Chap. 2 Network Models
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Transcript of Chap. 2 Network Models
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Chap. 2Chap. 2Network ModelsNetwork Models
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2.1 Layered Tasks2.1 Layered Tasks
Sender, Receiver and Carrier
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Layered TasksLayered Tasks
Hierarchy
Higher Layer
Middle Layer
Lower Layer
Services
The Each layer uses the services of the layer immediately below it.
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2.2 Internet Model2.2 Internet Model
Five Layer Internet Model
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Internet ModelInternet Model
Peer-to-peer Processes
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Peer-to-peer ProcessesPeer-to-peer Processes
Interfaces between Layers
Each interface defines what information and services a layer must provide for the layer above it.
Well defined interfaces and layer functions provide modularity to a network
Organizations of the layers
Network support layers : Layers 1, 2, 3
User support layer : Layer 5
It allows interoperability among unrelated software systems
Transport layer (Layer 4) : linking two subgroups
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Peer-to-peer ProcessesPeer-to-peer Processes
An exchange using the Internet model
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Physical LayerPhysical Layer
coordinates the functions required to transmit a bit
stream over a physical medium.
(deal with the mechanical and electrical specification of
the primary connections: cable, connector)
- Physical characteristics of interfaces and media
- Representation of bits
- Data rate : transmission rate
- Synchronization of bits
is responsible for transmitting individual bits from one
node to the next node
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Physical LayerPhysical Layer
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Data Link LayerData Link Layer
The data link layer is responsible for transmitting frames
from one node to the next.
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Data Link LayerData Link Layer
Major duties
Framing
Physical addressing
Flow control
Error control
Access control
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Data Link LayerData Link Layer
Hop-to-hop (node-to-node) delivery
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Data Link LayerData Link Layer
In Figure 2.8 a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link. At the data link level this frame contains physical addresses in the header. These are the only addresses needed. The rest of the header contains other information needed at this level. The trailer usually contains extra bits needed for error detection
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Network LayerNetwork Layer
The network layer is responsible for the delivery of
packets from the original source to the final destination.
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Network LayerNetwork Layer
Logical addressing
Routing
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Network LayerNetwork Layer
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Transport LayerTransport Layer
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Transport LayerTransport Layer
The transport layer is responsible for delivery of a message from
one process to another.
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Transport LayerTransport Layer
Port addressing
Segmentation and ressemblt
Connection control
Flow control
Error control
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Transport LayerTransport Layer
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Application LayerApplication Layer
The application layer is responsible for providing
services to the user.
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Application LayerApplication Layer
The major duties of the application
Mail services
File transfer and access
Remote log-in
Accessing the World Wide Web
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Summary of LayersSummary of Layers
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2.3 OSI Model2.3 OSI Model
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OSI Reference ModelOSI Reference Model
OSI : Open System Interconnection by ISO
Basic Reference Model : ISO-7498
Purpose of OSI Model
~ is to open communication between different systems without requiring changes to the logic of the underlying hardware and software.
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The ModelThe Model
OSI Model
~ is layered framework for the design of network systems that allows for communication across all types of computer systems
Layered Architecture
~ shows the layers involved when a message is sent from device A to device B
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Model (cont’d)Model (cont’d)
The OSI Model
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OSI LayersOSI Layers
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Model (cont’d)Model (cont’d)
Peer-to-peer process
~ process on each machine that communicate at a
given layer
Interfaces between Layers
~ defines what information and services a layer must
provide for the layer above it
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Applications for All Layers Applications for All Layers