[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: 00 01 02 03 04 draft-ietf-mpls-mldp-node-protection

Network Working Group                                  IJ. Wijnands, Ed.
Internet-Draft                                                  E. Rosen
Intended status: Standards Track                                 K. Raza
Expires: December 25, 2013                           Cisco Systems, Inc.
                                                             J. Tantsura
                                                                Ericsson
                                                                A. Atlas
                                                        Juniper Networks
                                                              Q. Quintin
                                                       Huawei Technology
                                                           June 23, 2013


                          mLDP Node Protection
              draft-wijnands-mpls-mldp-node-protection-04

Abstract

   This document describes procedures to support node protection for
   Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths
   (MP LSPs) built by LDP ("Label Distribution Protocol"), or simply
   mLDP.  In order to protect a node N, the Point of Local Repair (PLR)
   LSR of N must learn the Merge Point (MPT) LSR(s) of node N such that
   traffic can be redirected to them in case node N fails.  Redirecting
   the traffic around the failed node N depends on existing P2P LSPs
   originated from the PLR LSR to the MPT LSRs while bypassing LSR node
   N.

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 http://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 December 25, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the



Wijnands, et al.        Expires December 25, 2013               [Page 1]


Internet-Draft            mLDP Node Protection                 June 2013


   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
   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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions used in this document  . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  PLR Determination  . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Transit node procedure . . . . . . . . . . . . . . . . . .  4
     2.2.  MP2MP root node procedure  . . . . . . . . . . . . . . . .  5
     2.3.  PLR information encoding . . . . . . . . . . . . . . . . .  5
   3.  Using the tLDP session . . . . . . . . . . . . . . . . . . . .  7
   4.  Link or node failure . . . . . . . . . . . . . . . . . . . . .  9
     4.1.  Re-convergence after node/link failure . . . . . . . . . . 10
       4.1.1.  Node failure . . . . . . . . . . . . . . . . . . . . . 10
       4.1.2.  Link failure . . . . . . . . . . . . . . . . . . . . . 10
       4.1.3.  Switching to new primary path  . . . . . . . . . . . . 11
   5.  mLDP Capabilities for Node Protection  . . . . . . . . . . . . 11
     5.1.  PLR capability . . . . . . . . . . . . . . . . . . . . . . 12
     5.2.  MPT capability . . . . . . . . . . . . . . . . . . . . . . 12
     5.3.  The Protected LSR  . . . . . . . . . . . . . . . . . . . . 12
     5.4.  The Node Protection Capability . . . . . . . . . . . . . . 13
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   7.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 14
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15











Wijnands, et al.        Expires December 25, 2013               [Page 2]


Internet-Draft            mLDP Node Protection                 June 2013


1.  Introduction

   This document describes procedures to support node protection for
   Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths
   (MP-LSPs) built by LDP ("Label Distribution Protocol"), or simply
   mLDP.  In order to protect a node N, the Point of Local Repair (PLR)
   of N must learn the Merge Point (MPT) LSR(s) of node N such that
   traffic can be redirected to them in case node N fails.  Redirecting
   the traffic around the failed node N depends on existing P2P LSPs
   originating from the PLR LSR to the MPT LSR(s) while bypassing node
   N. The procedures to setup these P2P LSPs are outside the scope of
   this document, but one can imagine using RSVP-TE or LDP LFA based
   techniques to accomplish this.

   The solution described in this document signals the MPT LSR(s) to the
   PLR LSR(s) via a Targeted LDP (tLDP) session [RFC5036].  By having a
   tLDP session with the PLR, most of the (m)LDP features currently
   defined should just work, like Make-Before-Break (MBB), Graceful
   Restart (GR), Typed Wildcard FEC support, etc.  All this is achieved
   at the expense of having an additional tLDP session between an MPT
   and PLR LSR.

1.1.  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 [RFC2119].

