Network Engineering Overview - Nortel Meridian 1 Description, Installation And Operation

IP Telecommuter Engineering Guidelines Page 49 of 262
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Traditionally Meridian 1 networks rely on voice services such as LEC and
IXC private lines. With ITG technology, the Meridian 1 can now choose a
new kind of delivery mechanism, one that uses packet-switching over a data
network, specifically a corporate intranet. The role of the IP Line Card in this
regard is essentially to convert steady data stream digital voice into
fixed-length IP packets, and vice versa.
When a corporate data network is used to deliver voice traffic, it introduces
impairments, primarily delay and packet loss, at levels that are higher than
those delivered by voice networks. Delay between a speaker and listener
changes the dynamics and reduces the efficiency of conversations, whereas
delay variation and packet loss introduce glitches in the conversation. Simply
connecting IP Line card nodes to the corporate intranet without preliminary
capacity and performance assessment may result in unacceptable degradation
in the voice service; thus proper design procedures and principles must be
considered.
A simplified network block diagram showing the potential ITG
Telecommuter network is presented in the following Figure 15.
Note that when H.323 Clients are connected to the intranet, they will most
likely reach a subnet first, which will be the destination reference point for
any packet delay or loss measurement.
ITG Line 1.0/IP Telecommuter Description, Installation and Operation