SPRING Working Group G. Mirsky Internet-Draft ZTE Corp. Intended status: Standards Track J. Tantsura Expires: September 2, 2018 Nuage Networks I. Varlashkin Google M. Chen Huawei March 1, 2018 Bidirectional Forwarding Detection (BFD) in Segment Routing Networks Using MPLS Dataplane draft-mirsky-spring-bfd-05 Abstract Segment Routing (SR) architecture leverages the paradigm of source routing. It can be realized in the Multiprotocol Label Switching (MPLS) network without any change to the data plane. A segment is encoded as an MPLS label and an ordered list of segments is encoded as a stack of labels. Bidirectional Forwarding Detection (BFD) is expected to monitor any kind of paths between systems. This document defines how to use Label Switched Path Ping to bootstrap and control path in reverse direction of a BFD session on the Segment Routing static MPLS tunnel and applicability of BFD Demand mode to SR-MPLS domain. 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 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 September 2, 2018. Mirsky, et al. Expires September 2, 2018 [Page 1] Internet-Draft BFD in SPRING MPLS March 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 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 Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 2. Bootstrapping BFD session over Segment Routed tunnel . . . . 3 3. Use BFD Reverse Path TLV over Segment Routed MPLS Tunnel . . 4 4. Use Non-FEC Path TLV . . . . . . . . . . . . . . . . . . . . 4 5. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic Control Plane . . . . . . . . . . . . . . . . . . . . 6 6. Applicability of BFD Demand Mode in SR-MPLS Domain . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7.1. Non-FEC Path TLV . . . . . . . . . . . . . . . . . . . . 7 7.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction [RFC5880], [RFC5881], and [RFC5883] established the Bidirectional Forwarding Detection (BFD) protocol for IP networks. [RFC5884] and [RFC7726] set rules of using BFD Asynchronous mode over Multiprotocol Label Switching (MPLS) Label Switched Path (LSP). These latter standards implicitly assume that the egress BFD peer, which is the egress Label Edge Router (LER), will use the shortest path route regardless of the path the ingress LER uses to send BFD control packets towards it. Mirsky, et al. Expires September 2, 2018 [Page 2] Internet-Draft BFD in SPRING MPLS March 2018 This document defines use of LSP Ping for Segment Routing networks over MPLS dataplane [RFC8287] to bootstrap and control path of a BFD session from the egress to ingress LER using static MPLS tunnel. 1.1. Conventions used in this document 1.1.1. Terminology BFD: Bidirectional Forwarding Detection FEC: Forwarding Equivalence Class MPLS: Multiprotocol Label Switching SR-MPLS Segment Routing with MPLS data plane LSP: Label Switching Path LER: Label Edge Router SR Segment Routing 1.1.2. 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 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Bootstrapping BFD session over Segment Routed tunnel As demonstrated in [RFC8287] introduction of Segment Routing network domains with an MPLS data plane requires three new sub-TLVs that MAY be used with Target Forwarding Equivalence Class (FEC) TLV. Section 6.1 addresses use of the new sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute. For the case of LSP ping the [RFC8287] states that: Initiator MUST include FEC(s) corresponding to the destination segment. Initiator, i.e. ingress LSR, MAY include FECs corresponding to some or all of segments imposed in the label stack by the ingress LSR to communicate the segments traversed. It has been noted in [RFC5884] that a BFD session monitors for defects particular tuple. [RFC7726] clarified how to Mirsky, et al. Expires September 2, 2018 [Page 3] Internet-Draft BFD in SPRING MPLS March 2018 establish and operate multiple BFD sessions for the same tuple. Because only ingress edge router is aware of the SR- based explicit route the egress edge router can associate the LSP ping with BFD Discriminator TLV with only one of the FECs it advertised for the particular segment. Thus this document clarifies that: When LSP Ping is used to bootstrap a BFD session the FEC corresponding to the destination segment to be associated with the BFD session MUST be as the very last sub-TLV in the Target FEC TLV. Encapsulation of a BFD Control packet in Segment Routing network with MPLS dataplane MUST follow Section 7 [RFC5884] when IP/UDP header used and MUST follow Section 3.4 [RFC6428] without IP/UDP header being used. 3. Use BFD Reverse Path TLV over Segment Routed MPLS Tunnel For BFD over MPLS LSP case, per [RFC5884], egress LER MAY send BFD control packet to the ingress LER either over IP network or an MPLS LSP. Similarly, for the case of BFD over p2p segment tunnel with MPLS data plane, the ingress LER MAY route BFD control packet over IP network, as described in [RFC5883], or transmit over a segment tunnel, as described in Section 7 [RFC5884]. In some cases there may be a need to direct egress BFD peer to use specific path for the reverse direction of the BFD session by using the BFD Reverse Path TLV and following all procedures as defined in [I-D.ietf-mpls-bfd-directed]. 