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MPLS Working Group                                                G. Liu
Internet-Draft                                           ZTE Corporation
Intended status: Informational                              Y. Weigarten
Expires: April 21, 2014
                                                              M. Daikoku
                                                             T. Maruyama
                                                        KDDI Corporation
                                                        October 18, 2013


              MPLS-TP protection for interconnected rings
          draft-liu-mpls-tp-interconnected-ring-protection-05

Abstract

   The requirements for MPLS Transport Profile include a requirement
   (R93) that requires MPLS-TP must support recovery mechanisms for a
   network constructed from interconnected rings that protect user data
   that traverses more than one ring.  In particular, This includes
   protecting against cases of failure at the ring-interconnect nodes
   and links.  This document presents different scenario of
   interconnected rings and special mechanism to address recovery of the
   failure of ring-interconnect nodes and links.  .

   This document is a product of a joint Internet Engineering Task
   Force(IETF) / International Telecommunications Union
   Telecommunications Standardization Sector (ITU-T) effort to include
   an MPLS Transport Profile within the IETF MPLS and PWE3 architectures
   to support the capabilities and functionalities of a packet transport
   network as defined by the ITU-T.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 April 21, 2014.




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Copyright Notice

   Copyright (c) 2013 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may not be modified, and derivative works of it may not
   be created, and it may not be published except as an Internet-Draft.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   6
   3.  Recovery mechanism  . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Recovery mechanism for Dual-node interconnection  . . . .   7
     3.2.  Recovery mechanism for chained interconnection  . . . . .   9
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  URL References  . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   This document describes different interconnected ring scenario and a
   few special mechanisms to protect against the failure of the ring-
   interconnect nodes and links.  There are three common interconnection
   scenarios that we will address in this document:

   Dual-node interconnection - when the two rings are interconnected by
   two nodes from each ring (see Figure 1);

   Single-node interconnection - when the connection between the two
   rings is through a single node (see Figure 2).As the interconnnection
   node(LSR-A) is a single-point of failure, this scenario should be
   avoided in real network;




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   Chained interconnection - when a series of rings are connected
   through interconnection nodes that are part of both interconnected
   rings (see Figure 3)



               /LSR\******/LSR\******/LSR\xxxx/LSR\*****/LSR\******/LSR\
               \_C_/      \_B_/      \_A_/    \_6_/     \_1_/      \_2_/
                 *                     * x   x  *                    *
                 *     Ring #1         *  x x   *        Ring #2     *
                _*_        ___        _*_  x   _*_       ___        _*_
               /LSR\      /LSR\      /LSR\x x /LSR\     /LSR\      /LSR\
               \_D_/******\_E_/******\_F_/xxxx\_5_/*****\_4_/******\_3_/


                             *** physical link
                             xxx interconnection link



               Figure 1: Dual-node interconnection scenario




               ___            ___                 ___           ___
              /LSR\**********/LSR\               /LSR\*********/LSR\
              \_C_/          \_B_/*             *\_1_/         \_2_/
                *                  *           *                 *
                *                   *         *                  *
                *                    *       *                   *
               _*_                    * ___ *                   _*_
              /LSR\    Ring #1         /LSR\       Ring #2     /LSR\
              \_D_/                   *\_A_/*                  \_3_/
                *                    *       *                   *
                *                   *         *                  *
                *                  *           *                 *
               _*_             ___*             *___            _*_
              /LSR\           /LSR\             /LSR\          /LSR\
              \_E_/***********\_F_/             \_5_/**********\_4_/


                                  *** physical link



              Figure 2: Single-node interconnection scenario




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                ___        ___        ___       ___        ___
               /LSR\******/LSR\******/LSR\*****/LSR\******/LSR\
               \_C_/      \_B_/      \_A_/     \_1_/      \_2_/
                 *                     x                    *
                 *     Ring #1         x       Ring #2      *
                _*_        ___        _x_       ___        _*_
               /LSR\      /LSR\      /LSR\     /LSR\      /LSR\
               \_D_/******\_E_/******\_F_/*****\_4_/******\_3_/


                             *** physical link
                             xxx interconnection link



                 Figure 3: chained interconnected scenario

   Considering a traffic that traveres more than two rings.  Many
   interconnection scenarios could be existed in the same scenario, They
   will be mixed interconnection scenario;

   Dual-node and single-node mixed interconnection- when there exists a
   multi-ring traffic which traveres more than two rings. two of these
   rings are dual-node interconnection. while another two are single-
   node interconnection (see figure 5);

