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RFC 4497

 
 
 

Interworking between the Session Initiation Protocol (SIP) and QSIG

Part 4 of 4, p. 45 to 65
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Appendix A.  Example Message Sequences

A.1.  Introduction

   This appendix shows some typical message sequences that can occur for
   an interworking between QSIG and SIP.  It is informative.

   NOTE: For all message sequence diagrams, there is no message mapping
   between QSIG and SIP unless explicitly indicated by dotted lines.
   Also, if there are no dotted lines connecting two messages, this
   means that these are independent of each other in terms of the time
   when they occur.

   NOTE: Numbers prefixing SIP method names and response codes in the
   diagrams represent sequence numbers.  Messages bearing the same
   number will have the same value in the CSeq header.

   NOTE: In these examples, SIP provisional responses (other than 100)
   are shown as being sent reliably, using the PRACK method for
   acknowledgement.

A.2.  Message Sequences for Call Establishment from QSIG to SIP

   Below are typical message sequences for successful call establishment
   from QSIG to SIP

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A.2.1.  QSIG to SIP, using en bloc procedures on both QSIG and SIP

                           +-------------------+
                           |                   |
                           |     GATEWAY       |
        PISN               |                   |        IP NETWORK
        |                  +-----+------+------+                 |
        |                        |      |                        |
        |                        |      |                        |
        |   QSIG SETUP           |      |        1-INVITE        |
       1|----------------------->|......|----------------------->| 2
        |                        |      |                        |
        |                        |      |                        |
        | QSIG CALL PROCEEDING   |      |        1-100 TRYING    |
       3|<-----------------------|      |<-----------------------+ 4
        |                        |      |                        |
        |                        |      |                        |
        |   QSIG ALERTING        |      |        1-180 RINGING   |
       8|<-----------------------|......|<-----------------------+ 5
        |                        |      |                        |
        |                        |      |        2-PRACK         |
        |                        |      |----------------------->| 6
        |                        |      |        2-200 OK        |
        |                        |      |<-----------------------+ 7
        |                        |      |                        |
        |   QSIG CONNECT         |      |        1-200 OK        |
      11|<-----------------------|......|<-----------------------+ 9
        |                        |      |                        |
        |   QSIG CONNECT ACK     |      |        1-ACK           |
      12|----------------------->|      |----------------------->| 10
        |                        |      |                        |
        |<======================>|      |<======================>|
        |        AUDIO           |      |         AUDIO          |

   Figure 3: Typical message sequence for successful call establishment
   from QSIG to SIP, using en bloc procedures on both QSIG and SIP

   1  The PISN sends a QSIG SETUP message to the gateway to begin a
      session with a SIP UA.
   2  On receipt of the QSIG SETUP message, the gateway generates a SIP
      INVITE request and sends it to an appropriate SIP entity in the IP
      network based on the called number.
   3  The gateway sends a QSIG CALL PROCEEDING message to the PISN; no
      more QSIG INFORMATION messages will be accepted.
   4  The IP network sends a SIP 100 (Trying) response to the gateway.
   5  The IP network sends a SIP 180 (Ringing) response.

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   6  The gateway may send back a SIP PRACK request to the IP network
      based on the inclusion of a Require header or a Supported header
      with option tag 100rel in the initial SIP INVITE request.
   7  The IP network sends a SIP 200 (OK) response to the gateway to
      acknowledge the SIP PRACK request
   8  The gateway maps this SIP 180 (Ringing) response to a QSIG
      ALERTING message and sends it to the PISN.
   9  The IP network sends a SIP 200 (OK) response when the call is
      answered.
   10 The gateway sends a SIP ACK request to acknowledge the SIP 200
      (OK) response.
   11 The gateway maps this SIP 200 (OK) response to a QSIG CONNECT
      message and sends it to the PISN.
   12 The PISN sends a QSIG CONNECT ACKNOWLEDGE message in response to
      the QSIG CONNECT message.

