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MPLS WG                                                      K. Kompella
Internet-Draft                                                    W. Lin
Intended status: Standards Track                        Juniper Networks
Expires: September 9, 2020                                March 08, 2020


                        No Further Fast Reroute
                      draft-kompella-mpls-nffrr-00

Abstract

   There are several cases where, once Fast Reroute has taken place (for
   MPLS protection), a second fast reroute is undesirable, even
   detrimental.  This memo gives several examples of this, and proposes
   a mechanism to prevent further fast reroutes.

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
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   This Internet-Draft will expire on September 9, 2020.

Copyright Notice

   Copyright (c) 2020 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
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  EVPN (VPN/VPLS) Active-active Multihoming . . . . . . . .   3
     2.2.  RMR Protection  . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  General MPLS forwarding . . . . . . . . . . . . . . . . .   4
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  NFFRR for MPLS forwarding . . . . . . . . . . . . . . . .   6
     3.2.  Proposal  . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  NFFRR and SPRING  . . . . . . . . . . . . . . . . . .  10
     3.3.  NFFRR for MPLS Services . . . . . . . . . . . . . . . . .  10
     3.4.  NFFRR for RMR . . . . . . . . . . . . . . . . . . . . . .  11
   4.  Signaling NFFRR Capability  . . . . . . . . . . . . . . . . .  12
     4.1.  Signaling NFFRR Capability for MPLS Services with BGP . .  12
     4.2.  Signaling NFFRR Capability for MPLS Services with
           Targeted LDP  . . . . . . . . . . . . . . . . . . . . . .  12
     4.3.  Signaling NFFRR Capability for MPLS Forwarding  . . . . .  12
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   MPLS Fast Reroute (FRR) [RFC4090] [RFC5286] [RFC7490] is a useful and
   widely deployed tool for minimizing packet loss in the case of a link
   or node failure.  This has not only proven to be very effective, it
   is often the reason for using MPLS as a data plane.  FRR works for a
   variety of control plane protocols, including LDP, RSVP-TE, and
   SPRING.  Furthermore, FRR is often used to protect MPLS services such
   as IP VPN and EVPN.

   Having said this, there are case where, once FRR has taken place, if
   the packet encounters a second failure, a second FRR is not helpful,
   perhaps even disruptive.  For example, the packet may loop until TTL
   expires.  This can lead to link congestion and further packet loss.
   Thus, the attempt to prevent a packet from being dropped may instead
   affect many other packets.  Note that the "second" failure may simply
   be another manifestation of the same failure; see Figure 1.

   This memo proposes a mechanism for preventing further FRR once in
   cases where such further protection may be harmful.  Several examples
   where this is the case are demonstrated as motivation.  A solution
   using special-purpose labels (SPLs) is then offered.  Some mechanisms



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   for distributing the capability to avoid further fast reroutes are
   also discussed, although these may be better placed in other
   documents in other Working Groups.

1.1.  Terminology

   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.  Motivation

   A few cases are given where "further fast reroute" is harmful.  Some
   of the cases are for MPLS services; others for "plain" MPLS
   forwarding.

2.1.  EVPN (VPN/VPLS) Active-active Multihoming

   Consider the following topology for multihoming an Ethernet VPN (EVPN
   [RFC7432]) Customer Edge (CE) device for protection against the
   failure of a Provider Edge (PE) device or a PE-CE link.  To do so,
   there is a backup MPLS path between PE2 and PE3 (denoted by the
   starred line).

                      P1 ...         ... P3 --- PE2
                     /                         *   \ link1
                    /                         *     \
         CE1 --- PE1                          *      CE2
                    \                         *     /
                     \                         *   / link2
                      P2 ...         ... P4 --- PE3


                        Figure 1: EVPN Multihoming

   Suppose (known unicast) traffic goes from CE1 to CE2.  With active-
   active multihoming, this traffic will be load-balanced between PE2
   (to CE2 via link link1) and PE3 (to CE2 via link2).  If link1 were to
   fail, PE2 can still get traffic for CE2 by sending it over the backup
   path to PE3 (and similarly for PE3 if link2 fails).

   However, suppose CE2 is down.  PE2 will assume link1 is down and send
   traffic for CE2 to PE3 over the backup path.  PE3 (which thinks that
   link2 is down; note that the single real failure of CE2 being down is
   manifested as separate failures to PE2 and PE3) will protect this
   "second" failure by sending traffic for CE2 over the backup path to



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   PE2.  Thus, traffic will ping-pong between PE2 and PE3 until TTL
   expires.

