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Internet Engineering Task Force (IETF)                          M. ZhangRequest for Comments: 8564                           Huawei TechnologiesUpdates:7175,7177                                        S. PallagattiCategory: Standards Track                                         VmwareISSN: 2070-1721                                              V. Govindan                                                           Cisco Systems                                                              April 2019Support of Point-to-Multipoint Bidirectional Forwarding Detection (BFD)        in Transparent Interconnection of Lots of Links (TRILL)Abstract   Point-to-multipoint (P2MP) Bidirectional Forwarding Detection (BFD)   is designed to verify multipoint connectivity.  This document   specifies the support of P2MP BFD in Transparent Interconnection of   Lots of Links (TRILL).  Similar to TRILL point-to-point BFD, BFD   Control packets in TRILL P2MP BFD are transmitted using RBridge   Channel messages.  This document updates RFCs 7175 and 7177.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 athttps://www.rfc-editor.org/info/rfc8564.Zhang, et al.                Standards Track                    [Page 1]

RFC 8564                   P2MP BFD for TRILL                 April 2019Copyright Notice   Copyright (c) 2019 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   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .22.  Acronyms and Terminology  . . . . . . . . . . . . . . . . . .32.1.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .32.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .33.  Bootstrapping . . . . . . . . . . . . . . . . . . . . . . . .34.  A New RBridge Channel Message for P2MP BFD  . . . . . . . . .45.  Discriminators and Packet Demultiplexing  . . . . . . . . . .46.  Tracking Active Tails . . . . . . . . . . . . . . . . . . . .57.  Security Considerations . . . . . . . . . . . . . . . . . . .58.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .59.  References  . . . . . . . . . . . . . . . . . . . . . . . . .69.1.  Normative References  . . . . . . . . . . . . . . . . . .69.2.  Informative References  . . . . . . . . . . . . . . . . .7   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .7   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .81.  Introduction   TRILL supports multicast forwarding.  Applications based on TRILL   multicast may need quick detection of multicast failures using P2MP   BFD [RFC8562].  This document specifies TRILL support of P2MP BFD.   To use P2MP BFD, the head end needs to periodically transmit BFD   Control packets to all tails using TRILL multicast.  A new RBridge   Channel message is allocated for this purpose.   In order to execute the global protection of distribution used for   multicast forwarding [TRILL-TREES], the head needs to track the   active status of tails [RFC8563].  If the tail loses connectivity as   detected by not receiving the new RBridge Channel message from the   head, the tail should notify the head of the lack of multipointZhang, et al.                Standards Track                    [Page 2]

RFC 8564                   P2MP BFD for TRILL                 April 2019   connectivity with unicast BFD Control packets.  These unicast BFD   Control packets are transmitted using the existing RBridge Channel   message assigned to BFD Control [RFC7175].   This document updates [RFC7177] as specified inSection 3 and updates   [RFC7175] as specified in Sections4 and5.2.  Acronyms and Terminology2.1.  Acronyms   Data Label:  VLAN or Fine-Grained Label [RFC7172].   BFD:   Bidirectional Forwarding Detection   P2MP:  Point to Multipoint   TRILL: Transparent Interconnection of Lots of Links or Tunneled          Routing in the Link Layer2.2.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described inBCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all   capitals, as shown here.   Familiarity with [RFC6325], [RFC7175], and [RFC7178] is assumed in   this document.3.  Bootstrapping   The TRILL adjacency mechanism bootstraps the establishment of one-   hop TRILL BFD sessions [RFC7177].  Multi-hop sessions are expected to   be configured by the network manager.  A slight wording update to the   second sentence inSection 6 of [RFC7177] is required.   It currently reads:      If an RBridge supports BFD [RFC7175], it will have learned whether      the other RBridge has BFD enabled by whether or not a BFD-Enabled      TLV [RFC6213] was included in its Hellos.Zhang, et al.                Standards Track                    [Page 3]