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A.2.2.  QSIG to SIP, using overlap receiving on QSIG and en bloc sending
        on SIP

                        +------------------------+
     PISN               |         GATEWAY        |      IP NETWORK
                        |                        |
     |  QSIG SETUP      +--------+-------+-------+                |
    1|-------------------------->|       |                        |
     |                           |       |                        |
     |  QSIG SETUP ACK           |       |                        |
    2|<--------------------------|       |                        |
     |                           |       |                        |
     | QSIG INFORMATION          |       |                        |
    3|-------------------------->|       |                        |
     |                           |       |                        |
     | QSIG INFORMATION          |       |  1-INVITE              |
   3a|-------------------------->|.......|----------------------->|4
     | QSIG CALL PROCEEDING      |       |  1-100 TRYING          |
    5|<--------------------------|       |<-----------------------|6
     |                           |       |                        |
     | QSIG ALERTING             |       |  1-180 RINGING         |
   10|<--------------------------|.......|<-----------------------|7
     |                           |       |  2-PRACK               |
     |                           |       |----------------------->|8
     |                           |       |  2-200 OK              |
     |                           |       |<-----------------------|9
     | QSIG CONNECT              |       |  1-200 OK              |
   13|<--------------------------|.......|<-----------------------|11
     |                           |       |                        |
     | QSIG CONNECT ACK          |       |  1-ACK                 |
   14|-------------------------->|       |----------------------->|12
     |          AUDIO            |       |           AUDIO        |
     |<=========================>|       |<======================>|

   Figure 4: Typical message sequence for successful call establishment
   from QSIG to SIP, using overlap receiving on QSIG and en bloc sending
   on SIP

   1  The PISN sends a QSIG SETUP message to the gateway to begin a
      session with a SIP UA.  The QSIG SETUP message does not contain a
      Sending Complete information element.
   2  The gateway sends a QSIG SETUP ACKNOWLEDGE message to the PISN.
      More digits are expected.
   3  More digits are sent from the PISN within a QSIG INFORMATION
      message.
   3a More digits are sent from the PISN within a QSIG INFORMATION
      message.  The QSIG INFORMATION message contains a Sending Complete
      information element.

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   4  The Gateway generates a SIP INVITE request and sends it to an
      appropriate SIP entity in the IP network, based on the called
      number.
   5  The gateway sends a QSIG CALL PROCEEDING message to the PISN; no
      more QSIG INFORMATION messages will be accepted.
   6  The IP network sends a SIP 100 (Trying) response to the gateway.
   7  The IP network sends a SIP 180 (Ringing) response.
   8  The gateway may send back a SIP PRACK request to the IP network
      based on the inclusion of a Require header or a Supported header
      with option tag 100rel in the initial SIP INVITE request.
   9  The IP network sends a SIP 200 (OK) response to the gateway to
      acknowledge the SIP PRACK request.
   10 The gateway maps this SIP 180 (Ringing) response to a QSIG
      ALERTING message and sends it to the PINX.
   11 The IP network sends a SIP 200 (OK) response when the call is
      answered.
   12 The gateway sends an SIP ACK request to acknowledge the SIP 200
      (OK) response.
   13 The gateway maps this SIP 200 (OK) response to a QSIG CONNECT
      message and sends it to the PINX.
   14 The PISN sends a QSIG CONNECT ACKNOWLEDGE message in response to
      the QSIG CONNECT message.

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A.2.3.  QSIG to SIP, using overlap procedures on both QSIG and SIP

