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CCAMP WG                                                  O. Aboul-Magd

Document: draft-aboulmagd-ccamp-crldp-00.txt            Nortel Networks
Feb. 2002

     Supporting Call and Connection Control Separation using CR-LDP

Status of this Memo

   This document is an Internet-Draft and is in full conformance wit
   all provisions of Section 10 of RFC2026 [1].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
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   as reference material or to cite them other than as "work in

   The list of current Internet-Drafts can be accessed at
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1. Abstract

   There has been a recent activity towards the use of GMPLS-based
   protocols (CR-LDP and RSVP-TE) for automatic switched optical
   networks (ASON) at the ITU-T. ASON control plane requirements
   mandates the separate treatment of call and connection control. This
   draft proposes additional CR-LDP messages necessary for satisfying
   this goal.

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in RFC-2119 [2].

3. Introduction

   Automatic Switched optical networks (ASON) architecture [3] and
   GMPLS are progressing in parallel at the ITU-T and IETF
   respectively. As it has been pointed out in [4], the two efforts are
   complementary in the sense that GMPLS-based protocol could be used
   for the realization of ASON control plane. Recently GMPLS-based

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   protocols have been submitted to ITU-T [5,6] as possible candidates
   for ASON signaling implementation as defined in G.7713 [7].

   One important architecture principle of ASON is that call and
   connection control are treated separately. With this separation
   there could be the case where a single call has one or more
   connections associated to it. It is also quite possible to have a
   call with no connections associated to it, for example during
   recovery times.

   The current set of GMPLS signaling protocols, i.e. CR-LDP and RSVP-
   TE do not support this requirement. In reality the notion of a call
   is absent in both protocols. A label switched path (LSP), or a
   connection, is set end-to-end by assigning a set of labels on the
   different nodes along the path. Once an LSP is deleted, all the
   information regarding its end points is lost.

   This draft describes messages necessary to introduce call and
   connection control separation to CR-LDP.

4. CR-LDP Call Control

   As it has been stated in [8], (CR-)LDP employs four categories of
   messages. Those categories are:

   1. Discovery messages, use to announce and maintain the presence of
   a network element in the network

   2. Session messages, used to establish, maintain, and terminate LDP
   sessions between LDP pairs

   3. Advertisement messages, used to create, change, and delete label

   4. Notification messages, used to provide advisory information to
   signal error information.

   A new category related to query messages was introduced in [9] and
   is used to query different information related to an operational LSP

   The third category of the above list is the one that is supposed to
   be used for connection creation, deletion, and modification in an
   optical network. New connection is created by assigning a
   generalized ingress and egress labels at every node along the path
   of the connection. This process is achieved using Label Request and
   Label Mapping messages, which carry in their TLVs the necessary
   characteristics of the required connection. Label Request and Label
   Mapping requests and confirm the assignment of a generalized label
   to a connection. In a similar way Label Withdraw and Label Release
   Messages are used to delete a connection by releasing the label
   assigned to it.

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   The processes described here are all at the connection level since
   they all involve request, assignment, or release of a label. In
   contrast to that, with the separation of call and connection in
   mind, the setup of a call MUST not involve any of those processes. A
   call setup is mainly for the exchange of call control information
   between the two end points of a call. Thus there is the need for the
   introduction of a new category specifically for call control. The
   new category is called here "call control messages".

4.1 CR-LDP Call Control Messages

   This section describes those additional messages that are needed to
   support the separation of call and connection control requirements
   in ASON.

   A mechanism for call setup and deletion is needed for CR-LDP to
   support call control that is separate from that of the connection
   control part described previously. This mechanism necessitates the
   introduction of two CR-LDP messages, Call Setup and Call Delete

   The calling party sends the Call Setup message and it carries
   information related to the calling and called parties, e.g. their
   addresses, etc. It may also carry information related to the service
   level agreement (SLA) associated to a particular call.

   The Call Delete message could be initiated by any network entity
   (network or client) to terminate a call. All connections associated
   with this call have to be cleared before clearing the call.

   The formats and procedures for Call Setup and Call Delete are given
   in section 5.

4.2 Impact on Other (CR-)LDP Messages

   The introduction of call control messages is expected to have some
   impact on other (CR-)LDP messages in two ways. The first impact is
   related to new TLV added to some of the messages. For instance, with
   the call and connection control separation, it is necessary to
   introduce a call association indication to the Label Request message
   to indicate the call for which the requested connection is
   associated. The impact on LDP messages are described in section 6.

