Nortel Networks SRG 50 NN43001-307 - Manual (Page 20)

20 Description
ATTENTION
When a telephone or trunk in the main office calls an SRG IP Phone that has
switched to Local Mode due to WAN failure, the call is treated according to the
main office call redirection configuration (such as forwarding to voice mail or
continuous ringback).
In the event that the IP Phones at the branch office lose the connection to
the main office CS 1000 call server for any reason (WAN failure, main office
call server failure, main office Signaling Server failure), the SRG 50 reverts
to Local Mode automatically. Essentially, when VoIP connectivity is lost,
each IP Phone loses its Reliable UDP (RUDP) connection with the main
office Terminal Proxy Server (TPS). The IP Phones at the branch office
reboot and reregister to the SRG 50, placing them in Local Mode.
After this occurs, the IP Phones displays an indication on the display area
that the set is in Local Mode of operation. This display is configurable by
installers to meet local language and usage norms.
In Local Mode, the IP users connected at the branch office are under the
control of the SRG 50 call services. As such, the normal main office call
server features are not available. The SRG 50 offers a basic feature set
when in Local Mode which allows IP Phones to continue to make and
receive calls internally within the branch office and over the provisioned
local PSTN interfaces. Basic services, such as transfer, last number redial,
and single key access through the PSTN to a centralized voice messaging
system are supported. Local PSTN access and local Emergency Services
access is also supported. No local applications or Business Communication
Manager features are supported in Local Mode operation.
Analog devices continue to be under the control of the SRG 50 system. It
is the intent of Local Mode to provide continued access to the PSTN for
critical calls and emergency services.
In Local Mode, since the SRG 50 handles all call processing, calls
between two IP phones at the SRG 50 are handled locally as a simple
station-to-station call. When an IP Phone initiates a local PSTN call, the
SRG 50 routes the call to a trunk that is connected to the local PSTN.
Incoming DID calls are also handled by the SRG 50 and terminated on
the appropriate IP Phone.
In the event of a WAN failure, in Local Mode, the IP Phones do not have
access to the main office network over the VoIP trunks. If the appropriate
alternate routes are configured, calls will be routed to the main office or
other branch offices using the available PSTN trunks.
Nortel Communication Server 1000
Main Office Configuration Guide for SRG 50
NN43001-307 02.02 Standard
Release 5.0 3 December 2007
Copyright © 2005-2007, Nortel Networks
.