RFC 8564                   P2MP BFD for TRILL                 April 2019   Now it should read:      If an RBridge supports BFD (see [RFC7175] and [RFC8564]), it will      have learned whether the other RBridge has BFD enabled by whether      or not a BFD-Enabled TLV [RFC6213] was included in its Hellos.   In addition, a normative reference to this document is added toRFC7177 as a result of this update.4.  A New RBridge Channel Message for P2MP BFD   RBridge Channel protocol number 0x002 is defined for TRILL point-to-   point BFD Control packets in [RFC7175].  That RFC states that if the   M bit of the TRILL Header of the RBridge Channel packet containing a   BFD Control packet is nonzero, the packet is generally dropped.  In   P2MP BFD, the head is required to probe tails using multicast.  This   means the M bit will be set to 1.  For this reason, a new RBridge   Channel message (P2MP BFD Control), whose protocol code point is   0x007, is specified in this document.  An RBridge that supports P2MP   BFD MUST support the new RBridge Channel message for P2MP BFD.  The   capability to support the RBridge Channel message for P2MP BFD, and   therefore support performing P2MP BFD, is announced within the   RBridge Channel Protocols sub-TLV in Link State PDUs (LSPs)   [RFC7176].   As specified in [RFC7178], when the tail receives TRILL Data packets   sent as BFD RBridge Channel messages, it will absorb the packets   itself rather than deliver these packets to its attached end   stations.5.  Discriminators and Packet Demultiplexing   The processing inSection 3.2 of [RFC7175] generally applies except   that the test on the M bit in the TRILL Header is reversed.  If the M   bit is zero, the packet MUST be discarded.  If the M bit is one, it   is processed.   After the processing perSection 3.2 of [RFC7175], the tail   demultiplexes incoming BFD packets based on a combination of the   source address and My Discriminator as specified in [RFC8562].  In   addition to this combination, TRILL P2MP BFD requires that the tail   use the Data Label, which is either the inner VLAN or the Fine-   Grained Label [RFC7172], for demultiplexing.  If the tail needs to   notify the head about the failure of a multipath, the tail is   required to send unicast BFD Control packets using the same Data   Label as used by the head.Zhang, et al.                Standards Track                    [Page 4]

RFC 8564                   P2MP BFD for TRILL                 April 20196.  Tracking Active Tails   According to [RFC8562], the head has a session of type MultipointHead   that is bound to a multipoint path.  Multipoint BFD Control packets   are sent by this session over the multipoint path, and no BFD Control   packets are received by it.  Each tail dynamically creates a   MultipointTail per a multipoint path.  MultipointTail sessions   receive BFD Control packets from the head over multipoint paths.   An example use is when a multicast tree root needs to keep track of   all the receivers as in [TRILL-TREES]; this can be done by   maintaining a session of type MultipointClient per receiver that is   of interest, as described in [RFC8563].  See [RFC8563] for detailed   operations of tracking active tails.7.  Security Considerations   Multipoint BFD provides its own authentication but does not provide   encryption (see the Security Considerations in [RFC8562]).  As   specified in this document, the point-to-multipoint BFD payloads are   encapsulated in RBridge Channel messages that have been extended by   [RFC7978] to provide security.  [RFC7978] provides encryption only   for point-to-point extended RBridge Channel messages, so its   encryption facilities are not applicable to this document.  However,   [RFC7978] provides stronger authentication than that currently   provided in BFD.  Thus, there is little reason to use the BFD   security mechanisms if authentication per [RFC7978] is in use.  It is   expected that a future TRILL document will provide for group keying;   when that occurs, the use of RBridge Channel security [RFC7978] will   be able to provide both encryption and authentication.   For general multipoint BFD security considerations, see [RFC8562].   For general RBridge Channel security considerations, see [RFC7178].8.  IANA Considerations   IANA has allocated the following from the Standards Action [RFC8126]   range of the "RBridge Channel Protocols" registry, which is part of   the "Transparent Interconnection of Lots of Links (TRILL) Parameters"   registry.          Protocol          Number          ----------------  ------          P2MP BFD Control  0x007Zhang, et al.                Standards Track                    [Page 5]

