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Versions: (draft-deshmukh-teas-rsvp-rmr-extension) 00 01

TEAS WG                                                      A. Deshmukh
Internet-Draft                                               K. Kompella
Intended status: Standards Track                  Juniper Networks, Inc.
Expires: December 30, 2018                                 June 28, 2018


                        RSVP Extensions for RMR
                 draft-ietf-teas-rsvp-rmr-extension-01

Abstract

   Ring topology is commonly found in access and aggregation networks.
   However, the use of MPLS as the transport protocol for rings is very
   limited today.  draft-ietf-mpls-rmr-02 describes a mechanism to
   handle rings efficiently using MPLS.  This document describes the
   extensions to the RSVP-TE protocol for signaling MPLS label switched
   paths in rings.

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 December 30, 2018.

Copyright Notice

   Copyright (c) 2018 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
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   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




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  RSVP Extensions . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Session Object  . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  SENDER_TEMPLATE,FILTER_SPEC Objects . . . . . . . . . . .   5
   4.  Ring Signaling Procedures . . . . . . . . . . . . . . . . . .   5
     4.1.  Differences from regular RSVP-TE LSPs . . . . . . . . . .   5
     4.2.  LSP signaling . . . . . . . . . . . . . . . . . . . . . .   6
       4.2.1.  Path Propagation for RMR  . . . . . . . . . . . . . .   8
       4.2.2.  Resv Processing for RMR . . . . . . . . . . . . . . .   8
     4.3.  Protection  . . . . . . . . . . . . . . . . . . . . . . .   9
     4.4.  Ring changes  . . . . . . . . . . . . . . . . . . . . . .  10
     4.5.  Express Links . . . . . . . . . . . . . . . . . . . . . .  11
     4.6.  Bandwidth management  . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   This document extends RSVP-TE [RFC3209] to establish label-switched
   path (LSP) tunnels in the ring topology.  Rings are auto-discovered
   using the mechanisms mentioned in the [draft-ietf-mpls-rmr-02].
   Either IS-IS [RFC5305] or OSPF[RFC3630] can be used as the IGP for
   auto-discovering the rings.

   After the rings are auto-discovered, each node in the ring knows its
   clockwise(CW) and anti-clockwise (AC) ring neighbors and its ring
   links.  All of the express links in the ring also get identified as
   part of the auto-discovery process.  At this point, every node in the
   ring informs the RSVP protocol to begin the signaling of the ring
   LSPs.

   Section 2 covers the terminology used in this document.  Section 3
   presents the RSVP protocol extensions needed to support MPLS rings.
   Section 4 describes the procedures of RSVP LSP signaling in detail.





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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Terminology

   Assuming there are n nodes in the network, a ring gets formed by a
   subset of those n nodes {Ri, Ri+1, Ri+2,...Rn}.  We define the
   direction from node Ri to Ri+1 as "clockwise" (CW) and the reverse
   direction as "anti-clockwise" (AC).  As there might be several rings
   in a graph, each ring is identified by it's own distinct ring ID -
   RID.


                                R0 . . . R1
                              .             .
                           R7                 R2
              Anti-     |  .        Ring       .  |
              Clockwise |  .                   .  | Clockwise
                        v  .      RID = 17     .  v
                           R6                 R3
                              .             .
                                R5 . . . R4

                        Figure 1: Ring with 8 nodes

   The following terminology is used for ring LSPs:

   Ring ID (RID):  A non-zero number that identifies a ring; this is
      unique in a Service Provider's network.  A node may belong to
      multiple rings.

   Ring node:  A member of a ring.  Note that a device may belong to
      several rings.

   Node index:  A logical numbering of nodes in a ring, from zero up to
      one less than the ring size.  Used purely for exposition in this
      document.

   Ring neighbors:  Nodes whose indices differ by one (modulo ring
      size).

   Ring links:  Links that connect ring neighbors.




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   Express links:  Links that connect non-neighboring ring nodes.

   MP2P LSP:  Each LSP in the ring is a multipoint to point LSP such
      that LSP can have multiple ingress nodes and one egress node.

