User`s manual

SIP User's Manual 5. Web Management
Version 5.0 71 October 2006
Alternative routing (using this table) is commonly implemented when there is no response
to an INVITE message (after INVITE retransmissions). The gateway then issues an internal
408 ‘No Response’ implicit release reason. If this reason is included in the ‘Reasons for
Alternative Routing’ table, the gateway immediately initiates a call to the redundant
destination using the next matched entry in the ‘Tel to IP Routing’ table. Note that if a
domain name in this table is resolved to two IP addresses, the timeout for INVITE
retransmissions can be reduced by using the parameter ‘Number of RTX Before Hotswap’.
Note: If the alternative routing destination is the gateway itself, the call can be configured
to be routed back to PSTN. This feature is referred to as ‘PSTN Fallback’, meaning that if
sufficient voice quality is not available over the IP network, the call is routed through legacy
telephony system (PSTN).
Tip: Tel to IP routing can be performed either before or after applying the
number manipulation rules. To control when number manipulation is done,
set the RouteModeTel2IP parameter. For information on this parameter,
refer to refer to Table 6-10 on page 180.
¾ To configure the Tel to IP Routing table, take these 6 steps:
1. Open the ‘Tel to IP Routing’ screen (Protocol Management menu > Routing Tables
submenu > Tel to IP Routing option); the ‘Tel to IP Routing’ screen is displayed
(shown in Figure 5-8).
2. In the ‘Tel to IP Routing Mode’ field, select the Tel to IP routing mode (refer to Table
6-10).
3. In the ‘Routing Index' drop-down list, select the range of entries that you want to edit.
4. Configure the Tel to IP Routing table according to Table 5-6.
5. Click the Submit button to save your changes.
6. To save the changes so they are available after a power fail, refer to Section 5.9.2 on
page 124.
Figure 5-8: Tel to IP Routing Table Screen