4. Use Non-FEC Path TLV For the case of MPLS dataplane, Segment Routing Architecture [I-D.ietf-spring-segment-routing] explains that "a segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels." YANG Data Model for MPLS Static LSPs [I-D.ietf-mpls-static-yang] models outgoing MPLS labels to be imposed as leaf-list [RFC6020], i.e., as array of rt-types:mpls-label [RFC8294]. This document defines new optional Non-FEC Path TLV. The format of the Non-FEC Path TLV is presented in Figure 1 Mirsky, et al. Expires September 2, 2018 [Page 4] Internet-Draft BFD in SPRING MPLS March 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Non-FEC Path TLV Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Non-FEC Path ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Non-FEC Path TLV Format Non-FEC Path TLV Type is 2 octets in length and has a value of TBD1 (to be assigned by IANA as requested in Section 7.1). Length field is 2 octets long and defines the length in octets of the Non-FEC Path field. Non-FEC Path field contains a sub-TLV. Any Non-FEC Path sub-TLV (defined in this document or to be defined in the future) for Non-FEC Path TLV type MAY be used in this field. None or one sub-TLV MAY be included in the Non-FEC Path TLV. If no sub-TLV has been found in the Non-FEC Path TLV, the egress BFD peer MUST revert to using the reverse path selected based on its local policy. If there are more than one sub-TLV, then the Return Code in echo reply MUST be set to value TBD3 "Too Many TLVs Detected" (to be assigned by IANA as requested in Table 4). Non-FEC Path TLV MAY be used to specify the reverse path of the BFD session identified in the BFD Discriminator TLV. If the Non-FEC Path TLV is present in the echo request message the BFD Discriminator TLV MUST be present as well. If the BFD Discriminator TLV is absent when the Non-FEC Path TLV is included, then it MUST be treated as malformed Echo Request, as described in [RFC8029]. This document defines Static Routing MPLS Tunnel sub-TLV that MAY be used with the Non-FEC Path TLV. The format of the sub-TLV is presented in Figure 2. Mirsky, et al. Expires September 2, 2018 [Page 5] Internet-Draft BFD in SPRING MPLS March 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR MPLS Tunnel sub-TLV Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label Entry 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label Entry 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label Entry N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Segment Routing MPLS Tunnel sub-TLV The Segment Routing MPLS Tunnel sub-TLV Type is two octets in length, and has a value of TBD2 (to be assigned by IANA as requested in Section 7.1). The egress LSR MUST use the Value field as label stack for BFD control packets for the BFD session identified by the source IP address of the MPLS LSP Ping packet and the value in the BFD Discriminator TLV. Label Entries MUST be in network order. 5. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic Control Plane When Segment Routed domain with MPLS data plane uses distributed tunnel computation BFD Reverse Path TLV MAY use Target FEC sub-TLVs defined in [RFC8287]. 6. Applicability of BFD Demand Mode in SR-MPLS Domain [I-D.mirsky-bfd-mpls-demand] defines how Demand mode of BFD, specified in sections 6.6 and 6.18.4 of [RFC5880], can be used to monitor uni-directional MPLS LSP. Similar procedures can be following in SR-MPLS to monitor uni-directional SR tunnels: o ingress SR node bootstraps BFD session over SR-MPLS in Async BFD mode; o once BFD session is Up, the ingress node switches the egress BFD node into the Demand mode by setting D field in BFD Control packet it transmits; Mirsky, et al. Expires September 2, 2018 [Page 6] Internet-Draft BFD in SPRING MPLS March 2018 o if the egress BFD node detects the failure of the BFD session, it sends its BFD control packet to the ingress over the IP network with Poll sequence; o if the ingress node receives BFD control packet from remote node in Demand mode with Poll sequence and Diag field indicating the failure, the ingress transmits BFD control packet with Final over IP and switches the BFD over SR-MPLS back into Async mode, sending BFD Control packets one per second. 