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

Versions: 00 01 02 03 draft-ietf-mpls-app-aware-tldp

MPLS Working Group                                         Santosh Esale
INTERNET-DRAFT                                           Raveendra Torvi
Intended Status: Proposed Standard                          Chris Bowers
Expires: July 30, 2015                                  Juniper Networks

                                                              Luay Jalil
                                                                 Verizon

                                                             U. Chunduri
                                                           Ericsson Inc.

                                                              Zhenbin Li
                                                                  Huawei

                                                             Kamran Raza
                                                      Cisco Systems Inc.

                                                        January 26, 2015


                     Application-aware Targeted LDP
                   draft-esale-mpls-app-aware-tldp-03


Abstract

   Recent targeted LDP applications such as remote loop-free alternates
   (LFA) and BGP auto discovered pseudowire may automatically establish
   a tLDP session to any LSR in a network. The initiating LSR has
   information about the targeted applications to administratively
   control initiation of the session. However the responding LSR has no
   such information to control acceptance of this session. This document
   defines a mechanism to advertise and negotiate Targeted Applications
   Capability during LDP session initialization. As the responding LSR
   becomes aware of targeted applications, it may establish a limited
   number of tLDP sessions for certain applications. In addition, each
   targeted application is mapped to LDP Forwarding Equivalence Class
   (FEC) Elements to advertise only necessary LDP FEC-label bindings
   over the session.


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that



Esale, et al.            Expires July 30, 2015                  [Page 1]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html


Copyright and License Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   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  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1 Conventions Used in This Document  . . . . . . . . . . . . .  4
     1.2 Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  5
   2. Targeted Application Capability . . . . . . . . . . . . . . . .  5
     2.1 Encoding . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2 Procedures . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.3 LDP message procedures . . . . . . . . . . . . . . . . . . .  8
       2.3.1 Initialization message . . . . . . . . . . . . . . . . .  8
       2.3.2 Capability message . . . . . . . . . . . . . . . . . . .  8
   3. Targeted Application FEC Advertisement Procedures . . . . . . .  9
   4. Interaction of Targeted Application Capabilities and State
      Advertisement Control Capabilities  . . . . . . . . . . . . . . 10
   5. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     5.1 Remote LFA Automatic Targeted session  . . . . . . . . . . . 12



Esale, et al.            Expires July 30, 2015                  [Page 2]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


     5.2 FEC 129 Auto Discovery Targeted session  . . . . . . . . . . 13
     5.3 LDP over RSVP and Remote LFA targeted session  . . . . . . . 13
     5.4 mLDP node protection targeted session  . . . . . . . . . . . 13
   6  Security Considerations . . . . . . . . . . . . . . . . . . . . 14
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14
   8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 15
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 15
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16









































Esale, et al.            Expires July 30, 2015                  [Page 3]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


1  Introduction

   LDP can use the extended discovery mechanism to establish a tLDP
   adjacency and subsequent session as described in [RFC5036]. An LSR
   initiates extended discovery by sending a tLDP Hello to a specific
   address. The remote LSR decides either to accept or ignore a tLDP
   Hello based on local configuration only. For an application such as
   FEC 128 pseudowire, the remote LSR is configured with the source LSR
   address, so the remote LSR can use that information to accept or
   ignore a given tLDP Hello.

   Applications such as Remote LFA and BGP auto discovered pseudowire
   automatically initiate asymmetric extended discovery to any LSR in a
   network based on local state only. With these applications, the
   remote LSR is not explicitly configured with the source LSR address.
   so the remote LSR either responds to all LDP requests or ignores all
   LDP requests.

   In addition, since the session is initiated and established after
   adjacency formation, the responding LSR has no targeted applications
   information to choose the targeted application it is configured to
   support. Also, the initiating LSR may employ a limit per application
   on locally initiated automatic tLDP sessions, however the responding
   LSR has no such information to employ a similar limit on the incoming
   tLDP sessions. Further, the responding LSR does not know whether the
   source LSR is establishing a tLDP session for a configured or an
   automatic application or both.