   Thus, the attempt to protect traffic to CE2 may end up doing more
   harm than good, by congesting the backup path between PE2 and PE3 and
   by giving PE2 and PE3 useless work to do.

   A similar topology can be used in EVPN-Etree [RFC8317], EVPN-VPWS
   [RFC8214], IP VPN [RFC4364] or VPLS [RFC4761] [RFC4762].  In all
   these cases, the same looping behavior would occur for unicast
   traffic if CE2 is down.

2.2.  RMR Protection

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


                           Figure 2: RMR Looping

   In Resilient MPLS Rings (RMR), suppose traffic goes from a node, say
   R0, to a node, say R4, over a clockwise path.  Protection consists of
   switching this traffic onto the anti-clockwise path to R4.  This
   works well if a node or link between R0 or R4 is down.  However, if
   node R4 itself is down, its adjacent neighbor R3, will send the
   traffic anti-clockwise to R4; when this traffic reaches R4's other
   neighbor R5, it will return to N3, and so on, until TTL expires.
   [I-D.ietf-mpls-rmr] provides more details, and offers some means of
   mitigation.  This memo offers a more elegant solution.

2.3.  General MPLS forwarding

   Consider the following topology:











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            N1 --- N2 --- N3 --- N4
                   |       |
                   |       |
            N5 --- N6 --- N7 --- N8
                   |       |
                   |       |
                   N9 --- N10

                     Figure 3: General MPLS Forwarding

   Say link protection is configured for links N2-N3 and N6-N7.  Link
   N2-N3 is protected by a bypass tunnel N2-N6-N7-N3, and link N7-N3 is
   protected by a bypass tunnel N7-N6-N2-N3.  (These bypass tunnels may
   be set up using RSVP-TE [RFC3209] or via SPRING stacks [RFC8660].)
   Say furthermore that there is an LSP from N1 to N4 with path
   N1-N2-N3-N4, which asks for link protection.  If link N2-N3 fails,
   traffic will take the path N1-N2-N6-N7-N3-N4.

   Suppose, however, links N2-N3 and N7-N3 fail simultaneously.  This
   may happen if they share fate (e.g., go over a common fiber conduit);
   it may also appear to happen if node N3 fails.  Either way, first,
   the bypass protecting link N2-N3 kicks in, and traffic is sent to N3
   via N6 and N7.  However, when the traffic hits N7, the bypass for
   N7-N3 kicks in, and traffic is sent back to N2.  Thus the traffic
   will loop between N2 and N7 until TTL expires, in the process
   congesting links N2-N6 and N6-N7.

   Now consider an LSP: N5-N6-N7-N8.  The link N6-N7 may be protected by
   the bypass N6-N2-N3-N7 or by N6-N9-N10-N7, or by load-balancing
   between these two bypasses.  If both links N2-N3 and N6-N7 fail, then
   traffic that is protected via bypass N6-N2-N3-N7 will ping-pong
   between N6 and N2 until TTL expires; traffic protected via bypass
   N6-N9-N10-N7 will successfully make it to N8.  If link N6-N7 is
   protected by load-balancing across the two bypass paths, then about
   half the traffic will loop between N6 and N2, and the rest will make
   it to N8.

   While the above description is for protection using a bypass tunnel,
   the same principle applies to protection using Loop-Free Alternates
   [RFC5286] [RFC7490] or any of its variants (such as Topology
   Independent LFA).

3.  Solution

   To address this issue, we suggest the use of a SPL [RFC7274] called
   NFFRR (value TBD; suggested: 8).  An alternate would be to use an
   extended SPL, whereby a pair of labels indicates that no further fast
   route is desired.  However, in the case of SPRING MPLS bypass tunnels



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   (Section 3.2.1) of depth N, this would triple the label stack size.
   Using regular SPLs instead would only double the stack size.

3.1.  NFFRR for MPLS forwarding

   To illustrate, we'll first take the example of Figure 3, with MPLS
   paths signaled using RSVP-TE.  This method can be used for paths that
   use SPRING stacks, but this will be detailed in a later version.

