Movatterモバイル変換

Internet Engineering Task Force (IETF)                      C. PignataroRequest for Comments: 7884                                         CiscoCategory: Standards Track                                      M. BhatiaISSN: 2070-1721                                           Ionos Networks                                                               S. Aldrin                                                     Huawei Technologies                                                            T. Ranganath                                                                   Nokia                                                               July 2016OSPF Extensions to Advertise Seamless Bidirectional Forwarding Detection                     (S-BFD) Target DiscriminatorsAbstract   This document defines a new OSPF Router Information (RI) TLV that   allows OSPF routers to flood the Seamless Bidirectional Forwarding   Detection (S-BFD) Discriminator values associated with a target   network identifier.  This mechanism is applicable to both OSPFv2 and   OSPFv3.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7884.Pignataro, et al.            Standards Track                    [Page 1]

RFC 7884              S-BFD Discriminators in OSPF             July 2016Copyright Notice   Copyright (c) 2016 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1. Introduction ....................................................31.1. Relationship between OSPF and S-BFD ........................32. Implementation ..................................................32.1. S-BFD Discriminator TLV ....................................42.2. Flooding Scope .............................................43. Backward Compatibility ..........................................54. Security Considerations .........................................55. IANA Considerations .............................................66. References ......................................................66.1. Normative References .......................................66.2. Informative References .....................................6   Acknowledgements ...................................................7   Authors' Addresses .................................................7Pignataro, et al.            Standards Track                    [Page 2]

RFC 7884              S-BFD Discriminators in OSPF             July 20161.  Introduction   Seamless Bidirectional Forwarding Detection (S-BFD), specified in   [RFC7880], is a simplified mechanism for using BFD with many   negotiations eliminated.  This is achieved by using 4-octet   discriminators, unique within an administrative domain, to identify   the network targets.  These S-BFD Discriminators can be advertised by   the IGPs, and this document concerns itself with OSPF.  Specifically,   this document defines a new TLV (named the S-BFD Discriminator TLV)   to be carried within the OSPF Router Information (RI) Link State   Advertisement (LSA) [RFC7770].   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 inRFC 2119 [RFC2119].1.1.  Relationship between OSPF and S-BFD   This document implicitly defines a relationship between OSPF and   S-BFD.  S-BFD assigns one or more discriminators to each S-BFD   reflector node.  OSPF, in turn, learns about these from S-BFD and   floods them in the newly defined TLV.  After this information is   flooded, it is stored in all the OSPF nodes such that S-BFD   initiators can map out target nodes to target discriminators and can   therefore construct the S-BFD probe.   When multiple S-BFD Discriminators are advertised, how a given   discriminator is mapped to a specific use case is out of scope for   this document.2.  Implementation   This extension makes use of the Router Information (RI) Opaque LSA,   defined in [RFC7770], for both OSPFv2 [RFC2328] and OSPFv3 [RFC5340]   by defining a new OSPF Router Information (RI) TLV: the S-BFD   Discriminator TLV.   The S-BFD Discriminator TLV is OPTIONAL.  Upon receipt of the TLV, a   router may decide to install the S-BFD Discriminator in the BFD   target identifier table.   In the presence of multiple instances of the OSPFv2/OSPFv3 Router   Information LSA, the S-BFD Discriminators for an OSPF router are the   union of all discriminators advertised in all instances of the S-BFD   Discriminator TLV (seeSection 2.1) in all advertised non-MaxAge OSPF   Router Information LSAs.Pignataro, et al.            Standards Track                    [Page 3]

RFC 7884              S-BFD Discriminators in OSPF             July 20162.1.  S-BFD Discriminator TLV   The format of the S-BFD Discriminator TLV is 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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |              Type             |             Length            |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                         Discriminator 1                       |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                    Discriminator 2 (Optional)                 |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                               ...                             |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                    Discriminator n (Optional)                 |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Type - S-BFD Discriminator TLV Type (11)   Length - This field represents the total length of the      discriminator(s) that appears in the Value field, in octets.  Each      discriminator is 4 octets, so the Length is four times the number      of discriminators included in the TLV.  There is no optional      padding for this field.   Discriminator(s) - The Value field of the TLV includes the S-BFD      network target Discriminator value or values.   Routers that do not recognize the S-BFD Discriminator TLV Type will   ignore the TLV [RFC7770] and therefore will not learn S-BFD   Discriminators via OSPF.2.2.  Flooding Scope   The S-BFD Discriminator TLV is advertised within OSPFv2 Router   Information LSAs (Opaque type of 4 and Opaque ID of 0) or OSPFv3   Router Information LSAs (function code of 12), which are defined in   [RFC7770].  As such, elements of this procedure are inherited from   those defined in [RFC7770].   The flooding scope is controlled by the Opaque LSA type (as defined   in [RFC5250]) in OSPFv2 and by the S1/S2 bits (as defined in   [RFC5340]) in OSPFv3.  If the flooding scope is area local, then the   S-BFD Discriminator TLV MUST be carried within an OSPFv2 type 10   Router Information LSA or an OSPFV3 Router Information LSA with the   S1 bit set and the S2 bit clear.  If the flooding scope is the entirePignataro, et al.            Standards Track                    [Page 4]

