5.28.2. Special Notes 
The connection does not restart safe once the Setup of the alternate
route has been started i.e. once the Setup Message has been sent from
Node C, only first once the original connection has been switched to
the alternative route will the connection be "saved" again.
In Node C this will be with the incoming Connect message over the alternate
route and in Node A with the Disconnect of the original connection.
During the optimizations message flow the stations A and C cannot
invoke any features e.g. Consultation etc. With analogue stations the
try will simply be ignored and with digital the display "Please
Repeat" or "Not Possible" will be seen in the display.
Path Switching
OS4K will only execute Route Optimization when A receives primary
end. If C receives primary end, A will reject the PRPropose and initiate
its own reinvite afterwards.
Route Optimization in Hicom/HiPath uses B.1.2 Separate Switchover
of Each Direction of Transmission. For further information please see
the protocol specification ETSI 300-258/ISO 13863.
B.1.2. Separate Switchover of each direction of transmission.
With this approach, FE2 transmits on the new user information channel
as soon as it has been agreed with the next CC, whilst continuing to
transmit and receive on the old user information channel for transmission
and reception but also continues to transmit on the old user information
channel. On receipt of the PRS response/confirmation, FE2 switches over
to the new user information channel. On receipt of the PRS response/confirmation,
FE2 switches over to the new user information channel for reception as
well as transmission. Effectively the two directions of transmission
are switched over at different times, and any disruption in user information
due to signalling delays is eliminated.
Party A in switch A will switch to the new connection upon receipt
of the Route Optimization Setup.
Party C in switch C will switch to the new connection when the Route
Optimization Call Proc is received.
Switch A will only disconnect the old path upon receipt of the Disconnect
message received for the old connection.
Some problems have been reported related to loss of syllables/speech
at the beginning of the Route Optimization calls when systems are connected
via IP Trunking. This error happens due to delays in IP networks and
that H323 only switches the Payload first with the Route Optimization
Connect message (as per protocol because no Alert is sent). The delay
can be up to one second dependant on the quality of the IP network and
the number of IP Hops.
The "A" side is also designated upon the time to transfer
by receiving a Facility message containing ISOCallTransferComplete with
endDesignation Primary End. The "C" side of the connection
receives the same message, but with the EndDesignation Secondary End.
Once the Secondary End (destination of the transfer) has reached talk
state, either by callStatus answered in the ISOCallTransferComplete for
a transfer talking, or with a CTActive message for answer after a transfer
ringing will the Primary End then send a new Facility message with ISOPathReplacePropose
to initiate the Path Replacement.