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TCP/IP AND OSIPresented to: Dr.Hisham El Zouka

Presented by: Passant Wahdan

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OSI

Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s.

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The OSI model

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Summary of OSI Layers

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TCP/IP

The TCP/IP protocol suite was developed prior to the OSI model. Therefore, the layers in the TCP/IP protocol suite do not match exactly with those in the OSI model. The original TCP/IP protocol suite was defined as four software layers built upon the hardware. Today, however, TCP/IP is thought of as a five-layer model with the layers named similarly to the ones in the OSI model

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Layers in the TCP/IP Protocol Suite

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TCP/IP Layers

OSI TCP/IP

Application LayerApplication Layer　

Presentation Layer

Session Layer

 Transport Layer Transport Layer　

Network Layer  Internet Layer　

Data Link Layer Link Layer  Physical Layer

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TCP/IP and OSI model

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Similarity

Both are based on the concept of a stack of independent protocols.

The functionality of the layers is roughly similar.

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Difference

OSI makes the distinction between services, interfaces, and protocol.

Host on OSI implementations do not handle network operations.

TCP/IP does not originally clearly distinguish between services, interface, and protocol.

TCP/IP hosts participate in most network protocols.

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Difference(continue)

OSI emphasis on providing a reliable data transfer service, Each layer of the OSI model detects and handles errors, all data transmitted includes checksums. The transport layer checks source-destination reliability.

TCP/IP treats reliability as an end to end Problem. The transport layer handles all error detection and recovery, it was checksums, acknowledgments, and timeouts to control transmissions and provides end-to-end verification.

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Application Layer

Application provides a set of interfaces for applications to obtain access to networked services such as networked file transfer, message handling, and database query processing.

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Presentation LayerOSI TCP/IP

The Presentation Layer handles data format information. For outgoing messages, it converts data into a generic format that can survive the network transmission; for incoming messages, it converts data from its generic networked representation into a format that will make sense to the receiving application.

Presentation layer is not present in TCP/IP model. Instead this function is frequently handled within the applications in TCP/IP through External Data Representation Standard(XDR) and Multipurpose Internet Mail Extensions (MIME).

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Session LayerOSI TCP/IP

The Session layer handles session setup, data or message exchanges, and tear down when the session ends.

It also monitors session identification so only designated parties can participate and security services to control access to session information.

The TCP/IP model does not have a general session layer protocol.

In TCP/IP the term “sockets” and “ports” are used to describe the path over which cooperating application communicates.

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Transport (OSI)

The basic function of the transport layer is to accept data from the session layer, split it up into smaller units, pass it to the network layer, and ensure that the bits delivered are the same as the bits transmitted without modification, loss or duplication. If an error occurs during transmission, the transport layer must correct it. “If no acknowledgement is received, the transport layer can retransmit the packet or time-out the connection and signal an error.

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Transport (TCP/IP)

There are two standard transport protocols:

TCP implements a reliable data-stream protocol connection oriented

UDP implements an unreliable data-stream connectionless

• Primary difference is that UDP does not necessarily provide reliable data transmission

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Network

The network layer provides the functional and procedural means of transferring variable length data sequences from a source host on one network to a destination host on a different network while maintaining the quality of service requested by the Transport Layer.

TCP divides messages in datagrams of up to 64k length. Each datagram consists of a header and a text part. Besides some other information, the header contains the source and the destination address of the datagram. The service provided by IP is not reliable. Datagrams may be received in the wrong order or they may even get lost in the network.

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Data link

The main task of the data link layer is to take a raw transmission and transform it into a line that appears free of transmission errors in the network layer. It accomplishes this task by having the sender break the input data up into data frames, transmit the frames sequentially, and process the acknowledgment frames sent back by the receiver. The protocol packages the data into frames that contain source and destination addresses.

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Physical

The physical layer is concerned with transmitting raw bits over a communication channel. The design issues have to do with making sure that when one side sends a 1 bit, it is received by the other side as a 1 bit, not as a 0 bit.

The physical layer describes some type of cabling system as the transmission media. It also describes the network topology and how the transmission media is to be distributed. Some examples include the bus, star, and ring topologies.

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2.10 Eight layers architecture:

Related applications

Less related app

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2.10 Six layers architecture:

Link layer

Data link and physical layer deals with the same type of data

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References

William Stallings, chapter 2 local and metropolitan area networks, fifth edition: Pearson publication.

http://www.sans.org/reading_room/whitepapers/standards/osi-model-overview_543

http://solomon.ipv6.club.tw/Course/ProtocolEngineering/20100421-junnkeh-osi.ppt

http://erdos.csie.ncnu.edu.tw/~ccyang/TCPIP/Slides/Chap-02.ppt