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

Versions: (draft-raza-mpls-ldp-ip-pw-capability) 00 01 02 03 04 05 06 07 08 09 RFC 7473

Network Working Group                                       Kamran Raza
Internet Draft                                            Cisco Systems
Intended status: Standards Track
Expires: December 16, 2011                                 Sami Boutros
                                                          Cisco Systems

                                                          June 17, 2011


                         LDP IP and PW Capability

                draft-ietf-mpls-ldp-ip-pw-capability-00.txt


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), its areas, and its working groups.  Note that
   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/ietf/1id-abstracts.txt

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

   This Internet-Draft will expire on December 16, 2011.

Copyright Notice

   Copyright (c) 2011 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



Raza                    Expires December 2011                   [Page 1]


Internet-Draft          LDP IP and PW Capability               June 2011


   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.

Abstract

   Currently, no LDP capability is exchanged for LDP applications like
   IP label switching and L2VPN/PW signaling. When an LDP session comes
   up, an LDP speaker may unnecessarily advertise its local state for
   such LDP applications even when the peer session may be established
   for some other applications like ICCP. This document proposes a
   solution by which an LDP speaker announces its "incapability" or
   disability or non-support for IP label switching or L2VPN/PW
   application, hence disabling corresponding application state exchange
   over the established LDP session.

Table of Contents

  1. Introduction                                                     3
  2. Conventions used in this document                                3
  3. Non-negotiated LDP applications                                  4
     3.1. Application Control Capabilities                            4
   3.1.1. IP Label Switching Capability TLV                           4
   3.1.2. PW Signaling Capability TLV                                 5
     3.2. Procedures for Application Control Capabilities in an
          Initialization message                                      6
     3.3. Procedures for Application Control capabilities in a
          Capability message                                          7
  4. Operational Examples                                             8
     4.1. Disabling IP/PW label applications on an ICCP session       8
     4.2. Disabling IP Label Switching application on a PW session    8
     4.3. Disabling IP application dynamically on an established
          IP/PW session                                               9
  5. Security Considerations                                          9
  6. IANA Considerations                                              9
  7. Conclusions                                                     10
  8. References                                                      10
     8.1. Normative References                                       10
     8.2. Informative References                                     10
  9. Acknowledgments                                                 10




Raza                    Expires December 2011                   [Page 2]


Internet-Draft          LDP IP and PW Capability               June 2011


1. Introduction

  LDP Capabilities [RFC5561] introduced a mechanism to negotiate LDP
  capabilities for a given feature amongst peer LSRs. This mechanism
  insures that no unnecessary state is exchanged between peer LSRs
  unless corresponding feature capability is successfully negotiated
  between peers.

  While new features and applications, such as Typed Wildcard FEC
  [RFC5918], Inter-Chassis Communication Protocol [ICCP], mLDP
  [MLDP], make use of LDP capabilities framework for their feature
  negotiation, the earlier LDP features and applications like IP label
  switching and L2VPN/PW signaling [RFC4447] may cause unnecessary
  state exchange between LDP peers even when the given application is
  not enabled on one of the LDP speakers participating in a given
  session. For example, when bringing up and using an LDP peer session
  with a remote PE LSR for purely ICCP signaling purposes, the LDP
  speaker may unnecessarily advertise labels for IP (unicast) prefixes
  to this ICCP related LDP peer as per its default behavior. To avoid
  this unnecessary state advertisement and exchange, currently customers
  are typically required to configure/define some sort of LDP state
  (label) filtering policies on the box, which introduces operational
  overhead and complexity.

  This document proposes a solution by which an LDP speaker may announce
  its "incapability" (or disability) to its peer for IP Label Switching
  and/or L2VPN/PW Signaling application at session establishment time.
  This helps avoiding unnecessary state exchange for such feature
  applications. The proposal also state the mechanics to enable
  previously disabled application later during the session lifetime.
  The document introduces two new LDP Capabilities for IP label
  switching and L2VPN/PW applications to implement this proposal.

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [RFC2119].

   The term "IP" in this document refers to "IP unicast", unless
   otherwise explicitly stated.



Raza                    Expires December 2011                   [Page 3]


Internet-Draft          LDP IP and PW Capability               June 2011


3. Non-negotiated LDP applications

   For the applications that existed before LDP Capabilities [RFC5561]
   mechanics were defined, LDP speaker may advertise relevant
   application state to its peers after session establishment without
   waiting for any capabilities exchange and negotiation.

