Alternative Routing Based On Sip Responses - AudioCodes Mediant 800B User Manual

24.6.2 Alternative Routing Based on SIP Responses

The device can perform alternative routing based on the received SIP response code (i.e.,
4xx, 5xx, 6xx, or 8xx). If you have configured this response code in the Reasons for Tel-to-
IP Alternative Routing table, the device attempts to re-route the call to an alternative
destination, if configured. You can configure up to 10 SIP response codes in the Reasons
for Tel-to-IP Alternative Routing table.
Typically, the device performs alternative routing when there is no response at all to an
INVITE message. This is done after a user-defined number of INVITE re-transmissions,
configured by the SIPMaxRtx parameter. In such a scenario, the device issues itself the
SIP response code 408 (Request Timeout). You can also configure the device to perform
alternative routing for the following proprietary response codes that are issued by the
device itself:

805 IP Profile Call Limit: The device generates this response code when Call
Admission Control (CAC) limits are exceeded for an IP Group. The CAC rules are
configured in the IP Profile table (see ''Configuring IP Profiles'' on page 396). When
this occurs, the device sends a SIP 480 (Temporarily Unavailable) response to the
SIP entity.

806 Media Limits Exceeded: The device generates this response code when the call
is terminated due to crossed thresholds of QoE metrics such as MOS, packet delay,
and packet loss (configured in the Quality of Experience Profile table) and/or media
bandwidth (configured in the Bandwidth profile table). When this occurs, the device
sends a SIP 480 (Temporarily Unavailable) response to the SIP entity. This is
configured by 1) assigning an IP Group a QoE and/or Bandwidth profile that rejects
calls if the threshold is crossed, 2) configuring 806 in the Reasons for Tel-to-IP
Alternative Routing table and 3) configuring an alternative routing rule.
Note: The device also plays a tone to the endpoint whenever an alternative route is
used. This tone is played for a user-defined time, configured by the
AltRoutingToneDuration parameter.
Depending on configuration, the alternative routing is done using one of the following
configuration entities:

Tel-to-IP Routing Rules: You configure alternative routing rules for a specific routing
rule in the Tel-to-IP Routing table. If the destination of the "main" routing rule is
unavailable, the device searches the table for the next matching rule (e.g., destination
phone number), and if available attempts to re-route the call to the IP destination
configured for this alternative routing rule. For more information on configuring
alternative Tel-to-IP routing rules, see ''Configuring Tel-to-IP Routing Rules'' on page
495. The table below shows an example of alternative routing where the device uses
the first available alternative routing rule to re-route the initial, unsuccessful Tel-to-IP
call destination.
Table 24-7: Alternative Routing based on SIP Response Code Example
Main Route
Alternative Route #1
Alternative Route #2

Proxy Sets: Proxy Sets are used for Server-type IP Groups (e.g., an IP PBX or
User's Manual
Destination
IP Destination
Phone Prefix
40 10.33.45.68
40 10.33.45.70
40 10.33.45.72
Mediant 800B Gateway and E- SBC
SIP Response
408 Request
Timeout
486 Busy Here
200 OK
516
Rule Used?
No
No
Yes
Document #: LTRT-10296