MPLS Working Group F. Zhang Internet-Draft B. Wu Intended status: Standards Track X. Dai Expires: September 9, 2010 ZTE Corporation March 08, 2010 LDP Extensions for MPLS-TP PW OAM configuration draft-zhang-mpls-tp-pw-oam-config-01 Abstract This document describes a procedure for the configuration of the pseudowire (PW) virtual circuit connectivity verification (VCCV) Bidirectional Forwarding Detection (BFD) OAM mechanism through LDP extensions. As the other MPLS-TP PW OAM functionalities develop, the procedure may be changed to cover them. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 9, 2010. Copyright Notice Copyright (c) 2010 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 Zhang, et al. Expires September 9, 2010 [Page 1] Internet-Draft LDP extensions for TP PW OAM March 2010 (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 BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. Operation overviews . . . . . . . . . . . . . . . . . . . . . 3 3.1. Establishment of OAM Entities and Functions . . . . . . . 4 3.2. Deleting OAM Entities . . . . . . . . . . . . . . . . . . 5 4. LDP extensions . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. PW OAM configuration TLV . . . . . . . . . . . . . . . . . 6 4.2. Local Discriminator sub-TLV . . . . . . . . . . . . . . . 7 4.3. MEP_IDs . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.4. ME_IDs . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.4.1. IP Compatible ME-IDs . . . . . . . . . . . . . . . . . 8 4.4.2. ICC-based ME_IDs . . . . . . . . . . . . . . . . . . . 8 4.5. PW status TLV . . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative references . . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Zhang, et al. Expires September 9, 2010 [Page 2] Internet-Draft LDP extensions for TP PW OAM March 2010 1. Introduction This document describes a procedure for the configuration of the PW VCCV BFD OAM mechanism through LDP extensions. As the other MPLS-TP PW OAM functionalities develop, the procedure may be changed to cover them. PW VCCV provides end-to-end fault detection and diagnostics for PWs, and currently supports the following OAM mechanisms: ICMP Ping, LSP Ping, and BFD, as described in [RFC5085]. BFD has been chosen to cover MPLS-TP CC functionality [base-BFD], and an extended version of BFD, as described in [BFD-CV], can accomplish both MPLS-TP CC and CV, even signal the AC status. BFD for VCCV supports two modes of encapsulation - either IP/UDP encapsulated (with IP/UDP header) or PW-ACH encapsulated (with no IP/UDP header). The use of the VCCV control channel provides the context, based on the MPLS-PW label, required to bind and bootstrap the BFD session to a particular PW (FEC), see the analysis in [tp-oam-analysis]. But in order to identify certain extreme cases of misconnectivity and fill the requirements that the BFD mechanism MUST be the same for LSP, (MS-)PW and Section as well as for LSP Tandem Connection and PW Tandem Connection [BFD-CV], BFD still needs to use Discriminator values to identify the connection being verified at both ends of the PW. The discriminator values can be statically configured, or signaled via LSP-Ping [[tp-ping-bfd-procedure]. According to the requirements in [RFC5654], "The MPLS-TP control plane MUST support the configuration and modification of OAM maintenance points as well as the activation/deactivation of OAM when the transport path or transport service is established or modified", it is naturally to extend LDP for setting up BFD or BFD extended version in order to configure MPLS-TP CC and CV OAM functionalities during the PW setup. 2. Conventions used in this document 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 RFC2119. 3. Operation overviews Below, extension to LDP for setting up BFD or BFD extended version are defined in order to configure MPLS-TP CC and CV OAM functionalities during the PW setup. PW signaling [RFC4447] defines Zhang, et al. Expires September 9, 2010 [Page 3] Internet-Draft LDP extensions for TP PW OAM March 2010 two FECs used to signal PWs. Of these, FEC Type 129 along with AII Type 2 as defined in [RFC5003] fits the identification requirements of MPLS-TP, so the current version of this draft just focus on the P2P PW (FEC 129) along with AII type 2, P2MP PW will be studied in the future. The terms "ingress LER" and "egress LER" will not refer in this document to any direction in the forwarding plane, but only to the LER triggering the PW setup (ingress LER) and the one receiving the mapping message (egress LER). During the PW signaling, the Control Plane instance in the ingress and the egress LER announces the BFD OAM Configuration TLV (inside the interface parameters TLV carried by the mapping message, following the VCCV parameter field), which includes the "Local Discriminator" sub-TLV. During the BFD session the ingress LER will use as "MyDiscriminator" the value announced in the "Local Discriminator" (Mapping message sent) and as YourDiscriminator" the value received in the "Local Discriminator" (Mapping message received). The interval value of BFD control packets both in transmission and reception can be negotiated through BFD session itself, so the mapping message does not need to carry these time values. In the case BFD extended version should be configured, the ME ID and MEP ID do not need to be carried also, for they can be deduced from the advertised FEC(129) TLV, as described in the following sections. 