Nortel Communication Server 1000 Manual page 16

16 Overview
•
Q.931 MCDN interface
•
Q.931 public ISDN access interface
•
DPNSS1 private networking interface
DASS2 is specified in terms of the International Standards Organization
(ISO) reference model for Open Systems Interconnection (OSI). Level
1 (Physical) of the model is a 2.048 Mbit/s digital interface and level 2
(Data Link) is the Link Access Protocol (LAP) defined for DASS2. Level 3
(Network) is the message layer unique to DASS2.
Model works" (page 16)
Figure 1
How the OSI Model works
Each layer in the model depends on the services offered by the layer
below it and, in turn, builds on those services to perform a specific set of
communication functions. Protocols are the mechanism by which each
layer accomplishes its communication functions. It then offers these
functions to the layer above it in the form of its own set of services. Note
illustrates the OSI model.
Nortel Communication Server 1000
DASS2 Fundamentals
NN43001-571 04.01 4 June 2010
Copyright © 2007-2010 Nortel Networks. All Rights Reserved.
Figure 1 "How the OSI