PSTN (Public Switched Telephone Network) calls can also be rerouted to alternate SIP or SIP-Q gateways.
Assume that Lotus Sametime Unified Telephony is provisioned for tail-end hop-off. Whenever a Boca Raton subscriber dials a local number in San Jose, the PSTN gateway in San Jose is chosen as the first route out of the network, making this otherwise long-distance call a local call in San Jose and therefore less expensive.
This scenario, however, requires the RTP (Real-time Transport Protocol) media stream to go through the bandwidth-limited links that connect the Boca and the San Jose branch offices to the WAN.
If there is not enough bandwidth available in either link, the resource reservation is not successful and the RM (Resource Manager) function generates a negative response equivalent to a SIP 606 response code.
Lotus Sametime Unified Telephony then reroutes the call via the local gateway to reach the right number via the PSTN or SIP-Q gateway.
Parent topic: CAC (Call Admission Control) Rerouting
Rerouting a Call to a SIP Subscriber