            N1 --- N2 --- N3 --- N4       LSP N1 to N4:  L1->L2->null
                   |       |          Bypass for N2-N3:  L3->L4->null
                   |       |          Bypass for N7-N3:  L5->L6->null
            N5 --- N6 --- N7 --- N8       LSP N5 to N8:  L7->L8->null
                   |       |          Bypass1 for N6-N7: L9->L10->null
                   |       |          Bypass2 for N6-N7: L11->L12->null
                   N9 --- N10           (via N9-N10-N7)

                   Figure 4: Example Using RSVP-TE LSPs

             +------+----------+------+----------+----------+
             | Node | Action   | Next | New Pkt  | Comment  |
             +------+----------+------+----------+----------+
             | N1   | push L1  | N2   | [L1] pkt | ingress  |
             |      |          |      |          |          |
             | N2   | L1 -> L2 | N3   | [L2] pkt |          |
             |      |          |      |          |          |
             | N3   | pop L2   | N4   | pkt      | PHP      |
             |      |          |      |          |          |
             | N4   | fwd pkt  | -    | -        | continue |
             +------+----------+------+----------+----------+

                     Table 1: Forwarding from N1 to N4

   Note 1: "[L1 ...]" denotes the label stack on the packet; pkt is the
   original packet received at ingress.  "L1 -> L2" means swap label L1
   with L2.  "pop L2" means pop the top label L2.  "fwd pkt" means
   forward the packet as usual.














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              +------+----------+------+----------+---------+
              | Node | Action   | Next | New Pkt  | Comment |
              +------+----------+------+----------+---------+
              | N2   | push L3  | N6   | [L3] pkt | ingress |
              |      |          |      |          |         |
              | N6   | L3 -> L4 | N7   | [L4] pkt |         |
              |      |          |      |          |         |
              | N7   | pop L4   | N3   | pkt      | PHP     |
              +------+----------+------+----------+---------+

            Table 2: Forwarding over the bypass for link N2-N3

              +------+----------+------+----------+---------+
              | Node | Action   | Next | New Pkt  | Comment |
              +------+----------+------+----------+---------+
              | N7   | push L5  | N6   | [L5] pkt | ingress |
              |      |          |      |          |         |
              | N6   | L5 -> L6 | N2   | [L6] pkt |         |
              |      |          |      |          |         |
              | N2   | pop L6   | N3   | pkt      | PHP     |
              +------+----------+------+----------+---------+

              Table 3: Forwarding over Bypass1 for link N7-N3

            +------+----------+------+-------------+----------+
            | Node | Action   | Next | New Pkt     | Comment  |
            +------+----------+------+-------------+----------+
            | N1   | push L1  | N2   | [L1] pkt    | ingress  |
            |      |          |      |             |          |
            | N2   | L1 -> L2 | N3   | [L2] pkt    | N3 X     |
            |      |          |      |             |          |
            | N2   | push L3  | N6   | [L3 L2] pkt | PLR      |
            |      |          |      |             |          |
            | N6   | L3 -> L4 | N7   | [L4 L2] pkt |          |
            |      |          |      |             |          |
            | N7   | pop L4   | N3   | [L2] pkt    | merge    |
            |      |          |      |             |          |
            | N3   | pop L2   | N4   | pkt         | PHP      |
            |      |          |      |             |          |
            | N4   | fwd pkt  | -    | -           | continue |
            +------+----------+------+-------------+----------+

           Table 4: Forwarding from N1 to N4 if link N2-N3 fails

   Table 4 is obtained by composing Table 1 and Table 2.

   Note 2: "N3 X" means "next hop N3 unavailable (because link N2-N3
   failed)".



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            +------+----------+------+-------------+---------+
            | Node | Action   | Next | New Pkt     | Comment |
            +------+----------+------+-------------+---------+
            | N1   | push L1  | N2   | [L1] pkt    | ingress |
            |      |          |      |             |         |
            | N2   | L1 -> L2 | N3   | [L2] pkt    | N3 X    |
            |      |          |      |             |         |
            | N2   | push L3  | N6   | [L3 L2] pkt | PLR     |
            |      |          |      |             |         |
            | N6   | L3 -> L4 | N7   | [L4 L2] pkt |         |
            |      |          |      |             |         |
            | N7   | pop L4   | N3   | [L2] pkt    | N3 X'   |
            |      |          |      |             |         |
            | N7   | push L5  | N6   | [L5 L2] pkt |         |
            |      |          |      |             |         |
            | N6   | L5 -> L6 | N2   | [L6 L2] pkt | PLR     |
            |      |          |      |             |         |
            | N2   | pop L6   | N3   | [L2] pkt    | N3 X    |
            |      |          |      |             |         |
            | N2   | push L3  | N6   | [L3 L2]     | PLR     |
            |      |          |      |             |         |
            | etc  |          |      |             | loop!   |
            +------+----------+------+-------------+---------+

      Table 5: Forwarding from N1 to N4 if links N2-N3 and N7-N3 fail

   Table 5 is obtained by composing Table 1, Table 2 and Table 3.

