Snom 4S manual Call Initiation

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5.

[ S N O M 4 S N A T F I L T E R ]

The parameter “explanation” contains the explaining text that is added behind the code in the SIP response. Typical values are “Ok” or “Not Found”.

The parameter “contact” contains the contact that should be re- turned by the registration response. This parameter contains the expiry time that this contact will have. Typical values look like “<sip :1.2.3.4:5060;ua=345a20f784c9284>;expires=3600”. This param- eter may be present more than once if the application server has several bindings. If there is no binding, the parameter can be omit- ted.

If the UA does not reregister, the SBC will send a register request with an expiry time of zero seconds. This emulates the deregistration re- quest of the user agent.

5.4 Call Initiation

If the “Http URL for call” setting is set in the system settings, the SBC will consult the application server for every call that is being initi- ated.

A new call is identified by an unknown Call-ID and starts with an INVITE request. The SBC will perform the authentication steps before the call is initiated (see above). For a new call, the request from the SBC contains the following parameters:

The parameter “action” is set to “start”. By looking at this param- eter, the application server can easily find out that it should do a call start.

The parameter “from_uri” contains the URI part of the From-header. Typically, this has the form “sip:albert@einstein”. Note that the port number and parameters may also be present in this parameter.

The parameter “to_uri” contains the URI part of the To-header like the “from_uri” parameter.

The parameter “uri” contains the request-URI.

The parameter “callid” contains the Call-ID of the call.

The parameter “from_ua” is set to “true” if the SBC believes that the call comes from a client endpoint.

56 • Web Server Integration

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Contents Snom 4S NAT Filter Admin Manual Snom 4S NAT Filter Version Table of Contents Snmp Overview Features ApplicationsSnom technology AG Overview Architecture NAT Filter and SIPNAT Symmetrical RTP Signalling SIPHow does NAT work? Media RTP Classification of User AgentsProbing Media Paths Role of the NAT FilterOptimizing the Media Path for Symmetrical NATSBC Behaviour RegisteringRTP Relay Snom technology AG Scaling and Redundancy NATDetecting the right NAT Filter STUN/ICE-Aware User Agents Requirements on User AgentsNon NAT-Aware User Agents Defining the Maximum Session Time Architecture Installation WindowsInstallation Snom technology AG Installation Snom technology AG Linux Rpm -ihv snomnatf-2.10.*.rpm Installation Logging Port BindingStandard Port Random Port System Settings LoggingPreparing Recovery General Outound ProxyMedia Ports Port BudgetsMedia Relay Controlling RoutingMultiple 2xx Handling Maximum Packet Size ChallengingTrusted Addresses Removing Headers Silence SuppressionConnection Oriented Media Clir Addresses Codec ControlWeb Server Integration Timeout Settings Register TimeoutsCall Timeouts Security Settings Snom technology AG Outbound Proxy List System Information Server LogTrace Call History Current Ports Currently Handled UA Memory StatisticsConfiguration Web Server Integration Authentication Interface to the Web ServerSnom technology AG Web Server Integration Registration Call Initiation Snom technology AG Call Termination Snom technology AG Web Server Integration Setup of the SBC Setup of the ToolsAvailable OID OIDSnom technology AG Snmp Checklist for Installation Checklist for Installation Reader‘s Feedback Snom technology AG All rights reserved