User guide

Chapter 5: Phone Book Configuration
Multi-Tech Systems, Inc. MVPGSM 87
Clicking on the Advanced button brings up the Alternate Routing secondary screen. This feature provides an
alternate path for calls if the primary IP network cannot or does not respond within the timeframe of the
Round Trip Delay. Often in cases of failure, call traffic is temporarily diverted into the PSTN. However, this
feature could also be used to divert traffic to a redundant (backup) unit in case one SIP end point fails. The
user must specify the IP address of the alternate route for each destination pattern entry in the Outbound
Phonebook.
Alternate Routing Field Definitions
Field Name Values Description
Alternate IP
Address
n.n.n.n Alternate destination for call traffic in case of excessive network delay.
Round Trip
Delay
Default is
300
milliseconds
The Round Trip Delay is the criterion for judging when a data pathway is
considered blocked. When the delay exceeds the threshold specified here, the
data stream will be diverted to the alternate destination specified as the
Alternate IP Address.
The Alternate Routing function facilitates PSTN Failover protection, that is, it allows you to re-route VOIP
calls automatically if the VOIP system fails. The MultiVOIP GSM can be programmed to respond to excessive
delays in the transmission of voice packets, which the MultiVOIP GSM interprets as a failure of the IP
network. Upon detecting an excessive delay in transmission of voice packets (overly high “latency” in the
network) the MultiVOIP GSM diverts the call to another of its channels, allowing the call to go back out to
the wireless network to reach the remote end using a land line.