3.  RSVP Extensions

   Due to the new ring LSP semantics, the signaling-message
   identification of ring LSPs will be different than the regular RSVP
   LSPs.  So, a new C-Type is defined here for the SESSION object.  This
   new C-Type will help to clearly differentiate ring LSPs from regular
   LSPs.  In addition, new flags are introduced in the SESSION object to
   represent the ring direction of the corresponding Path message.

3.1.  Session Object

   Class = SESSION, LSP_TUNNEL_IPv4 C-Type = TBD

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Ring anchor node address                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |        Ring Flags             |        Ring Instance ID       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Ring ID                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                              SESSION Object

   Ring anchor node address:   IPv4 address of the anchor node.  Each
      anchor node creates a LSP addressed to itself.

   Ring Instance ID:   A 16-bit identifier used in the SESSION.  This
      Ring Instance ID is useful for graceful ring changes.  If a new
      node is being added to the ring(resulting in signaling of a larger
      ring) or some existing node goes down(resulting in signaling of a
      smaller ring), in those cases, anchor node creates a new tunnel
      with a different Ring Instance ID.

   Ring ID:   A 32-bit number that identifies a ring; this is unique in
      some scope of a Service Provider's network.  This number remains
      constant throughout the existence of ring.

   Ring Flags:   For each ring, the anchor node starts signaling of a
      ring LSP.  Ring LSP named RLi, anchored on node Ri, consists of
      two counter-rotating unicast LSPs that start and end at Ri.  One
      LSP will be in the clockwise direction and other LSP will be in



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      the anti-clockwise direction.  A ring LSP is "multipoint": any
      node along the ring can use LSP RLi to send traffic to Ri; this
      can be in either the CW or AC directions, or both (i.e., load
      balanced).  Two new flags are defined in the SESSION object which
      define the ring direction of the corresponding Path message.

   ClockWise(CW) Direction  0x01:   This flag indicates that the
      corresponding Path message is traveling in the ClockWise(CW)
      direction along the ring.

   Anti-ClockWise(AC) Direction  0x02:   This flag indicates that the
      corresponding Path message is traveling in the Anti-ClockWise(AC)
      direction along the ring.

3.2.  SENDER_TEMPLATE,FILTER_SPEC Objects

   There will be no changes to the SENDER_TEMPLATE and FILTER_SPEC
   objects.  The format of the above 2 objects will be similar to the
   definitions in RFC 3209.  [RFC3209] Only the semantics of these
   objects will slightly change.  This will be explained in section
   Section 4.6 below.

4.  Ring Signaling Procedures

   A ring node indicates in its IGP updates the ring LSP signaling
   protocols that it supports.  This can be LDP and/or RSVP-TE.
   Ideally, each node should support both.  If the ring is configured
   with RSVP as the signaling protocol, then once a ring node R_i knows
   the RID, its ring links and directions, it kicks off ring RSVP LSP
   signaling automatically.

4.1.  Differences from regular RSVP-TE LSPs

   Ring LSPs differ from regular RSVP-TE LSPs in several ways:

   1.  Ring LSPs (by construction) form a loop.

   2.  Ring LSPs are multipoint-to-point.  Any ring node can inject
   traffic into a ring LSP.

   3.  The bandwidth of a ring LSP can change hop-by-hop.

   4.  Ring LSPs are protected without the use of bypass or detour LSPs.
   Protection is handled by the ring LSP traversing in the opposite
   direction.






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4.2.  LSP signaling

   After the ring auto-discovery process, each anchor node creates a LSP
   addressed to itself.  This ring LSP contains of a pair of counter-
   rotating unicast LSPs.  So, for a ring containing N nodes, there will
   be 2N total LSPs signaled.

   There is no need for ERO object in the Path message.  The Path
   message for ring LSPs has the following format:


        <Path Message> ::=  <Common Header> [ <INTEGRITY> ]
                                <SESSION> <RSVP_HOP>
                                <TIME_VALUES>
                                <LABEL_REQUEST>
                                [ <SESSION_ATTRIBUTE> ]
                                <sender descriptor list>

        <sender descriptor list> ::= <sender descriptor>|
                                         <sender descriptor list> <sender descriptor>
        <sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>



   The anchor node creates 2 Path messages traveling in opposite
   directions.  The SESSION format MUST be as per the description in
   Section 3.1.  The anchor node which creates the LSP will insert it's
   own address in the "Ring anchor node address" field of the SESSION
   object.  So effectively, the Path messages are addressed to the
   originating node itself.