                        +----------------------+
     PISN               |        GATEWAY       |         IP NETWORK
                        |                      |
     |  QSIG SETUP      +-------+-------+------+                  |
   1 |------------------------->|       |                         |
     |                          |       |                         |
     |  QSIG SETUP ACK          |       |                         |
   2 |<-------------------------|       |                         |
     |                          |       |                         |
     | QSIG INFORMATION         |       |                         |
   3 |------------------------->|       |                         |
     | QSIG INFORMATION         |       | 1-INVITE                |
   3 |------------------------->|.......|------------------------>|4
     |                          |       | 1-484                   |
     |                          |       |<------------------------|5
     |                          |       | 1-ACK                   |
     |                          |       |------------------------>|6
     | QSIG INFORMATION         |       | 2-INVITE                |
   7 |------------------------->|.......|------------------------>|4
     |                          |       | 2-484                   |
     |                          |       |<------------------------|5
     |                          |       | 2-ACK                   |
     |                          |       |------------------------>|6
     |                          |       |                         |
     | QSIG INFORMATION         |       |                         |
     | Sending Complete IE      |       | 3-INVITE                |
   8 |------------------------->|.......|------------------------>|10
     | QSIG CALL PROCEEDING     |       | 3-100 TRYING            |
   9 |<-------------------------|       |<------------------------|11
     |                          |       |                         |
     | QSIG ALERTING            |       | 3-180 RINGING           |
   15|<-------------------------|.......|<------------------------|12
     |                          |       | 4-PRACK                 |
     |                          |       |------------------------>|13
     |                          |       | 4-200 OK                |
     |                          |       |<------------------------|14
     | QSIG CONNECT             |       | 3-200 OK                |
   18|<-------------------------|.......|<------------------------|16
     |                          |       |                         |
     | QSIG CONNECT ACK         |       | 3-ACK                   |
   19|------------------------->|       |------------------------>|17
     |         AUDIO            |       |         AUDIO           |
     |<========================>|       |<=======================>|
     |                          |       |                         |

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   Figure 5: Typical message sequence for successful call establishment
   from QSIG to SIP, using overlap procedures on both QSIG and SIP

   1  The PISN sends a QSIG SETUP message to the gateway to begin a
      session with a SIP UA.  The QSIG SETUP message does not contain a
      Sending complete information element.
   2  The gateway sends a QSIG SETUP ACKNOWLEDGE message to the PISN.
      More digits are expected.
   3  More digits are sent from the PISN within a QSIG INFORMATION
      message.
   4  When the gateway receives the minimum number of digits required to
      route the call, it generates a SIP INVITE request and sends it to
      an appropriate SIP entity in the IP network based on the called
      number
   5  Due to an insufficient number of digits, the IP network will
      return a SIP 484 (Address Incomplete) response.
   6  The SIP 484 (Address Incomplete) response is acknowledged.
   7  More digits are received from the PISN in a QSIG INFORMATION
      message.  A new INVITE is sent with the same Call-ID and From
      values but an updated Request-URI.
   8  More digits are received from the PISN in a QSIG INFORMATION
      message.  The QSIG INFORMATION message contains a Sending Complete
      information element.
   9  The gateway sends a QSIG CALL PROCEEDING message to the PISN; no
      more information will be accepted.
   10 The gateway sends a new SIP INVITE request with an updated
      Request-URI field.
   11 The IP network sends a SIP 100 (Trying) response to the gateway.
   12 The IP network sends a SIP 180 (Ringing) response.
   13 The gateway may send back a SIP PRACK request to the IP network
      based on the inclusion of a Require header or a Supported header
      with option tag 100rel in the initial SIP INVITE request.
   14 The IP network sends a SIP 200 (OK) response to the gateway to
      acknowledge the SIP PRACK request.
   15 The gateway maps this SIP 180 (Ringing) response to a QSIG
      ALERTING message and sends it to the PISN.
   16 The IP network sends a SIP 200 (OK) response when the call is
      answered.
   17 The gateway sends a SIP ACK request to acknowledge the SIP 200
      (OK) response.
   18 The gateway maps this SIP 200 (OK) response to a QSIG CONNECT
      message.
   19 The PISN sends a QSIG CONNECT ACKNOWLEDGE message in response to
      the QSIG CONNECT message.

