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Packets, Packet Switching and The OSI Model

Packets, Packet Switching and The OSI Model. Packets. Transmissions are broken up into smaller units or data transmissions called packets. Example A file (might be an mp3 sound file) is divided into packets. It does not matter what the transmission is. It could be Word

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Packets, Packet Switching and The OSI Model

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  1. Packets, Packet Switching and The OSI Model

  2. Packets • Transmissions are broken up into smaller units or data transmissions called packets Example A file (might be an mp3 sound file) is divided into packets. It does not matter what the transmission is. It could be Word document, a PowerPoint or an MP3 PACKET PACKET PACKET PACKET

  3. Packets and OSI • After transmission is divided into packets extra information required to make sure it all goes back together correctly. The OSI model helps to look after this. • The OSI model also provides much more information which is included with each package.

  4. OSI 7 Layer Model Originally Created by Bob Baker Modified 2006 Graham Betts More Information on OSI • OSI “Open System Interconnection” • OSI is not a protocol but a list of protocols divided between 7 layers with each layer having a different set of functions. • Each packet is layered/packaged with protocols from each of the layers as it is processed. • The process of layering the protocols around each package is called encapsulation. The final encapsulated data packet is called a frame.

  5. Open Systems Interconnection Originally Created by Bob Baker Modified 2006 Graham Betts • OSI Reference model • Layer 7 application • Layer 6 presentation • Layer 5 session • Layer 4 transport • Layer 3 network • Layer 2 data link • Layer 1 physical Sender Receiver File Each file is divided into packets Each Packet will then be Encapsulated with PROTOCOLS The encapsulated Packet is calleda frame The protocols Will be added systematically Layer By layer File File The received frame is then unpacked in the opposite order Transmission Medium

  6. Layer 7 application Layer 6 presentation Layer 5 session Layer 4 transport Layer 3 network Layer 2 data link Layer 1 physical Identification, authentication Format conversion Set-up coordinate conversation Ensures error-free transfer Routing of data through network Error control and synchronisation Placing signals on the carrier Services Performed at Each Layer Originally Created by Bob Baker Modified 2006 Graham Betts

  7. Layer 7 application Layer 6 presentation Layer 5 session Layer 4 transport Layer 3 network Layer 2 data link Layer 1 physical E-mail, Web browser, Directory POP, SMTP, FTP, HTTP, DNS Sockets TCP IP PPP, Ethernet, Token ring 100baseT Examples of protocols Originally Created by Bob Baker Modified 2006 Graham Betts More on Protocols

  8. Application Application Presentation Presentation H6 data T6 Session Session H5 data T5 Transport Transport H4 data T4 FRAME FRAME FRAME Network Network (packet) H3 data T3 Data Link Data Link H2 data T2 Physical Physical H1 data T1 Preamble Destination Address Source Address Data Padding CRC A typical frame Encapsulation Originally Created by Bob Baker Modified 2006 Graham Betts Device 1 Device 2 data packet carrier FRAME

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