   The SESSION flags of these 2 Path messages are different.  The Path
   message sent to the CW neighbor MUST have the CW flag set in the
   SESSION object to signal the LSP going in the clockwise direction.
   The Path message sent to the AC neighbor MUST have the AC flag set to
   signal the LSP in the anti-clockwise direction.

   When an incoming Path message is received at the ring node Ri, it
   consults the results of auto-discovery to find the appropriate ring
   neighbor.  If the incoming Path message has CW direction flag set,
   then Ri includes its own SENDER_DESCRIPTOR in the path message and
   forwards the Path message to its CW ring neighbor(Ri+1).  Similarly
   if the incoming Path message has AC direction flag set, then Ri
   includes its own SENDER_TEMPPLATE and forwards that Path message to
   it's AC ring neighbor(Ri-1).  Thus, there is no need of ERO in the
   Path message.  The Path message is routed locally at each ring based
   on the ring auto-discovery calculations.




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   The RESV message for ring LSPs also uses the new RING_IPv4 SESSION
   object.  When the Path message originated from the anchor node Ri
   reaches back to Ri, Ri generates a Resv message.  Note that this
   means that anchor node is both Ingress and Egress for the Path
   message.  The Resv message copies the same ring flags as received in
   the corresponding Path message.  So, a Resv message for a CW LSP goes
   in the AC direction (unlike the Path message, which goes CW).  This
   is done to correctly match Path and corresponding Resv messages at
   transit ring nodes.  Upon receiving Resv message with CW flag set,
   the ring node will forward the Resv message to its AC neighbor.

   Each ring node Ri allocates CW and AC labels for each ring LSP RLx(x
   between i..n).  As the signaling propagates around the ring, CW and
   AC labels are exchanged.  When Ri receives CW and AC labels for LSP
   RLx from its ring neighbors, primary and fast reroute (FRR) paths for
   RLx are installed at Ri.

   Consider the following three nodes of the ring, and their signaling
   interactions for LSP RL5 originating from anchor node R5:


                            P5_CW ->     P5_CW ->
                            Q5_CW <-     Q5_CW <-
            ... ------ R7 --------- R8 --------- R9 ------ ...
                            P5_AC <-     P5_AC <-
                            Q5_AC ->     Q5_AC ->

   P corresponds to the Path message and Q corresponds to the Resv
   message.

   As explained above, an RMR LSP consists of two counter-rotating ring
   LSPs that start and end at the same node, say R1.  As such, this
   appears to cause a loop, something that is normally avoided by RSVP-
   TE.  There are some benefits to this:

   Having a ring LSP form a loop allows the anchor node R1 to ping
   itself and thus verify the end-to-end operation of the LSP.  This, in
   conjunction with link-level OAM, offers a good indication of the
   operational state of the LSP.  Also, having R1 to be the ingress
   means that R1 can initiate the Path messages for the two ring LSPs.
   This avoids R1 having to coordinate with its neighbors to signal the
   LSPs, and simplifies the case where a ring update changes R1's ring
   neighbors.  The cost of this is a little more signaling and a couple
   more label entries in the LFIB.  However, we will let experiences
   from implementation guide us when we evaluate this approach.






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4.2.1.  Path Propagation for RMR

   Ring LSPs are MP2P in nature.  It means that every non-egress node is
   also an ingress and a merge-point for the LSP.  Focussing on ring-
   LSP-0 (i.e ring-LSPs starting at R0):

   R0---->R1---->R2---->R3---->R4---->R5---->R6--->R7--->R0(CW LSP)
   R0---->R7---->R6---->R5---->R4---->R3---->R2--->R1--->R0(ACW LSP)

   Each ring node inserts a new SENDER_TEMPLATE object into an incoming
   Path message.  The procedure for that is as follows:

   When a ring node R3 receives a Path message initiated by anchor node
   R0(for anchor lsp "lsp0"), R3 SHOULD make a copy of the received Path
   message for "lsp0".  R3 then inserts a new sender-template object
   into the Path message for "lsp0".  In the sender-template object, R3
   uses the sender address as the loopback address of node R3 and lsp-id
   = X.  R3 then forwards this modified Path message to it's ring
   neighbor.