   The terms "node" is used to refer to an LSR and used interchangeably.
   The terms "PLR" and "MPT" are used as shorthand to refer to "PLR LSR"
   and "MPT LSR" respectively.

1.2.  Terminology

   mLDP:  Multipoint extensions to LDP.

   PLR:  Point of Local Repair (the LSR that redirects the traffic to
      one or more Merge Point LSRs).

   MPT:  Merge Point (the LSR that merges the backup LSP with primary
      LSP.  Note, there can be multiple MPT LSRs for a single MP-LSP
      node protection).

   tLDP:  Targeted LDP session.







Wijnands, et al.        Expires December 25, 2013               [Page 3]


Internet-Draft            mLDP Node Protection                 June 2013


   MP LSP:  Multi-Point LSP (either a P2MP or MP2MP LSP).


2.  PLR Determination

   In order for a MPT to establish a tLDP session with the PLR, it first
   has to learn the PLR for a particular MP LSP.  It is the
   responsibility of the protected node N to advertise the PLR address
   to the MPT.  The PLR address for a MP LSP on node N is the address of
   the upstream LDP peer, but only when node N is NOT the root node of
   the MP2MP LSP.  If node N is the root node, the procedures are
   slightly different as described in Section 2.2.  The procedures that
   follow assume that all the participating nodes (N, PLRs, MPTs) are
   enabled (e.g. by a user configuration) to support and implement this
   feature.

2.1.  Transit node procedure

   Below we are describing the procedures when the protected node is a
   transit node along the path to the root.

            root
             ^
             |
           (LSR1)
          .  |  .
         .   |   .
        .   (N)   .
        .   /  \  .
         . /    \.
       (LSR2)  (LSR3)
          |      |
                      Figure 1.

   N: The node being protected,
   ...: Backup LSPs from LSR1 to the LSR2 and LSR3.


   Node N uses the root address of the MP LSP to determine the upstream
   LSR for a given MP LSP following the procedures as documented in
   [RFC6388] section 2.4.1.1.  The upstream LSR in figure 1 is LSR1
   because it is the first hop along the shortest path to reach the root
   address.  After determining the upstream LSR, node N (which is
   feature enabled), MUST advertise the address of LSR1 as the PLR
   address to the downstream members of the MP LSP (i.e.  LSR2 and LSR3)
   if the given downstream member has announced support for node
   protection (see Section 5) for Capability negotiation).  For the
   format and encoding of PLR address information, see Section 2.3.



Wijnands, et al.        Expires December 25, 2013               [Page 4]


Internet-Draft            mLDP Node Protection                 June 2013


2.2.  MP2MP root node procedure

   In this section we are describing the procedures for when the
   protected node is the root of a MP2MP LSP.  Consider figure 2 below;

             |
           (LSR1)
          .  |  .
         .   |   .
        .   (N)   . root
        .   /  \  .
         . /    \.
      (LSR2)....(LSR3)
         |        |
                      Figure 2.

   N: The MP2MP root node being protected.
   ...: Backup LSPs between LSR1, LSR2 and LSR3.

   Assume that LSR1, LSR2 and LSR3 are all members of a MP2MP LSP for
   which N is the root node.  Since N is the root of the MP2MP LSP,
   there is no upstream LSR and no 'single' PLR LSR for protecting node
   N. In order to protect node N, all the directly connected members of
   the MP2MP must participate in protecting node N by acting both as PLR
   and MPT LSR.  An LSR will act as MPT for traffic coming from the
   other LSR(s) and it will act as PLR for traffic it is sending to the
   other LSR(s).  Since node N knows the members of the MP2MP LSP, it
   will advertise the member list to its directly connected members,
   excluding the member it is sending to.  For example, node N will
   advertise {LSR3,LSR1} list to LSR2 excluding LSR2 from it.  Instead
   of advertising a single PLR when node N is not the root, a list of
   PLRs is advertised using the procedures documented in Section 2.3.