   Note 3: "N3 X'" means "next hop N3 unavailable because link N7-N3 is
   down.

   Note 4: While the impact of a loop is pretty bad, the impact of an
   ever-growing label stack (not illustrated here) and possible
   associated fragmentation on transit nodes may be worse.

3.2.  Proposal

   An LSR (typically a PLR) that wishes to prevent further FRRs after
   the first one can push an SPL, namely NFFRR, onto the label stack as
   follows:











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      +------+----------------+------+-------------------+----------+
      | Node | Action         | Next | New Pkt           | Comment  |
      +------+----------------+------+-------------------+----------+
      | N1   | push L1        | N2   | [L1] pkt          | ingress  |
      |      |                |      |                   |          |
      | N2   | L1 -> L2       | N3   | [L2] pkt          | N3 X     |
      |      |                |      |                   |          |
      | N2   | push L3, NFFRR | N6   | [L3 NFFRR L2] pkt | PLR      |
      |      |                |      |                   |          |
      | N6   | L3 -> L4       | N7   | [L4 NFFRR L2] pkt |          |
      |      |                |      |                   |          |
      | N7   | pop L4, NFFRR  | N3   | [L2] pkt          | merge    |
      |      |                |      |                   |          |
      | N3   | pop L2         | N4   | pkt               | PHP      |
      |      |                |      |                   |          |
      | N4   | fwd pkt        | -    | -                 | continue |
      +------+----------------+------+-------------------+----------+

     Table 6: Forwarding from N1 to N4 if link N2-N3 fails with NFFRR

   Note 5: N2 can insert an NFFRR label only if it knows that all LSRs
   in the path can process it correctly.  See Section 4 for some details
   on how this capability is communicated.

      +------+----------------+------+-------------------+----------+
      | Node | Action         | Next | New Pkt           | Comment  |
      +------+----------------+------+-------------------+----------+
      | N1   | push L1        | N2   | [L1] pkt          | ingress  |
      |      |                |      |                   |          |
      | N2   | L1 -> L2       | N3   | [L2] pkt          | N3 X     |
      |      |                |      |                   |          |
      | N2   | push L3, NFFRR | N6   | [L3 NFFRR L2] pkt | PLR      |
      |      |                |      |                   |          |
      | N6   | L3 -> L4       | N7   | [L4 NFFRR L2] pkt |          |
      |      |                |      |                   |          |
      | N7   | pop L4         | N3   | [NFFRR L2] pkt    | N3 X     |
      |      |                |      |                   |          |
      | N7   | check NFFRR    | -    | -                 | drop pkt |
      +------+----------------+------+-------------------+----------+

   Table 7: Forwarding from N1 to N4 if links N2-N3 and N7-N3 fail with
                                   NFFRR

   Note 6: "check NFFRR" means that, before N7 applies FRR (because link
   N7-N3 is down), N7 checks the label below the top label (or in this
   case, because of PHP, the top label itself).  If this is the NFFRR
   label, N7 drops the packet rather than apply FRR.




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3.2.1.  NFFRR and SPRING

   Suppose that, to protect link N2-N3, a bypass tunnel N2-N6-N7-N3 were
   instantiated using SPRING MPLS [RFC8660], in particular, using
   adjacency SIDs.  If the corresponding labels for links N6-N7 and
   N7-N3 were L20 and L21, the bypass would consist of pushing the label
   stack [L20 L21] onto the packet and sending the packet to N6.  To
   indicate that FRR has already occurred and to drop the packet rather
   than to try to protect the packet again, N2 would have to push [L20
   NFFRR L21 NFFRR] onto the packet before sending it to N6.  If the
   packet came from N1 with label L1, N2 would send a packet with label
   stack [L20 NFFRR L21 NFFRR L2] to N6.

   N6 would see L20, pop it, note the NFFRR label and pop it, then
   attempt to send the packet to N7.  If the link N6-N7 is down, N6
   drops the packet.  Otherwise, N7 gets the packet, sees L21, pops it,
   sees NFFRR, pops it and tries to send the packet to N3.  If link
   N7-N3 is down, N7 drops the packet.  Otherwise, N3 gets the packet
   with L2, swaps with with L3 and sends it to N4.

   Note that with SPRING MPLS, the NFFRR label needs to be repeated for
   each label in the bypass stack.  Hence the request for a "regular"
   SPL rather than an extended SPL.