   So at this point, when Path messages heads out at R3, there will be 4
   different SENDER_TEMPLATE objects in the outgoing Path message for
   lsp0:

          -----------------------------------------------------
         |SENDER_TEMPLATE_0 : SENDER_ADDRESS = R0, LSP_ID = 1 |
          -----------------------------------------------------
         |SENDER_TEMPLATE_1 : SENDER_ADDRESS = R1, LSP_ID = 1 |
          -----------------------------------------------------
         |SENDER_TEMPLATE_2 : SENDER_ADDRESS = R2, LSP_ID = 1 |
          -----------------------------------------------------
         |SENDER_TEMPLATE_3 : SENDER_ADDRESS = R3, LSP_ID = 1 |
          -----------------------------------------------------

4.2.2.  Resv Processing for RMR

   When Egress node R0 receives the modified Path message, it replies
   with the a Resv message containing multiple FLOW_DESCRIPTOR objects.
   There should be 1 FLOW_DESCRIPTOR object corresponding to each of the
   SENDER_TEMPLATE object in the incoming Path message.  The SESSION
   object of the Resv message will exactly match with the received Path
   message.

   [RFC 3209] already supports receiving a Resv message with multiple
   flow-descriptors in it, as described in section 3.2 in that document.
   In each flow-descriptor there is a separate:





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   a.  FLOW_SPEC object corresponding to the SENDER_TSPEC that was sent
   in the Path message which could be admitted after admission-control
   downstream, and

   b.  FILTER_SPEC object corresponding to SENDER_TEMPLATE that was sent
   in the Path message that could be admitted after admission-control
   downstream.

   Each transit node removes the FLOW-DESCRIPTOR corresponding to itself
   from the Resv message before sending the Resv message upstream.

4.3.  Protection

   In the rings, there are no protection LSPs -- no node or link bypass
   LSPs, no standby LSPs and no detours.  Protection is via the "other"
   direction around the ring, which is why ring LSPs are in counter-
   rotating pairs.  Protection works in the same way for link, node and
   ring LSP failures.

   Since each ring LSP is a MP2P LSP, any ring node can inject traffic
   onto a LSP whose anchor might be a different ring node.  To achieve
   the above, an ingress route will be installed as follows at every
   ring node J, for a given ring-LSP with anchor Rk (say 1.2.3.4).


            1.2.3.4  ->  (Push CL_J+1,K, NH: R_J+1)       # CW
                     ->  (Push AL_J-1,K, NH: R_J-1)       # AC

                     CL = Clockwise label
                     AL = Anti-Clockwise label


   Traffic will either be load balanced in the CW and AC directions or
   the traffic will be sent on just CW or AC lsp based on parameters
   such as hop-count, policy etc.

   Also, 2 transit routes will be installed for the anchor LSP
   transiting from node Rj as follows:













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            CL_J,K ->  SWAP(CL_J+1,K,  NH: R_J+1)              #CW
                   ->  SWAP(AL_J-1,K , NH: R_J-1)              #AC

                       CL = Clockwise label
                       AL = Anti-Clockwise label
                       CW NH has weight 1, AC NH has higher-weight.


            AL_J,K -> SWAP(AL_J-1,K , NH: R_J-1)  #AC
                   -> SWAP(CL_J+1,K,  NH: R_J+1)  #CW

                       CL = Clockwise label
                       AL = Anti-Clockwise label
                       AC NH has weight 1, CW NH has higher weight.



