Internet Draft David Allan Document: draft-allan-y17iw-overview-00.txt Nortel Networks Category: Informational June 2003 An overview of Y.17iw Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Copyright Notice Copyright(C) The Internet Society (2003). All Rights Reserved. Abstract This internet draft provides an overview of ITU-T draft recommendation Y.17iw "OAM functionality for ATM-MPLS interworking". Sub-IP ID Summary [to be removed when published] WHERE DOES IT FIT IN THE PICTURE OF THE SUB-IP WORK Fits in the MPLS, and PWE3 boxes. WHY IS IT TARGETED AT THESE WGs This draft shows that LSP-PING and Y.1711 can be considered to be complementary tools in the suite of options to measure and instrument MPLS. Allan et.al Expires August 2003 Page 1 Overview of Y.17iw 1. Introduction Y.17iw is a draft recommendation coming from the collaboration of ITU-T SG13 Questions 3 and 5. Y.17iw is focused on fault management interworking between [Y1711] and [I610] in two scenarios, network interworking (overlay), and service interworking (peer). This draft is purely informational. 2. Terminology The terminology used in the appendices is directly as written in the ITU-T draft recommendation (for consistency) and borrows from [Y1711] and [I610]. The relevant terms are: defect: Interruption of the capability of a transport entity (e.g. network connection) to transfer user or OAM information. far end termination - LSP ingress near end termination - LSP egress VCLC - virtual channel link connection VPLC - virtual path link connection Other definitions are provided with the reference models in sections 4 and 5. 3. Principles Y.17iw treats the ATM and MPLS/PW components of the connectivity between CEs as separate maintenance entities. The maintenance entities have defect states that act as inputs into either the client maintenance entity (network interworking or PW scenario) or peer maintenance entity (service interworking or L2VPN interworking scenario) and trigger appropriate OAM actions (described in the appendices). There is no actual interworking or translation of the OAM protocols per se. Allan Expires December 2003 Page 2 Overview of Y.17iw 4. Network Interworking Reference Models CE1 CE2 | | | VCLC | F5 |< ======== >|< ======== >|< ======== >| Virtual / \ Channel --------/ \-------- Level / \ / | VPLC | \ F4 |< ======== >|< ======== >|< ======== >| Virtual | | | | Path PW | | PW Level end | | end service | | service PE1 PE2 --------/ \-------- / \ / \ |< ======== >|< ======== >|< ======== >| PW / \ Level --------/ \-------- / \ / \ |< ======== >|< ======== >|< ======== >| PSN / \ Tunnel --------/ \-------- Level / \ / \ F3 etc. |< ======== >|< ======== >|< ======== >| Figure 1: Mapping I.610 OAM hierarchy onto PWE Network Reference Model Figure 1 illustrates that in the network interworking or overlay scenario, the PW and PSN layers assume specific position in the overall hierarchy. W.r.t. to the I.610 model, the PW and PSN layers are a direct insertion between the F3 and F4 OAM layers. < ---------------------------------------> IWE ME < ------ >|< ---------------- >|< ------ > ATM1 ME | | EATM ME | | ATM2 ME | | | | | |-------------- >| | | | LSP1 ME | | | |< --------------| | | | LSP2 ME | | PE PE Figure 2: Network Interworking Reference Model Allan Expires December 2003 Page 3 Overview of Y.17iw Figure 2 illustrates the reference model for the network interworking scenario. The overall e2e ATM connection is uniquely identified (IEW-ME). The component of the ATM connections extending across each attachment circuit (ATM1-ME and ATM2-ME) are uniquely identified. The component of the ATM connection carried by the PW is uniquely identified (EATM-ME). Each PW LSP has a unique direction and is a unique maintenance entity (LSP1/2 ME). 5. Service Interworking Reference Model MPLS/PW ME PE ATM ME ---------------- ------ > |--Payload IW--| F4 or F5 |X X| < ------------- > CE < ------ |---OAM IW-----| ---------------- Figure 3: Service Interworking of a VCC or VPC and a PW/LSP Figure 3 illustrates that the LSP and the ATM VCC/VPC are peer maintenance entities. The extraction of 'native service' at the payload level is a distinct and separate function from the interworking of the maintenance entity defect states. 6. Applicability The procedures for the network interworking scenario outlined in appendix 'A' are applicable to the PWE3 draft [ATM_ENCAP]. The procedures for the service interworking scenario outlined in appendix 'B' are applicable to [SAJASSI]. 