   It should be noted that the MP2MP root node protection mechanism
   don't replace the Root Node Redundancy (RNR) procedures as described
   in [RFC6388] section 7.  The node protection procedures in this draft
   will help restoring traffic for the existing MP2MP LSPs after node
   failure, but a new root node has to be elected eventually in order to
   allow new MP2MP LSPs to be created.

2.3.  PLR information encoding

   The upstream LSR address is conveyed via an LDP Notification message
   with MP Status, where the MP status contains a new "PLR Status Value
   Element" that specifies the address of the PLR.

   The new "PLR Status Value Element" is encoded as follows;




Wijnands, et al.        Expires December 25, 2013               [Page 5]


Internet-Draft            mLDP Node Protection                 June 2013


   PLR Status Element:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type =  TBA-1 |           Length              |  Addr Family  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Addr Fam cont | Num PLR entry |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   |                         PLR entry (0 or more)                 ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where

      Type: PLR Status Value Element (Type TBA-1 to be assigned by IANA)

      Length: The Length field encodes the length of the Status Value
      following the Length field.  The encoded Length varies based on
      the Address Family and the number of PLR entries.

      Address Family: Two octet quantity containing a value from IANA's
      "Address Family Numbers" registry that encodes the address family
      for the PLR Address encoded in the PLR entry.

      Num PLR entry: Number of "PLR entries" encoded in the Status Value
      Element, followed by "Num PLR entry" field (please see format of a
      PLR entry below).


   The format of a "PLR Entry" is as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|        Reserved             |       PLR address             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                  PLR address (cont)                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where

      A bit: 0 = Withdraw, 1 = Add.

      Reserved: 15 bits, must be zero on transmit and ignored on receipt





Wijnands, et al.        Expires December 25, 2013               [Page 6]


Internet-Draft            mLDP Node Protection                 June 2013


      PLR address: PLR Address encoded according to Address Family field
      encoded in the PLR Status Value Element.

   The size of a "PLR Entry" is the 2 octets ("A bit + Reserved") + PLR
   address length.  The length of the PLR address is depending on the
   Address Family as encoded in the PLR Status Value Element.  The size
   of a "PLR entry" is 6 octets and 18 octets respectively for an IPv4
   PLR address and an IPv6 PLR address.

   If the PLR address on N changes for a given MP LSP, N needs to
   trigger a new PLR Status to update the MPT(s).  A node N can
   advertise or withdraw a given PLR from its PLR set by setting "A bit"
   to 1 or 0 respectively in corresponding PLR entry.  Removing a PLR
   address is likely due to a link failure, see the procedures as
   documented in Section 4.1.  To remove all PLR addresses belonging to
   the encoded Address Family, an LSR N MUST encode PLR Status Value
   Element with no PLR entry and "Num PLR entry" field MUST be set to
   zero.

   Along with the PLR MP Status a MP FEC TLV MUST be included in the LDP
   Notification message so that a receiver is able to associate the PLR
   Status with the MP LSP.


3.  Using the tLDP session

   The receipt of a PLR MP Status (with PLR addresses) for a MP LSP on a
   receiving LSR makes it an MPT for node protection.  If not already
   established, the MPT LSR MUST establish a tLDP session with all of
   the learned PLR addresses using the procedures as documented in
   [I-D.ietf-mpls-targeted-mldp].

   Using Figure 1 as the reference topology, let us assume that both
   LSR2 and LSR3 are MPTs and have established a tLDP session with the
   PLR being LSR1.  Assume that both LSR2 and LSR3 have a FEC <R,X> with
   a upstream LSR N and label Ln assigned to FEC towards N. The MPTs
   will create a secondary upstream LSR (using the received PLR address)
   and assigned a Label Lpx to FEC <R,X> towards PLR for it.  The MPTs
   will do that for each PLR address that was learned for the MP LSP.
   In this example, the MPTs will have a FEC <R,X> with two local labels
   associated with it.  Ln that was assigned to N via the normal mLDP
   procedures, and Label Lpx that was assigned for PLR (LSR1) for the
   purpose of node protecting MP LSP via node N. Note, when the
   protected node is a MP2MP root node, there will be an upstream LSR
   for each PLR address that was advertised along with a unique Label
   Lpx.

