PBX-to-PBX Calls

PBX-to-PBX Calls
PBX-to-PBX calls, as shown in Figure 3-5, originate at a PBX at one site and terminate at
a PBX at another site while using the network as the transport between the two locations.
Many business environments connect sites with private tie trunks. When migrating to a
converged voice and data network, this same tie-trunk connection can be emulated across
an IP network. Modern PBX connections to a network are typically digital T1 or E1 with
channel associated signaling (CAS) or Primary Rate Interface (PRI) signaling, although
PBX connections can also be analog.
128 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
V V
PBX
Gateway Gateway
Configured
to Dial:
“555-0199”
555-0199
Ring!!
IP WAN
Note PBX-to-PBX calls are another form of toll-bypass.
An example of a PBX-to-PBX call is one staff member calling another staff member at a
remote office. The call is sent from the local PBX, through a voice-enabled router, across
the IP network, through the remote voice-enabled router, and terminated on the remote
office PBX.
Cisco Unified
Communications
Manager
Site A
Cisco Unified
Communications
Manager
Site B
IP
IP WAN
Si Si
Figure 3-6 Intercluster Trunk Calls
An example of an intercluster trunk call is one staff member calling another staff member
at a remote office using an IP phone. The call setup is handled by the Cisco Unified
Communications Managers at each location. After the call is set up, the IP phones generate
Real-time Transport Protocol (RTP) segments that carry voice data between sites.