Application Principles - Nortel Communication Server 1000 Manual

that, while services are used between layers within a signaling entity
(switch), protocols operate within the same layer of the OSI model but
between different signaling entities.
The OSI layering approach effectively divides the complex task of
communication between network signaling entities into a series of more
easily manageable pieces, each of which can be modified without affecting
the other pieces. This allows more flexible evolution and compatibility with
the ongoing standards activities.
Figure 2 "The structure of the OSI Model together with the functions of
each layer" (page 17)
the functions of each layer.
Figure 2
The structure of the OSI Model together with the functions of each layer

Application principles

Transmission system
The 2.048 Mbit/s digital transmission is divided into 32 timeslots,
numbered 0-31. Timeslots 1-15 and 17-31 provide 30 traffic channels.
Timeslot 0 is used as a synchronization channel. DASS2 is a
message-based signaling system that uses a common signaling channel
in timeslot 16. Each traffic channel has an associated LAP. The LAPs
shows the structure of the OSI Model and describes
Nortel Communication Server 1000
DASS2 Fundamentals
NN43001-571 04.01 4 June 2010
Copyright © 2007-2010 Nortel Networks. All Rights Reserved.
Application principles 17