One of the benefits of the integrated CAC (Call Admission Control) solution is Lotus Sametime Unified Telephony's ability to provide rerouting via the PSTN (Public Switched Telephone Network) in case there is not enough bandwidth in the applicable bandwidth-limited link, whether this link is between branch offices or from the branch office to the WAN.
Rerouting of calls to SIP subscribers via the PSTN can be performed if the following conditions are met:
The called SIP subscriber is registered from a survivable branch.
The called SIP subscriber resides in that survivable branch. This means that the called SIP subscriber is registered with its provisioned survivable SIP EP (Endpoint) (its SIP proxy). The administration of the called SIP subscriber to become survivable is enabled by assigning the survivable SIP proxy as the associated SIP endpoint to the SIP subscriber.
The called subscriber has a valid public E.164 number.
- Furthermore one of the following conditions have to be met:
The calling SIP subscriber is calling from a different survivable branch.
- The calling SIP subscriber is directly registered with Lotus Sametime Unified Telephony.
The calling device is a SIP EP (SIP gateway) that has the rerouting option set, and there is a last diverting user for the call which is a provisioned Lotus Sametime Unified Telephony SIP subscriber.
Assume that a SIP subscriber in the Boca Raton, Florida, branch calls a SIP subscriber in the San Jose, California, branch. This scenario requires the RTP (Real-time Transport Protocol) payload to route 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 sends a negative response equivalent to a SIP 606 response code. Lotus Sametime Unified Telephony then reroutes the call between these two subscribers through their local SIP gateways and the PSTN.
Parent topic: CAC (Call Admission Control)
Rerouting Based on SIP Response Codes and WAN Outages
Rerouting PSTN (Public Switched Telephone Network) Calls to Alternate Gateways
Enhanced CAC-Restricted Subscriber Rerouting
Enhanced CAC Restricted Subscriber Rerouting for Endpoints