Alternative Routing Upon Sip 3Xx With Multiple Contacts; Pstn Fallback - AudioCodes Mediant 3000 User Manual

User's Manual

25.5.3 Alternative Routing upon SIP 3xx with Multiple Contacts

You can configure how the device handles received SIP 3xx responses that contain
multiple alternative contacts. The 3xx response indicates that the original destination is
unavailable (e.g., 301 Moved Permanently – user cannot be found) and that the call can be
redirected to alternative destinations specified in the SIP Contact headers.
Configured by the '3xx Use Alt Route Reasons' parameter, the device can handle the
receipt of 3xx responses using one of the following methods:

The device tries each contact sequentially, listed in the Contact headers, until a
successful destination is found. If a contact responds with a SIP 486 or 600, the
device does not try to redirect the call to the next contact and drops the call.

The device tries each contact sequentially, listed in the Contact headers. If a SIP 6xx
Global Failure response is received during this process (e.g., 600 Busy Everywhere),
the device does not try to redirect the call to the next contact and drops the call.

The device redirects the call to the first contact listed in the Contact header. If the
contact responds with a SIP response that is configured in the Reasons for Tel-to-IP
Alternative Routing table (see ''Alternative Routing Based on SIP Responses'' on page
444), the device tries to redirect the call to the next contact, and so on. If a contact
responds with a response that is not configured in the table, the device does not try to
redirect the call to the next contact and drops the call.
Note:
to redirect the call to the next contact. Instead, the device continues with the regular
authentication process, as indicated by these response types.

25.5.4 PSTN Fallback

The PSTN Fallback feature enables the device to re-route a Tel-to-IP call to the legacy
PSTN using one of its trunks if the IP destination is unavailable. For example, if poor voice
quality is detected over the IP network, the device attempts to re-route the call to the
PSTN.
The steps for configuring alternative Tel-to-IP routing to the legacy PSTN are summarized
below.

To configure alternative Tel-to-IP routing to the legacy PSTN:
1. Configure an alternative routing rule in the Outbound IP Routing table with the same
call matching characteristics (e.g., phone number destination), but where the
destination is the IP address of the device itself.
2. Configure an IP-to-Tel routing rule in the Inbound IP Routing table to route calls
received from the device (i.e., its IP address) to a specific Trunk Group connected to
the PSTN. This configuration is necessary as the re-routed call is now considered an
IP-to-Tel call. For configuring IP-to-Tel routing rules, see ''Configuring the Inbound IP
Routing Table'' on page 437.
Version 6.8
If a SIP 401 or 407 response is received from a contact, the device does not try
447
25. Routing
Mediant 3000