   Dual-node and chained mixed interconnection-when there exist both
   dual-node interconnection and chained interconnection in this
   scenario (see figure 4);

   single-node and chained mixed interconnection-when there exist both
   single-node interconnection and chained interconnection in this
   scenario(see figure 6);

   Dual-node, single-node and chained mixed interconnection-when there
   exist all three interconnection scenrios in this scenario including
   Dual-node interconnnection, single-node interconnection and chained
   interconnnection( see figure 7);









                                                                       ___



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               /LSR\******/LSR\xx/LSR\****/LSR\     /LSR\**** /LSR\***/LSR\
               \_C_/      \_B_/  \_A_/    \_6_/     \_1_/     \_2_/   \_H_/
                 *          * x x  *         *       *          x       *
                               x                     *          x       *
                 * Ring  1  * x x  * Ring 2  *  .....*Ring  3   x Ring 4*
                _*_         *x  x_*_       _*_      ___        ___    ___
               /LSR\      /LSR\  /LSR\     /LSR\     /LSR\*****/LSR\**/LSR\
               \_D_/******\_E_/xx\_5_/*****\_4_/    \_k_/      \_L_/  \_M_/


                             *** physical link
                             xxx interconnection link



        Figure 4: Dual-node and chained mixed interconnect scenario



                                                                       ___
               /LSR\******/LSR\xx/LSR\****/LSR\     /LSR\             /LSR\
               \_C_/      \_B_/  \_A_/    \_6_/     \_1_/            *\_H_/
                 *          * x x  *         *       *   *         *    *
                               x                     *    *  ___ *      *
                 * Ring  1  * x x  * Ring 2  *  .....*Ring 3/LSR\ Ring 4*
                _*_         *x  x_*_        _*_      ___  * \_L_/*     ___
               /LSR\      /LSR\  /LSR\     /LSR\    /LSR\*          * /LSR\
               \_D_/******\_E_/xx\_5_/*****\_4_/    \_k_/             \_M_/


                             *** physical link
                             xxx interconnection link



      Figure 5: Dual-node and single-node mixed interconnect scenario



                                                                       ___
               /LSR\******/LSR\**/LSR\****/LSR\     /LSR\             /LSR\
               \_C_/      \_B_/  \_A_/    \_6_/     \_1_/            *\_H_/
                 *                 x         *       *   *         *    *
                                                     *    *  ___ *      *
                 * Ring  1         x Ring 2  *  .....*Ring 3/LSR\ Ring 4*
                _*_          _    _x_       _*_      ___  * \_L_/*     ___
               /LSR\      /LSR\  /LSR\     /LSR\    /LSR\*          * /LSR\
               \_D_/******\_E_/**\_5_/*****\_4_/    \_k_/            *\_M_/



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                             *** physical link
                             xxx interconnection link



       Figure 6: Chained and single-node mixed interconnect scenario



                                                                       ___
               /LSR\******/LSR\xx/LSR\****/LSR\**** /LSR\             /LSR\
               \_C_/      \_B_/  \_A_/    \_6_/     \_1_/            *\_H_/
                 *          * x x  *         x       x   *         *    *
                               x                     x    *  ___ *      *
                 * Ring  1  * x  x * Ring 2  xRing 5 xRing 3/LSR\ Ring 4*
                _*_         *x   x_*_       _x_      ___  * \_L_/*     ___
               /LSR\      /LSR\  /LSR\     /LSR\****/LSR\*          * /LSR\
               \_D_/******\_E_/xx\_5_/*****\_4_/    \_k_/            *\_M_/


                             *** physical link
                             xxx interconnection link



      Figure 7: Dual-node,chained and single-node mixed interconnect
                                 scenario

   For a multi-ring traffic, It will be across more than one ring just
   like above seven scenarios.  If a failure happens on a multi-ring
   path, quick recovery is necessary requirement for multi-ring traffic.

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 RFC-2119.

   OAM: Operations, Administration, Maintenance

   LSP: Label Switched Path.

