RFC 4497
Interworking between the Session Initiation Protocol (SIP) and QSIG
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
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.
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.
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.
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.
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 | |<========================>| |<=======================>| | | | |
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.
A.3. Message sequences for call establishment from SIP to QSIG
Below are typical message sequences for successful call establishment from SIP to QSIGA.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.
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.
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.
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.
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.
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.
A.4. Message Sequence for Call Clearing from QSIG to SIP
Below are typical message sequences for Call Clearing from QSIG to SIPA.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.
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
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.
A.5. Message Sequence for Call Clearing from SIP to QSIG
Below are typical message sequences for Call Clearing from SIP to QSIGA.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.
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.
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.
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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