Configuring Alternative Routing (Based On Connectivity And Qos) - AudioCodes Mediant 800 MSBG User Manual

8.3.6 Configuring Alternative Routing (Based on Connectivity and
QoS)
The Alternative Routing feature enables reliable routing of Tel-to-IP calls when a Proxy isn't
used. The device periodically checks the availability of connectivity and suitable Quality of
Service (QoS) before routing. If the expected quality cannot be achieved, an alternative IP
route for the prefix (phone number) is selected.
The following parameters are used to configure the Alternative Routing mechanism:
AltRoutingTel2IPEnable
AltRoutingTel2IPMode
IPConnQoSMaxAllowedPL
IPConnQoSMaxAllowedDelay
8.3.6.1 Alternative Routing Mechanism
When the device routes a Tel-to-IP call, the destination number is compared to the list of
prefixes defined in the 'Outbound IP Routing Table' (described in ''Configuring the
Outbound IP Routing Table'' on page 165). This table is scanned for the destination
number's prefix starting at the top of the table. For this reason, you must enter the main IP
route above any alternative route in the table. When an appropriate entry (destination
number matches one of the prefixes) is found, the prefix's corresponding destination IP
address is verified. If the destination IP address is disallowed (or if the original call fails and
the device has made two additional attempts to establish the call without success), an
alternative route is searched in the table and used for routing the call.
8.3.6.2 Determining the Availability of Destination IP Addresses
To determine the availability of each destination IP address (or host name) in the routing
table, one or all of the following user-defined methods are applied:
QoS: The QoS of an IP connection is determined according to RTCP statistics of
previous calls. Network delay (in msec) and network packet loss (in percentage) are
separately quantified and compared to a certain (configurable) threshold. If the
calculated amounts (of delay or packet loss) exceed these thresholds, the IP
connection is disallowed.
DNS resolution: When host name is used (instead of IP address) for the destination
route, it is resolved to an IP address by a DNS server. Connectivity and QoS are then
applied to the resolved IP address.
8.3.6.3 PSTN Fallback
The PSTN Fallback feature enables the device to redirect PSTN originated calls back to
the legacy PSTN network if a destination IP route is unsuitable (disallowed) for voice traffic
at a specific time. To enable PSTN fallback, assign the device's IP address as an
alternative route to the desired prefixes. Note that calls (now referred to as IP-to-Tel calls)
can be re-routed to a specific Hunt Group using the Routing parameters (see ''Configuring
iptotelrouteMP500>'' on page 172).
SIP User's Manual 442
Mediant 800 MSBG
Document #: LTRT-12804