   TLV: Type Length Value

   PSC:Protection Switching Coordination

   SD:Signal Degrade




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   SF:Signal Fail

   MPLS-TP:Multi-Protocol Label Switching Transport Profile

3.  Recovery mechanism

   In the following subsection, It proposes different mechanism that may
   be applied for traffic recovery for different interconnection
   scenario.  In general, It may be possible to provide protection
   against the failure of a ring node/link by using a single-ring
   protection mechanism.  These cases are out of scope for this
   document.At the same time, It is also possible to configure an end-
   to-end protection path to protect a multi-ring traffic which will
   across multi-ring.  While this protection mechanism does not scale
   very well.  We need to consider special mechanism to address recovery
   from failures of the interconnecting nodes and links

3.1.  Recovery mechanism for Dual-node interconnection

   Under this scenario , When interconnection link(LSRA-LSR6) has a
   failure as shown in figure 8. it is possible use 1:1 linear
   protection mechanism to protect the failure of segment(LSRA-LSR6) by
   using one of the protection tunnels (LSRA-LSRF-LSR5-LSR6 or LSRA-
   LSRF-LSR6 or LSRA-LSR5-LSR6) .



               /LSR\******/LSR\******/LSR\x||x/LSR\*****/LSR\******/LSR\
               \_C_/      \_B_/      \_A_/    \_6_/     \_1_/      \_2_/
                 *                     * x   x  *                    *
                 *     Ring #1         *  x x   *        Ring #2     *
                _*_        ___        _*_  x   _*_       ___        _*_
               /LSR\      /LSR\      /LSR\x x /LSR\     /LSR\      /LSR\
               \_D_/******\_E_/******\_F_/xxxx\_5_/*****\_4_/******\_3_/


                             *** physical link
                             xxx interconnection link
                             || failure



   Figure 8: interconnection link failure for dual-node interconnection

   When the interconnection node(LSRA or LSR6) detects a SF or SD on the
   interconnection link(LSRA-LSR6), LSRA or LSR6 will send SF or SD
   failure message to its peer node.  Then they push the multi-ring
   traffic into its corresponding protection tunnel to another end



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   point(LSRA or LSR6) of the segment . When the peer node (LSR6 or
   LSRA) receives the traffic packet from its protection tunnel, it will
   POP the outer label of protection tunnel and return back to the
   original working tunnel(LSRA-LSRB-LSRC or LSR6-LSR1-LSR2) of another
   ring(ring 1 or ring 2) to transport the multi-ring traffic.

   When the interconnection node(LSRA or LSR6) has a failure as shown in
   figure 9.  The end node of the segment detects the failure of the
   interconnection node, It should send failure messge to the backup
   interconnection node(LSRF or LSR5) to active its corresponding
   protection path that goes to the backup interconnection node(LSRF or
   LSR5) to trasnport the multi-ring traffic.  At the same time, the
   backup interconnection node should active its corresponding
   protection path that goes to another primary interconnection
   node(LSR6 or LSRA) of another ring.Then the multi-ring traffic should
   return back to the original working path to be transported in another
   ring.



                                      ##
               /LSR\******/LSR\******/LSR\xxxx/LSR\*****/LSR\******/LSR\
               \_C_/      \_B_/      \_A_/    \_6_/     \_1_/      \_2_/
                 *                     * x   x  *                    *
                 *     Ring #1         *  x x   *        Ring #2     *
                _*_        ___        _*_  x   _*_       ___        _*_
               /LSR\      /LSR\      /LSR\x x /LSR\     /LSR\      /LSR\
               \_D_/******\_E_/******\_F_/xxxx\_5_/*****\_4_/******\_3_/


                             *** physical link
                             xxx interconnection link
                             ## node failure


   Figure 9: interconnection node failure for dual-node interconnection

   For example , When LSRC directly detects or is informed of a failure
   on the interconnection node LSRA. it will send a failure message to
   notify the backup interconnection node LSRF to active its protection
   path(LSRC-LSRD-LSRE-LSRF) to transport the multi-ring traffic.At the
   same time, When LSRF receives the failure message from LSRC ,it
   should still active its corresponding protection path that goes to
   another primary interconnection node LSR6 to transport the multi-ring
   traffic.The corresponding protection path may be one of the two paths
   (LSRF-LSR5-LSR6 or LSRF-LSR6).  Then the multi-ring traffic will be
   transported by its original working path(LSR6-LSR1-LSR2) to another
   peer node LSR2.



