2. Protocol
• A protocol is a set of rules that governs the
communications between computers on a
network.
• In order for two computers to talk to each other,
they must be speaking the same language.
• Many different types of network protocols and
standards are required to ensure that your
computer can communicate with another
computer located on the next desk or half-way
around the world.
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3. Protocol
• The OSI (Open Systems Interconnection)
Reference Model defines seven layers and
TCP/IP defines four layers of networking
protocols.
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5. OSI Reference Model
• Application layer.
• Presentation layer.
• Session layer.
• Transport layer.
• Network layer.
• Data link layer
• Physical layer.
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6. Physical layer
• The physical layer is only responsible for sending
bit from one computer to another.
• The physical layer is not concerned with the
mean of bits.
• It deals with the physical connection to the
network.
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7. Data link layer
• Data link layer is only responsible for data flow
over a single link from one device to another.
• It accepts the packets from the network layer
and packages the information in to data units
called frames, to be presented to the physical
layer for transmission.
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8. Network layer.
• Network layer makes routing decisions and
forwards packets for devices that are further
away then a single link.
• The network layer translate logical network
addresses in to physical machine addresses.
• This layer also determines the quality of services
and route a message will take there is several
ways a message can get to its destination.
• It also breaks the data in to chunks.
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9. Transport layer
• The transport layer ensure that packets are
delivered error free, in sequence and with no
losses or duplications.
• The transport layer typically sends an
acknowledgment to the originator for messages
received.
• TL also control the dialog between two process,
determining who can transmit and who can
receive at what point during the communication.
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10. Session layer
• Session layer allows applications on separate
computers to share a connection called a
session.
• This layer provide services such as name
lookup and security to allow programs to find
each other and establish the communication
link.
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11. Presentation layer
• This layer translates data between the formats
the network requires and the formats the
computer expects.
• Data translation, compression and encryption.
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12. Application layer
• Application layer is the topmost layer also
know as GUI. Graphic User interface.
• It provide services that direct support the user
application.
• Such as database, email files and folders etc.
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