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A.3.  Message sequences for call establishment from SIP to QSIG

   Below are typical message sequences for successful call establishment
   from SIP to QSIG

A.3.1.  SIP to QSIG, using en bloc procedures

                        +----------------------+
     IP NETWORK         |        GATEWAY       |              PISN
                        |                      |
     |                  +-------+-------+------+                  |
     |                          |       |                         |
     |                          |       |                         |
     |     1-INVITE             |       | QSIG SETUP              |
   1 |------------------------->|.......|------------------------>|3
     |     1-100 TRYING         |       | QSIG CALL PROCEEDING    |
   2 |<-------------------------|       |<------------------------|4
     |     1-180 RINGING        |       | QSIG ALERTING           |
   6 |<-------------------------|.......|<------------------------|5
     |                          |       |                         |
     |                          |       |                         |
     |     2-PRACK              |       |                         |
   7 |------------------------->|       |                         |
     |     2-200 OK             |       |                         |
   8 |<-------------------------|       |                         |
     |     1-200 OK             |       | QSIG CONNECT            |
   11|<-------------------------|.......|<------------------------|9
     |                          |       |                         |
     |     1-ACK                |       | QSIG CONNECT ACK        |
   12|------------------------->|       |------------------------>|10
     |         AUDIO            |       |         AUDIO           |
     |<========================>|       |<=======================>|
     |                          |       |                         |

   Figure 6: Typical message sequence for successful call establishment
   from SIP to QSIG, using en bloc procedures

   1  The IP network sends a SIP INVITE request to the gateway.
   2  The gateway sends a SIP 100 (Trying) response to the IP network.
   3  On receipt of the SIP INVITE request, the gateway sends a QSIG
      SETUP message.
   4  The PISN sends a QSIG CALL PROCEEDING message to the gateway.
   5  A QSIG ALERTING message is returned to indicate that the end user
      in the PISN is being alerted.
   6  The gateway maps the QSIG ALERTING message to a SIP 180 (Ringing)
      response.

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   7  The IP network can send back a SIP PRACK request to the IP network
      based on the inclusion of a Require header or a Supported header
      with option tag 100rel in the initial SIP INVITE request.
   8  The gateway sends a SIP 200 (OK) response to acknowledge the SIP
      PRACK request.
   9  The PISN sends a QSIG CONNECT message to the gateway when the call
      is answered.
   10 The gateway sends a QSIG CONNECT ACKNOWLEDGE message to
      acknowledge the QSIG CONNECT message.
   11 The QSIG CONNECT message is mapped to a SIP 200 (OK) response.
   12 The IP network, upon receiving a SIP INVITE final response (200),
      will send a SIP ACK request to acknowledge receipt.

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A.3.2.  SIP to QSIG, using overlap receiving on SIP and en bloc sending
        on QSIG

                        +----------------------+
     IP NETWORK         |        GATEWAY       |               PISN
                        |                      |
     | 1-INVITE         +-------+-------+------+                  |
   1 |------------------------->|       |                         |
     |     1-484                |       |                         |
   2 |<-------------------------|       |                         |
     |     1-ACK                |       |                         |
   3 |------------------------->|       |                         |
     |     2-INVITE             |       |                         |
   1 |------------------------->|       |                         |
     |     2-484                |       |                         |
   2 |<-------------------------|       |                         |
     |     2- ACK               |       |                         |
   3 |------------------------->|       |                         |
     |     3-INVITE             |       | QSIG SETUP              |
   4 |------------------------->|.......|------------------------>|6
     |     3-100 TRYING         |       | QSIG CALL PROCEEDING    |
   5 |<-------------------------|       |<------------------------|7
     |     3-180 RINGING        |       | QSIG ALERTING           |
   9 |<-------------------------|.......|<------------------------|8
     |                          |       |                         |
     |                          |       |                         |
     |     4-PRACK              |       |                         |
   10|------------------------->|       |                         |
     |     4-200 OK             |       |                         |
   11|<-------------------------|       |                         |
     |     3-200 OK             |       | QSIG CONNECT            |
   14|<-------------------------|.......|<------------------------|12
     |                          |       |                         |
     |     3-ACK                |       | QSIG CONNECT ACK        |
   15|------------------------->|       |------------------------>|13
     |         AUDIO            |       |         AUDIO           |
     |<========================>|       |<=======================>|
     |                          |       |                         |

   Figure 7: Typical message sequence for successful call establishment
   from SIP to QSIG, using overlap receiving on SIP and en bloc sending
   on QSIG

   1  The IP network sends a SIP INVITE request to the gateway.
   2  Due to an insufficient number of digits, the gateway returns a SIP
      484 (Address Incomplete) response.
   3  The IP network acknowledges the SIP 484 (Address Incomplete)
      response.

