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

7.7
7.7.1
7.7.2
7.7.3
SIP User's Manual
http://ArtTel.ru
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 gateway 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.

Alternative Routing Mechanism

When a Tel IP call is routed through the gateway, the call's destination number is
compared to the list of prefixes defined in the Tel to IP Routing table (described in 'Tel to IP
Routing Table' on page 129). The Tel to IP Routing table is scanned for the destination
number's prefix starting at the top of the table. When an appropriate entry (destination
number matches one of the prefixes) is found; the prefix's corresponding destination IP
address is checked. If the destination IP address is disallowed, an alternative route is
searched for in the following table entries.
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 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.
The gateway matches the rules starting at the top of the table. For this reason, enter the
main IP route above any alternative route.

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 (configurable) 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.

Relevant Parameters

The following parameters (described in 'General Parameters' on page 127) are used to
configure the Alternative Routing mechanism:
AltRoutingTel2IPEnable
AltRoutingTel2IPMode
IPConnQoSMaxAllowedPL
IPConnQoSMaxAllowedDelay
342
MediaPack Series
Document #: LTRT-65409