Page 16 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

• Transport Layer Protocols: TCP (Transmission Control Protocol) ensures reliable, connection-oriented
communication, while UDP (User Datagram Protocol) offers connectionless, lightweight communication.
• Application Layer Protocols: These include HTTP for web browsing, SMTP for email, and FTP for file
transfer, among many others.

OSI & Internet Architecture
OSI Model

OSI stands for Open Systems Interconnection. It has been developed by ISO International Organization for
Standardization in the year 1984.
In the OSI reference model, the communications between a computing system are split into seven different
abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

1 Physical Layer
• It is the lowest layer of the OSI model.
• It is responsible for the actual physical connection between the devices.
• This layer converts the digital bits into electrical, optically or via radio waves.
Some Functions of Physical layer

Data Transmission - The various transmission modes possible are Simplex, full-duplex and half-duplex.
Line Configuration - It helps in providing Physical Medium and Interface decisions
Signals - It determines the type of the signal used for transmitting the information.
Topology - It helps in Physical Topology (Mesh, Star, Bus, Ring) decisions (Topology through which we can
connect the devices with each other)
Physical Layer devices - are Modem, Hub, Repeater and Cables.
2 Data Link Layer(DDL)

The data link layer is responsible for the node-to-node delivery of the message.
• The data link provides a efficient & reliable communication between two or more devices.
• Defines the format of the data on the network.
• It is the responsibility of the data link layer to transmit it to the Host using its MAC address.
• It contains two sub-layers

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CITS : IT&ITES - Computer Software Application - Lesson 01-17