   The receipt of a FEC Label Mapping alone over the tLDP session from



Wijnands, et al.        Expires December 25, 2013               [Page 7]


Internet-Draft            mLDP Node Protection                 June 2013


   MPT on a PLR conveys the label information but does not convey the
   node being protected.  The information about a protected node is
   known to the MPT LSR and needs to be communicated to the PLR as well.
   For this reason, the FEC Label Mapping (FEC <R,X> : Lpx) sent by the
   MPT over the tLDP session to the PLR MUST include a Status TLV with
   MP Status including a new LDP MP status Value Element called the
   "Protected Node Status Value Element".  This new value element is
   used to specify the address of the node being protected.  The
   "Protected Node Status Value Element" has the following format;


     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Type = TBA-2  |           Length              | Addr  Family  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Addr Fam cont |        Node address                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Node address continued                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type : Protected Node Status Value Element (Type TBA-2 to be
      assigned by IANA)

      Length: The Length field encodes the length of the Status Value
      following the Length field.  The encoded Length varies based on
      the Address Family and is 6 octets (for Address Family + IPv4
      address and 18 octets for Address Family + IPv6 address.

      Address Family: Two octet quantity containing a value from IANA's
      "Address Family Numbers" registry that encodes the address family
      for the Node Address.

      Node address: Protected node address encoded according to Address
      Family field.

   When a PLR receives a Label Mapping for FEC <R,X> that includes a
   Protected Node Status, it will only use that label binding once the
   Node advertised in the Status value becomes unreachable.  If the LSP
   is a MP2MP LSP, the PLR would have assigned a Label Mapping for the
   upstream MP2MP FEC Element to the MPT ([RFC6388] section 3) for FEC
   <R,X>.  This label binding on the MPT MUST only be used once node N
   becomes unreachable.

   The procedures to determine if a node is unreachable is a local
   decision and not spelled out in this draft.  Typical link failure or
   Bidirectional Forwarding Detection (BFD) can be used to determine and
   detect node unreachability.



Wijnands, et al.        Expires December 25, 2013               [Page 8]


Internet-Draft            mLDP Node Protection                 June 2013


4.  Link or node failure

   Consider the following topology;


               root
                ^
                |
            . (LSR1)
          .   / |  .
         .  (M) |   .
         .    \ |    .
          .    (N)   .
           .   /  \  .
            . /    \.
          (LSR2)  (LSR3)
             |      |
                        Figure 3.

   N: The node being protected
   M: The backup node to protect link LSR1 - N
   ...; Backup LSPs from LSR1 to LSR2 and LSR3.


   Assume that LSR1 is the PLR for protected node N, LSR2 and LSR3 are
   MPTs for node N. When LSR1 discovered that node N is unreachable, it
   can't determine whether it is the 'LSR1 - N' link or node N that
   failed.  In Figure 3, the link between LSR1 and N is also protected
   using Fast ReRoute (FRR) [RFC4090] link protection via node M. LSR1
   MAY potentially invoke 2 protection mechanisms at the same time,
   redirection the traffic due to link protection via node M to N, and
   for node protection directly to LSR1 and LSR2.  If only the link
   failed, LSR2 and LSR3 will receive the packets twice due to the two
   protection mechanisms.  To prevent duplicate packets to be forwarded
   to the receivers on the tree, LSR2 and LSR3 need to determin which
   upstream node to accept the packets from.  So, either from the
   primary upstream LSR N or from the secondary upstream LSR1, but never
   both at the same time.  The selection between the primary upstream
   LSR or (one or more) secondary upstream LSRs (on LSR2 and LSR3) is
   based on the reachability of the protected node N. As long as N is
   reachable, N is the primary upstream LSR who is accepting the MPLS
   packets and forwarding them.  Once N becomes unreachable, the
   secondary upstream LSRs (LSR1 in our example) are activated.  Note
   that detecting if N is unreachable is a local decision and not
   spelled out in this draft.  Typical link failure or Bidirectional
   Forwarding Detection (BFD) can be used to determine and detect node
   unreachability.