   Suppose a packet headed in anti-clockwise direction towards R5 and it
   arrives at node R7.  Lets say that now R7 learns there is a link
   failure in the AC direction.  R7 reroutes this packet back onto the
   clockwise direction.  This reroute action is pre-programmed in the
   LFIB, to minimize the time between detection of a fault and the
   corresponding recovery action.

   At this time, R7 also sends a notification to R0 that the AC
   direction is not working.  R0 modifies it's ingress route(for R5 LSP)
   by removing the AC direction LSP's route.  Thus, R0 switches traffic
   to the CW direction.

   These notification propagate CW until each traffic source on the ring
   CW of the failure uses the CW direction.For RSVP-TE, this
   notification is sent in the form of PathErr message.

   To provide this notification, the ring node detecting failure SHOULD
   send a Path Error message with error code of "Notify" and an error
   value field of ("Tunnel locally repaired").  This Path Error code and
   value is same as defined in RFC 4090[RFC4090] for the notification of
   local repair.

   Note that the failure of a node or a link will not necessarily affect
   all ring LSPs.  Thus, it is important to identify the affected LSPs
   and only switch the affected LSPs.

4.4.  Ring changes

   A ring node can go down resulting in a smaller ring or a new node can
   be added to the ring which will increase the ring size.  In both of




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   the above cases, the ring auto-discovery process SHOULD kick in and
   it SHOULD calculate a new ring with the changed ring nodes.

   When the ring auto-discovery process is complete, IGP will signal
   RSVP to begin the MBB process for the existing ring LSPs.  For this
   MBB process, the anchor node will create a new Path message with a
   different Ring Instance ID in the SESSION object.  All other fields
   in the SESSION Object will remain same as the existing Path
   message(before the ring change).

   This new Path message will then propagate along the ring neighbors in
   the same way as the original Path message.  Each ring neighbor SHOULD
   forward the Path message to it's appropriate neighbor based on the
   new auto-discovery calculations.

   For the ring links which are common between the old and new LSPs, the
   LSPs will share resources(SE style reservation) on those ring links.
   Note that here we are using Ring Instance ID in the SESSION object to
   share resources instead of the LSP_ID in the SENDER_TEMPLATE
   Object(which is used in RSVP-TE for sharing resources as described in
   RFC 3209 [RFC4090]).  The LSP_ID use is reserved for a different
   functionality as described in section Section 4.6.

4.5.  Express Links

   The details for signaling over express links will be given in a
   future version.

4.6.  Bandwidth management

   For RSVP-TE LSPs, bandwidths may be signaled in both directions.
   However, these are not provisioned either; rather, one does "reverse
   call admission control".  When a service needs to use an LSP, the
   ring node where the traffic enters the ring attempts to increase the
   bandwidth on the LSP to the egress.  If successful, the service is
   admitted to the ring.















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                               . R0 . . . R1
                              . __________|| .
                             . /   ________|  .
                           R7 /  /            R2
              Anti-     |  . /  /              .  |
              Clockwise |  . | /               .  | Clockwise
                        v  . | \               .  v
                           R6   \             R3
                              .  \           .
                                R5 . . . R4

               Figure 2: BW Management in Ring with 8 nodes

   Let's say that Ring node R5 wants to increase the BW for the LSP
   whose egress is at node R1.  To achieve this BW increase, Ring node
   R5 has to increase BW along the LSP anchored at node R1(say lsp1).

   R5 makes a copy of the existing ring Path message for lsp1.  R5 then
   modifies the sender-template object from the copied Path message for
   "lsp1".  In the sender-template object, R5 uses the sender address as
   the loopback address of node R5 and lsp-id = X+1.  R5 also modifies
   the TSPEC object which represents the BW increase/decrease in this
   new Path message.  R5 then forwards this new Path message to it's
   ring neighbor.  The original anchor Path message has sender address
   as loopback address of R1.

   Now, let's say, node 5 wants to increase BW again for lsp1, then R5
   adds a new SENDER_TEMPLATE object in the existing Path message for
   "lsp1" with sender address as loopback of node 5 and lsp-id = X+2.
   So at this point, there will be 2 different SENDER_TEMPLATE objects
   corresponding to node 5 in the outgoing path message.