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   4  The IP network sends a new SIP INVITE request with the same Call-
      ID and updated Request-URI.
   5  The gateway now has all the digits required to route the call to
      the PISN.  The gateway sends back a SIP 100 (Trying) response.
   6  The gateway sends a QSIG SETUP message.
   7  The PISN sends a QSIG CALL PROCEEDING message to the gateway.
   8  A QSIG ALERTING message is returned to indicate that the end user
      in the PISN is being alerted.
   9  The gateway maps the QSIG ALERTING message to a SIP 180 (Ringing)
      response.
   10 The IP network can send back a SIP PRACK request to the IP network
      based on the inclusion of a Require header or a Supported header
      with option tag 100rel in the initial SIP INVITE request.
   11 The gateway sends a SIP 200 (OK) response to acknowledge the SIP
      PRACK request.
   12 The PISN sends a QSIG CONNECT message to the gateway when the call
      is answered.
   13 The gateway sends a QSIG CONNECT ACKNOWLEDGE message to
      acknowledge the CONNECT message.
   14 The QSIG CONNECT message is mapped to a SIP 200 (OK) response.
   15 The IP network, upon receiving a SIP INVITE final response (200),
      will send a SIP ACK request to acknowledge receipt.

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A.3.3.  SIP to QSIG, using overlap procedures on both SIP and QSIG

                        +----------------------+
     IP NETWORK         |        GATEWAY       |               PISN
                        |                      |
     | 1-INVITE         +-------+-------+------+                  |
   1 |------------------------->|       |                         |
     |     1-484                |       |                         |
   2 |<-------------------------|       |                         |
     |     1-ACK                |       |                         |
   3 |------------------------->|       |                         |
     |     2-INVITE             |       | QSIG SETUP              |
   4 |------------------------->|.......|------------------------>|6
     |     2-100 TRYING         |       | QSIG SETUP ACK          |
   5 |<-------------------------|       |<------------------------|7
     |     3- INVITE            |       | QSIG INFORMATION        |
   8 |------------------------->|.......|------------------------>|10
     |     3-100 TRYING         |       |                         |
   9 |<-------------------------|       | QSIG CALL PROCEEDING    |
     |                          |       |<------------------------|11
   13|     3-180 RINGING        |       | QSIG ALERTING           |
     |<-------------------------|.......|<------------------------|12
     |     2-484                |       |                         |
   14|<-------------------------|       |                         |
     |     2-ACK                |       |                         |
   15|------------------------->|       |                         |
     |     4-PRACK              |       |                         |
   16|------------------------->|       |                         |
     |     4-200 OK             |       |                         |
   17|<-------------------------|       |                         |
     |     3-200 OK             |       | QSIG CONNECT            |
   20|<-------------------------|.......|<------------------------|18
     |                          |       |                         |
     |     3-ACK                |       | QSIG CONNECT ACK        |
   21|------------------------->|       |------------------------>|19
     |         AUDIO            |       |         AUDIO           |
     |<========================>|       |<=======================>|
     |                          |       |                         |

   Figure 8: Typical message sequence for successful call establishment
   from SIP to QSIG, using overlap procedures on both SIP and QSIG

   1  The IP network sends a SIP INVITE request to the gateway.
   2  Due to an insufficient number of digits, the gateway returns a SIP
      484 (Address Incomplete) response.
   3  The IP network acknowledges the SIP 484 (Address Incomplete)
      response.

