Normal and local mode overview, Normal mode, Local mode – Nortel Networks SRG50 User Manual
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Chapter 4 CS 1000 considerations
35
SRG50 Configuration Guide
Normal and local mode overview
Normal mode and local mode overview provides a description of the following sections:
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“Recovery to normal mode” on page 37
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“Testing the telephone in local mode” on page 37
Normal mode
IP Phones that are physically located at the SRG but are registered with the main office are
operating in normal mode. In normal mode, the main office provides centralized call processing to
all applications transparently to all IP Phones at the Branch Office.
Users of the SRG IP Phones receive the features, applications, 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
Users at the branch office may be in local mode, or survivable mode for two different reasons:
1
IP Phone may have just booted up.
2
IP Phone cannot communicate to the main office because of a WAN failure or a failure of the
main office components.
In the event that the IP Phones at the branch office lose the connection to the main office CS1000
call server for any reason (WAN failure, main office call server failure, main office Signaling
Server failure), the SRG50 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 re-register to the
SRG50, placing them in local mode.
Once this has occurred, 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 SRG50 call
services. As such, the normal main office call server features are not available. The SRG50 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
Note: 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).