Manual

89

When registered, calls made using an EBU 3326/SIP prole behave dierently than normal. The address eld, regardless
of whether it is a SIP URI or an IP address, is forwarded to the server. No connecon aempt is made unl the server
responds.
If the server accepts the address, the call will be aempted. If not, an error message will appear in the status line. There
are many possible reasons for call rejecon by a server. Some examples are:
1 The server does not support direct connecon to IP addresses (if the address is in this format).
2 The server does not recognize the address.
3 The server does not forward calls beyond it’s own domain.
4 The server does not support the chosen codec.
5 The called device does not support the chosen codec.
6 The address is a POTS telephone number, and POTS interworking is not supported.
7 The address is a POTS telephone number, and no credit is available (most services charge for this).
The basic entries provided will allow support for the vast majority of EBU 3326/SIP-based applicaons. However, there
are inevitably situaons where the defaults don’t work. We’ve provided some advanced opons that can help. As
always, these opons are located in the  and can be made visible by selecng the  box.
 - Universally, SIP connecons are supposed to use UDP port  to negoate calls between
devices (and between servers and devices). Note that this is only the negoaon channel—actual
audio data is passed on the RTP ports. Changing this port number will change which incoming ports are
used to iniate connecons and to which ports connecon requests are sent. Obviously, the change
must be made on both devices, and this change will essenally make your codec incompable with
industry-standard VoIP devices.
 - This is one of two port numbers used for audio data transfer (the port number directly
above this is used as well). Because this port number is negoated at the beginning of a call (over the
IP port), this port may be changed without breaking compability. Note that many SIP standard devices
use port 5004 for this funcon. Due to the negoaon, it is not important that these numbers match
on each end. Changing this port to 5004 can actually have an adverse eect, since 5004 is the default
port for other services on Comrex codecs.
 - See the next secon,  for more informaon.
 - See the next secon,  for more informaon.
 - Only applies to  mode. This variable determines how oen the codec
“phones home” if registered with a SIP server. It’s important that the codec periodically “ping” the
server, so the server can nd the codec for incoming calls. It can be adjusted primarily to compensate
for rewall routers that have shorter or longer binding mings, i.e., the router may have a tendency to
“forget” that the codec is ready to accept incoming calls and block them.