Internet Engineering Task Force V. Govindan Internet-Draft C. Pignataro Updates: 5885 (if approved) Cisco Systems Intended status: Standards Track June 30, 2015 Expires: January 1, 2016 Seamless BFD for VCCV draft-gp-pals-seamless-vccv-01 Abstract This document extends the procedures and Connectivity Verification (CV) types already defined for Bidirectional Forwarding Detection (BFD) for Virtual Circuit Connectivity Verification (VCCV) to define Seamless BFD (S-BFD) for VCCV. This document will be extended in future to include definition of procedures for S-BFD over Tunnels. This document extends the CV values defined in RFC5885. 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 January 1, 2016. Copyright Notice Copyright (c) 2015 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 Govindan & Pignataro Expires January 1, 2016 [Page 1] Internet-Draft Seamless BFD for VCCV June 2015 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. S-BFD Connectivity Verification . . . . . . . . . . . . . . . 3 2.1. Co-existence of S-BFD and BFD capabilites . . . . . . . . 4 2.2. S-BFD CV Operation . . . . . . . . . . . . . . . . . . . 4 2.2.1. S-BFD Initiator Operation . . . . . . . . . . . . . . 4 2.2.2. S-BFD Reflector Operation . . . . . . . . . . . . . . 4 2.2.2.1. S-BFD Reflector Demultiplexing . . . . . . . . . 5 2.2.2.2. S-BFD Reflector transmission of control packets . 5 2.2.2.3. S-BFD Reflector advertisement of target discriminators using LDP . . . . . . . . . . . . 5 2.2.2.4. S-BFD Reflector advertisement of target discriminators using L2TP . . . . . . . . . . . . 5 2.2.2.5. Provisioning of S-BFD Reflector target discriminators . . . . . . . . . . . . . . . . . 5 2.2.2.6. Probing of S-BFD Reflector target discriminators using alert discriminators . . . . . . . . . . . 5 2.3. S-BFD Encapsulation . . . . . . . . . . . . . . . . . . . 6 2.4. S-BFD CV Types . . . . . . . . . . . . . . . . . . . . . 6 3. Capability Selection . . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV . 7 5.2. L2TPv3 CV Types for the VCCV Capability AVP . . . . . . . 8 5.3. PW Associated Channel Type . . . . . . . . . . . . . . . 8 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 7. Contributing Authors . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Background BFD for VCCV [RFC5885] defines the CV types for BFD using VCCV, protocol operation and the required packet encapsulation formats. This document extends those procedures, CV type values to enable S-BFD [I-D.ietf-bfd-seamless-base] operation for VCCV. The new S-BFD CV Types are PW demultiplexer-agnostic, and hence applicable for both MPLS and Layer Two Tunneling Protocol version 3 (L2TPv3) pseudowire demultiplexers. This document concerns itself Govindan & Pignataro Expires January 1, 2016 [Page 2] Internet-Draft Seamless BFD for VCCV June 2015 with the S-BFD VCCV operation over single-segment pseudowires (SS- PWs). The scope of this document is as follows: This specification describes procedures only for S-BFD asynchronous mode. S-BFD Echo mode is outside the scope of this specification. S-BFD operation for fault detection and status signaling is outside the scope of this specification. 1.1. Requirements Language 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 in [RFC2119]. 2. S-BFD Connectivity Verification S-BFD protocol provides continuity check services by monitoring the S-BFD control packets sent and received over the VCCV channel of the PW. The term is used throughout this document to be consistent with [RFC5885]. This section defines the CV types to be used for S-BFD. It also defines the procedures for S-BFD discriminator advertisement for the SBD reflector and the procedure for S-BFD Initiator operation. Two CV Types are defined for S-BFD. Table 1 summarizes the S-BFD CV Types, grouping them by encapsulation (i.e., with versus without IP/ UDP headers) for fault detection only. S-BFD for fault detection and status signaling is outside the scope of this specification. Govindan & Pignataro Expires January 1, 2016 [Page 3] Internet-Draft Seamless BFD for VCCV June 2015 +---------------------------------------+-----------+---------------+ | | Fault | Fault | | | Detection | Detection and | | | Only | Status | | | | Signaling | +---------------------------------------+-----------+---------------+ | S-BFD, IP/UDP Encapsulation (with | TBD1 | N/A | | IP/UDP Headers) | (Note1) | | | | | | | S-BFD, PW-ACH Encapsulation when | TBD2 | N/A | | using MPLS PW or L2SS Encapsulation | (Note2) | | | when using L2TP PW (without IP/UDP | | | | Headers) | | | +---------------------------------------+-----------+---------------+ Table 1: Bitmask Values for BFD CV Types Two new bits are requested from IANA to indicate S-BFD operation. 