   This document proposes and describes a solution to advertise Targeted
   Application Capability, consisting of a targeted application list,
   during initialization of a tLDP session. It also defines a mechanism
   to enable a new application and disable an old application after
   session establishment. This capability advertisement provides the
   responding LSR with the necessary information to control the
   acceptance of tLDP sessions per application. For instance, an LSR may
   accept all BGP auto discovered tLDP sessions as defined in [RFC6074]
   but may only accept limited number of Remote LFA tLDP sessions as
   defined in [I-D.draft-ietf-rtgwg-remote-lfa]

   Also, targeted LDP application is mapped to LDP FEC element type to
   advertise specific application FECs only, avoiding the advertisement
   of other unnecessary FECs over a tLDP session.

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].



Esale, et al.            Expires July 30, 2015                  [Page 4]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


1.2 Terminology

   This document uses terminology discussed in [I-D.draft-ietf-mpls-ldp-
   ip-pw-capability] along with others defined in this document.

    TAC   : Targeted Application Capability
    TAE   : Targeted Application Element
    TA-Id : Targeted Application Identifier
    SAC   : State Advertisement Control Capability

2. Targeted Application Capability

2.1 Encoding

   An LSR MAY advertise that it is capable to negotiate a targeted LDP
   application list over a tLDP session by using the Capability
   Advertisement as defined in [RFC5561].

   A new optional capability TLV is defined, 'Targeted Application
   Capability (TAC)'. Its encoding 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| Targeted App. Cap.(IANA)|             Length              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |S|  Reserved   |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                                                               |
     ~                 Targeted App. Cap. data                       ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     As described in [RFC5561]
     U: set to 1. Ignore, if not known.
     F: Set to 0. Do not forward.
     S: MUST be set to 1 or 0 to advertise or withdraw the Targeted
        Application Capability TLV respectively.

     Targeted Application Capability data:
       A Targeted Applications Capability data consists of none, one
       or more 32 bit Targeted Application Elements. Its encoding is
       as follows:

       Targeted Application Element(TAE)

        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



Esale, et al.            Expires July 30, 2015                  [Page 5]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E|    Targ. Appl. Id           |       Reserved                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Targeted Application Identifier (TA-Id):
       a 16 bit Targeted Application Identifier value.

       E-bit: The enable bit indicates whether the sender is
         advertising or withdrawing the Targeted Application.
         The E-bit value is used as follows:

           1 - The TAE is advertising the targeted application.
           0 - The TAE is withdrawing the targeted application.

     The length of TAC depends on the number of TAEs. For instance,
     if two TAEs are added, the length is set to 9.


2.2 Procedures

   At tLDP session establishment time, a LSR MAY include a new
   capability TLV, Targeted Application Capability (TAC) TLV, as an
   optional TLV in the LDP Initialization message. The TAC TLV's
   Capability data MUST consists of none, one or more Targeted
   Application Element(TAE) each pertaining to a unique Targeted
   Application Identifier(TA-Id) that a LSR supports over the session.
   If the receiver LSR receives the same TA-Id in more than one TAE, it
   MUST process the first element and ignore the duplicate elements. If
   the receiver LSR receives an unknown TA-Id in a TAE, it MUST silently
   ignore such a TAE and continue processing the rest of the TLV.

   If the receiver LSR does not receive the TAC in the Initialization
   message or it does not understand the TAC TLV, the TAC negotiation
   MUST be considered unsuccessful and the session establishment MUST
   proceed as per [RFC5036]. On the receipt of a valid TAC TLV, an LSR
   MUST generate its own TAC TLV with TAEs consisting of unique TA-Ids
   that it supports over the tLDP session. If there is at least one TAE
   common between the TAC TLV it has received and its own, the session
   MUST proceed to establishment as per [RFC5036]. If not, A LSR MUST
   send a 'Session Rejected/Targeted Application Capability Mis-Match'
   Notification message to the peer and close the session. The
   initiating LSR SHOULD tear down the corresponding tLDP adjacency
   after send or receipt of a 'Session Rejected/Targeted Application
   Capability Mis-Match' Notification message to or from the responding
   LSR respectively.

