AudioCodes Mediant 1000B SBA - Figure 13-3: Reasons for Alternative Routing

Installation & Maintenance Manual 13. Configuring the Mediation Server with the PSTN Gateway
Version 6.8 147 Microsoft Lync Server
3. When the PSTN Gateway receives a SIP 503 response from the Mediation Server in
response to an INVITE, it re-sends the INVITE to the redundant Mediation Server
(located at the datacenter). To achieve this, you need to configure the receipt of a SIP
503 response as a reason for IP alternative routing:
a. Open the 'Reasons for Alternative Routing' page (Configuration tab > VoIP
menu > GW and IP to IP > Routing > Alternative Routing Reasons).
Figure 13-3: Reasons for Alternative Routing Page
b. Under the Tel to IP Reasons group, from the 'Reason 1' drop-down list, select
503.
c. Click Submit.
d. Open the 'SIP General Parameters' page (Configuration tab > VoIP menu > SIP
Definitions > General Parameters).
Figure 13-4: SIP General Parameters Page
e. In ‘Fake Retry After’ field, enter the time '60' (in seconds). When the PSTN
Gateway receives a SIP 503 response (from the Mediation Server) without a
Retry-After header, the PSTN Gateway behaves as if the 503 response includes
a Retry-After header with this user-defined period.
f. Click Submit.
g. On the toolbar, click Burn to save the changes to the PSTN gateway flash
memory.