MPLS Working Group L. Han Internet-Draft China Mobile Intended status: Standards Track F. Yang Expires: January 14, 2021 Huawei Technologies July 13, 2020 Signal Degrade Indication Used in Segment Routing over MPLS Network draft-han-mpls-sdi-sr-00 Abstract This document describes the typical use cases for signal degrade indication used in SR over MPLS networks. To satisfy the use cases and requirements of signal degrade indication, two extensions based on the BFD protocol and MPLS-TP OAM mechanisms are given respectively. Requirements Language 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 in RFC 2119 [RFC2119]. 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 January 14, 2021. Copyright Notice Copyright (c) 2020 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 Han & Yang Expires January 14, 2021 [Page 1] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 (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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. BFD Indication Mechanism . . . . . . . . . . . . . . . . . . 4 5. MPLS-TP Indication Mechanism . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction The importance and necessity of signal degrade notification used in Segment Routing over MPLS networks is discussed in [I-D.yang-mpls-ps-sdi-sr]. When signal degrade is detected, this information could be extended by means of protocols to perform the performance monitoring, fault management, and trigger of protection mechanism etc. Extensions on control plane, forwarding plane, management plane, and/or combination of any of them could be utilized to support the function of signal degrade indication. This document provides two protocol extensions used in SR over MPLS networks, by specifying the encapsulations and behaviors in detail. In some of SR over MPLS networks, BFD [RFC5880] or enhanced SBFD [RFC7880] is widely utilized as the failure detection mechanism because of its' simplicity and efficiency characteristics. The indication of signal degrade could be adopted as one of the reasons of BFD state changes. In other SR over MPLS networks, MPLS-TP OAM [ITU-T G.8113.1] mechanisms are used instead of BFD or SBFD. In this scenario, the extension based on the OAM PDU format is proposed in this document to support the signal degarde indication. Han & Yang Expires January 14, 2021 [Page 2] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 2. Terminology MPLS: Multiprotocol Label Switching SR: Segment Routing BFD: Bidirectional Forwarding Detection SBFD: Seamless BFD LER: Label Edge Router LSR: Label Switching Router MPLS-TP: Multiprotocol Label Switching - Tranport Profile OAM: Operation, Administration and Maintena GAL: Generic Associated Channel Label G-ACh: Generic Associated Channel (G-ACh) PDU: Protocol Data Unit CCM: Continuity Check Message 3. Overview The use cases and requirements have been discussed in [I-D.yang-mpls-ps-sdi-sr]. This document narrows the scope to the multi-hop SR over MPLS network, signal degrade is detected simply based on the physical bit error statistic on port level, no matter if the PHY is with or without forward error correction (FEC). Port level statistic is the intuitive approach to be best understood in the equipment and network systems. In practice of deployment, flexible configuration of the watermark to trigger the indication of signal degrade is preferred. As mentioned in [I-D.yang-mpls-ps-sdi-sr], signal degrade can happen in any link or node in SR over MPLS networks, such as LERs and LSRs. LERs can detect the signal degrade fault, or directly trigger the protecton switch mechanisms once it detects the signal degrade reaches at a certain level. However, LSRs may need further considerations. In SR over MPLS networks, since only the headend LER knows all the segments in the label stack, the intermediate LSRs does not know the entire label stack. There is no other choice of forwarding path to avoid the impact of signal degrade on the LSR. Thus, the signal degrade information should be spread to other LSRs Han & Yang Expires January 14, 2021 [Page 3] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 and LERs, and consequent behaviors on LSRs or LERs are executed depending on the choices of the protection mechanisms. The notification mechanism is best used through a forwarding protocol, not through the centralized Network Management System (NMS) or a SDN controller, to make sure the notification could be fast enough. Furthermore, carrying the signal degrade information in a control protocol is considered as well. In this case, the extensions of BFD control packet format and MPLS-TP CCM OAM PDU format are made to spread the signal degrade information. Though the signal degrade detection is limited to be monitored based on the physical link, the indication of signal degrade is preferred at the transport path level, e.g. MPLS PWs, MPLS LSPs, or MPLS Sections. In this case, Generic Associated Channel (G-ACh) defined in [RFC5586] is proposed as the best choice to satisfy this requirement. The Generic Associated Channel packet format used in SR over MPLS network is shown in Figure 1. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label | EXP |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | GAL Label (13) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0001 | 0000 | 00000000 | Channel Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 G-ACh Packet Format in SR over MPLS 4. BFD Indication Mechanism Working together with the G-Ach, IP/UDP/BFD packet formats are encapsulated and shown in Figure 2. The IP, UDP and BFD headers stay intact within the generic associated channel. The Diagnostic code specifies the local system's reason for the last change in session state. The definition of the Values is specified in Section 4.1 of [RFC5880]. The Reserved values from 9 to 31 can be extended to support the signal degrade indication. The registration to support the indication and removal of the signal degrade indication should be applied to IANA. Han & Yang Expires January 14, 2021 [Page 4] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | GAL Label (13) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0001 | 0000 | 00000000 | Channel Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vers | IHL | TOS | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Flag | Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TTL | Prot | Header Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Vers | Diag |Sta|P|F|C|A|D|M| Detect Mult | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | My Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Your Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Desired Min TX Interval | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Required Min RX Interval | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Required Min Echo RX Interval | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Authentication (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: BFD Packet Format in SR over MPLS 5. MPLS-TP Indication Mechanism ITU-T G.8113.1 defines the OAM PDU formats used in MPLS-TP networks. Figure 3 shows the OAM PDU format used within the SR over MPLS networks. If the LSR node detects the signal degrade, OAM CCM message is chosen to indicate the signal degrade via the forwarding plane. The OpCode value 0x01 in OAM PDU field indicates the CCM PDU message type. Han & Yang Expires January 14, 2021 [Page 5] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | GAL Label (13) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0001 | 0000 | 00000000 | Channel Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MEL | Version | OpCode(0x01) | Flag | TLV Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OAM PDU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |End TLV| +-+-+-+-+ Figure 3 G.8113.1 OAM PDU Format in SR over MPLS The reservation bits in Flag format in CCM OAM PDU message can be used as the error notification indication (EI) to indicate signal degrade, as shown in Figure 4. LSRs fills the EI field and transmits the OAM message to the other LSRs or LERs so that the degrade information can be learned. 0 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ |RDI| EI| Resv | Period | +---+---+---+---+---+---+---+---+ Figure 4 Extended Flags Format EI (1 bit): Error notification indication, 0 indicates no error, 1 indicates error, to notify the signal degradation error. 6. IANA Considerations The document requires the definition of the new indication and removal of the signal degrade indication in BFD Value code. Moreover, the EI bit definition is required to be assigned by ITU-T. 7. Security Considerations This document has no security consideration. 8. Acknowledgements TBD Han & Yang Expires January 14, 2021 [Page 6] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 9. References 9.1. 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, . 9.2. Informative References [I-D.yang-mpls-ps-sdi-sr] Yang, F., Han, L., and J. Zhao, "Problem Statement of Signal Degrade Indication for Segment Routing over MPLS Network", draft-yang-mpls-ps-sdi-sr-00 (work in progress), March 2020. [ITU-T_G8113.1] ITU-T, "ITU-T G.8113.1: Operations, administration and maintenance mechanisms for MPLS-TP in packet and maintenance mechanisms for MPLS-TP in packet transport networks", April 2016. [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009, . [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, . [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, . [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018, . Authors' Addresses Liuyan Han China Mobile No.32 Xuanwumen west street Beijing 100053 China Email: hanliuyan@chinamobile.com Han & Yang Expires January 14, 2021 [Page 7] Internet-Draft draft-han-mpls-sdi-sr-00 July 2020 Fan Yang Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: shirley.yangfan@huawei.com Han & Yang Expires January 14, 2021 [Page 8]