Wijnands, et al.        Expires December 25, 2013               [Page 9]


Internet-Draft            mLDP Node Protection                 June 2013


4.1.  Re-convergence after node/link failure

   Consider the following topology;

               root
                ^
             _  |
           /. (LSR1)
         /.   /. |  .\
        /.  (M). |   .\
      (P).    \. |    .\
        \.     ( N )   .(Q)
         \.   /     \   ./
          \. /       \ ./
         (LSR2)     (LSR3)
            |          |
                        Figure 4.

   N: The node being protected.
   M: The backup node to protect link 'LSR1 - N'.
   P and Q: The nodes on the new primary path after N failure.
   ...: P2P backup LSPs.

   Assume that LSR1 has detected that Node N is unreachable and invoked
   both the Link Protection and Node Protection procedures as described
   in this draft.  LSR1 is acting as PLR and sending traffic over both
   the backup P2P LSP to node N (via M) and the P2P LSPs directly to
   LSR2 and LSR3, acting as MPT LSRs.  The sequence of events are
   depending on whether the link 'LSR1 - N' has failed or node N itself.
   The node's downsteam from the protected node (and participating in
   node protection) MUST have the capability to determin that the
   protected node became unreachable.  Otherwise the procedures below
   can not be applied.

4.1.1.  Node failure

   If node N failed, both LSR2 and LSR3 will have changed the primary
   upstream LSR to the secondary upstream LSR (LSR1) due to node N being
   unreachable.  With that, the label bindings previously assigned to
   LSR1 will be activated on the MPTs (LSR2 and LSR3) and the label
   binding to N will be disabled.  Traffic is now switched over the
   label bindings that where installed for node protection.

4.1.2.  Link failure

   If the link 'LSR1 - N' has failed, both LSR2 and LSR3 will not change
   the primary upstream LSR because node N is still reachable.  LSR2 and
   LSR3 will receive traffic over two different bindings, the primary



Wijnands, et al.        Expires December 25, 2013              [Page 10]


Internet-Draft            mLDP Node Protection                 June 2013


   label binding assigned to node N (due to link protection via node M)
   as well as over the binding assigned to LSR1 for the node protection.
   Since the secondary upstream LSRs have not been activated, the
   traffic received due to node protection will be dropped.  Node N will
   re-converge and update LSR2 and LSR3 (Section 2.3) with the
   information that the PLR address (LSR1) is no longer applicable and
   must be removed.  In response, LSR2 and LSR3 MUST sent a Label
   Withdraw to LSR1 to withdraw the label binding.  This will stop the
   traffic being forwarded over the backup P2P LSPs for node protection.
   LSR1 will respond back with a Label Release as soon as the binding
   has been removed.

4.1.3.  Switching to new primary path

   The network will eventually re-converge and a new best path to the
   root will be found by LSR2 and LSR3.  LSR2 will find that P is its
   new primary upstream LSR to reach the Root and LSR3 will find Q. Note
   that although the current active upstream LSR can either be node N or
   LSR1 (depending on link or node failure), it does not matter for the
   following procedures.  Both LSR2 and LSR3 SHOULD use the Make-Before-
   Break (MBB) procedures as described in [RFC6388] section 8 to switch
   to the new primary upstream node.  As soon as the new primary
   upstream LSRs P and Q are activated, a Label Withdraw message MUST be
   sent to the old upstream LSR.  Note that an upstream LSR switchover
   from a tLDP neighbor to a directly connected LDP neighbor is no
   different compared to switching between two directly connected
   neighbors.  After the Label Withdraw message has been received by
   LSR1 or node N, forwarding will stop and a Label Release will be
   sent.

