--- 1/draft-ietf-ospf-segment-routing-msd-11.txt 2018-05-10 08:13:35.215874576 -0700 +++ 2/draft-ietf-ospf-segment-routing-msd-12.txt 2018-05-10 08:13:35.239875145 -0700 @@ -1,23 +1,23 @@ OSPF Working Group J. Tantsura Internet-Draft Nuage Networks Intended status: Standards Track U. Chunduri -Expires: November 8, 2018 Huawei Technologies +Expires: November 10, 2018 Huawei Technologies S. Aldrin Google, Inc P. Psenak Cisco Systems - May 07, 2018 + May 09, 2018 Signaling MSD (Maximum SID Depth) using OSPF - draft-ietf-ospf-segment-routing-msd-11 + draft-ietf-ospf-segment-routing-msd-12 Abstract This document defines a way for an OSPF Router to advertise multiple types of supported Maximum SID Depths (MSDs) at node and/or link granularity. Such advertisements allow entities (e.g., centralized controllers) to determine whether a particular SID stack can be supported in a given network. This document defines only one type of MSD, but defines an encoding that can support other MSD types. Here the term OSPF means both OSPFv2 and OSPFv3. @@ -30,21 +30,21 @@ 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 https://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 8, 2018. + This Internet-Draft will expire on November 10, 2018. Copyright Notice Copyright (c) 2018 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 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -57,27 +57,27 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 3. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5 4. Using Node and Link MSD Advertisements . . . . . . . . . . . 6 5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 + 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7 - 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 7 - 10.2. Informative References . . . . . . . . . . . . . . . . . 8 + 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 + 10.2. Informative References . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction When Segment Routing(SR) paths are computed by a centralized controller, it is critical that the controller learns the Maximum SID Depth(MSD) that can be imposed at each node/link on a given SR path to insure that the SID stack depth of a computed path doesn't exceed the number of SIDs the node is capable of imposing. @@ -167,35 +167,49 @@ | MSD Type and Value ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Figure 1: Node MSD TLV The Type: TBD1 Length: variable (minimum of 2, multiple of 2 octets) and represents the total length of value field. - Value: consists of one or more pairs of a 1 octet sub-type (IANA + Value: consists of one or more pairs of a 1 octet type (IANA Registry) and 1 octet value. MSD Type 1 (IANA Section), MSD and the Value field contains the MSD of the originating router. Node MSD is a number in the range of 0-255. 0 represents lack of the ability to impose MSD stack of any depth; any other value represents that of the node. This value SHOULD represent the minimum value supported by a node. Other MSD Types are reserved for future extensions. This TLV is applicable to OSPFv2 and to OSPFv3 [RFC5838] and is optional. The scope of the advertisement is specific to the deployment. + When multiple Node MSD TLVs are received from a given router, the + receiver MUST use the first occurrence of the TLV in the Router + Information LSA. If the Node MSD TLV appears in multiple Router + Information LSAs that have different flooding scopes, the Node MSD + TLV in the Router Information LSA with the area-scoped flooding scope + MUST be used. If the Node MSD TLV appears in multiple Router + Information LSAs that have the same flooding scope, the Node MSD TLV + in the Router Information (RI) LSA with the numerically smallest + Instance ID MUST be used and subsequent instances of the Node MSD TLV + MUST be ignored. The RI LSA can be advertised at any of the defined + opaque flooding scopes (link, area, or Autonomous System (AS)). For + the purpose of Node MSD TLV advertisement, area-scoped flooding is + REQUIRED. + 3. Link MSD sub-TLV The link sub-TLV is defined to carry the MSD of the interface associated with the link. MSD values may be learned via a hardware API or may be provisioned. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -222,28 +236,30 @@ Registry) and 1 octet value. MSD Type 1 (IANA Section), MSD and the Value field contains Link MSD of the router originating the corresponding LSA as specified for OSPFv2 and OSPFv3. Link MSD is a number in the range of 0-255. 