Avaya Nortel Communication Server 1000 Manual page 67

Calls that are ringing are handled as follows:
•
•
Held calls
From the ACF feature perspective, held calls are considered to be
established. This means that the call is preserved on the Call Server
despite TLAN subnet or LTPS failure. The IP Phone itself is unaware of the
state of any held call.
Phase 0/1 IP Phones
Phase 0/1 phones do not support ACF.
Feature key labels
If user-defined feature key labels have been changed but no datadump has
been performed, the changes are lost if there is a Call Server failure.
SIP telephones
SIP telephones appear as IP Peer endpoints to the system. See
calls" (page
NAT devices
The ACF feature cannot handle the case of a NAT device changing the
media path mapping between the IP Phone private address and public
address during the failover period. There is no way to discover the mapping
while the port is in use. For instance, if a main office failure occurs and the
user re-registers in local mode, NAT mapping is changed and the active call
cannot survive.
Control messages
The LTPS sends the Audio Stream Control and LEDs Control commands
in separate messages. If a failure occurs in the time between the two
messages, the Audio Stream and LEDs states may not be synchronized.
For example, it is possible for the Audio Stream to be muted and a network
failure to occur at just the right moment to prevent the LED Control message
for the mute LED from being received by the IP Phone.
Held Calls
When an idle IP Phone (one without an active speech path) re-registers,
a firmware download can occur, if needed. If that IP Phone actually had
calls on hold, this means the held calls cannot be retrieved until after the
firmware download is finished.
Copyright © 2003–2008, Nortel Networks
.
If the IP Phone originating the ringing call unregisters, the call is
released by the Call Server.
If the IP Phone receiving the call unregisters, the call receives CFNA
treatment if possible.
66).
Nortel Communication Server 1000
IP Line Fundamentals
NN43100-500 02.02 Standard
Release 5.5 4 February 2008
Active Call Failover for IP Phones 67
"IP Peer