLV type (TBD2) in OSPF Extended Link TLV Sub-TLV registry, for the Network-to-Router Metric Sub-TLV. o A new Sub-TLV type (TBD3) in Types for sub-TLVs of TE Link TLV (Value 2) registry, for the Network-to-Router TE Metric Sub-TLV. 5. Security Considerations This document does not introduce new security risks. Existing security considerations in OSPFv2 and OSPFv3 apply. 6. References 6.1. Normative References Zhang, et al. Expires March 2, 2017 [Page 6] Internet-Draft ospf-two-part-metric August 2016 [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, . [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, DOI 10.17487/RFC4915, June 2007, . [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., "Traffic Engineering Extensions to OSPF Version 3", RFC 5329, DOI 10.17487/RFC5329, September 2008, . [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [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, . 6.2. Informative References [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-10 (work in progress), May 2016. [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . Zhang, et al. Expires March 2, 2017 [Page 7] Internet-Draft ospf-two-part-metric August 2016 [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast and Point-to-Multipoint Interface Type", RFC 6845, DOI 10.17487/RFC6845, January 2013, . [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. McPherson, "OSPF Stub Router Advertisement", RFC 6987, DOI 10.17487/RFC6987, September 2013, . Appendix A. Acknowledgements The authors would like to thank Abhay Roy, Hannes Gredler, Peter Psenak and Eric Wu for their comments and suggestions. The RFC text was produced using Marshall Rose's xml2rfc tool. Zhang, et al. Expires March 2, 2017 [Page 8] Internet-Draft ospf-two-part-metric August 2016 Appendix B. Contributors' Addreses David Dubois General Dynamics C4S 400 John Quincy Adams Road Taunton, MA 02780 EMail: dave.dubois@gd-ms.com Vibhor Julka Individual EMail: vjulka1@yahoo.com Tom McMillan L3 Communications, Linkabit 9890 Towne Centre Drive San Diego, CA 92121 EMail: tom.mcmillan@l-3com.com Authors' Addresses Zhaohui 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 Acee Lindem Cisco Systems 301 Midenhall Way Cary, NC 27513 Email: acee@cisco.com Zhang, et al. Expires March 2, 2017 [Page 9]