7. IANA Considerations 7.1. Non-FEC Path TLV IANA is requested to assign new TLV type from the from Standards Action range of the registry "Multiprotocol Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" as defined in the Table 1. +-------+------------------+---------------+ | Value | TLV Name | Reference | +-------+------------------+---------------+ | TBD1 | Non-FEC Path TLV | This document | +-------+------------------+---------------+ Table 1: New Non-FEC Path TLV IANA is requested to create new Non-FEC Path sub-TLV registry for the Non-FEC Path TLV as described in Table 2. +-------------+---------------+-------------------------------------+ | Range | Registration | Note | | | Procedures | | +-------------+---------------+-------------------------------------+ | 0-16383 | Standards | This range is for mandatory TLVs or | | | Action | for optional TLVs that require an | | | | error message if not recognized. | | 16384-31743 | Specification | Experimental RFC needed | | | Required | | | 32768-49161 | Standards | This range is for optional TLVs | | | Action | that can be silently dropped if not | | | | recognized. | | 49162-64511 | Specification | Experimental RFC needed | | | Required | | | 64512-65535 | Private Use | | +-------------+---------------+-------------------------------------+ Table 2: Non-FEC Path sub-TLV registry Mirsky, et al. Expires September 2, 2018 [Page 7] Internet-Draft BFD in SPRING MPLS March 2018 IANA is requested to allocate following values from the Non-FEC Path sub-TLV registry as defined in Table 3. +-------+-------------------------------------+---------------+ | Value | Description | Reference | +-------+-------------------------------------+---------------+ | 0 | Reserved | This document | | TBD2 | Segment Routing MPLS Tunnel sub-TLV | This document | | 65535 | Reserved | This document | +-------+-------------------------------------+---------------+ Table 3: New Segment Routing Tunnel sub-TLV 7.2. Return Code IANA is requested to create Non-FEC Path sub-TLV subregistry for the new Non-FEC Path TLV. assign a new Return Code value from the "Multi- Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters" registry, "Return Codes" sub-registry, as follows using a Standards Action value. +--------+-------------------------+---------------+ | Value | Description | Reference | +--------+-------------------------+---------------+ | X TBD3 | Too Many TLVs Detected. | This document | +--------+-------------------------+---------------+ Table 4: New Return Code 8. Security Considerations Security considerations discussed in [RFC5880], [RFC5884], [RFC7726], and [RFC8029] apply to this document. 9. Acknowledgements TBD 10. References 10.1. Normative References [I-D.ietf-mpls-bfd-directed] Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen, "Bidirectional Forwarding Detection (BFD) Directed Return Path", draft-ietf-mpls-bfd-directed-08 (work in progress), December 2017. Mirsky, et al. Expires September 2, 2018 [Page 8] Internet-Draft BFD in SPRING MPLS March 2018 [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", draft-ietf-spring-segment-routing-15 (work in progress), January 2018. [I-D.mirsky-bfd-mpls-demand] Mirsky, G., "BFD in Demand Mode over Point-to-Point MPLS LSP", draft-mirsky-bfd-mpls-demand-02 (work in progress), October 2017. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, . [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, DOI 10.17487/RFC5881, June 2010, . [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, June 2010, . [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, June 2010, . [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed., "Proactive Connectivity Verification, Continuity Check, and Remote Defect Indication for the MPLS Transport Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011, . [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. Aldrin, "Clarifying Procedures for Establishing BFD Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, DOI 10.17487/RFC7726, January 2016, . Mirsky, et al. Expires September 2, 2018 [Page 9] Internet-Draft BFD in SPRING MPLS March 2018 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., Aldrin, S., and M. Chen, "Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures", RFC 8029, DOI 10.17487/RFC8029, March 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8287] Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya, N., Kini, S., and M. Chen, "Label Switched Path (LSP) Ping/Traceroute for Segment Routing (SR) IGP-Prefix and IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017, . 10.2. Informative References [I-D.ietf-mpls-static-yang] Saad, T., Raza, K., Gandhi, R., Liu, X., and V. Beeram, "A YANG Data Model for MPLS Static LSPs", draft-ietf-mpls- static-yang-05 (work in progress), February 2018. [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [RFC8294] Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger, "Common YANG Data Types for the Routing Area", RFC 8294, DOI 10.17487/RFC8294, December 2017, . Authors' Addresses Greg Mirsky ZTE Corp. Email: gregimirsky@gmail.com Jeff Tantsura Nuage Networks Email: jefftant.ietf@gmail.com Mirsky, et al. Expires September 2, 2018 [Page 10] Internet-Draft BFD in SPRING MPLS March 2018 Ilya Varlashkin Google Email: Ilya@nobulus.com Mach(Guoyi) Chen Huawei Email: mach.chen@huawei.com Mirsky, et al. Expires September 2, 2018 [Page 11]