Avaya Nortel Communication Server 1000 Manual page 69

ELAN subnet failure
The ACF state cannot be determined on the LTPS side during an ELAN
subnet failure. This is because the ACF state is stored on the Call Server
and it is not possible to send the ACF state on the LTPS side when the
ELAN subnet has failed.
When the ELAN subnet is down, the isetShow command always outputs
the ACF state as UNKNOWN for all established calls (the state is shown as
busy-UNK).
Feature interactions
This section shows the ACF feature interactions with Virtual Office and
Branch Office.
Branch Office
When the first failed IP Phone re-registers in local mode, the branch office
Call Server looks up the far-end branch IP Phone local TN using the
specified far-end IP address and builds a local call.
The call can be rebuilt only if both the IP Phones are branch users of the
same branch office.
Example: A regular main office IP Phone talks to the branch IP Phone
registered with the main office. A failure occurs on the main office, so that
the branch IP Phone cannot register in normal mode again, and re-registers
in local mode. Even if the main office IP Phone survives the failure, the
call cannot be rebuilt because the call becomes an IP Peer call between
the branch office and main office. This call becomes Partial Rebuilt and
exists until released.
Virtual Office
It is possible that active IP Phone A, that was logged on to IP Phone B
before the failure, cannot re-register with the Call Server, because IP Phone
C performed a Virtual Office logon and uses IP Phone A TN. In this case, the
Signaling Server/Voice Gateway Media Card locally handles the Release,
Onhook and Mute events coming from IP Phone A in the Logged Out state.
Survivable Remote Gateway
The Survivable Remote Gateway (SRG) 1.0 and SRG 50 do not support
ACF. If the IP Phone is an SRG user, the active call, either in normal mode
or local mode, does not survive a failure.
Copyright © 2003–2008, Nortel Networks
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Nortel Communication Server 1000
IP Line Fundamentals
NN43100-500 02.02 Standard
Release 5.5 4 February 2008
Active Call Failover for IP Phones 69