Using NS3000/iX Network Services (36920-90008)
16 Chapter 1
Introduction to NS 3000/iX
Network Architecture
Network Architecture
A network architecture speciļ¬es the transmission tasks of distinct
hardware and software modules or layers. The architecture of
NS 3000/iX is based on the seven-layer OSI (Open Systems
Interconnection) model (Figure 1-1) developed by the International
Standards Organization (ISO). One of the purposes of having a layered
architecture is to make the complexities of data communications
transparent to the high-level user. Some familiarity with the tasks
performed at different levels may be helpful.
Figure 1-1 OSI Model
The highest layer regulates user services, while the lowest layer
regulates the actual transmission of bits from one node to another. Each
computer system in the network is called a node. At each layer one or
more protocols is responsible for carrying out the appropriate tasks. A
protocol is a set of rules that specify software message format. From a
logical point of view, the protocol entity at each level communicates
with the corresponding protocol entity at the same level on another
node. In reality, except for the physical transmission of data to another
node, each protocol entity communicates with other protocols at the
layer immediately above and below its own.