3.1. Establishment of OAM Entities and Functions Assuming there is one PW needs to be setup between LSR1 and LSR2. (1) LSR1 MUST setup the OAM sink function to be prepared to receive OAM messages but MUST suppress any OAM alarms (e.g., due to missing or unidentified OAM messages). The Mapping message MUST be sent with the "OAM Alarms Enabled" cleared, "OAM MEP Entities desired" set, "OAM MIP Entities desired" set in the PW status code. (2) When the Mapping message arrives at the receiver LSR2, it MUST establish and configure OAM entities according to the OAM information provided in mapping message. If this is not possible, a Label Release message SHOULD be sent and neither the OAM entities nor the PW SHOULD be established. If OAM entities are established successfully, the OAM Source function MUST be prepared to Send OAM messages. At the same time, LSR2 needs to setup the OAM sink function to be prepared to receive OAM messages but MUST suppress any OAM alarms (e.g., due to missing or unidentified OAM messages). The Zhang, et al. Expires September 9, 2010 [Page 4] Internet-Draft LDP extensions for TP PW OAM March 2010 Mapping message MUST be sent with the "OAM Alarms Enabled" cleared, "OAM MEP Entities desired" set, "OAM MIP Entities desired" set in the PW status code. (3) When LSR1 receives the Mapping message, it completes any pending OAM configuration and enables the OAM source function to send OAM messages. After this round, OAM entities are established and configured for the PW and OAM messages MAY already be exchanged. OAM alarms can now be enabled. The LSR1, while still keeping OAM alarms disabled sends a LDP Notification message with "OAM Alarms Enabled" PW status flag set. LSR2 enables the OAM alarms after processing the LDP Notification message. LSR1 enables OAM alarms after it receives the LDP Notification message from LSR2. Data plane OAM is now fully functional. 3.2. Deleting OAM Entities In some cases it may be useful to remove some or all OAM entities and functions from one PW without actually tearing down the connection. To avoid any spurious alarm, the following procedure should be followed: (1) LSR1/LSR2 SHOULD send Notification message with "OAM Alarms" cleared but unchanged OAM configuration. After that, (2) LSR1 SHOULD delete OAM source functions, then send Notification message with "OAM MEP Entities desired" and "OAM MIP Entities desired" cleared. (3) LSR2 SHOULD delete OAM source and sink functions, and then send Notification message with "OAM MEP Entities desired" and "OAM MIP Entities desired" cleared. Then, LSR1 SHOULD delete OAM sink functions. 4. LDP extensions Zhang, et al. Expires September 9, 2010 [Page 5] Internet-Draft LDP extensions for TP PW OAM March 2010 4.1. PW OAM configuration TLV 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| Type (IANA) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Vers.| PHB | |V|C| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ sub TLVs ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: PW OAM configuration TLV Type: indicates a new type, the "PW OAM Configuration TLV" (IANA to define). Length: indicates the total length including sub-TLVs. Version: identifies the BFD protocol version. PHB: Identifies the Per-Hop Behavior (PHB) to be used for periodic continuity monitoring messages. C: BFD CC OAM functon should be configured V: BFD CV OAM function should be configured (C MUST be set at the same time). The BFD CC OAM Configuration MUST include the following sub-TLVs in the Mapping message: Local Discriminator" sub-TLV (described in paragraph 4.2) The BFD CV OAM Configuration May include the following sub-TLVs except the "Local Discriminator" sub-TLV during the Mapping message: "ICC based ME-IDs" sub-TLV (described in paragraph 4.4.2) If the receiving LER does not support this PW OAM configuration TLV, it must be ignored and return a Notification message. Zhang, et al. Expires September 9, 2010 [Page 6] Internet-Draft LDP extensions for TP PW OAM March 2010 4.2. Local Discriminator sub-TLV The Local Discriminator sub-TLV is depicted below. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| Type (IANA) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Local Discriminator sub-TLV Type: indicates a new type, the Local Discriminator sub TLV (1) (IANA to define) Length: indicates the total length of the TLV including padding. Local Discriminator: A unique, nonzero discriminator value generated by the transmitting system and referring to itself, used to demultiplex multiple BFD sessions between the same pair of systems. This Discriminator will be signaled both by the ingress LSR and the egress LSR in the Mapping message respectively. If the receiving LER does not support this Local Discriminator format, it must be ignored and return a Notification message. 4.3. MEP_IDs In order to automatically generate MEP_IDs for MPLS-TP PWs, this draft is apt to use the AII associated with that end of the PW. The AII is composed of three fields. These are the Global_ID, the Prefix, and the AC_ID. The Global_ID used in this document is identical to the Global_ID defined in [RFC5003]. The Node_ID is used as the Prefix. The AC_ID is as defined in [RFC5003]. In this way, the definition is in accordance with the suggestion in the draft [tp-identifier], and there is no need to carry MEP_ID in the mapping message. 4.4. ME_IDs Zhang, et al. Expires September 9, 2010 [Page 7] Internet-Draft LDP extensions for TP PW OAM March 2010 4.4.1. IP Compatible ME-IDs In order to automatically generate ME_IDs for MPLS-TP PWs, it is convenient to use the corresponding PW identifier. In an MPLS-TP environment, a PW is identified by a set of identifiers which can be mapped directly to the elements required by FEC 129 and AII Type 2, so there is no need to carry ME_IDs in the mapping messages also. 4.4.2. ICC-based ME_IDs ME ID for PWs MAY use the globally unique ICC-based format. This ME ID format MAY be used to identify SME, LME, LTCME, PME and PTCME independently on LER/T-PE addressing schemes as well as of the FECs used to identify the PW. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| ME ID Type | Length = 20 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | MEG ID | + (13 bytes) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: ICC-based ME_ID TLV ME ID Type: it identifies the specific format, value = TBD. Length: indicates the total length and it is set to 20. ME ID value: the ME ID is a string of up to thirteen characters, each character being either alphabetic (i.e. A-Z) or numeric (i.e. 0-9) characters. It consists of two subfields: the ICC (as defined in section 3) followed by a unique ME ID code (UMC). The UMC MUST be unique within the organization identified by the ICC. If the receiving LER does not support this ME ID format, it must be ignored and return a Notification message. Zhang, et al. Expires September 9, 2010 [Page 8] Internet-Draft LDP extensions for TP PW OAM March 2010 4.5. PW status TLV In this document, three new PW status flags are defined: "OAM Alarms Enabled", "OAM MEP Entities desired", "OAM MIP Entities desired". 5. IANA Considerations TBD. 6. Security Considerations TBD. 7. Acknowledgement The author would like to thank Hongbo Wei for his useful discussion. 8. References 8.1. Normative references [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006. [RFC5003] Metz, C., Martini, L., Balus, F., and J. Sugimoto, "Attachment Individual Identifier (AII) Types for Aggregation", RFC 5003, September 2007. [RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007. [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, September 2009. 8.2. Informative References [BFD-CV] Fulignoli, A., Boutros, S., and M. Vigoureux, "MPLS-TP BFD for Proactive CC-CV and RDI", July 2009. Zhang, et al. Expires September 9, 2010 [Page 9] Internet-Draft LDP extensions for TP PW OAM March 2010 [base-BFD] Katz, D. and D. Ward, "Bidirectional Forwarding Detection", January 2010. [tp-identifier] Bocci, M. and G. Swallow, "MPLS-TP Identifiers", July 2009. [tp-oam-analysis] Sprecher, N., Van Helvoort, H., Bellagamba, E., and Y. Weingarten, "MPLS-TP OAM Analysis", March 2010. [tp-ping-bfd-procedure] Bahadur, N., Aggarwal, R., Nadeau, T., Sprecher, N., and Y. Weingarten, "LSP-Ping and BFD for MPLS-TP", July 2009. Authors' Addresses Fei Zhang ZTE Corporation 4F,RD Building 2,Zijinghua Road Yuhuatai District,Nanjing 210012 P.R.China Phone: +86 025 52877612 Email: zhang.fei3@zte.com.cn Bo Wu ZTE Corporation 4F,RD Building 2,Zijinghua Road Yuhuatai District,Nanjing 210012 P.R.China Phone: +86 025 52877276 Email: wu.bo@zte.com.cn Xuehui Dai ZTE Corporation 4F,RD Building 2,Zijinghua Road Yuhuatai District,Nanjing 210012 P.R.China Phone: +86 025 52877612 Email: dai.xuehui@zte.com.cn Zhang, et al. Expires September 9, 2010 [Page 10]