Determining The Availability Of Destination Ip Addresses; Pstn Fallback As A Special Case Of Alternative Routing; Relevant Parameters - AudioCodes Mediant 2000 User Manual

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.
7.9.2

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 (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.
7.9.3

PSTN Fallback as a Special Case of Alternative Routing

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 trunk group using the Routing parameters (refer to ''IP to Trunk Group
Routing'' on page 181).
7.9.4

Relevant Parameters

The following parameters (described in ''Routing General Parameters'' on page 171) are
used to configure the Alternative Routing mechanism:
AltRoutingTel2IPEnable
AltRoutingTel2IPMode
IPConnQoSMaxAllowedPL
IPConnQoSMaxAllowedDelay
SIP User's Manual 362
Mediant 2000
Document #: LTRT-68808