   If both the peers advertise TAC, an LSR decides to establish or close
   a tLDP session based on the negotiated targeted application list. For



Esale, et al.            Expires July 30, 2015                  [Page 6]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   instance, suppose a initiating LSR advertises A, B and C as TA-Ids.
   Further, suppose the responding LSR advertises C, D and E as TA-Ids.
   Than the negotiated TA-Id, as per both the LSRs is C. In the second
   instance, suppose a initiating LSR advertises A, B and C as TA-Ids
   and the responding LSR, which acts as a passive LSR, advertises all
   the applications - A, B, C, D and E that it supports over this
   session. Than the negotiated targeted application as per both the
   LSRs are A, B and C. In the last instance, suppose the initiating LSR
   advertises A, B and C as a TA-Ids and the responding LSR advertises D
   and E as TA-Ids, than the negotiated targeted applciations as per
   both the LSRs is none. The Responding LSR sends 'Session
   Rejected/Targeted Application Capability Mis-Match' Notification
   message to the initiating LSR and may close the session.

   When the responding LSR playing the active role in LDP session
   establishment receives a 'Session Rejected/Targeted Application
   Capability Mis-Match' Notification message, it MUST set its session
   setup retry interval to a maximum value, as 0xffff. The session MAY
   stay in non-existent state. When it detects a change in the
   initiating LSR configuration or local LSR configuration pertaining to
   TAC TLV, it MUST clear the session setup back off delay associated
   with the session to re-attempt the session establishment. A LSR
   detects configuration change on the other LSR with the receipt of
   tLDP Hello message that has a higher configuration sequence number
   than the earlier tLDP Hello message.

   When the initiating LSR playing the active role in LDP session
   establishment receives a 'Session Rejected/Targeted Application
   Capability Mis-Match' Notification message, either it MUST close the
   session and tear down the corresponding tLDP adjacency or it MUST set
   its session setup retry interval to a maximum value, as 0xffff.

   If it decides to tear down the associated tLDP adjacency, the session
   is destroyed on the initiating as well as the responding LSR. The
   initiating LSR MAY take appropriate actions if it is unable to bring
   up the tLDP session. For instance, if an automatic session intended
   to support the Remote LFA application is rejected by the responding
   LSR, the initiating LSR may inform the IGP to calculate another PQ
   node [I-D.draft-ietf-rtgwg-remote-lfa] for the route or set of
   routes. More specific actions are a local matter and outside the
   scope of this document.

   If it sets the session setup retry interval to maximum, the session
   MAY stay in a non-existent state. When this LSR detects a change in
   the responding LSR configuration or its own configuration pertaining
   to TAC TLV, it MUST clear the session setup back off delay associated
   with the session to re-attempt the session establishment.




Esale, et al.            Expires July 30, 2015                  [Page 7]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   After a tLDP session has been established with TAC capability, the
   initiating and responding LSR MUST distribute FEC-label bindings for
   the negotiated applications only. For instance, if the tLDP session
   is established for BGP auto discovered pseudowire, only FEC 129 label
   bindings MUST be distributed over the session. Similarly, a LSR
   operating in downstream on demand mode MUST request FEC-label
   bindings for the negotiated applications only.

   If the Targeted Application Capability and Dynamic Capability, as
   described in [RFC5561], are negotiated during session initialization,
   TAC MAY be re-negotiated after session establishment by sending an
   updated TAC TLV in LDP Capability message. The updated TAC TLV
   carries TA-Ids with incremental update only. The updated TLV MUST
   consist of one or more TAEs with E-bit set or E-bit off to advertise
   or withdraw the new and old application respectively. This may lead
   to advertisements or withdrawals of certain types of FEC-Label
   bindings over the session or tear down of the tLDP adjacency and
   subsequently the session.

