Reference Model 1. Layered network Why network are layered ?! -Easy to change -Easy to troubleshoot...
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Transcript of Reference Model 1. Layered network Why network are layered ?! -Easy to change -Easy to troubleshoot...
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Layered network
• Why network are layered ?!
- Easy to change - Easy to troubleshoot- Give general idea of each layer
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OSI• History :- Developed By ISO (international standard
organization)- OSI shortened from ( open system Inter
connection)- OSI has 7 layers and there were principle to
arrive to these seven layers 1)- layers should be created where different
abstraction is needed.2) Each layer should perform specific function.
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OSI (cont)
3) The function of each layer should defined looking to protocol.
4) Minimize information flow5) Not too small not too large
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Data link layer
• Transform row data into data frames and send it to receiver and the receiver will send acknowledgment frame .
• Flow control .
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Network Layer
• Routing packets from source to destination• Control congestion.• Solve problems of addressing.
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Transport Layer• Accept data from above split it up into smaller
units pass these to network layer and ensure all these pieces arrives correctly to other end.
• Error free point-to-point connection• End – to – end layer
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Session layer • Start or establish the connection between
users of different machines , and it offers:1-dialog control.2-token management.3-syncronization.
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TCP/IPHistory:ARPANET “research network sponsored by
D.O.D to connect universities and governments institution using leased telephone line .
What led's to producing TCP/IP ?
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1) Internet layer
-Deliver packet to desired destination.-Defining official packet format and
protocol called (IP)“internet protocol”.
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2)Transport LayerMain job to allow peer entities in source and
destination to carry on conversation.
has two protocols:1) TCP _ transmission control protocol.- Reliable connection oriented protocol- Flow control2)UDP _ User Datagram Protocol- Unreliable connection protocol.
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Comparison Between OSI and TCP/IP
• Similarities - both based on concept of stack of
independent protocols.- layers in both models have the same
function.
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Comparison Between OSI and TCP/IP
• Differences1)there are Three concepts that are centralizedto OSI Model:1- services 2- interfaces 3- protocols
2)number of layers.3)Connectionless and connection oriented
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Critique of OSI Model and protocols
1.Bad timing .2.Bad technology.3.Bad implementation.4.Bad politics.