62 VoIP Subscriber Gateways
unchecked, all URI elements (user, host and port–subscriber number, IP address and
UDP/TCP port) will be analyzed upon receiving an incoming call. If all URI elements
match, the call will be assigned to the subscriber port.
- Transmit symbol '#' as %23 – when checked, send hash symbol (#) in SIP URI as escape
sequence '%23', otherwise–as '#' symbol.
- 100rel – utilization of reliable provisional responses (RFC3262):
Supported – reliable provisional responses are supported;
Required – reliable provisional responses are mandatory;
Disabled — reliable provisional responses are disabled;
SIP protocol defines two types of responses for connection initiating request (INVITE)–
provisional and final. 2хх, 3хх, 4хх, 5хх and 6хх-class responses are final and their transfer is reliable,
with ACK message confirmation. 1хх-class responses, except for '100 Trying' response, are provisional,
without confirmation (rfc3261). These responses contain information on the current INVITE request
processing step, therefore loss of these responses is unacceptable. Utilization of reliable provisional
responses is also stated in SIP (rfc3262) protocol and defined by '100rel' tag presence in the initiating
request. In this case, provisional responses are confirmed with PRACK message.
Setting operation for outgoing communications:
- Supported – send the following tag in 'INVITE' request–supported: 100rel. In this case,
communicating gateway may transfer provisional responses reliably or unreliably–as it
deems fit;
- Required – send the following tags in 'INVITE' request–supported: 100rel and required:
100rel. In this case, communicating gateway should perform reliable transfer of
provisional replies. If communicating gateway does not support reliable provisional
responses, it should reject the request with message 420 and provide the following tag–
unsupported: 100rel, In this case, the second INVITE request will be sent without the
following tag–required: 100rel.
- Off – do not send any of the following tags in INVITE request–supported: 100rel and
required: 100rel. In this case, communicating gateway will perform unreliable transfer of
provisional replies.
Setting operation for incoming communications:
- Supported, Required – when the following tag is received in 'INVITE' request–supported:
100rel, or required: 100rel, perform reliable transfer of provisional replies. If there is no
supported: 100rel tag in INVITE request, the gateway will perform unreliable transfer of
provisional replies;
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