PX323OS
H.323 Protocol Stack
Release 2.3
User Guide
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COPYRIGHT 1999 LUCENT TECHNOLOGIES
ALL RIGHTS RESERVED
PRINTED IN THE U.S.A.
THIS MATERIAL IS PROTECTED BY THE COPYRIGHT AND TRADE SECRET LAWS OF
THE UNITED STATES AND OTHER COUNTRIES. IT MAY NOT BE REPRODUCED,
DISTRIBUTED OR ALTERED IN ANY FASHION BY ANY ENTITY (EITHER INTERNAL OR
EXTERNAL TO LUCENT TECHNOLOGIES), EXCEPT IN ACCORDANCE WITH
APPLICABLE AGREEMENTS, CONTRACTS, OR LICENSING, WITHOUT THE EXPRESS
WRITTEN CONSENT OF THE BUSINESS MANAGEMENT OWNER OF THE MATERIAL
Notice
Every effort was made to ensure that the information in this document was complete
and accurate at the time of printing. However, information is subject to change.
Trademarks
elemedia is a registered trademark of Lucent Technologies, Inc. All Rights Reserved
Microsoft NetMeeting is a trademark of The Microsoft Corporation.
UNIX is a registered trademark of Novell, Inc., in the United States and other countries,
licensed exclusively through X/Open Company Ltd.
Warranty
Lucent Technologies provides no warranty for this product.
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1 INTRODUCTION ............................................................................................................................ 1
1.1 THE ITU H.323 STANDARD........................................................................................................1
1.2 WHAT’S IN THE STACK?.............................................................................................................1
1.3 OBJECT-ORIENTED DESIGN ........................................................................................................2
1.4 PREREQUISITES...........................................................................................................................2
1.5 SUPPORTING DOCUMENTATION PROVIDED BY ELEMEDIA........................................................2
1.6 OTHER AVAILABLE SUPPORTING DOCUMENTATION................................................................3
2 STRUCTURE OF THE STACK ..................................................................................................... 5
2.1 INTRODUCTION...........................................................................................................................5
2.2 THE FIVE CONTROL CLASSES....................................................................................................5
2.3 UNDERSTAND THE CONTROL CLASSES ......................................................................................5
2.4 THE CONNECTIONMANAGER CLASS .........................................................................................6
2.4.1 PURPOSE AND USE OF THIS CLASS..........................................................................................6
2.4.2 INCOMING CALLS: LISTENING FOR A CALL..............................................................................6
2.4.3 INCOMING CALLS: ACCEPT OR REJECT THE CALL...................................................................6
2.4.4 OUTGOING CALLS ..................................................................................................................6
2.4.5 THE CONNECTION-PROCESSING ENTITY ASSOCIATION ...........................................................7
2.4.6 THE FINAL TCP-SIGNALING CHANNEL ASSOCIATION .............................................................7
2.4.7 HANDLING MULTIPLE CONNECTIONS......................................................................................7
2.5 THE H225CSPROTOCOL CLASS ................................................................................................7
2.5.1 PURPOSE AND USE OF THIS CLASS..........................................................................................7
2.5.2 THE VALUE OF LOW LEVEL CONTROL....................................................................................8
2.5.3 AUTONOMOUS STATE TRANSITIONS .......................................................................................8
2.5.4 INCOMING Q.931 MESSAGES..................................................................................................8
2.5.5 OUTGOING Q.931 MESSAGES .................................................................................................9
2.5.6 SUPPORTING CLASSES ............................................................................................................9
2.6 THE H245PROTOCOL CLASS .....................................................................................................9
2.6.1 PURPOSE AND USE OF THIS CLASS..........................................................................................9
2.6.2 SUPPORTING CLASSES ............................................................................................................9
2.7 THE H225RASPROTOCOL CLASS ..............................................................................................9
2.7.1 PURPOSE AND USE OF THIS CLASS..........................................................................................9
2.7.2 RAS TIMERS AND RETRY COUNTERS....................................................................................10
2.7.3 SENDING AND RECEIVING RAS MESSAGES...........................................................................10
2.7.4 SUPPORTING CLASSES ..........................................................................................................10
2.7.5 DERIVATION OF RAS MESSAGES..........................................................................................10
2.5 THE RTPSESSION CLASS..........................................................................................................11
2.5.1 PURPOSE AND USE OF THIS CLASS........................................................................................11
2.5.2 SUPPORTING CLASSES ..........................................................................................................11
3 CALL FLOWS ............................................................................................................................... 13
4
3.1 APPLICATION CALL CONTROL CLASSES .................................................................................13
3.2 CALL FLOW ILLUSTRATIONS ...................................................................................................13
3.2.1 Q.931 SETUP IN THE DIRECT POINT-TO-POINT H.323 MODEL...............................................13
3.3 SET UP THE MEDIA CONTROL FROM ENDPOINT 1 TO ENDPOINT 2........................................15
3.3.1 RESPONSIBILITY OF THE APPLICATION ..................................................................................15
3.4 H.245 SETUP FOR MEDIA CONTROL........................................................................................15
3.5 TEAR DOWN A CALL.................................................................................................................18
3.6 Q.931 SETUP FOR THE GATEKEEPER-ROUTED MODEL ..........................................................19
4 A SAMPLE MEDIA SERVER PROGRAM - MS ........................................................................ 23
4.1 UNDERSTANDING THE MS PROGRAM .......................................................................................23
4.2 MULTITHREADED PROGRAM....................................................................................................23
4.3 CONFIGURATION OF MEDIA SERVER.......................................................................................24