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   4  The IP network sends a new SIP INVITE request with the same
      Call-ID and updated Request-URI.
   5  The gateway now has all the digits required to route the call to
      the PISN.  The gateway sends back a SIP 100 (Trying) response to
      the IP network.
   6  The gateway sends a QSIG SETUP message.
   7  The PISN needs more digits to route the call and sends a QSIG
      SETUP ACKNOWLEDGE message to the gateway.
   8  The IP network sends a new SIP INVITE request with the same
      Call-ID and From values and updated Request-URI.
   9  The gateway sends back a SIP 100 (Trying) response to the IP
      network.
   10 The gateway maps the new SIP INVITE request to a QSIG INFORMATION
      message.
   11 The PISN has all the digits required and sends back a QSIG CALL
      PROCEEDING message to the gateway.
   12 A QSIG ALERTING message is returned to indicate that the end user
      in the PISN is being alerted.
   13 The gateway maps the QSIG ALERTING message to a SIP 180 (Ringing)
      response.
   14 The gateway sends a SIP 484 (Address Incomplete) response for the
      previous SIP INVITE request.
   15 The IP network acknowledges the SIP 484 (Address Incomplete)
      response.
   16 The IP network can send back a SIP PRACK request to the IP network
      based on the inclusion of a Require header or a Supported header
      with option tag 100rel in the initial SIP INVITE request.
   17 The gateway sends a SIP 200 (OK) response to acknowledge the SIP
      PRACK request.
   18 The PISN sends a QSIG CONNECT message to the gateway when the call
      is answered.
   19 The gateway sends a QSIG CONNECT ACKNOWLEDGE message to
      acknowledge the QSIG CONNECT message.
   20 The QSIG CONNECT message is mapped to a SIP 200 (OK) response.
   21 The IP network, upon receiving a SIP INVITE final response (200),
      will send a SIP ACK request to acknowledge receipt.

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A.4.  Message Sequence for Call Clearing from QSIG to SIP

   Below are typical message sequences for Call Clearing from QSIG to
   SIP

A.4.1.  QSIG to SIP, subsequent to call establishment

                         +-------------------+
                         |                   |
                         |     GATEWAY       |
     PISN                |                   |         IP NETWORK
      |                  +-----+------+------+                 |
      |                        |      |                        |
      |                        |      |                        |
      |     QSIG DISCONNECT    |      |   2- BYE               |
     1|----------------------->|......|----------------------->|4
      |     QSIG RELEASE       |      |        2-200 OK        |
     2|<-----------------------|      |<-----------------------|5
      |     QSIG RELEASE COMP  |      |                        |
     3|----------------------->|      |                        |
      |                        |      |                        |
      |                        |      |                        |
      |                        |      |                        |

   Figure 9: Typical message sequence for call clearing from QSIG to
   SIP, subsequent to call establishment

   1  The PISN sends a QSIG DISCONNECT message to the gateway.
   2  The gateway sends back a QSIG RELEASE message to the PISN in
      response to the QSIG DISCONNECT message.
   3  The PISN sends a QSIG RELEASE COMPLETE message in response.  All
      PISN resources are now released.
   4  The gateway maps the QSIG DISCONNECT message to a SIP BYE request.
   5  The IP network sends back a SIP 200 (OK) response to the SIP BYE
      request.  All IP resources are now released.

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A.4.2.  QSIG to SIP, during establishment of a call from SIP to QSIG

                              +-------------------+
                              |                   |
                              |     GATEWAY       |
           PISN               |                   |       IP NETWORK
           |                  +-----+------+------+                |
           |                        |      |                       |
           |                        |      |                       |
           |     QSIG DISCONNECT    |      |   1- 4XX / 6XX        |
          1|----------------------->|......|---------------------->|4
           |     QSIG RELEASE       |      |        1- ACK         |
          2|<-----------------------|      |<----------------------|5
           |     QSIG RELEASE COMP  |      |                       |
          3|----------------------->|      |                       |
           |                        |      |                       |
           |                        |      |                       |