RFC 8564                   P2MP BFD for TRILL                 April 20199.  References9.1.  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,              <https://www.rfc-editor.org/info/rfc2119>.   [RFC6325]  Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.              Ghanwani, "Routing Bridges (RBridges): Base Protocol              Specification",RFC 6325, DOI 10.17487/RFC6325, July 2011,              <https://www.rfc-editor.org/info/rfc6325>.   [RFC7172]  Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and              D. Dutt, "Transparent Interconnection of Lots of Links              (TRILL): Fine-Grained Labeling",RFC 7172,              DOI 10.17487/RFC7172, May 2014,              <https://www.rfc-editor.org/info/rfc7172>.   [RFC7175]  Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee,              "Transparent Interconnection of Lots of Links (TRILL):              Bidirectional Forwarding Detection (BFD) Support",RFC 7175, DOI 10.17487/RFC7175, May 2014,              <https://www.rfc-editor.org/info/rfc7175>.   [RFC7176]  Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt,              D., and A. Banerjee, "Transparent Interconnection of Lots              of Links (TRILL) Use of IS-IS",RFC 7176,              DOI 10.17487/RFC7176, May 2014,              <https://www.rfc-editor.org/info/rfc7176>.   [RFC7177]  Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H., and              V. Manral, "Transparent Interconnection of Lots of Links              (TRILL): Adjacency",RFC 7177, DOI 10.17487/RFC7177, May              2014, <https://www.rfc-editor.org/info/rfc7177>.   [RFC7178]  Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.              Ward, "Transparent Interconnection of Lots of Links              (TRILL): RBridge Channel Support",RFC 7178,              DOI 10.17487/RFC7178, May 2014,              <https://www.rfc-editor.org/info/rfc7178>.   [RFC7978]  Eastlake 3rd, D., Umair, M., and Y. Li, "Transparent              Interconnection of Lots of Links (TRILL): RBridge Channel              Header Extension",RFC 7978, DOI 10.17487/RFC7978,              September 2016, <https://www.rfc-editor.org/info/rfc7978>.Zhang, et al.                Standards Track                    [Page 6]

RFC 8564                   P2MP BFD for TRILL                 April 2019   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.   [RFC8562]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,              Ed., "Bidirectional Forwarding Detection (BFD) for              Multipoint Networks",RFC 8562, DOI 10.17487/RFC8562,              April 2019, <https://www.rfc-editor.org/info/rfc8562>.   [RFC8563]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,              Ed., "Bidirectional Forwarding Detection (BFD) Multipoint              Active Tails",RFC 8563, DOI 10.17487/RFC8563, April 2019,              <https://www.rfc-editor.org/info/rfc8563>.9.2.  Informative References   [RFC6213]  Hopps, C. and L. Ginsberg, "IS-IS BFD-Enabled TLV",RFC 6213, DOI 10.17487/RFC6213, April 2011,              <https://www.rfc-editor.org/info/rfc6213>.   [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,              <https://www.rfc-editor.org/info/rfc8126>.   [TRILL-TREES]              Zhang, M., Senevirathne, T., Pathangi, J., Banerjee, A.,              and A. Ghanwani, "TRILL: Resilient Distribution Trees",              Work in Progress,draft-ietf-trill-resilient-trees-09,              January 2018.Acknowledgements   The authors would like to thank Gayle Noble and Donald Eastlake 3rd   for their comments and suggestions.Zhang, et al.                Standards Track                    [Page 7]

RFC 8564                   P2MP BFD for TRILL                 April 2019Authors' Addresses   Mingui Zhang   Huawei Technologies   No.156 Beiqing Rd. Haidian District   Beijing  100095   China   Email: zhangmingui@huawei.com   Santosh Pallagatti   Vmware   Email: santosh.pallagatti@gmail.com   Vengada Prasad Govindan   Cisco Systems   Email: venggovi@cisco.comZhang, et al.                Standards Track                    [Page 8]