3.3.  NFFRR for MPLS Services

   First, we illustrate known unicast EVPN forwarding:

          +------+-------------+-------+-------------+---------+
          | Node | Action      | Next  | Packet      | Comment |
          +------+-------------+-------+-------------+---------+
          | PE1  | send to CE2 | PE2   | [T1 S2] pkt | EVPN    |
          |      |             |       |             |         |
          | PE2  | send to CE2 | link1 | pkt         | done!   |
          +------+-------------+-------+-------------+---------+

   Note: T1/T2/T3 are the transport labels for PE1/PE3/PE2 to reach
   PE2/PE2/PE3 respectively.  S2/S3 are the service labels announced by
   PE2/PE3 for CE2.

   Then, we show what happens when CE2 is down without NFFRR:










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          +------+-------------+-------+-------------+---------+
          | Node | Action      | Next  | Packet      | Comment |
          +------+-------------+-------+-------------+---------+
          | PE1  | send to CE2 | PE2   | [T1 S2] pkt | EVPN    |
          |      |             |       |             |         |
          | PE2  | send to CE2 | link1 | --          | link1 X |
          |      |             |       |             |         |
          | PE2  | send to CE2 | PE3   | [T3 S3] pkt | eFRR    |
          |      |             |       |             |         |
          | PE3  | send to CE2 | link2 | --          | link2 X |
          |      |             |       |             |         |
          | PE3  | send to CE2 | PE2   | [T2 S2] pkt | eFRR    |
          |      |             |       |             |         |
          | PE2  | send to CE2 | link1 | --          | link1 X |
          |      |             |       |             |         |
          | PE2  | send to CE2 | PE3   | [T3 S3] pkt | eFRR    |
          |      |             |       |             |         |
          | ...  |             |       |             | loop!   |
          +------+-------------+-------+-------------+---------+

   Note: link1/link2 X means link1/link2 is down.  eFRR refers to EVPN
   multihoming FRR.

   In the case of MPLS services such as EVPN Figure 1, the NFFRR label
   is inserted below the service label, as shown below:

     +------+-------------+-------+-------------------+-------------+
     | Node | Action      | Next  | Packet            | Comment     |
     +------+-------------+-------+-------------------+-------------+
     | PE1  | send to CE2 | PE2   | [T1 S2] pkt       | EVPN        |
     |      |             |       |                   |             |
     | PE2  | send to CE2 | link1 | --                | link1 X     |
     |      |             |       |                   |             |
     | PE2  | send to CE2 | PE3   | [T3 S2 NFFRR] pkt | eFRR        |
     |      |             |       |                   |             |
     | PE3  | send to CE2 | link2 | --                | link2 X     |
     |      |             |       |                   |             |
     | PE3  | drop pkt    | --    | --                | check NFFRR |
     +------+-------------+-------+-------------------+-------------+

   Note: "check NFFRR" is as above.

3.4.  NFFRR for RMR

   As described in Figure 2, packets will loop until TTL expires if the
   destination node in an RMR ring (here, R4) fails.  The solution in
   this case is that the first node to apply RMR protection (R3) pops
   the current RMR transport label being used, sees that the next label



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   is not NFFRR (so protection is allowed), pushes an NFFRR label and
   then the RMR transport label for the reverse direction.

   When R5 receives the packet, it sees that the next link is down, pops
   the RMR transport label, sees the NFFRR label and drops the packet.
   Thus, the loop is avoided.

4.  Signaling NFFRR Capability

4.1.  Signaling NFFRR Capability for MPLS Services with BGP

   The ideal choice would be an attribute consisting of a bit vector of
   node capabilities, one bit of which would be the capability of
   processing the NFFRR SPL below the BGP service label.  This would be
   used by BGP L2VPN, BGP VPLS, EVPN, E-Tree and E-VPWS.  An alternative
   is to use the BGP Capabilities Optional Parameter
   [I-D.ietf-idr-next-hop-capability].  Details to be worked out.

4.2.  Signaling NFFRR Capability for MPLS Services with Targeted LDP

   One approach to signaling NFFRR capability for MPLS services signaled
   with targeted LDP is to introduce a new LDP TLV called the NFFRR
   Capability TLV as an Optional Parameter in the Label Mapping Message
   [RFC5036].  This TLV has Type TBD (suggested: 0x0207) and Length 0.

   Another approach is to use LDP Capabilities [RFC5561]; this approach
   has the advantage that it deals with capabilities on a node basis
   rather than on a per label mapping basis.  However, there don't
   appear to be other documents using this approach.