   Figure 10: Typical message sequence for call clearing from QSIG to
   SIP, during establishment of a call from SIP to QSIG (gateway has
   not sent a final response to the SIP INVITE request)

   1  The PISN sends a QSIG DISCONNECT message to the gateway
   2  The gateway sends back a QSIG RELEASE message to the PISN in
      response to the QSIG DISCONNECT message
   3  The PISN sends a QSIG RELEASE COMPLETE message in response.  All
      PISN resources are now released.
   4  The gateway maps the QSIG DISCONNECT message to a SIP 4xx-6xx
      response
   5  The IP network sends back a SIP ACK request in response to the SIP
      4xx-6xx response.  All IP resources are now released

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A.4.3.  QSIG to SIP, during establishment of a call from QSIG to SIP

                             +-------------------+
                             |                   |
                             |     GATEWAY       |
         PISN                |                   |         IP NETWORK
          |                  +-----+------+------+                 |
          |                        |      |                        |
          |                        |      |                        |
          |     QSIG DISCONNECT    |      |   1- CANCEL            |
         1|----------------------->|......|----------------------->|4
          |     QSIG RELEASE       |      |1-487 Request Terminated|
         2|<-----------------------|      |<-----------------------|5
          |     QSIG RELEASE COMP  |      |                        |
         3|----------------------->|      |   1- ACK               |
          |                        |      |----------------------->|6
          |                        |      |                        |
          |                        |      |   1- 200 OK            |
          |                        |      |<-----------------------|7
          |                        |      |                        |

   Figure 11: Typical message sequence for call clearing from QSIG to
   SIP, during establishment of a call from QSIG to SIP (gateway has
   received a provisional response to the SIP INVITE request but not a
   final response)

   1  The PISN sends a QSIG DISCONNECT message to the gateway.
   2  The gateway sends back a QSIG RELEASE message to the PISN in
      response to the QSIG DISCONNECT message.
   3  The PISN sends a QSIG RELEASE COMPLETE message in response.  All
      PISN resources are now released.
   4  The gateway maps the QSIG DISCONNECT message to a SIP CANCEL
      request (subject to receipt of a provisional response, but not of
      a final response).
   5  The IP network sends back a SIP 487 (Request Terminated) response
      to the SIP INVITE request.
   6  The gateway, on receiving a SIP final response (487) to the SIP
      INVITE request, sends back a SIP ACK request to acknowledge
      receipt.
   7  The IP network sends back a SIP 200 (OK) response to the SIP
      CANCEL request.  All IP resources are now released.

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A.5.  Message Sequence for Call Clearing from SIP to QSIG

   Below are typical message sequences for Call Clearing from SIP to
   QSIG

A.5.1.  SIP to QSIG, subsequent to call establishment

                             +-------------------+
                             |                   |
                             |     GATEWAY       |
          IP NETWORK         |                   |              PISN
          |                  +-----+------+------+                 |
          |                        |      |                        |
          |                        |      |                        |
          |   2- BYE               |      |     QSIG DISCONNECT    |
         1|----------------------->|......|----------------------->|3
          |                        |      |     QSIG RELEASE       |
          |                        |      |<-----------------------|4
          |        2-200 OK        |      |     QSIG RELEASE COMP  |
         2|<-----------------------|      |----------------------->|5
          |                        |      |                        |
          |                        |      |                        |

   Figure 12: Typical message sequence for call clearing from SIP to
   QSIG, subsequent to call establishment

   1  The IP network sends a SIP BYE request to the gateway.
   2  The gateway sends back a SIP 200 (OK) response to the SIP BYE
      request.  All IP resources are now released.
   3  The gateway maps the SIP BYE request to a QSIG DISCONNECT message.
   4  The PISN sends back a QSIG RELEASE message to the gateway in
      response to the QSIG DISCONNECT message.
   5  The gateway sends a QSIG RELEASE COMPLETE message in response.
      All PISN resources are now released.