   Currently, the most important non-negotiated applications include:

   o  IP [v4 and v6] label switching

   o  L2VPN/PW signaling

   To disable unnecessary state exchange for such LDP applications, two
   new capabilities are being introduced in this document. These new
   capabilities allow an LDP speaker to notify its LDP peer at the
   session establishment time when one or more LDP "Non-negotiated
   applications" are not required/configured on the sender side. Upon
   receipt of such capability, if supported, the receiving LDP speaker
   MUST disable the advertisement of application state towards the
   sender. These capabilities can also be sent later in a Capability
   message to either disable these applications, or to enable
   previously disabled applications.

3.1. Application Control Capabilities

   To control advertisement of state related to non-negotiated LDP
   applications, namely IP Label switching and L2VPN/PW signaling, two
   new capability TLVs are defined as described in the following
   subsections.

3.1.1. IP Label Switching Capability TLV

   The IP Label Switching capability is a new Capability Parameter
   defined with the following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|0| IP Label Sw. Cap (IANA)   |           Length (2)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1| Reserved    | AF Bitmap     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The value of the U-bit for the IP capability parameter TLV MUST be
   set to 1 so that a receiver MUST silently ignore this TLV if unknown


Raza                    Expires December 2011                   [Page 4]


Internet-Draft          LDP IP and PW Capability               June 2011


   to it, and continue processing the rest of the message. Once
   advertised, this capability cannot be withdrawn and hence the S-bit
   must always be set to 1 both in Initialization message and Capability
   message. The capability data associated with this TLV is 1 octet long
   "Address Family Bitmap", and hence the TLV length MUST be set to 2.

   The Capability data "Address Family Bitmap" is defined as:


    7 6 5 4 3 2 1 0
   +-+-+-+-+-+-+-+-+
   |   AF bitmap   |
   +-+-+-+-+-+-+-+-+

   Where:

       bit0: IPv4 label switching application

       bit1: IPv6 label switching application

       bit2-7: Reserved.

   A bit in the bitmap is set to 0 or 1 to disable or enable
   respectively a corresponding IP application.

   As described earlier, "IP Label Switching" Capability Parameter TLV
   MAY be included by an LDP speaker in an Initialization message to
   signal to its peer LSR that state exchange for IPv4 and/or IPv6
   application(s) need to be disabled on a given peer session. This TLV
   can also be sent later in a Capability message to selectively enable
   or disable IPv4/v6 label switching application(s).

3.1.2. PW Signaling Capability TLV

   The "PW Signaling" capability is a new Capability Parameter defined
   with the following format:

    0                   1                   2                   3

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|0|  PW Sig. Cap (IANA)       |           Length (2)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1| Reserved    |E| Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



Raza                    Expires December 2011                   [Page 5]


Internet-Draft          LDP IP and PW Capability               June 2011


   The value of the U-bit for the PW capability parameter TLV MUST be
   set to 1 so that a receiver MUST silently ignore this TLV if unknown
   to it, and continue processing the rest of the message. Once
   advertised, this capability cannot be withdrawn and hence the S-bit
   MUST always be set to 1 in Initialization message or Capability
   message. The capability data associated with this TLV is 1 octet long
   and hence the TLV length MUST be set to 2.

   The capability data is defined as following byte:

   7 6 5 4 3 2 1 0
   +-+-+-+-+-+-+-+-+
   |E|   Reserved  |
   +-+-+-+-+-+-+-+-+


   Where E-bit (Enable bit) is used to control PW signaling application
   by setting it to 0 and 1 to disable and enable the application
   respectively.

   As described earlier, PW Signaling Capability Parameter TLV MAY be
   included by an LDP speaker in an Initialization message to signal to
   its peer LSR that state exchange for PW application need to be
   disabled on given peer session. This TLV can also be sent later in a
   Capability message to enable/disable the PW Signaling application.

3.2. Procedures for Application Control Capabilities in an
     Initialization message

   LDP Capabilities [RFC5561] dictate that the S-bit of capability
   parameter in an Initialization message MUST be set to 1 and SHOULD be
   ignored on receipt.

   An LDP speaker determines (e.g. via some local configuration or
   default policy) if they need to disable IP and/or L2VPN/PW
   applications with a peer LSR. If there is a need to disable, then the
   IP and/or PW application capability TLVs need to be included in the
   Initialization message with respective application bits set to 0 to
   indicate application disable, where the application bit refers to a
   bit in "Address Family Bitmap" of the "IP Label Switching" Capability
   or E-bit in "PW Signaling" Capability.