2.1. Co-existence of S-BFD and BFD capabilites Since the CV types for S-BFD and BFD are unique, BFD and S-BFD capabilities can be advertised concurrently. 2.2. S-BFD CV Operation 2.2.1. S-BFD Initiator Operation The S-BFD Initiator SHOULD bootstrap S-BFD sessions after it learns the discriminator of the remote target identifier through one or more of the following methods: 1. Advertisements of S-BFD discriminators made through AVP/ TLVs defined in L2TP/ LDP. 2. Provisioning of S-BFD discriminators. 3. Probing remote S-BFD discriminators through S-BFD Alert discriminators [I-D.akiya-bfd-seamless-alert-discrim] S-BFD Initiator operation MUST be according to the specifications in Section 7.2 of [I-D.ietf-bfd-seamless-base]. 2.2.2. S-BFD Reflector Operation When as pseudowire signalling protocol such as LDP or L2TPv3 is in use the S-BFD Reflector advertises its target discriminators using that signalling protocol. When static PWs are in use the target Govindan & Pignataro Expires January 1, 2016 [Page 4] Internet-Draft Seamless BFD for VCCV June 2015 discriminator of S-BFD needs to be provisioned on the S-BFD Initiator nodes. All point to point pseudowires are bidirectional, the S-BFD Reflector therefore reflects the S-BFD packet back to the Initiator using the VCCV channel of the reverse direction of the PW on which it was received. It is observed that the reflector has enough information to reflect the S-BFD Async packet received by it back to the S-BFD initiator using the fields of the L2TPv3 headers. S-BFD Reflector operation for BFD protocol fields MUST be according to the specifications in Section TBD of [I-D.ietf-bfd-seamless-base]. 2.2.2.1. S-BFD Reflector Demultiplexing TBD 2.2.2.2. S-BFD Reflector transmission of control packets The procedures of S-BFD Reflector described in [I-D.ietf-bfd-seamless-base] apply for S-BFD using VCCV. 2.2.2.3. S-BFD Reflector advertisement of target discriminators using LDP TBD. 2.2.2.4. S-BFD Reflector advertisement of target discriminators using L2TP The S-BFD Reflector MUST use the AVP [I-D.gp-l2tpext-sbfd-discriminator] defined for advertising its target discriminators using L2TP. 2.2.2.5. Provisioning of S-BFD Reflector target discriminators S-BFD target discriminators MAY be provisioned when static PWs are used. 2.2.2.6. Probing of S-BFD Reflector target discriminators using alert discriminators S-BFD alert discriminators MAY be used to probe S-BFD target discriminators. If a node implements S-BFD reflector, it SHOULD Govindan & Pignataro Expires January 1, 2016 [Page 5] Internet-Draft Seamless BFD for VCCV June 2015 respond to Alert discriminator requests received from potential S-BFD Initiators. 2.3. S-BFD Encapsulation Unless specified differently below, the encapsulation of S-BFD packets is the identical the method specified in Sec.3.2 [RFC5885] and in [RFC5880] for the encapsulation of BFD packets. o IP/UDP BFD Encapsulation (BFD with IP/UDP Headers) * The destination UDP port for the IP encapsulated S-BFD packet MUST be 7784 [I-D.ietf-bfd-seamless-base]. * The encapsulation of the S-BFD header fields MUST be according to Sec.7.2.2 of [I-D.ietf-bfd-seamless-base]. o PW-ACH/ L2SS BFD Encapsulation (BFD without IP/UDP Headers) * The encapsulation of S-BFD packets using this format MUST be according to Sec.3.2 of [RFC5885] with the exception of the PW- ACH/ L2SS type. * When VCCV carries PW-ACH/ L2SS-encapsulated S-BFD (i.e., "raw" S-BFD), the PW-ACH (pseudowire CW's) or L2SS' Channel Type MUST be set to TBD2 to indicate "S-BFD Control, PW-ACH/ L2SS- encapsulated" (i.e., S-BFD without IP/UDP headers; see Section 5.3). This is to allow the identification of the encased S-BFD payload when demultiplexing the VCCV control channel. 2.4. S-BFD CV Types 3. Capability Selection When multiple S-BFD CV Types are advertised, and after applying the rules in [RFC5885], the set that both ends of the pseudowire have in common is determined. If the two ends have more than one S-BFD CV Type in common, the following list of S-BFD CV Types is considered in the order of the lowest list number CV Type to the highest list number CV Type, and the CV Type with the lowest list number is used: 1. TBD1 - S-BFD IP/UDP-encapsulated, for PW Fault Detection only. 2. TBD2 - S-BFD PW-ACH/ L2SS-encapsulated (without IP/UDP headers), for PW Fault Detection only. Govindan & Pignataro Expires January 1, 2016 [Page 6] Internet-Draft Seamless BFD for VCCV June 2015 The order of capability selection between S-BFD and BFD is defined as follows: +--------------------------+-----------+-----------+----------------+ | Advertised capabilities | BFD Only | SBFD Only | Both S-BFD and | | of PE1/ PE2 | | | BFD | +--------------------------+-----------+-----------+----------------+ | BFD Only | BFD | None | BFD Only | | | | (Note1) | | | | | | | | S-BFD Only | None | S-BFD | S-BFD only | | | (Note1) | | | | | | | | | Both S-BFD and BFD | BFD only | S-BFD | Both SBFD and | | | | only | BFD | +--------------------------+-----------+-----------+----------------+ Table 2: Capability Selection Matrix for BFD and S-BFD Note1: Can we mandate failing the bringup of the PW in case of a capability mismatch? 