AudioCodes Mediant 3000, User Manual

Page: 367 / 872

Version 6.6 367 Mediant 3000
User's Manual 24. Routing
24.4 IP Destinations Connectivity Feature
The device can be configured to check the integrity of the connectivity to IP destinations of
Tel-to-IP routing rules in the Outbound IP Routing table. The IP Connectivity feature can be
used for the Alternative Routing feature, whereby the device attempts to re-route calls from
unavailable Tel-to-IP routing destinations to available ones (see 'Alternative Routing Based
on IP Connectivity' on page
368 ).
The device supports the following methods for checking the connectivity of IP destinations:

Network Connectivity: The device checks the network connectivity of the IP
destination using one of the following methods configured by the 'Alt Routing Tel to IP
Connectivity Method' parameter:
•
Ping: The device periodically (every seven seconds) pings the IP destination.
•
SIP OPTIONS: The device sends "keep-alive" SIP OPTIONS messages to the IP
destination. If the device receives a SIP 200 OK in response, it considers the
destination as available. If the destination does not respond to the OPTIONS
message, then it is considered unavailable. You can configure the time interval
for sending these OPTIONS messages, using the 'Alt Routing Tel to IP Keep
Alive Time' parameter.
These parameters are configured in the Routing General Parameters page
(
Configuration tab > VoIP menu > GW and IP to IP > Routing > General
Parameters ), as shown below:
Figure 24-5: IP Connectivity Method in Routing General Parameters Page

Quality of Service (QoS): You can enable the device to check the QoS of IP
destinations. The device measures the QoS according to RTCP statistics of previously
established calls with the IP destination. The RTCP includes packet delay (in
milliseconds) and packet loss (in percentage). If these measured statistics exceed a
user-defined threshold, the destination is considered unavailable. Note that if call
statistics is not received within two minutes, the QoS data is reset. These thresholds
are configured using the following parameters:
•
'Max Allowed Packet Loss for Alt Routing' (IPConnQoSMaxAllowedPL): defines
the threshold value for packet loss after which the IP destination is considered
unavailable.
•
'Max Allowed Delay for Alt Routing' (IPConnQoSMaxAllowedDelay): defines the
threshold value for packet delay after which the IP destination is considered
unavailable
These parameters are configured in the Routing General Parameters page, as shown
below:
Figure 24-6: IP QoS Thresholds in Routing General Parameters Page

DNS Resolution: When a host name (FQDN) is used (instead of an IP address) for
the IP destination, it is resolved into an IP address by a DNS server. The device
checks network connectivity and QoS of the resolved IP address. If the DNS host
name is unresolved, the device considers the connectivity of the IP destination as
unavailable.