4.4 USER INTERFACE THREAD .......................................................................................................24
4.4.1 COMMAND SET ....................................................................................................................24
4.4.2 COMMAND PROCESSING.......................................................................................................25
4.5 MESSAGE QUEUES ....................................................................................................................25
4.5.1 MESSAGING CAPABILITY ......................................................................................................25
4.5.2 PURPOSE OF MESSAGE QUEUES............................................................................................25
4.5.3 AN EXAMPLE OF USING QUEUES - SENDTOEXCHANGE() ......................................................25
4.5.4 WHY THE USER INTERFACE SENDS A MESSAGE TO EXCHANGE ..............................................25
4.6 CALLBACK FUNCTIONS AND STACK STATES ...........................................................................26
4.6.1 WHAT ARE CALLBACK FUNCTIONS?.....................................................................................26
4.6.2 STATE MACHINE MAINTAINED BY THE STACK......................................................................26
4.6.3 STATE OF THREADS PRIOR TO CALL SETUP ..........................................................................26
4.6.4 MS PROGRAM LIMITATIONS ...............................................................................................26
5 MEDIA SERVER (MS) PROGRAM - CALL SIGNALING ......................................................... 29
5.1 FUNCTIONS OF EXCHANGE (EXCHANGE.CPP) ...............................................................................29
5.1.1 EXCHANGE MESSAGES ...........................................................................................................29
5.2 RAS MANAGEMENT IN A GATEKEEPER ENVIRONMENT .........................................................29
5.2.1 PLACING A CALL ..................................................................................................................29
5.2.2 CALL HANGUP......................................................................................................................30
5.2.3 SHUTDOWN REQUEST...........................................................................................................30
5.2.4 REMOTE CONNECTION REQUEST...........................................................................................30
5.2.5 TABLE OF ACTIVE CALLS ......................................................................................................30
5.3 FUNCTIONS OF THE CALL CLASS (CALL.CPP)..........................................................................30
5.3.1 CALL THREAD PROCESSING...................................................................................................30
5.3.2 PLACING A CALL...................................................................................................................30
5.3.3 ACCEPTING A CALL ..............................................................................................................31
5.3.4 GATEKEEPER CONCERNS WHEN CONNECTION IS MADE.......................................................32
6 MEDIA SERVER PROGRAM - MS ............................................................................................. 33
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6.1 FUNCTIONS OF MEDIA SESSION (RTPSTUFF.CPP) ....................................................................33
6.1.1 HOW IS A MEDIA SESSION STARTED? ...................................................................................33
6.1.2 ESTABLISH LOGICAL CHANNEL AND CREATE A NEW MEDIA THREAD...................................33
6.1.3 MONITORING MEDIA TRAFFIC ..............................................................................................33
6.1.4 DATA PACKET TRANSMISSION..............................................................................................33
6.1.5 INCOMING PACKETS .............................................................................................................33
6.2 CODERS.....................................................................................................................................34
6.2.1 CURRENT IMPLEMENTATION.................................................................................................34
6.2.2 USER CODERS ......................................................................................................................34
7 H.450 SUPPLEMENTARY SERVICES ....................................................................................... 35
7.1 OVERVIEW OF H.450 SUPPLEMENTARY SERVICES .................................................................35
7.2 H.450 SERVICES SUPPORTED BY THE ELEMEDIA STACK ........................................................35
7.3 CLASSES WHICH PROVIDE SUPPORT.......................................................................................35
7.4 OTHER SUPPORTING CLASSES .................................................................................................36
7.5 METHODS THAT PROVIDE SUPPORT........................................................................................36
7.6 HOW TO USE THE SUPPLEMENTARY FEATURES......................................................................37
7.7 MODIFICATIONS TO THE MS PROGRAM SAMPLE APPLICATION..............................................37
7.7.1 RELEASE ENHANCEMENTS ...................................................................................................37
8 FAST CONNECT ........................................................................................................................... 39
8.1 WHAT IS FAST CONNECT?........................................................................................................39
8.2 FAST CONNECT SUPPORT BY THE ELEMEDIA PROTOCOL STACK...........................................39
8.3 HOW TO USE THE FAST CONNECT FEATURES .........................................................................39
8.4 FAST CONNECT MODIFICATIONS TO THE MS PROGRAM SAMPLE APPLICATION....................39
8.5 METHOD CALLS........................................................................................................................40
9 INTEROPERABILITY ISSUES ................................................................................................... 41
9.1 MICROSOFT NETMEETING™...................................................................................................41
9.2 SELSIUS PHONE.........................................................................................................................41
10 ITU STANDARDS DOCUMENTATION LIST ......................................................................... 43
10.1 OPERATIVE STANDARDS ..............................................................................................................43
10.2 H-SERIES RECOMMENDATIONS ...................................................................................................43
10.3 G-SERIES RECOMMENDATIONS ...................................................................................................43
10.4 FOR MORE INFORMATION ...........................................................................................................44
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