4. Security Considerations Security measures described in [RFC5885] and [I-D.ietf-bfd-seamless-base] are to be followed. 5. IANA Considerations 5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV The VCCV Interface Parameters Sub-TLV codepoint is defined in [RFC4446], and the VCCV CV Types registry is defined in [RFC5085]. This section lists the new BFD CV Types. IANA has augmented the "VCCV Connectivity Verification (CV) Types" registry in the Pseudowire Name Spaces reachable from [IANA]. These are bitfield values. CV Type values TBD are specified in Section 2 of this document. Govindan & Pignataro Expires January 1, 2016 [Page 7] Internet-Draft Seamless BFD for VCCV June 2015 MPLS Connectivity Verification (CV) Types: Bit (Value) Description Reference =========== =========== ============== TBD1(0xY) S-BFD IP/UDP-encapsulated, this document for PW Fault Detection only TBD2(0xZ) S-BFD PW-ACH/L2SS-encapsulated, this document for PW Fault Detection only 5.2. L2TPv3 CV Types for the VCCV Capability AVP This section lists the new requests for S-BFD CV Types to be added to the existing "VCCV Capability AVP" registry in the L2TP name spaces. The Layer Two Tunneling Protocol "L2TP" Name Spaces are reachable from [IANA]. IANA is requested to assign the following L2TPv3 Connectivity Verification (CV) Types in the VCCV Capability AVP Values registry. VCCV Capability AVP (Attribute Type 96) Values ---------------------------------------------- L2TPv3 Connectivity Verification (CV) Types: Bit (Value) Description Reference =========== =========== ============== TBD1(0xY) S-BFD IP/UDP-encapsulated, this document for PW Fault Detection only TBD2(0xZ) S-BFD L2SS-encapsulated, this document for PW Fault Detection only 5.3. PW Associated Channel Type As per the IANA considerations in [RFC5586], IANA is requested to allocate the following Channel Types in the "MPLS Generalized Associated Channel (G-ACh) Types" registry: IANA has reserved a new Pseudowire Associated Channel Type value as follows: Registry: TLV Value Description Follows Reference ------ ---------------------------------- ------- --------------- TBD2 S-BFD Control, PW-ACH/L2SS No [This document] encapsulation (without IP/UDP Headers) Govindan & Pignataro Expires January 1, 2016 [Page 8] Internet-Draft Seamless BFD for VCCV June 2015 6. Acknowledgements Authors would like to thank Nobo Akiya, Stewart Bryant, Pawel Sowinski and Greg Mirsky for providing the core inputs of this document and for performing thorough reviews and providing number of comments. Authors would also like to thank Yuanlong for comments received. 7. Contributing Authors Mallik Mudigonda Cisco Systems Email: mmudigon@cisco.com 8. References 8.1. Normative References [I-D.akiya-bfd-seamless-alert-discrim] Akiya, N., Pignataro, C., and D. Ward, "Seamless Bidirectional Forwarding Detection (S-BFD) Alert Discriminator", draft-akiya-bfd-seamless-alert-discrim-03 (work in progress), October 2014. [I-D.gp-l2tpext-sbfd-discriminator] Govindan, V. and C. Pignataro, "Advertising S-BFD Discriminators in L2TPv3", draft-gp-l2tpext-sbfd- discriminator-00 (work in progress), March 2015. [I-D.ietf-bfd-seamless-base] Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J. Networks, "Seamless Bidirectional Forwarding Detection (S-BFD)", draft-ietf-bfd-seamless-base-05 (work in progress), June 2015. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006. [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006. [RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007. Govindan & Pignataro Expires January 1, 2016 [Page 9] Internet-Draft Seamless BFD for VCCV June 2015 [RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, June 2009. [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010. [RFC5885] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", RFC 5885, June 2010. 8.2. Informative References [IANA] Internet Assigned Numbers Authority, "Protocol Registries", . Authors' Addresses Vengada Prasad Govindan Cisco Systems Email: venggovi@cisco.com Carlos Pignataro Cisco Systems Email: cpignata@cisco.com Govindan & Pignataro Expires January 1, 2016 [Page 10]