   When it is determined that after re-convergence there is no more
   interest in the tLDP session between the MPT and the PLR, the tLDP
   session MAY be taken down.  It is possible that having no more
   interest in the tLDP session is temporarily due to link flapping.  In
   order to avoid the tLDP session from flapping, it is RECOMMENDED to
   apply a delay before tearing down the session.  Determining the delay
   is a local implementation matter.


5.  mLDP Capabilities for Node Protection

   In order to describe the capabilities of the participating LSRs , we
   are organizing it per role in the network i.e., Point of Local Repair
   (PLR), Merge Point (MPT), and Protected Node (as depicted in Fig 1).







Wijnands, et al.        Expires December 25, 2013              [Page 11]


Internet-Draft            mLDP Node Protection                 June 2013


5.1.  PLR capability

   A PLR node should handle the following conditions;

   1.  Accept an incoming tLDP session from the MPT LSR.

   2.  Support the receipt of a "Protected Node Status Value Element"
       status in a MP Status TLV over tLDP session.

   3.  Upon node failure detection, capable of switching traffic towards
       one or more MPT(s) over P2P LSP (bypassing N) using the labels
       previously advertised for MP LSPs over the tLDP session.

   An LSR capable of performing these actions will advertise it self as
   PLR capable in the Node Protection capability (see Section 5.4).
   This is a unidirectional capability announced from PLR to the
   protected LSR.

5.2.  MPT capability

   An MPT node should handle the following conditions;

   1.  Support the receipt of "PLR Status Value Element" in a MP Status
       TLV from a protected node N.

   2.  Support to transmit "Protected Node Status Value Element" in a MP
       Status TLV to a PLR.

   A LSR capable of performing these actions will advertise itself as
   the MPT capable in the Node Protection capability (see Section 5.4).
   This is a unidirectional capability from MPT to the protected LSR.

5.3.  The Protected LSR

   A protected node should handle the following conditions;

   1.  Determine the PLR and MPT capability for directly connected
       upstream and downstream LSRs for a given MP FEC.

   2.  Support transmitting of "PLR Status Value Element" in a MP Status
       TLV to one or more downstream MPT LSRs.

   The protected LSR does not advertise any capability for mLDP Node
   Protection because it does not need to receive any of the defined MP
   Status values as described above.  However, the protected node does
   play an important role in the signaling and setup of the node
   protection.  For a given FEC, the protected node can only send PLR
   information to a downstream LSR if the PLR has signaled the PLR



Wijnands, et al.        Expires December 25, 2013              [Page 12]


Internet-Draft            mLDP Node Protection                 June 2013


   capability and the downstream LSR has signaled the MPT capability.
   When the downstream LSR (acting as MPT) receives the PLR status, it
   can implicitly infer that the advertised LSR(s) are PLR capable.  The
   MPT LSR can now proceed with setting up a tLDP session with the
   PLR(s) and MP LSP node protection signaling.

5.4.  The Node Protection Capability

   We define a single capability "MP Node Protection Capability" to
   announce the PLR and MPT capability.

   The format of the capability parameter TLV is as follows:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F| Type = TBA-3              |           Length = 2          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S| Reserved    |P|M| Reserved  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Where

      U/F bits: MUST be set to 1 and 0 respectively (as per [RFC5561])

      Type: MP Node Protection Capability (Type = TBA-3 to be assigned
      by IANA)

      Length: MUST be set to 2.

      S bit: Set to 1 to announce and 0 to withdraw the capability (as
      per [RFC5561])

      P bit: PLR capable for MP LSP node protection

      M bit: MPT capable for MP LSP node protection

      Reserved: Must be zero on transmit and ignored on receipt

   The above capability can be sent in an LDP Initialization message to
   announce capability at the session establishment time, or it can be
   sent in LDP Capability message to dynamically update (announce or
   withdraw) its capability towards its peer using procedures specified
   in [RFC5561].