7. References [ATM ENCAP] Martini et.al., "Encapsulation Methods for Transport of ATM Cells/Frame Over IP and MPLS Networks", IETF Internet Draft draft-ietf-pwe3-atm-encap-01.txt, February 2003 [I610] ITU-T Recommendation I.610 (1999), "B-ISDN Operation and Maintenance Principles and Functions" [I732] ITU-T Recommendation I.732 (1996), "Functional Characteristics of ATM equipment" [SAJASSI] Sajassi et.al., "L2VPN Interworking", IETF Internet Draft draft-sajassi-l2vpn-interworking-01, March 2003 [Y1711] ITU-T Recommendation Y.1711 (2002), "OAM mechanism for MPLS networks" [Y17IW] ITU-T Draft Recommendation Y.17iw, "OAM functionality for ATM-MPLS interworking", May 2003 Allan Expires December 2003 Page 4 Overview of Y.17iw 8. Author's Address David Allan Nortel Networks Phone: 1-613-763-6362 3500 Carling Ave. Email: dallan@nortelnetworks.com Ottawa, Ontario, CANADA 9. Full Copyright Statement "Copyright (C) The Internet Society (2003). Except as set forth below, authors retain all their rights. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for rights in submissions defined in the IETF Standards Process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/S HE REPRESENTS (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Allan Expires December 2003 Page 5 Overview of Y.17iw Appendix 'A': Procedures for the Network Interworking Scenario OAM interworking is confined to being an interaction of the near end defect handling state machine for the MPLS LSP and the transported ATM VCCs and/or VPCs. The MPLS LSP defect state acts as an input to the ATM layer management function (described in [I732]). An MPLS layer defect acts as a transmission path (TP) failure indicator to the ATM layer management function. Note that the possibility of dTTSI_Mismerge/dTTSI_Misbranch MPLS layer defects means that TP failure can occur without interruption of F4/F5 flows and user traffic at the ATM layer. This is addressed by the transition to AIS state. 1) Upon entry of the LSP-ME near end to a defect state. The egress IWF will instruct the ATM layer management function of each IWE-ME that is a client of the unavailable LSP-ME to enter e- t-e-AIS-generation condition and seg-AIS-generation condition with corresponding suppression of user traffic transiting the EATM-ME. 2) Upon exit of the LSP-ME near end from a defect state. The egress IWF will instruct the ATM layer management function to exit end-to-end and seg AIS generation condition and re-enable transit of IWE traffic across the IWF. 3) ATM LMI Other ATM Layer Management Interface functions are unaffected. Allan Expires December 2003 Page 6 Overview of Y.17iw Appendix 'B': Procedures for the "Service Interworking" Scenario 1) Transition of MPLS near end termination from defect-free to a defect state: The MPLS termination connection point upon transition from defect- free to a defect state as a result of an MPLS layer defect or serving layer defect will direct the ATM termination point to - Enter e-t-e_AIS_cell generation condition - Enter seg-AIS_cell generation condition - Suspend e2e CC cell generation, if enabled - Suspend seg-CC cell generation, if enabled 2) Transition of MPLS near end termination from a defect state to the defect-free state: The MPLS near end termination connection point upon transition from a defect state to the defect-free state as a result of correction of an MPLS layer defect or serving layer defect will direct the ATM termination point to: - release e-t-e-AIS and seg_AIS generation condition, - resume e2e and seg CC cell generation (if activated) - and enable forwarding of user traffic. 3) Transition of MPLS far end termination from defect-free to a defect state: The MPLS far end termination connection point upon transition from the defect-free to a defect state as a result of notification of an MPLS layer defect or serving layer defect will direct the ATM termination point to enter e-t-e_RDI_cell generation condition. 4) Transition of MPLS far end termination from a defect state to the defect free state: The MPLS far end termination connection point upon transition from a defect state to the defect free state as a result of the absence of notification of an MPLS layer defect or serving layer defect will direct the ATM termination point to release e-t-e-RDI generation condition. 5) Entrance of ATM termination into e2e-AIS-state or seg_AIS_state: The ATM termination upon entry into the e2e-AIS-state or seg_AIS_state will direct the MPLS far end termination to initiate FDI generation and to suspend CV generation. A new defect type is required and is for further study. The ATM termination MAY enter the e2e-RDI-generation state. 6) Release of e2e-AIS-state and seg_AIS_state at the ATM termination: Allan Expires December 2003 Page 7 Overview of Y.17iw The ATM termination upon release of both the e2e-AIS-state and seg_AIS_state will direct the MPLS far end termination to cease FDI generation and resume CV generation (if configured to do so). 6) Entrance of ATM termination into e2e-RDI-state or seg_RDI_state: The ATM termination upon entry into either the e2e-RDI-state or seg_RDI_state will direct the MPLS far end termination to initiate BDI generation. 7) Release of e2e-RDI-state and seg_RDI_state: The ATM termination upon release from both the e2e-RDI-state and seg_RDI_state will direct the MPLS far end termination to cease BDI generation. Allan Expires December 2003 Page 8