          -----------------------------------------------------
         |SENDER_TEMPLATE_0 : SENDER_ADDRESS = R0, LSP_ID = 1 |
          -----------------------------------------------------
         |SENDER_TEMPLATE_1 : SENDER_ADDRESS = R1, LSP_ID = 1 |
          -----------------------------------------------------
         |                  ........                          |
          -----------------------------------------------------
         |SENDER_TEMPLATE_5 : SENDER_ADDRESS = R5, LSP_ID = 1 |
          -----------------------------------------------------
         |SENDER_TEMPLATE_5 : SENDER_ADDRESS = R5, LSP_ID = 2 |
          -----------------------------------------------------

   Similarly, if node R6 wants to increase the BW for "lsp1", it SHOULD
   create a new Path message containing SENDER_TEMPLATE object with
   sender address = loopback of node 6 and lsp-id = Y+1.  Thus, it



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   should be noted that each ring-node independently tracks its own lsp-
   ID that is currently in-use on a given RMR sub-LSP.  This lsp-ID
   value will (could) be different for each ring-node for a given ring
   sub-LSP.

   If sufficient BW is available all the way towards ring node R1, then
   this new Path message reaches node R1.  R1 generates a Resv message
   with the correct FILTER_SPEC object corresponding to the received
   SENDER_TEMPLATE object.  This Resv message will also have the correct
   FLOWSPEC object as per the requested bandwidth.

   If sufficient BW is not available at some downstream (say node R9),
   then ring node R9 SHOULD generate a PathErr message with the
   corresponding Sender Template Object.  When node R5 receives this
   PathErr message, R5 understands that the BW increase was not
   successful.  Note that the existing established bandwidths for lsp1
   are not affected by this new PathErr message.

   When ring node R5 no longer needs the BW reservation, then ring node
   R5 SHOULD originate a new Path message with the appropriate Sender
   Template Object containing 0 BW as described above.  Every downstream
   node SHOULD then remove bandwidth allocated on the corresponding link
   on receipt of this Path message.

   Also, note that as part of this BW increase or decrease process, any
   ring node does not actually change any label associated with the LSP.
   So, the label remains same as it was signaled initially when the
   anchor LSP came up.

5.  Security Considerations

   It is not anticipated that either the notion of MPLS rings or the
   extensions to various protocols to support them will cause new
   security loopholes.  As this document is updated, this section will
   also be updated.

6.  Contributors

       Ravi Singh
       Juniper Networks, Inc.
       1133 Innovation Way
       Sunnyvale, CA  94089
       USA

       Email: ravis@juniper.net






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       Santosh Esale
       Juniper Networks, Inc.
       1133 Innovation Way
       Sunnyvale, CA  94089
       USA

       Email: sesale@juniper.net

       Raveendra Torvi
       Juniper Networks, Inc.
       10 Technology Park Dr
       Westford, MA  01886
       USA

       Email: rtorvi@juniper.net

7.  IANA Considerations

   Requests to IANA will be made in a future version of this document.

8.  References

8.1.  Normative References

   [I-D.ietf-mpls-rmr]
              Kompella, K. and L. Contreras, "Resilient MPLS Rings",
              draft-ietf-mpls-rmr-07 (work in progress), March 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

8.2.  Informative References

   [I-D.dai-mpls-rsvp-te-mbb-label-reuse]
              Dai, M. and M. Chaudhry, "MPLS RSVP-TE MBB Label Reuse",
              draft-dai-mpls-rsvp-te-mbb-label-reuse-01 (work in
              progress), September 2015.

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997, <https://www.rfc-editor.org/info/rfc2205>.



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   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
              Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              DOI 10.17487/RFC4090, May 2005,
              <https://www.rfc-editor.org/info/rfc4090>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

Authors' Addresses

   Abhishek Deshmukh
   Juniper Networks, Inc.
   10 Technology Park Dr
   Westford, MA  01886
   USA

   Email: adeshmukh@juniper.net


   Kireeti Kompella
   Juniper Networks, Inc.
   1133 Innovation Way
   Sunnyvale, CA  94089
   USA

   Email: kireeti@juniper.net














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