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SMG digital gateway
4.1.7.5
SIP Protocol Configuration Tab
SIP/SIP-T/SIP-I Options Configuration
Keep-alive control by messages OPTIONS
—a function that controls direction availability by sending
OPTIONS requests; when a direction is not available, the redundant trunk group is used for the call.
This function also analyses the received OPTIONS response that allows avoiding the use of the
100rel, replaces,
and
timer
features, which are configured in this direction, in case the opposite
party does not support them. The parameter defines the request transmission period and may
take values in the range of 30–3,600 seconds.
Always transmit SDP in provisional responses
—allows early forwarding of voice frequency path.
For example, when unchecked, SMG sends reply 180 without SDP session description; according
to this reply, the outgoing party plays the ringback tone; when checked, SMG sends reply 180 with
SDP session description and the ringback is played by the incoming party.
"In-band signal" with 183+SDP transmission
—issues SIP-reply 183 with SDP session description for
voice frequency path forwarding upon receipt of the CALL PROCEEDING or PROGRESS messages
from ISDN PRI that contain the progress indicator = 8 (in-band signal).