0 represents lack of the ability to impose MSD stack of any depth; any other value represents that of the particular link MSD value. Other MSD Types are reserved for future extensions. - If these TLVs are advertised multiple times, only the first instance - of the TLV is used by receiving OSPF routers. This situation SHOULD - be logged as an error. + If this TLV is advertised multiple times in the same OSPFv2 Extended + Link Opaque LSA, only the first instance of the TLV is used by + receiving OSPFv2 routers. This situation SHOULD be logged as an + error. - If these TLV is advertised multiple times for the same link in - different LSAs originated by the same OSPF router, the TLV with the - smallest Opaque ID/Link State ID is used by receiving OSPF routers. - This situation MAY be logged as a warning. + If this TLV is advertised multiple times for the same link in + different OSPFv2 Extended Link Opaque LSAs originated by the same + OSPFv2 router, the OSPFv2 Extended Link TLV in the OSPFv2 Extended + Link Opaque LSA with the smallest Opaque ID is used by receiving + OSPFv2 routers. This situation may be logged as a warning. 4. Using Node and Link MSD Advertisements When Link MSD is present for a given MSD type, the value of the Link MSD MUST take preference over the Node MSD. When a Link MSD type is not signalled but the Node MSD type is, then the value of that Link MSD type MUST be considered as the corresponding Node MSD type value. In order to increase flooding efficiency, it is RECOMMENDED, that routers with homogenous link MSD values advertise just the Node MSD value. @@ -252,22 +268,22 @@ for a given MSD type is specific to the MSD type. Generally it can only be inferred that the advertising node does not support advertisement of that MSD type. However, in some cases the lack of advertisement might imply that the functionality associated with the MSD type is not supported. The correct interpretation MUST be specified when an MSD type is defined. 5. Base MPLS Imposition MSD The Base MPLS Imposition MSD (BMI-MSD) signals the total number of - MPLS labels a node is capable of imposing, including any service/ - transport labels. + MPLS labels a node is capable of imposing, including all + service/transport/special labels. Absence of BMI-MSD advertisements indicates solely that the advertising node does not support advertisement of this capability. 6. IANA Considerations This document requests IANA to allocate TLV type (TBD1) from the OSPF Router Information (RI) TLVs Registry as defined by [RFC4970]. IANA has allocated the value 12 through the early assignment process. Also, this document requests IANA to allocate a sub-TLV type (TBD2) @@ -289,59 +305,68 @@ 0 Reserved This document 1 Base MPLS Imposition MSD This document 2-250 Unassigned This document 251-254 Experimental This document 255 Reserved This document Figure 3: MSD Types Codepoints Registry 7. Security Considerations - Security concerns for OSPF are addressed in [RFC7474] and [RFC5310]. - Further security analysis for OSPF protocol is done in [RFC6853] - including analysis of both the above documents. Security - considerations, as specified by [RFC7770] are applicable to this - document. + Security concerns for OSPF are addressed in [RFC7474]. Further + security analysis for OSPF protocol is done in [RFC6863] including + analysis of both the above documents. Security considerations, as + specified by [RFC7770], [RFC7684] and [RFC8362] are applicable to + this document. - Advertisement of the additional information defined in this document - that is false, e.g. MSD that is incorrect may result: in a path + Advertisement of an incorrect MSD value may result: in a path computation failing and the service unavailable or instantiation of a path that can't be supported by the head-end (the node performing the imposition). 8. Contributors The following people contributed to this document: Les Ginsberg - Email: ginsberg@cisco.com 9. Acknowledgements - The authors would like to thank Acee Lindem, Stephane Litkowski and - Bruno Decraene for their reviews and valuable comments. + The authors would like to thank Acee Lindem, Ketan Talaulikar, + Stephane Litkowski and Bruno Decraene for their reviews and valuable + comments. 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, . [RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July 2007, . + [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., + "Security Extension for OSPFv2 When Using Manual Key + Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, + . + + [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and @@ -367,24 +392,25 @@ Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., and J. Hardwick, "PCEP Extensions for Segment Routing", draft-ietf-pce-segment-routing-11 (work in progress), November 2017. [RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and R. Aggarwal, "Support of Address Families in OSPFv3", RFC 5838, DOI 10.17487/RFC5838, April 2010, . - [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, . + [RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security + According to the Keying and Authentication for Routing + Protocols (KARP) Design Guide", RFC 6863, + DOI 10.17487/RFC6863, March 2013, + . [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", RFC 7752, DOI 10.17487/RFC7752, March 2016, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017,