 send a C_GET_GROUPRLIST message to the MSIP server, asking for the list of groups. The MSIP server replies with S_START_GROUPLIST, followed by S_CONT_GROUPLIST, if required. The S_CONT_GROUPLIST is required C 2009 by Taylor & Francis Group, LLC Multipoint Extensions for SIP MSIP Server 1 MSIP Client 1 MSIP Client 2 MSIP Client 3 Start C_USER_LOGIN S_USER_LOGIN C_USER_LOGIN S_USER_LOGIN S_USER_UPDATE C_USER_LOGIN S_USER_LOGIN PASSWRG C_USER_LOGIN S_USER_LOGIN PASSOK S_USER_UPDATE S_USER_UPDATE C_PASS_CHG S_PASS_CHG Flag = PASS_OK C_STS_CHG FIGURE 13.7 Messages flow from MSIP server start-up and before starting a session. if the number of groups is very big and their information cannot fit in one message. After the MSIP client receives all the information, it builds the users list, which contains all the information about all users having accounts in the MSIP server. User names are in the form of name@server. The MSIP client can also send C_GET_CONFLIST to the MSIP server, to ask for a list of the sessions it is invited to. The MSIP server replies with S_START_CONFLIST followed by S.CONT.CONFLIST, if required. The S_CONT_CONFLIST is required if the number of sessions is very big and their information cannot fit in one message. Figure 13.8 shows the messages flow for pre-create while Figure 13.9 shows the messages flow for a pre-join session. After the MSIP client builds user information, it can start a session by send- ing a CLCREATE.CONF message to the MSIP server. The C_CREATE_CONF message contains the session name, session priority, session control crite- ria, and chairman info (i.e., chairman name, chairman id, chairman group id, and chairman flags). When the MSIP server receives this message, it checks for an available session slot. If no slot is available, it sends back an © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security MSIP Server 1 MSIP Client 1 MSIP Client 2 MSIP Client 3 Pre create session C_GET_USERLIST S_START_USERLIST S_CONT_USERLIST If required S_USER_UPDATE C