4.3.  Signaling NFFRR Capability for MPLS Forwarding

   The authors suggest signaling a router's ability to process the NFFRR
   SPL using the Link State Router TE Node Capabilities [RFC5073], which
   works for both IS-IS and OSPF.  A new TE Node Capability bit, the N
   bit (suggested value 5) indicates that the advertising node is
   capable of processing the NFFRR SPL.

5.  IANA Considerations

   If this draft is deemed useful, an SPL for NFFRR will need to be
   allocated.  We suggest the early allocation of label 8 for this.

   Furthermore, means of signaling the ability to process the NFFRR SPL
   should be defined for IS-IS, OSPF, LDP and BGP.

   The following update is suggested for the Link State Router TE Node
   Capabilities registry:



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                     +-----+-------+----------------+
                     | Bit | Name  | Reference      |
                     +-----+-------+----------------+
                     |   5 | NFFRR | This docusment |
                     +-----+-------+----------------+

   The following update is suggested for the TLV Type Name Space of the
   Label Distribution Protocol (LDP) Parameters registry:

                    +--------+-------+----------------+
                    | Type   | Name  | Reference      |
                    +--------+-------+----------------+
                    | 0x0207 | NFFRR | This docusment |
                    +--------+-------+----------------+

6.  Security Considerations

   A malicious or compromised LSR can insert NFFRR into a label stack,
   preventing FRR from occurring.  If so, protection will not kick in
   for failures that could have been protected, and there will be
   unnecessary packet loss.

7.  References

7.1.  Normative References

   [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>.

   [RFC5036]  Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
              "LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
              October 2007, <https://www.rfc-editor.org/info/rfc5036>.

   [RFC5073]  Vasseur, J., Ed. and J. Le Roux, Ed., "IGP Routing
              Protocol Extensions for Discovery of Traffic Engineering
              Node Capabilities", RFC 5073, DOI 10.17487/RFC5073,
              December 2007, <https://www.rfc-editor.org/info/rfc5073>.

   [RFC7274]  Kompella, K., Andersson, L., and A. Farrel, "Allocating
              and Retiring Special-Purpose MPLS Labels", RFC 7274,
              DOI 10.17487/RFC7274, June 2014,
              <https://www.rfc-editor.org/info/rfc7274>.

   [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>.



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7.2.  Informative References

   [I-D.ietf-idr-next-hop-capability]
              Decraene, B., Kompella, K., and W. Henderickx, "BGP Next-
              Hop dependent capabilities", draft-ietf-idr-next-hop-
              capability-05 (work in progress), June 2019.

   [I-D.ietf-mpls-rmr]
              Kompella, K. and L. Contreras, "Resilient MPLS Rings",
              draft-ietf-mpls-rmr-12 (work in progress), October 2019.

   [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>.

   [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>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC4761]  Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
              <https://www.rfc-editor.org/info/rfc4761>.

   [RFC4762]  Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
              LAN Service (VPLS) Using Label Distribution Protocol (LDP)
              Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
              <https://www.rfc-editor.org/info/rfc4762>.

   [RFC5286]  Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
              IP Fast Reroute: Loop-Free Alternates", RFC 5286,
              DOI 10.17487/RFC5286, September 2008,
              <https://www.rfc-editor.org/info/rfc5286>.

   [RFC5561]  Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
              Le Roux, "LDP Capabilities", RFC 5561,
              DOI 10.17487/RFC5561, July 2009,
              <https://www.rfc-editor.org/info/rfc5561>.







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   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC7490]  Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
              So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
              RFC 7490, DOI 10.17487/RFC7490, April 2015,
              <https://www.rfc-editor.org/info/rfc7490>.

   [RFC8214]  Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
              Rabadan, "Virtual Private Wire Service Support in Ethernet
              VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
              <https://www.rfc-editor.org/info/rfc8214>.

   [RFC8317]  Sajassi, A., Ed., Salam, S., Drake, J., Uttaro, J.,
              Boutros, S., and J. Rabadan, "Ethernet-Tree (E-Tree)
              Support in Ethernet VPN (EVPN) and Provider Backbone
              Bridging EVPN (PBB-EVPN)", RFC 8317, DOI 10.17487/RFC8317,
              January 2018, <https://www.rfc-editor.org/info/rfc8317>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

Authors' Addresses

   Kireeti Kompella
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA  94089
   United States

   Email: kireeti.kompella@gmail.com


   Wen Lin
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA  94089
   United States

   Email: wlin@juniper.net






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