5. Call Setup and Call Delete Messages

   This section describes the encoding of the two messages related to
   CR-LDP call control.

5.1 Call Setup Message

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   The format of the Call Setup message is:

   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| Call Setup (TBD)          |      Length                   |
   |                           Message ID                          |
   |                Calling Party Number TLV                       |
   |                Called Party Number TLV                        |
   |                      Call ID TLV                              |

   Message ID:
        32-bit value used to identify this message

   Calling Party Number TLV:
      The address of the party that is initiating the call request. It
     has the same format as the Transport Network Assigned (TNA)
     address in [10]

   Called Party Number TLV:
      The address of the called party. It has the same format as the
     TNA in [10]

   Call ID TLV:
      The purpose of the call identifier (Call ID) TLV is to locally
     identify a call in the context of separated call and connection
     control environment.

      The format of the Call Identifier TLV is:

     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| Call ID (TBD)             |      Length                   |
     |                           Call ID                             |

      The Calling party initiates a call setup by sending the Call
     Setup message. The Call Setup message SHALL contain all the
     information required by the network to process the call. In
     Particular the calling and called party addresses.

      The Call Setup message MUST include call identifier TLV. The call
     control entity shall identify the call using the selected
     identifier for the lifetime of the call.

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      The Call Setup message shall progress through the network to the
     called party. The called party may accept or reject the incoming
     call. An LDP Notification message with the appropriate status code
     (to be defined) shall be used to inform the calling party whether
     the setup is successful. The call can be rejected by either the
     network, e.g. for policy reasons, or by the called party.

5.2 Call Delete Message

    The format of the Call Setup message is:

   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| Call Delete (TBD)         |      Length                   |
   |                           Message ID                          |
   |                Calling Party Number TLV                       |
   |                Called Party Number TLV                        |
   |                      Call ID TLV                              |

   Message ID:
        32-bit value used to identify this message

   Calling Party Number TLV:
      Same as for Call Setup Message

   Called Party Number TLV:
      Same as for Call Setup message

   Call ID TLV:
      Same as for Call Setup message

      The Call Delete message is sent by any entity of the network to
     indicate the desire to terminate an already established call. The
     Call Setup message SHALL contain all the information required by
     the network to process the call. In Particular the calling and
     called party addresses. Confirmation of call deletion is indicated
     to the request initiator using a Notification message with the
     appropriate status code.

6. Impact on Other LDP Messages

   The separation of call and connection control allows one or more
   connection to be associated to the same call. This will have an
   impact on existing LDP messages relevant to the establishment and
   deletion of a connection (LSP). The full impact on LDP messages in

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   terms of additional TLVs and procedures will be addressed in future
   revisions pf the draft.

7. Security Considerations

   This draft doesn't introduce any new security issues other than
   those defined in RFC 3036 and RFC 3212

8. References

   1  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
      9, RFC 2026, October 1996.

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

   3  M. Mayer, Ed., "Architecture for Automatic Switched Optical
      Networks (ASON)", ITU G.8080/Y1304, V1.0, October 2001

   4  O. Aboul-Magd, et. al., "Automatic Switched Optical Networks
      (ASON) Architecture and its Related Protocols", draft-ietf-ipo-
      ason-02.txt, work in progress, Feb. 2002.

   5  S. Shew, "A Proposal for DCM Signaling Using GMPLS CR-LDP", ITU
      Contribution, WD25, Feb. 2002.

   6  D. Pendarakis, "Proposal for G.7713.2 Based on GMPLS", ITU
      Contribution, WD06, Feb. 2002

   7  Z. Lin, Ed., "Distributed Call and Connection Management", ITU
      G.7713/Y.1704, October 2001

   8  Anderson, L., et. al., "LDP Specification", RFC 3036, January

   9 P. Ashwood-Smith, et. al., "MPLS LDP Query Message Description",
      draft-ietf-mpls-lsp-query-txt.03, work in progress, August 2001.

   10 Rajagopalan, B. Editor, "User Network Interface (UNI) 1.0
      Signaling Specifications", OIF Contribution, OIF2000.125.7,
      October 2001

9. Author's Addresses

   Osama Aboul-Magd

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   Nortel Networks
   P.O. Box 3511, Station "C"
   Ottawa, Ontario, Canada
   K1Y - 4H7
   Phone: 613-763-5827
   Email: osama@nortelnetworks.com

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