   The Targeted Application Capability is advertised on tLDP session
   only. If the tLDP session changes to link session, a LSR should
   withdraw it with S bit set to 0, which indicates wildcard withdrawal
   of all TAE elements. Similarly, if the link session changes to tLDP,
   a LSR should advertise it via the Capability message. If the
   capability negotiation fails, this may lead to destruction of the
   tLDP session.

   Also, currently the remote LSR accepts asymmetric extended Hellos by
   default or by appropriate configuration. With this document, the LSR
   MUST accept tLDP hellos in order to then accept or reject the tLDP
   session based on the application information.

2.3 LDP message procedures

2.3.1 Initialization message disbaled
  1. The S-bit of the Targeted Application Capability TLV MUST be
     set to 1 to advertise Targeted Application Capability and
     SHOULD be ignored on the receipt.

  2. The E-bit of the Targeted Application Element MUST be set to 1 to
     enable Targeted application and SHOULD be ignored on the receipt.

  3. An LSR MAY add State Control Capability by mapping Targeted
     Application Element to State Advertisement Control (SAC) Elements
     as defined in Section 4.

2.3.2 Capability message




Esale, et al.            Expires July 30, 2015                  [Page 8]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


  The initiating or responding LSR may re-negotiate the TAC after local
  configuration change with the Capability message.

  1. The S-bit of Targeted Application Capability is set to 1 or 0
     to advertise or withdraw it.

  2. After configuration change, If there is no common TAE between
     its new TAE list and peers TAE list, the LSR MUST send a
     'Session Rejected/Targeted Application Capability Mis-Match'
     Notification message and close the session.

  3. If there is a common TAE, a LSR MAY also update SAC Capability
     based on updated TAC as described in section 4 and sends the
     updated TAC and SAC capabilities in a Capability message to
     the peer.

  4. A receiving LSR processes the Capability message with TAC TLV.
     If the S-bit is set to 0, the TAC is disabled for the session.
     After that, the session may remain in established state or
     torn down based on [RFC5036] rules.

  5. If the S-bit is set to 1, a LSR process a list of TAEs from
     TACs capability data with E-bit set to 1 or 0 to update the
     peers TAE. Also, it updates the negotiated TAE list over the
     tLDP session.

3. Targeted Application FEC Advertisement Procedures

   The targeted LDP application MUST be mapped to LDP FEC element types
   as follows to advertise only necessary LDP FEC-Label bindings over
   the tLDP session.


     Targeted Application   Description              FEC mappings
   +----------------------+------------------------+------------------+
   |LDPv4 Tunneling       | LDP IPv4 over RSVP-TE  | IPv4 FEC         |
   |                      | or other MPLS tunnel   |                  |
   +----------------------+------------------------+------------------+
   |                      |                        |                  |
   |LDPv6 Tunneling       | LDP IPv6 over RSVP-TE  | IPv6 FEC         |
   |                      | or other MPLS tunnel   |                  |
   +----------------------+------------------------+------------------+
   |mLDP Tunneling        | mLDP over RSVP-TE or   | P2MP FEC         |
   |                      | or other MPLS tunnel   | MP2MP FEC        |
   |                      |                        | HSMP-downstream  |
   |                      |                        | FEC              |
   |                      |                        | HSMP-upstream FEC|
   +----------------------+------------------------+------------------+



