160 How the Branch Office feature works
"MG 1000B Core interoperability" (page 176)
"Network Wide Redundancy Phase II and Network Music" (page 176)
IntroductionThe Branch Office connects to the main office using Vir tual Trunksover
the LAN or WAN. Virtual Trunksare software components that provide the
trunking features of the Meridian Customer-Defined Networking (MCDN)
feature set. The main office and the Branch Office are configured as
Electronic Switched Network (ESN) nodes, connected by Virtual Trunks.
The MG 1000B Core provides a trunk gatewayto the PSTN. Access to
PSTN digital or analog trunks at the Branch Office occurs through the
MCDN Virtual Trunk.
For more information on Virtual Trunks, refer to IP PeerNetworking
Installation and Commissioning (NN43001-313) . For more information
about Electronic Switched Networking (ESN), refer to Electronic Switched
Network: Signaling and Transmission Guidelines (NN43001-280).
Normal Mode and Local Mode operation

Normal Mode

The Main Office provides central call processing for the Branch Office
Internet Telephones in Normal Mode. The Branch Office Internet
Telephonesare configured at the Main Office Call Server. These telephones
are registered to the Main Office Line Terminal ProxySer ver(LTPS) and are
controlled by the Call Server at the Main Office in Normal Mode.
Users of the MG 1000B IP Phones receive the features, key layout, and
tones of the main office Call Server. This provides feature and application
transparency between the Branch Office and the main office.

Local Mode

Devices that are physicallylocated with the Branch Office and are controlled
by the Branch Office call server are in local mode. These devices consist
of analog (500/2500-type) or digital telephones, analog or digital devices,
and may include IP Phones. Normally, IP Phones are registered to the
main office in Normal Mode, however,when the IP Phone cannot reach the
main office, it reverts to Local Mode.
If the Branch Office Internet Telephoneloses communication with the Main
Office, the Call server in the Branch Office provides the call processing
for the telephone. While the Branch Office Internet Telephones are have
service at the Branch Office, the telephone display showsLocal Mode.
In Local Mode, IP Phones receive only those features and tones that are
provisioned on the Branch Office.
Nortel Communication Server 1000
Branch Office Installation and Commissioning
NN43001-314 01.02 Standard
Release 5.0 20 June 2007
Copyright© 2007, Nor tel Networks
.