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SIP Module |
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The SIP module implements the SIP Registrar. Users configure their SIP devices (IP phones, AV conferencing tools, Instant Messaging tools) to connect to the CommuniGate Pro SIP module when they go on-line. The SIP module registers the users by remembering the network (IP) addresses they use. Each user may have several registrations active if that user has several communication devices in the on-line mode (the office IP Phone, the desktop computer, the instant messaging program on a laptop). Registrations allow SIP users to communicate with each other without the knowledge of the network addresses being used, using just the "SIP identificators".
SIP identificators have the same form as E-mail addresses: username@domainName. In the CommuniGate Pro system, the user SIP identificator is the name of the user Account, so the user SIP identificator name is the same as the user E-mail address.
The SIP Module uses the CommuniGate Pro Router mechanism to process all SIP identificators. As a result, all CommuniGate Pro Aliases, Forwarders, and Router records are available for SIP communications, too.
The SIP Module allows users to initiate sessions (phone calls, chats, etc.) with other SIP users within the same CommuniGate Pro Domain, with users of other Domains on the same server, or with SIP users served by other, remote SIP servers.
When a SIP session is being initiated, a caller SIP client program (or UA - user agent program)
sends a request to the SIP server with the SIP identificator of the callee. The SIP server
checks the identificator, and if it is served by a remote SIP server, relays (proxies) the
request to that remote server. If the SIP identificator belongs to a local user, the SIP server
retrieves the active registration for that user and relays the request to the callee UA.
If the callee accepts the request, the callee UA sends the response back to the server,
and the server relays it back to the caller UA. As a result, both caller and callee learn their
actual network addresses, and they now establish the negotiates communication link (audio, video, etc.) directly,
bypassing the SIP server.
The session initiation schema described above works correctly only if both parties can communicate directly. If there is a firewall or a NAT device between the parties, direct communication is not possible. In this case, the CommuniGate Pro SIP module builds and manages the necessary media proxies, relaying not only the SIP protocol requests and responses, but the actual media data, too.
The CommuniGate Pro SIP module supports UDP and TCP connections, and it also supports secure (TLS) communications over TCP connections.
Certain SIP operations (such as registration) require user authentication. All CommuniGate Pro Account passwords can be used for authenitcation. The BASIC and DIGEST authentication methods are supported.
To configure the SIP module, use a Web browser to connect to the CommuniGate Pro Server WebAdmin Interface, and open the SIP page in the Settings realm. To configure the SIP module, you should have the Can Modify Settings access right.
Use the Log setting to specify what kind of information the SIP module should put in the Server Log. Usually you should use the Failure (unrecoverable problems only), Major (session establishment reports), or Problems (failures, session establishment and non-fatal errors) levels. But when you experience problems with the SIP module, you may want to set the Log Level setting to Low-Level or All Info: in this case protocol-level or link-level details will be recorded in the System Log. When the problem is solved, set the Log Level setting to its regular value, otherwise your System Log files will grow in size very quickly.
The SIP module records in the System Log are marked with the following tags:
The Transport panel allows you to configure the network-level options:
The CommuniGate Pro Server detects the session initiation requests that are sent from one side of NAT to the other side (a request from a LAN client to a party on the Internet and vice versa). In this case, the Server assigns a local server port (or a pair of ports, depending on the protocol) to a media stream proxy. The Server then modifies the session initiation request to direct the traffic from both sides to that proxy, which relays the data between the "LAN leg" and the "Internet leg" of the media connection.
In order to support Media Strea Proxy functionality, make sure that the LAN and NAT data is specified correctly on the LAN IPs settings page.
The Windows Messenger 5.0 is supported, earlier versions of this application are not supported.
The CommuniGate Pro SIP module should have the Advertise NTLM option enabled.
The Windows Messenger audio and video sessions use standard RTP media protocols and these sessions
can be used over a NAT/Firewall.
The Windows Messenger Instant Messaging uses the SIP protocol for media transfer and Instant
Messaging sessions can be used over a NAT/Firewall.
The Windows Messenger File Transfer, Whiteboard, Application Sharing, and Remote Assistance
sessions use non-standard protocols and these sessions currently cannot be used over a NAT/Firewall.