Configuring Alternative Routing (Based On Connectivity And Qos); Alternative Routing Mechanism; Determining The Availability Of Destination Ip Addresses - AudioCodes MediaPack MP-124 User Manual

SIP User's Manual
8.2.5 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
8.2.5.1

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 'Tel to IP Routing' (described in ''Configuring the Tel to IP Routing''
on page 138). 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.
Destination IP address is disallowed if no ping to the destination is available (ping is
continuously initiated every seven seconds), when an inappropriate level of QoS was
detected or when a DNS host name is not resolved. The QoS level is calculated according
to delay or packet loss of previously ended calls. If no call statistics are received for two
minutes, the QoS information is reset.
8.2.5.2

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:
Connectivity: The destination IP address is queried periodically (currently only by
ping).
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.
Version 6.2 247
8. IP Telephony Capabilities
February 2011