service primitives six service primitives that provide a simple connection-oriented service...
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Service Primitives
Six service primitives that provide a simple connection-oriented service
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Service Primitives
A simple client-server interaction using acknowledged datagrams.
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OSI Model
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2-1 LAYERED TASKS2-1 LAYERED TASKS
A network model is a layered architecture•Task broken into subtasks•Implemented separately in layers in stack•Functions need in both systems•Peer layers communicate
Protocol: •A set of rules that governs data communication•It represents an agreement between the communicating devices
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Layered Architecture
A layered modelEach layer performs a subset of the required
communication functionsEach layer relies on the next lower layer to perform
more primitive functionsEach layer provides services to the next higher layer.Each layer provides services to the next higher layerChanges in one layer should not require changes in
other layersThe processes on each machine at a given layer arecalled peer-to-peer process
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Tasks involved in sending a letter
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2-2 THE OSI MODEL2-2 THE OSI MODEL
Established in 1947, the International Standards Established in 1947, the International Standards Organization (Organization (ISOISO) is a multinational body dedicated to ) is a multinational body dedicated to worldwide agreement on international standards.worldwide agreement on international standards.
An ISO standard that covers all aspects of network An ISO standard that covers all aspects of network communications is the Open Systems Interconnection communications is the Open Systems Interconnection ((OSIOSI) model. It was first introduced in the late 1970s. ) model. It was first introduced in the late 1970s.
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ISO is the organization.OSI is the model.
Note
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Seven layers of the OSI model
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The interaction between layers in the OSI model
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An exchange using the OSI model
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The physical layer is responsible for movements ofindividual bits from one hop (node) to the next.
Note
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Function of Physical layer
• Physical characteristics of interfaces and media• Representation of bits• Data rate• Synchronization of bits• Line configuration (point-to-point or multipoint)• Physical topology (mesh, star, ring or bus)• Transmission mode ( simplex, half-duplex or duplex
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Physical layer
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The data link layer is responsible for moving frames from one hop (node) to the next.
Note
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Data link layer
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Hop-to-hop delivery
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Function of data link layer
• Framing• Physical addressing• Flow control• Error control• Access control
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The network layer is responsible for the delivery of individual packets from
the source host to the destination host.
Note
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Network layer
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Source-to-destination delivery
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Function of network layer
• Source-to-destination delivery• Responsible from the delivery of packets from
the original • source to the final destination• Functions
– Logical addressing– routing
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Transport layer
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The transport layer is responsible for the delivery of a message from one process to another.
Note
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Function of transport layer
• Port addressing• Segmentation and reassembly• Connection control ( Connection-oriented or
connection-less)• Flow control• Error control
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Reliable process-to-process delivery of a message
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Session layer
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The session layer is responsible for dialog control and synchronization.
Note
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Function of session layer
• It establishes, maintains and synchronize the interaction between communicating system
• Dialog control• Synchronization (checkpoints)
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Presentation layer
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The presentation layer is responsible for translation, compression, and encryption.
Note
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Function of presentation layer
• Concerned with the syntax and semantics of the information exchanged between two system
• Translation ( EBCDIC-coded text file ASCII-coded file)
• Encryption and Decryption• Compression
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Application layer
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The application layer is responsible for providing services to the user.
Note
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Function of application layer
• Network virtual terminal (Remote log-in)• File transfer and access• Mail services• Directory services (Distributed Database)• Accessing the World Wide Web
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Summary of layers
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OSI layer-Summary
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