RFC 7884              S-BFD Discriminators in OSPF             July 2016   IGP domain, then the S-BFD Discriminator TLV MUST be carried within   an OSPFv2 type 11 Router Information LSA or OSPFv3 Router Information   LSA with the S1 bit clear and the S2 bit set.   When the S-BFD reflector is deactivated, the OSPF speaker advertising   a particular S-BFD Discriminator MUST originate a new Router   Information LSA that no longer includes the corresponding S-BFD   Discriminator TLV, provided there are other TLVs in the LSA.  If   there are no other TLVs in the LSA, it MUST either send an empty   Router Information LSA or purge it by prematurely aging it.   For intra-area reachability, the S-BFD Discriminator TLV information   regarding a specific target identifier is only considered current and   usable when the router advertising that information is itself   reachable via OSPF calculated paths in the same area of the LSA in   which the S-BFD Discriminator TLV appears.  In the case of   domain-wide flooding, i.e., where the originator is sitting in a   remote area, the mechanism described inSection 5 of [RFC5250] should   be used.   Although the S-BFD Discriminators may change when enabling the S-BFD   functionality or via an explicit configuration event, such changes   are expected to occur very rarely.  Such changes in information will   require that the S-BFD Discriminator TLV in OSPF be advertised.   A change in information in the S-BFD Discriminator TLV MUST NOT   trigger any SPF computations at a receiving router.3.  Backward Compatibility   The S-BFD Discriminator TLV defined in this document does not   introduce any interoperability issues.   A router not supporting the S-BFD Discriminator TLV will just   silently ignore the TLV, as specified in [RFC7770].4.  Security Considerations   This document defines OSPF extensions to distribute the S-BFD   Discriminator within an administrative domain.  Hence, the security   of S-BFD Discriminator distribution relies on the security of OSPF.   OSPF provides no encryption mechanism for protecting the privacy of   LSAs and, in particular, the privacy of the S-BFD Discriminator   advertisement information.  However, this is not a concern, as there   isn't any need to hide the Discriminator value that can be used to   reach the reflectors.Pignataro, et al.            Standards Track                    [Page 5]

RFC 7884              S-BFD Discriminators in OSPF             July 20165.  IANA Considerations   IANA has defined a registry for TLVs carried in the Router   Information LSA defined in [RFC7770].  IANA has assigned a new TLV   codepoint (11) for the S-BFD Discriminator TLV in the "OSPF Router   Information (RI) TLVs" registry.        Value      TLV Name                 Reference        -----      --------                 ----------        11         S-BFDRFC 7884                   Discriminator6.  References6.1.  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,              <http://www.rfc-editor.org/info/rfc2119>.   [RFC2328]  Moy, J., "OSPF Version 2", STD 54,RFC 2328,              DOI 10.17487/RFC2328, April 1998,              <http://www.rfc-editor.org/info/rfc2328>.   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF              for IPv6",RFC 5340, DOI 10.17487/RFC5340, July 2008,              <http://www.rfc-editor.org/info/rfc5340>.   [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, <http://www.rfc-editor.org/info/rfc7770>.   [RFC7880]  Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.              Pallagatti, "Seamless Bidirectional Forwarding Detection              (S-BFD)",RFC 7880, DOI 10.17487/RFC7880, July 2016,              <http://www.rfc-editor.org/info/rfc7880>.6.2.  Informative References   [RFC5250]  Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The              OSPF Opaque LSA Option",RFC 5250, DOI 10.17487/RFC5250,              July 2008, <http://www.rfc-editor.org/info/rfc5250>.Pignataro, et al.            Standards Track                    [Page 6]

RFC 7884              S-BFD Discriminators in OSPF             July 2016Acknowledgements   The authors would like to thank Nobo Akiya, Les Ginsberg, Mach Chen,   and Peter Psenak for insightful comments and useful suggestions.Authors' Addresses   Carlos Pignataro   Cisco Systems, Inc.   Email: cpignata@cisco.com   Manav Bhatia   Ionos Networks   Email: manav@ionosnetworks.com   Sam Aldrin   Huawei Technologies   Email: aldrin.ietf@gmail.com   Trilok Ranganath   Nokia   Email: trilok.ranganatha@nokia.comPignataro, et al.            Standards Track                    [Page 7]