User guide

Chapter 4—Configuring your VOIP
Multi-Tech Systems, Inc. 43
SPP
Single Port Protocol was developed by Multi-Tech to allow for dynamic IP addressing when it is set to
Registrar/Client mode. The other choice, Direct mode, has IP addresses assigned to the gateways. The table
below describes all fields in the general SPP Call Signaling screen.
SPP call signaling
Field Name
Values
Description
Mode
Direct,
Client, or
Registrar
In direct mode, all VOIP gateways have static IP addresses assigned to them.
In registrar/client mode, one VOIP gateway serves as registrar and all other gateways,
being its clients, point to that registrar. The registrar assigns IP addresses dynamically.
General Options
Port
port
The UDP port on which data transmission will occur. Each client VOIP has its own port. If
two client VOIPs are both behind the same firewall, then they must have different ports
assigned to them.
If there are two clients and each is behind a different firewall, then the clients could have
different port numbers or the same port number. Default port number = 10000.
Re-transmission
50 - 5000ms
If packets are lost (as indicated by absence of an acknowledgment) then the endpoint
will retransmit the lost packets after this designated time duration has elapsed. Default =
2000 milliseconds.
Max Re-
transmission
0 - 20
Number of times the VOIP will re-transmit a lost packet if no acknowledgment has been
received. Default = 3.
Client Options
Client Option fields are active only in registrar/client mode and only for client VOIP units.