Administrator's Guide

Chapter 10. SIP Services
Base retransmission timeout for SIP requests
When the Telecommuting Module sends out a SIP request, it will expect a reply within a
certain time. If no reply has been received within the Base retransmission timeout, the
Telecommuting Module will start resending the request.
Maximum number of retransmissions for INVITE requests
When the Telecommuting Module sends out an INVITE request, it will wait for a reply until
the Base retransmission timeout and then start to retransmit the request. The time intervals
between retransmissions will double for each new retransmission.
Example: If the Base retransmission timeout is 0.5 seconds and the Maximum number
of retransmissions is 6, the INVITE requests will be sent with intervals of 0.5 s, 1 s, 2 s, 4
s, 8 s, and 16 s.
Maximum number of retransmissions for non-INVITE requests
When the Telecommuting Module sends out a request which is not an INVITE request, it
will wait for a reply until the Base retransmission timeout and then start to retransmit the
request. The time intervals between retransmissions will double for each new retransmission
until the interval reaches 4 seconds. After that, retransmissions will be made with a 4-second
interval.
Example: If the Base retransmission timeout is 0.5 seconds and the Maximum number
of retransmissions is 7, the requests will be sent with intervals of 0.5 s, 1 s, 2 s, 4 s, 4 s, 4 s,
and 4 s.
Maximum SIP packet size
This setting allows you to set a limit to the size of SIP packets. A high value will increase
performance, but use more memory. A low value will decrease performance, but use less
memory.
Save
Saves the Sessions and Media configuration to the preliminary configuration.
Cancel
Reverts all of the above fields to their previous configuration.
Remote SIP Connectivity
If you are at a hotel or somewhere else where you find yourself behind a NAT-ing device that
does not understand SIP, you will have use of the SIP Remote Connectivity of 3Com VCX
IP Telecommuting Module. This will help your client to traverse the NAT, even if the device
doing the NAT does not understand SIP. The SIP Remote Connectivity is only available if
you have installed the Remote Connectivity module.
If you have a STUN-capable SIP client, you need just turn on the STUN server of the
Telecommuting Module to make the client work behind NAT. If you have a SIP client that
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