Esale, et al.            Expires July 30, 2015                  [Page 9]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   |                      |                        |                  |
   |LDPv4 Remote LFA      | LDPv4 over LDPv4 or    | IPv4 FEC         |
   |                      | other MPLS tunnel      |                  |
   +----------------------+------------------------+------------------+
   |LDPv6 Remote LFA      | LDPv6 over LDPv6 or    | IPv6 FEC         |
   |                      | other MPLS tunnel      |                  |
   +----------------------+------------------------+------------------+
   |                      |                        |                  |
   |LDP FEC 128 PW        | LDP FEC 128 Pseudowire | FEC 128          |
   +----------------------+------------------------+------------------+
   |                      |                        |                  |
   |LDP FEC 129 PW        | LDP FEC 129 Pseudowire | FEC 129          |
   +----------------------+------------------------+------------------+
   |                      |                        | FEC types as     |
   |LDP Session Protection| DP session protection  | per protected    |
   |                      | other MPLS tunnel      | session          |
   +----------------------+------------------------+------------------+
   |LDP ICCP              | LDP Inter-chasis       |                  |
   |                      | control protocol       | None             |
   +----------------------+------------------------+------------------+
   |                      |                        |                  |
   |LDP P2MP PW           | LDP P2MP Pseudowire    | P2MP PW FEC      |
   +----------------------+------------------------+------------------+
   |                      |                        | P2MP FEC         |
   |mLDP Node Protection  | mLDP node protection   | MP2MP FEC        |
   |                      |                        | HSMP-downstream  |
   |                      |                        | FEC              |
   |                      |                        | HSMP-upstream FEC|
   +----------------------+------------------------+------------------+
   |                      |                        |                  |
   |IPv4 intra-area FECs  | IPv4 intra-area FECs   | IPv4 FECs        |
   +----------------------+------------------------+------------------+
   |                      |                        |                  |
   |IPv6 intra-area FECs  | IPv6 intra-area FECs   | IPv6 FECs        |
   +----------------------+------------------------+------------------+


4. Interaction of Targeted Application Capabilities and State
   Advertisement Control Capabilities

   As described in this document, the set of TAEs negotiated between two
   LDP peers advertising TAC represents the willingness of both peers to
   advertise state information for a set of applications. The set of
   applications negotiated by the TAC mechanism is symmetric between the
   two LDP peers. In the absence of further mechanisms, two LDP peers
   will both advertise state information for the same set of
   applications.




Esale, et al.            Expires July 30, 2015                 [Page 10]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   As described in [I-D.draft-ietf-mpls-ldp-ip-pw-capability], State
   Advertisement Control(SAC) TLV can be used by an LDP speaker to
   communicate its interest or disinterest in receiving state
   information from a given peer for a particular application.  Two LDP
   peers can use the SAC mechanism to create asymmetric advertisement of
   state information between the two peers.

   The TAC negotiation facilitates the awareness of targeted
   applications to both the peers. It enables them to advertise only
   necessary LDP FEC-label bindings corresponding to negotiated
   applications. With the SAC, the responding LSR is not aware of
   targeted applications. Thus it may be unable to communicate its
   interest or disinterest to receive state information from the peer.
   However after TAC mechanism makes the responding LSR aware of
   targeted application, the SAC mechanism may be used to communicate
   its disinterest in receiving state information from the peer for a
   particular negotiated application.

   Thus, the TAC mechanism enables two LDP peers to symmetrically
   advertise state information for negotiated targeted applications.
   Further, the SAC mechanism enables both of them to asymmetrically
   disable receipt of state information for some of the already
   negotiated targeted applications. Collectively, both TAC and SAC
   mechanisms can be used to control the FEC-label bindings that are
   advertised over the tLDP session. For instance, suppose the
   initiating LSR establishes a tLDP session to the responding LSR for
   Remote LFA and FEC 129 PW targeted applications with TAC. So each LSR
   advertises the corresponding FEC-Label bindings.  Further, suppose
   the initiating LSR is not the PQ node for responding LSRs Remote LFA
   IGP calculations. In such a case, the responding LSR may use the SAC
   mechanism to convey its disinterest in receiving state information
   for Remote LFA targeted LDP application.

