FREE online courses on Information Technology - Chapter 8 NETWORK &
COMMUNICATIONS IN I T - What is a Protocol
Transmission involves protocols, which are sets of rules and
procedures to control the flow of data between points. Both the sending and
receiving stations need to follow the same procedures. For example, if blocks
are being sent, both stations must agree that the transmission is to be in block
mode. A protocol can also increase the efficiency of transmission by reducing
the amount of data that must be sent for control purposes.
We must control the following:
¨
Setting up a session
¨
Establishing a path from nodes 1 to n
¨
Linking devices together
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The hardware sending and interpreting the data.
Protocols are also used to handle
the following:
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Detecting and correction of errors
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Formatting
¨
Line control
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Message sequencing
The International Standards
Organization (ISO) has suggested a layered architecture to facilitate
communications among different types of equipment. The seven logical layers are
as follows (numbering follows the ISO designation of levels):
-
Application: The window through which applications gain access to the services
provided by the model.
-
Presentation: Service here are concerned with data transformation, formatting,
and syntax.
-
Session: A set of rules to set up and terminate data streams between network
nodes.
-
Transport: Guarantees that the transfer of information occurs correctly after a
route is established throughout the network.
-
Network: Arranges a logical connection between a source and destination on the
network based on available data paths in the network.
- Data
link: Describes how a device accesses the medium in the physical layer and
identifies data formats, procedures to correct transmission errors, and so on.
-
Physical: The lowest level in the model consists of a set of rules to specify
the electrical and physical connection between devices.
The highest levels should remain similar
across equipment, whereas lower levels depend more on the devices and
manufactures involved.