   An LDP speaker that supports the "IP Label Switching" and/or "PW
   Signaling" capability MUST interpret those TLVs in a received
   Initialization message such that it disables the advertisement of the


Raza                    Expires December 2011                   [Page 6]


Internet-Draft          LDP IP and PW Capability               June 2011


   application state towards the sender LSR for IP (v4 and/or v6) and/or
   L2VPN/PW applications if their application control bits are set to 0.
   If a receiving LDP speaker does not understand the capability TLVs,
   then it MUST respond to the sender with "Unsupported TLV"
   Notification as described in LDP Capabilities [RFC5561]. Upon receipt
   of such Notification, the sender MAY still continue to block/disable
   its outbound state advertisement towards the peer for the requested
   disabled applications.

   Once this capability has been sent by sender LSR and received and
   understood by the receiver LSR, then both these LSRs MUST NOT
   exchange any state related to the disabled applications until and
   unless these applications are explicitly enabled again (e.g. via the
   same Capability TLV sent in a Capability message with corresponding
   application control bit set to 1).

   "IP Label Switching" and "PW Signaling" capability TLVs are
   unilateral/uni-directional in nature. This means that the receiving
   LSR may not need to send a similar capability TLV in an
   Initialization or Capability message towards the sender. This
   unilateral behavior also conforms to the procedures defined in the
   Section 6 of LDP Capabilities [RFC5561].

3.3. Procedures for Application Control capabilities in a Capability
   message

   If the LDP peer supports "Dynamic Announcement Capability" [RFC5561],
   then an LDP speaker can send IP Label Switching and/or PW Signaling
   capability in a Capability message. Once advertised, these
   capabilities cannot be withdrawn and hence the S-bit of the TLV MUST
   be set to 1 when sent in a Capability message.

   An LDP speaker may decide to send this TLV towards an LDP peer if any
   of its IP and/or L2VPN/PW signaling applications gets disabled, or if
   previously disabled IP and/or L2VPN/PW applications gets enabled
   again. In this case, LDP speaker constructs the TLVs with appropriate
   application control bitmap and sends the corresponding capability
   TLVs in a Capability message. Furthermore, the LDP speaker also
   withdraws application(s) related advertised state (such as label
   bindings) from its peer.

   Upon receipt of those TLVs in a Capability message, the receiving LDP
   speaker reacts in the same manner as it reacts upon the receipt of
   those TLVs in an Initialization message. Additionally, the receiving
   LDP speaker withdraws the application(s) related advertised state
   (such as label bindings) from the sending LDP speaker. If the
   receiving LDP speaker does not understand or support either Dynamic


Raza                    Expires December 2011                   [Page 7]


Internet-Draft          LDP IP and PW Capability               June 2011


   Announcement capability or received Application Control capability
   TLV ("IP Label Switching" or "PW Signaling"), it MUST respond with
   "Unsupported Capability" notification to the sender of the Capability
   message.

4. Operational Examples

4.1. Disabling IP/PW label applications on an ICCP session

   Consider two PE routers, LSR1 and LSR2, which understand/support "IP
   Label Switching" and "PW Signaling" capability TLVs. These LSR have
   an established LDP session due to ICCP application in order to
   exchange ICCP state related to dual-homed devices connected to these
   LSRs. Let us assume that LSR1 is provisioned not to exchange any
   label bindings related to IP (v4/v6) prefixes and PW layer2 FEC
   (FEC128/129) with LSR2.

   To indicate its "disability" for the IP/PW applications, the LSR1
   will include both the "IP Label Switching" capability TLV (with
   bit0-1 of "Address Family Bitmap" set to 0) and "PW Signaling"
   capability TLV (with E-bit set to 0) in the Initialization message.
   Upon receipt of those TLVs in Initialization message, the LSR2 will
   disable any IP/PW address/label binding state advertisement towards
   LSR1 after session establishment.

   The LSR1 will also disable any IP/PW address/label binding state
   towards LSR2, irrespective of the fact whether or not LSR2 could
   disable the corresponding application state advertisement towards
   LSR1.