   For a given tLDP session, the TAC mechanism can be used without the
   SAC mechanism, and the SAC mechanism can be used without the TAC
   mechanism. It is useful to discuss the behavior when TAC and SAC
   mechanisms are used on the same tLDP session. The TAC mechanism MUST
   take precedence over the SAC mechanism with respect to enabling
   applications for which state information will be advertised. For a
   tLDP session using the TAC mechanism, the LDP peers MUST NOT
   advertise state information for an application that has not been
   negotiated in the most recent TAE list (referred to as an un-
   negotiated application).  This is true even if one of the peers
   announces its interest in receiving state information that
   corresponds to the un-negotiated application by sending a SAC TLV.
   In other words, when TAC is being used, SAC cannot and should not
   enable state information advertisement for applications that have not
   been enabled by TAC.



Esale, et al.            Expires July 30, 2015                 [Page 11]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   On the other hand, the SAC mechanism MUST take precedence over the
   TAC mechanism with respect to disabling state information
   advertisements. If an LDP speaker has announced its disinterest in
   receiving state information for a given application to a given peer
   using the SAC mechanism, its peer MUST NOT send state information for
   that application, even if the two peers have negotiated that the
   corresponding application via the TAC mechanism.


   For the purposes of determining the correspondence between targeted
   applications defined in this document and application state as
   defined in [I-D.draft-ietf-mpls-ldp-ip-pw-capability] an LSR MUST use
   the following mappings:

      LDPv4 Tunneling - IPv4 Prefix-LSPs
      LDPv6 Tunneling - IPv6 Prefix-LSPs
      LDPv4 Remote LFA - IPv4 Prefix-LSPs
      LDPv6 Remote LFA - IPv6 Prefix-LSPs
      LDP FEC 128 PW - FEC128 P2P-PW
      LDP FEC 129 PW - FEC129 P2P-PW


   An LSR MUST map Targeted Application to LDP capability as follows:

      mLDP Tunneling - P2MP Capability, MP2MP Capability
                       and HSMP LSP Capability TLV
      mLDP node protection - P2MP Capability, MP2MP Capability
                             and HSMP LSP Capability TLV

5. Use cases

5.1 Remote LFA Automatic Targeted session

   An LSR determines that it needs to form an automatic tLDP session to
   remote LSR based on IGP calculation as described in [I-D.draft-ietf-
   rtgwg-remote-lfa] or some other mechanism, which is outside the scope
   of this document. The LSR forms the tLDP adjacency and during session
   setup, constructs an Initialization message with Targeted
   Applications Capability (TAC) with Targeted Application Element (TAE)
   as Remote LFA. The receiver LSR processes the LDP Initialization
   message and verifies whether it is configured to accept a Remote LFA
   tLDP session. If it is, it may further verify that establishing such
   a session does not exceed the configured limit for Remote LFA
   sessions. If all these conditions are met, the receiver LSR may
   respond back with an Initialization message with TAC corresponding to
   Remote LFA, and subsequently the session may be established.

   After the session has been established with TAC capability, the



Esale, et al.            Expires July 30, 2015                 [Page 12]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   sender and receiver LSR distribute IPv4 or IPv6 FEC label bindings
   over the session. Further, the receiver LSR may determine that it
   does not need these FEC label bindings. So it may disable the receipt
   of these FEC label bindings by mapping targeted application element
   to state control capability as described in section 4.

5.2 FEC 129 Auto Discovery Targeted session

   BGP auto discovery MAY determine whether an LSR needs to initiate an
   auto-discovery tLDP session with a border LSR. Multiple LSRs MAY try
   to form an auto discovered tLDP session with a border LSR. So, a
   service provider may want to limit the number of auto discovered tLDP
   sessions a border LSR may accept. As described in Section 2, LDP may
   convey targeted applications with TAC TLV to border LSR. A border LSR
   may establish or reject the tLDP session based on local
   administrative policy. Also, as the receiver LSR becomes aware of
   targeted applications, it can also employ an administrative policy
   for security. For instance, it can employ a policy 'accept all auto-
   discovered session from source-list'.

   Moreover, the sender and receiver LSR MUST exchange FEC 129 label
   bindings only over the tLDP session.