   An LSR that supports the PLR functionality LSR MAY send this
   capability to its downstream MP peers with "P" bit set; whereas, an



Wijnands, et al.        Expires December 25, 2013              [Page 13]


Internet-Draft            mLDP Node Protection                 June 2013


   LSR that supports an the MPT functionality MAY send this capability
   to its upstream peer with "M" bit set.  Moreover, an LSR that
   supports both the PLR and MPT functionality MAY sent this capability
   to its peers with both "P" and "M" bit set.


6.  Security Considerations

   The same security considerations apply as those for the base mLDP
   specification, as described in [RFC6388].


7.  IANA considerations

   IANA is requested to allocate two new code points from the "LDP MP
   Status Value Element type" registry within the Label Distribution
   Protocol (LDP) Parameters;

      Value | Name                                   | Reference
      ------+----------------------------------------+-----------
      TBA-1 | PLR Status Value Element               | this doc
      ------+----------------------------------------+-----------
      TBA-2 | Protected Node Status Value Element    | this doc

   IANA is requested to assign a new code points for a new Capability
   Parameter TLV.  The code point should be assigned from the IETF
   Consensus range of the "TLV Type Name Space" registry within the LDP
   Parameters.  The lowest available new code point after 0x0970 should
   be used.

      Value | Description                   | Reference | Notes/Reg Date
      ------+-------------------------------+-----------+---------------
      TBA-3 | MP Node Protection Capability | This doc  |


8.  Acknowledgments

   The authors like to thank Nagendra Kumar, Duan Hong, Martin
   Vigoureux, Kenji Fujihira and Loa Andersson for their comments on
   this draft.


9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.



Wijnands, et al.        Expires December 25, 2013              [Page 14]


Internet-Draft            mLDP Node Protection                 June 2013


   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.

   [RFC6388]  Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
              "Label Distribution Protocol Extensions for Point-to-
              Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, November 2011.

   [RFC5561]  Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
              Le Roux, "LDP Capabilities", RFC 5561, July 2009.

   [I-D.ietf-mpls-targeted-mldp]
              Napierala, M. and E. Rosen, "Using LDP Multipoint
              Extensions on Targeted LDP Sessions",
              draft-ietf-mpls-targeted-mldp-01 (work in progress),
              January 2013.

9.2.  Informative References

   [RFC4090]  Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
              Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              May 2005.


Authors' Addresses

   IJsbrand Wijnands (editor)
   Cisco Systems, Inc.
   De kleetlaan 6a
   Diegem  1831
   Belgium

   Email: ice@cisco.com


   Eric Rosen
   Cisco Systems, Inc.
   1414 Massachusetts Avenue
   Boxborough  MA 01719
   USA

   Email: erosen@cisco.com









Wijnands, et al.        Expires December 25, 2013              [Page 15]


Internet-Draft            mLDP Node Protection                 June 2013


   Kamran Raza
   Cisco Systems, Inc.
   2000 Innovation Drive
   Ottawa  Ontario K2K-3E8
   Canada

   Email: skraza@cisco.com


   Jeff Tantsura
   Ericsson
   300 Holger Way
   San Jose  CA 95134
   USA

   Email: jeff.tantsura@ericsson.com


   Alia Atlas
   Juniper Networks
   10 Technology Park Drive
   Westford  MA  01886
   USA

   Email: akatlas@juniper.net


   Quintin Zhao
   Huawei Technology
   125 Nagog Technology Park
   Acton  MA  01719
   USA

   Email: quintin.zhao@huawei.com

















Wijnands, et al.        Expires December 25, 2013              [Page 16]


Html markup produced by rfcmarkup 1.122, available from https://tools.ietf.org/tools/rfcmarkup/