315-4PN33

The network layer is an agency layer. Business of this layer is to con-
trol the exchange of binary data between stations that are not directly
connected. It is responsible for the logical connections of layer 2 com-
munications. Layer 3 supports the identification of the single network
addresses and the establishing and disconnecting of logical commu-
nication channels. Additionally, layer 3 manages the prior transfer of
data and the error processing of data packets. IP (Internet Protocol) is
based on Layer 3.
Layer 4 connects the network structures with the structures of the
higher levels by dividing the messages of higher layers into segments
and passes them on to the network layer. Hereby, the transport layer
converts the transport addresses into network addresses. Common
transport protocols are: TCP, SPX, NWLink and NetBEUI.
The session layer is also called the communication control layer. It
relieves the communication between service deliverer and the
requestor by establishing and holding the connection if the transport
system has a short time fail out. At this layer, logical users may com-
municate via several connections at the same time. If the transport
system fails, a new connection is established if needed. Additionally
this layer provides methods for control and synchronization tasks.
This layer manages the presentation of the messages, when different
network systems are using different representations of data. Layer 6
converts the data into a format that is acceptable for both communi-
cation partners. Here compression/decompression and encrypting/
decrypting tasks are processed. This layer is also called interpreter. A
typical use of this layer is the terminal emulation.
The application layer is the link between the user application and the
network. The tasks of the application layer include the network serv-
ices like file, print, message, data base and application services as
well as the according rules. This layer is composed from a series of
protocols that are permanently expanded following the increasing
needs of the user.
7.3
Basics - Terms
A network res. LAN (Local Area Network) provides a link between dif-
ferent stations that enables them to communicate with each other.
Network stations consist of PCs, IPCs, TCP/IP adapters, etc. Network
stations are separated by a minimum distance and connected by
means of a network cable. The combination of network stations and
the network cable represent a complete segment. All the segments of
a network form the Ethernet (physics of a network).
In the early days of networking the Triaxial- (yellow cable) or thin
Ethernet cable (Cheapernet) was used as communication medium.
This has been superseded by the twisted-pair network cable due to
its immunity to interference. The CPU has a twisted-pair connector.
The twisted-pair cable consists of 8 cores that are twisted together in
pairs. Due to these twists this system is provides an increased level
of immunity to electrical interference. For linking please use twisted
pair cable which at least corresponds to the category 5. Where the
Layer 3 - Network layer
Layer 4 - Transport
layer
Layer 5 - Session layer
Layer 6 - Presentation
layer
Layer 7 - Application
layer
Network (LAN)
Twisted Pair
VIPA System 300S Deployment Ethernet communication - productive
Basics - Terms
HB140 | CPU | 315-4PN33 | GB | 14-43 109