5.3 LDP over RSVP and Remote LFA targeted session

   A LSR may want to establish a tLDP session to a remote LSR for LDP
   over RSVP tunneling and Remote LFA applications. The sender LSR may
   add both these applications as a unique Targeted Application Element
   in the Targeted Application Capability data of a TAC TLV. The
   receiver LSR MAY have reached a configured limit for accepting Remote
   LFA automatic tLDP sessions, but it may also be configured to accept
   LDP over RSVP tunneling. In such a case, the tLDP session is formed
   for both LDP over RSVP and Remote LFA applications as both needs same
   FECs - IPv4 and/or IPv6.

5.4 mLDP node protection targeted session

   A merge point LSR may determines that it needs to form automatic tLDP
   session to the upstream point of local repair (PLR) LSR for MP2P and
   MP2MP LSP node protection as described in the [I-D.draft-ietf-mpls-
   mldp-node-protection]. The MPT LSR may add a new targeted LDP
   application - mLDP protection, as a unique TAE in the Targeted
   Application Capability Data of a TAC TLV and send it in the
   Initialization message to the PLR. If the PLR is configured for mLDP
   node protection and establishing this session does not exceed the
   limit of either mLDP node protection sessions or automatic tLDP
   sessions, the PLR may decide to accept this session. Further, the PLR
   responds back with the initialization message with a TAC TLV that has



Esale, et al.            Expires July 30, 2015                 [Page 13]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   one of the TAEs as - mLDP protection and the session proceeds to
   establishment as per [RFC5036].


6  Security Considerations

   The Capability procedure described in this document will apply and
   does not introduce any change to LDP Security Considerations section
   described in [RFC5036].

   As described in [RFC5036], DoS attacks via Extended Hellos can be
   addressed by filtering Extended Hellos using access lists that define
   addresses with which Extended Discovery is permitted.  Further, as
   described in section 5.2 of this document, a LSR can employ a policy
   to accept all auto-discovered Extended Hellos from the configured
   source addresses list.

   Also for the two LSRs supporting TAC, the tLDP session is only
   established after successful negotiation of the TAC. When there is no
   common targeted LDP application between two LSRs due to
   administrative policy, the tLDP session is not established.

7  IANA Considerations

   This document requires the assignment of a new code point for a
   Capability Parameter TLVs from the IANA managed LDP registry "TLV
   Type Name Space", corresponding to the advertisement of the Targeted
   Applications capability. IANA is requested to assign the lowest
   available value after 0x050B.

      Value  Description                       Reference
      -----  --------------------------------  ---------
      TBD1   Targeted Applications capability  [This draft]

   This document requires the assignment of a new code point for a
   status code from the IANA managed registry "STATUS CODE NAME SPACE"
   on the Label Distribution Protocol (LDP) Parameters page,
   corresponding to the notification of session Rejected/Targeted
   Application Capability Mis-Match. IANA is requested to assign the
   lowest available value after 0x0000004B.

      Value  Description                       Reference
      -----  --------------------------------  ---------
      TBD2   Session Rejected/Targeted
             Application Capability Mis-Match  [This draft]


   This document also creates a new name space 'the LDP Targeted



Esale, et al.            Expires July 30, 2015                 [Page 14]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


   Application Identifier' on the Label Distribution Protocol (LDP)
   Parameters page, that is to be managed by IANA. The range is 0x0001-
   0xFFFE, with the following values requested in this document.

             0x0000: Reserved
             0x0001: LDPv4 Tunneling
             0x0002: LDPv6 Tunneling
             0x0003: mLDP Tunneling
             0x0004: LDPv4 Remote LFA
             0x0005: LDPv6 Remote LFA
             0x0006: LDP FEC 128 PW
             0x0007: LDP FEC 129 PW
             0x0008: LDP Session Protection
             0x0009: LDP ICCP
             0x000A: LDP P2MP PW
             0x000B: mLDP Node Protection
             0x000C: LDPv4 Intra-area FECs
             0x000D: LDPv6 Intra-area FECs
             0xFFFF: Reserved

   Following the policies outlined in IANA, Targeted Application
   Identifiers in the range 0x0001 - 0x1FFF are allocated through an
   IETF Consensus action, and Targeted Application Identifiers in the
   range 0x2000 - 0x7FFE are allocated as First Come First Served.