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3.2.  Recovery mechanism for chained interconnection

   For this scenario , When only a failure is detected on the
   interconnection link by interconnection node. since the failure
   should not affect the multi-ring traffic. no action is need to be
   taken.  When a failure happens on the segment of the multi-ring path
   and the interconnection link at the same time ,just as shown in
   figure 10.  The end node of the multi-ring path directly detects or
   is informed of the two failures, Then it will active the protection
   path that goes to the backup interconnection node to transport the
   multi-ring traffic.  After the backup interconnection node receives
   the failure message , it will active its corresponding protection
   path that goes to the end node of another ring





                ___        ___        ___       ___        ___
               /LSR\**||**/LSR\******/LSR\*****/LSR\******/LSR\
               \_C_/      \_B_/      \_A_/     \_1_/      \_2_/
                 *                     x                    *
                 *     Ring #1        ||       Ring #2      *
                _*_        ___        _x_       ___        _*_
               /LSR\      /LSR\      /LSR\     /LSR\      /LSR\
               \_D_/******\_E_/******\_F_/*****\_4_/******\_3_/


                             *** physical link
                             xxx interconnection link
                             || failure



    Figure 10: interconnection link failure for chained interconnected
                                 scenario

   For example, there are a failure on both link(LSRC-LSRB) and (LSRA-
   LSRF) at the same time as shown in figure.10.  When LSRC detects or
   is notified of the segment failure on both the segment of ring 1 and
   the interconnection link.  It will send a failure message to the
   backup interconnection node LSRF, Then LSRF will active its
   corresponding protection path(LSRF-LSR4-LSR3-LSR2) of ring 2 to
   transport the multi-ring traffic.







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   When a interconnection node has a failure for the chained
   interconnection scenario, both peer node of the two rings will detect
   the failure by segment OAM.  So they should switch into the multi-
   ring protection path to transport the multi-ring traffic.





                ___        ___        _##_      ___        ___
               /LSR\******/LSR\******/LSR\*****/LSR\******/LSR\
               \_C_/      \_B_/      \_A_/     \_1_/      \_2_/
                 *                     x                    *
                 *     Ring #1         x       Ring #2      *
                _*_        ___        _x_       ___        _*_
               /LSR\      /LSR\      /LSR\     /LSR\      /LSR\
               \_D_/******\_E_/******\_F_/*****\_4_/******\_3_/


                             *** physical link
                             xxx interconnection link
                             ##  node failure



    Figure 11: interconnection node failure for chained interconnected
                                 scenario

   Just as the failure scenario in figure 11.  When an interconnection
   node LSRA has a failure, the peer node(LSRC and LSR2) of ring 1 and
   ring 2 must detect the node failure by segment OAM , Then they will
   active protection switch and transport the protected multi-ring
   traffic by its corresponding protection path(LSRC-LSRD-LSRE-LSRF-
   LSR4-LSR3-LSR2) to LSR2.  Then the protected traffic will return back
   to the original working path to be transported.

4.  Security Considerations

   TBD

5.  IANA Considerations

   TBD.

6.  Acknowledgments

   TBD .




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7.  References

7.1.  Normative References

   [RFC5654]  IETF, "MPLS-TP requirement ", September 2009.

   [RFC5921]  IETF, "MPLS-TP framework ", July 2010.

   [RFC6372]  N. Sprecher, A. Farrel, ., "Multiprotocol Label Switching
              Transport Profile Survivability Framework", September
              2011.

   [RFC6378]  S. Bryant, N. Sprecher, A. Fulignoli Y. Weingarten, .,
              "MPLS transport profile Linear Protection", September
              2011.

   [RFC6974]  Y. Weingarten,S. Bryant,D. Ceccarelli, ., "Applicability
              of MPLS Transport Profile for Ring Topologies", July 2013.

7.2.  URL References

   [MPLS-TP-22]
              IETF - ITU-T Joint Working Team, 2008,
              <http://www.example.com/dominator.html>.

Authors' Addresses

   Guoman Liu
   ZTE Corporation
   No.50, Ruanjian Ave, Yuhuatai District
   Nanjing  210012
   P.R.China

   Phone: +86 025 88014227
   Email: liu.guoman@zte.com.cn


   Yaacov Weingarten
   34 Hagefen St Karnei
   Shomron  44853
   Israel

   Phone: +972-9-775 1827
   Email: wyaacov@gmail.com







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   Masahiro Daikoku
   KDDI Corporation
   Garden Air Tower,Iidabashi, Chiyoda-ku
   Tokyo  102-8460
   Japan

   Email: ms-daikoku@kddi.com


   Takeshi Maruyama
   KDDI Corporation
   Garden Air Tower,Iidabashi, Chiyoda-ku
   Tokyo  102-8460
   Japan

   Email: ta-maruyama@kddi.com



































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