Call Set Up Times; Look Ahead Routing - NEC NEAX 2000 IPS Reference Manual

Chapter 14 Common Channel Inter-Office Signaling (CCIS)

Call Set Up Times

Standard tie line networks typically require from two to eight seconds to complete the set up of
a call and return ring back tone to the caller. With a CCIS network, call set up times are much
lower averaging from 100 msec. to two seconds depending on the number of systems in the
network.

Look Ahead Routing

In a standard non-CCIS network using tie lines to connect two nodes, when a station in node A
calls a station in node B a tie line is seized and the call set up information is transmitted (in
band) to attempt to ring down the called station. If that station is busy, busy tone is heard
through the tie line from the destination system. This acceptable practice has been used for
many years in spite of how inefficient it may be. The above scenario illustrates why many non-
CCIS tie line networks require tie line usage for calls that never get completed. This is not very
efficient and often results in customers needing to purchase more voice/data tie lines then
what would really be needed if an intelligent network were employed.
The intelligent CCIS network provides a Look Ahead Routing feature that helps to reduce the
load on network tie lines (voice/data channels) thereby reducing the total number of voice/data
channels (tie lines) required between two nodes. When an on-net call is placed to a remote
node, the system will "Look Ahead" to the destination system to determine if the called station
is available. This is accomplished by communications between the systems over the D
channel. If the called station is not available, busy tone is provided to the calling party locally
and a voice/data channel (tie line) is not used. This provides a decrease in the overall number
of tie lines needed to carry the traffic loads between network nodes, further reducing ongoing
operation costs and system hardware requirements.
The benefits of Look Ahead Routing are also realized in applications where trunk facilities are
strategically distributed throughout the network. CCIS will "Look Ahead" when a user in node A
tries to access a trunk facility from node B. A tie line from node A to node B would only be
used if the trunk facility requested is available.
NEAX 2000 IPS Request For Proposal (RFP) Reference Guide Page 14-11
NDA-24349, Issue 4