8. Acknowledgments

   The authors wish to thank Nischal Sheth, Hassan Hosseini, Kishore
   Tiruveedhul, Loa Andersson, Eric Rosen, Yakov Rekhter, Thomas
   Beckhaus, Tarek Saad and Lizhong Jin for doing the detailed review.
   Thanks to Manish Gupta and Martin Ehlers for their input to this work
   and for many helpful suggestions.

9  References

9.1  Normative References


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

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

   [I-D.draft-ietf-mpls-ldp-ip-pw-capability] Kamran Raza, Sami Boutros,
              "Disabling IPoMPLS and P2P PW LDP Application's State
              Advertisement", draft-ietf-mpls-ldp-ip-pw-capability-09



Esale, et al.            Expires July 30, 2015                 [Page 15]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


              (work in progress), October 15, 2014.

   [I-D.draft-ietf-mpls-mldp-node-protection] IJ. Wijnands, E. Rosen, K.
              Raza, J. Tantsura, A. Atlas, Q. Zhao, "mLDP Node
              Protection", draft-ietf-mpls-mldp-node-protection-02 (work
              in progress), November 13, 2014.

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

9.2  Informative References

   [I-D.draft-ietf-rtgwg-remote-lfa] S. Bryant, C. Filsfils, S. Previdi,
              M. Shand, N. So, "Remote LFA FRR", draft-ietf-rtgwg-
              remote-lfa-10 (work in progress), September 26, 2014.

   [RFC6074] E. Rosen, B. Davie, V. Radoaca, and W. Luo, "Provisioning,
              Auto-Discovery, and Signaling in Layer 2 Virtual Private
              Networks (L2VPNs)"

   [RFC4762] M. Lasserre, and V. Kompella, "Virtual Private LAN Service
              VPLS) Using Label Distribution Protocol (LDP) Signaling",
              RFC 4762, January 2007.

   [RFC4447] L. Martini, E. Rosen, El-Aawar, T. Smith, and G. Heron,
              "Pseudowire Setup and Maintenance using the Label
              Distribution Protocol", RFC 4447, April 2006.

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space", RFC
              5331, August 2008.


Authors' Addresses

              Santosh Esale
              Juniper Networks
              1194 N. Mathilda Ave.
              Sunnyvale, CA  94089
              US
              EMail: sesale@juniper.net


              Raveendra Torvi
              Juniper Networks
              10 Technology Park Drive.
              Westford, MA 01886
              US



Esale, et al.            Expires July 30, 2015                 [Page 16]


INTERNET DRAFT     <draft-esale-mpls-app-aware-tldp>    January 26, 2015


              EMail: rtorvi@juniper.net


              Chris Bowers
              Juniper Networks
              1194 N. Mathilda Ave.
              Sunnyvale, CA  94089
              US
              EMail: cbowers@juniper.net


              Luay Jalil
              Verizon
              1201 E Arapaho Rd.
              Richardson, TX  75081
              US
              Email: luay.jalil@verizon.com


              Uma Chunduri
              Ericsson Inc.
              300 Holger Way
              San Jose, California  95134
              US
              Email: uma.chunduri@ericsson.com



              Zhenbin Li
              Huawei Bld No.156 Beiqing Rd.
              Beijing  100095
              China
              Email: lizhenbin@huawei.com


              Kamran Raza
              Cisco Systems, Inc.
              2000 Innovation Drive
              Ottawa, ON K2K-3E8
              Canada
              E-mail: skraza@cisco.com










Esale, et al.            Expires July 30, 2015                 [Page 17]


Html markup produced by rfcmarkup 1.121, available from https://tools.ietf.org/tools/rfcmarkup/