4.2. Disabling IP Label Switching application on a L2VPN/PW session

   Now, consider LSR1 and LSR2 have an established session due to
   L2VPN/PW application just to exchange PW (FEC128/129) label
   bindings for VPWS/VPLS services amongst them. Since in most typical
   deployments, there is no need to exchange IP (v4/v6) address/label
   bindings amongst the PE LSRs, let us assume that LSR1 is provisioned
   to disable IP (v4/v6) application on given PW session towards LSR2.

   To indicate its disability for IP application, the LSR1 will include
   the "IP Label Switching" capability TLV in the Initialization
   message with bit0-1 (IPv4, IPv6) in "Address Family Bitmap" set to
   zero. Upon receipt of this TLV in Initialization message, the LSR2
   will disable any IP address/label binding state advertisement
   towards LSR1.




Raza                    Expires December 2011                   [Page 8]


Internet-Draft          LDP IP and PW Capability               June 2011


   The LSR1 will also disable any IP address/label binding state
   towards LSR2, irrespective of the fact whether or not LSR2 could
   disable the corresponding IP application state advertisement towards
   LSR1.

4.3. Disabling IP application dynamically on an established IP/PW
   session

   Assume that LSRs from previous sections were initially provisioned to
   exchange both IP and PW state over the session between them, and also
   support "Dynamic Announcement" capability [RFC5561]. Now, assume that
   LSR1 is dynamically provisioned to disable IP label switching with
   LSR2. In this case, LSR1 will first withdraw all its IP label state
   by sending a single Label Withdraw message with IP Prefix Typed
   Wildcard FEC using the mechanics described in [RFC5918], and Address
   Withdraw message to withdraw its addresses. LSR1 will also send IP
   Label Switching capability TLV in Capability message towards LSR2
   with bit0-1 (IPv4, IPv6) in "Address Family Bitmap" set to zero. Upon
   receipt of this TLV, LSR2 will also disable IP label switching
   towards LSR1 and withdraw all previous IP application label/address
   state using the same mechanics as described earlier for LSR1. The
   disability of IP label switching dynamically should not impact
   L2VPN/PW application on given session, and both LSRs should continue
   to exchange PW Signaling application related state.

5. Security Considerations

  The proposal introduced in this document does not introduce any new
  security considerations beyond that already apply to the base LDP
  specification [RFC5036] and [RFC5920].

6. IANA Considerations

  The document introduces following two new capability parameter TLVs
  and requests following LDP TLV code point assignment by IANA:

   o  "IP Label Switching" Capability TLV (requested codepoint: 0x50C)

   o  "PW Signaling" Capability TLV       (requested codepoint: 0x50D)









Raza                    Expires December 2011                   [Page 9]


Internet-Draft          LDP IP and PW Capability               June 2011


7. Conclusions

   The document proposed a solution using LDP Capabilities [RFC5561]
   mechanics to disable unnecessary state exchange, if/as desired,
   between LDP peers for currently non-negotiated IP/PW applications.

8. References

8.1. Normative References

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

   [RFC5918] Asati, R., Minei, I., and Thomas, B. "Label Distribution
             Protocol Typed Wildcard FEC", RFC 5918, August 2010.

   [ICCP]    Martini, L., Salam, S., and Matsushima, S., "Inter-Chassis
             Communication Protocol for L2VPN PE Redundancy", draft-
             ietf-pwe3-iccp-04.txt, Work in Progress, October 2010.

   [MLDP]    Minei, I., Kompella, K., Wijnands, I., and Thomas, B., "LDP
             Extensions for Point-to-Multipoint and Multipoint-to-
             Multipoint Label Switched Paths", draft-ietf-mpls-ldp-p2mp
             -10.txt, Work in Progress, July 2010.

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

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

8.2. Informative References

   [RFC5036] Andersson, L., Menei, I., and Thomas, B., Editors, "LDP
             Specification", RFC 5036, September 2007.

   [RFC5920] Fang, L. et al., "Security Framework for MPLS and GMPLS
             Networks", RFC 5920, July 2010.

9. Acknowledgments

   The authors would like to thank Eric Rosen for his valuable input and
   comments.

   This document was prepared using 2-Word-v2.0.template.dot.



Raza                    Expires December 2011                   [Page 10]


Internet-Draft          LDP IP and PW Capability              June 2011


Authors' Addresses

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

  Sami Boutros
  Cisco Systems, Inc.
  3750 Cisco Way,
  San Jose, CA 95134, USA.
  E-mail: sboutros@cisco.com


































Raza                    Expires December 2011                   [Page 11]


Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/