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A.5.2.  SIP to QSIG, during establishment of a call from QSIG to SIP

                             +-------------------+
                             |                   |
                             |     GATEWAY       |
          IP NETWORK         |                   |              PISN
          |                  +-----+------+------+                 |
          |                        |      |                        |
          |                        |      |                        |
          |   1- 4XX / 6XX         |      |     QSIG DISCONNECT    |
         1|----------------------->|......|----------------------->|3
          |                        |      |     QSIG RELEASE       |
          |                        |      |<-----------------------|4
          |        1- ACK          |      |     QSIG RELEASE COMP  |
         2|<-----------------------|      |----------------------->|5
          |                        |      |                        |
          |                        |      |                        |
          |                        |      |                        |

   Figure 13: Typical message sequence for call clearing from SIP to
   QSIG, during establishment of a call from QSIG to SIP (gateway has
   not previously received a final response to the SIP INVITE request)

   1  The IP network sends a SIP 4xx-6xx response to the gateway.
   2  The gateway sends back a SIP ACK request in response to the SIP
      4xx-6xx response.  All IP resources are now released.
   3  The gateway maps the SIP 4xx-6xx response to a QSIG DISCONNECT
      message.
   4  The PISN sends back a QSIG RELEASE message to the gateway in
      response to the QSIG DISCONNECT message.
   5  The gateway sends a QSIG RELEASE COMPLETE message in response.
      All PISN resources are now released.

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A.5.3.  SIP to QSIG, during establishment of a call from SIP to QSIG

                             +-------------------+
                             |                   |
                             |     GATEWAY       |
         IP NETWORK          |                   |              PISN
          |                  +-----+------+------+                 |
          |                        |      |                        |
          |                        |      |                        |
          |   1- CANCEL            |      |     QSIG DISCONNECT    |
         1|----------------------->|......|----------------------->|4
          |                        |      |     QSIG RELEASE       |
          |                        |      |<-----------------------|5
          |1-487 Request Terminated|      |     QSIG RELEASE COMP  |
         2|<-----------------------|      |----------------------->|6
          |                        |      |                        |
          |   1- ACK               |      |                        |
         3|----------------------->|      |                        |
          |                        |      |                        |
          |   1- 200 OK            |      |                        |
         4|<-----------------------|      |                        |

   Figure 14: Typical message sequence for call clearing from SIP to
   QSIG, during establishment of a call from SIP to QSIG (gateway has
   sent a provisional response to the SIP INVITE request but not a final
   response)

   1  The IP network sends a SIP CANCEL request to the gateway.
   2  The gateway sends back a SIP 487 (Request Terminated) response to
      the SIP INVITE request.
   3  The IP network, on receiving a SIP final response (487) to the SIP
      INVITE request, sends back a SIP ACK request to acknowledge
      receipt.
   4  The gateway sends back a SIP 200 (OK) response to the SIP CANCEL
      request.  All IP resources are now released.
   5  The gateway maps the SIP 4xx-6xx response to a QSIG DISCONNECT
      message.
   6  The PISN sends back a QSIG RELEASE message to the gateway in
      response to the QSIG DISCONNECT message.
   7  The gateway sends a QSIG RELEASE COMPLETE message in response.
      All PISN resources are now released.

Top      Up      ToC       Page 64 
Authors' Addresses

   John Elwell
   Siemens plc
   Technology Drive
   Beeston
   Nottingham, UK, NG9 1LA

   EMail: john.elwell@siemens.com


   Frank Derks
   NEC Philips Unified Solutions
   Anton Philipsweg 1
   1223 KZ Hilversum
   The Netherlands

   EMail: frank.derks@nec-philips.com


   Olivier Rousseau
   Alcatel Business Systems
   32,Avenue Kleber
   92700 Colombes
   France

   EMail: Olivier.Rousseau@alcatel.fr


   Patrick Mourot
   Alcatel Business Systems
   1,Rue Dr A.  Schweitzer
   67400 Illkirch
   France

   EMail: Patrick.Mourot@alcatel.fr

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