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Protocol Hierarchies

file. file. Network Service. Network Service. Network. Protocol Hierarchies. First networks: hardware comes first Increased complexity  network architecture becomes more important. Layered Protocols. From structured programming concepts Modular implementation

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Protocol Hierarchies

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  1. file file NetworkService NetworkService Network Protocol Hierarchies • First networks: hardware comes first • Increased complexity  network architecture becomes more important ECE 766 Computer Interfacing and Protocols

  2. Layered Protocols • From structured programming concepts • Modular implementation • Distribute responsibilities to different layers • Problems to be addressed: • Addressing • Transmission mode and data transfer (channels) • Error detection and recovery • Message fragmentation • Order of delivery • Buffering ECE 766 Computer Interfacing and Protocols

  3. Layer N Peer Protocol Layer N Layer N Layered Protocols • Each layer has a predefined set of functions • Layers provide services to their immediate upper layers, hiding the details of the service • Peer layers communicate using a Peer Protocol • Layers are separated from each others with interfaces • Service provided at Service Access Points (SAP) passing control information and data ECE 766 Computer Interfacing and Protocols

  4. Host 1 Host 2 Layer 5 Protocol Layer 5 Layer 5 M M Interface Layer 4 Protocol Layer 4 Layer 4 H4 M H4 M Interface Layer 3 Protocol Layer 3 Layer 3 H3 H4 M1 H3 M2 H3 H4 M1 H3 M2 Interface Layer 2 Protocol Layer 2 Layer 2 H2 H3 H4 M1 T2 H2 H3 M2 T2 H2 H3 H4 M1 T2 H2 H3 M2 T2 Interface Layer 1 Protocol Layer 1 Layer 1 Physical Medium Layered Protocols Host 1 Host 2 ECE 766 Computer Interfacing and Protocols

  5. ISO’s OSI Model • OSI: Open System Interconnection • Model is not a protocol itself; it is a set of functional specifications • “Open”  accessible, not proprietary • First conceptual design, then implementation • Consists of 7 layers • ISO has also produced standards that are not part of the model ECE 766 Computer Interfacing and Protocols

  6. Host 1 Host 2 Application Protocol Application Application Interface Presentation Protocol Presentation Presentation Interface Session Protocol Session Session Interface Transport Protocol Transport Transport Communication Network Interface Internal Subnet Protocols Network LayerHost-RouterProtocol Network LayerHost-RouterProtocol Network Network Network Network Interface Data Link LayerHost-RouterProtocol Data Link LayerHost-RouterProtocol Data Link Data Link Data Link Data Link Interface Physical LayerHost-RouterProtocol Physical LayerHost-RouterProtocol Physical Physical Physical Physical OSI Layers ECE 766 Computer Interfacing and Protocols

  7. OSI Layers 1. Physical: Transmission of unstructured data stream over physical medium Data Unit: Bit Aspects: Mechanical Electrical Functional Procedural ECE 766 Computer Interfacing and Protocols

  8. OSI Layers 2. Data Link: Transforms the physical layer to a reliable link to achieve node-to-node delivery Data Unit: Frame • Framing: Creation, detection, acknowledgment • Physical addressing • Flow control • Error control • Access control  MAC ECE 766 Computer Interfacing and Protocols

  9. OSI Layers 3. Network: End-to-end delivery of packets across the network Data Unit: Packet • Logical addressing • Routing 4. Transport: End-to-end delivery of the entire message • Service point addressing (port) • Connection and flow control • Error control ECE 766 Computer Interfacing and Protocols

  10. OSI Layers 5. Session: Dialog control and additional synchronization 6. Presentation: Data format translation, encryption, and compression 7. Application: Tools to access the network ECE 766 Computer Interfacing and Protocols

  11. OSI Model • Biggest contribution: Distinction of services, interfaces, and protocols • OSI model is very useful to classify other protocol stacks • Protocol implementations never became popular ECE 766 Computer Interfacing and Protocols

  12. TCP/IP Model • Developed by DARPA • Main goal: Resilience to loss of network hardware • Model developed after protocol implementation, merely a description of the protocols The model never became popular • 4 Layer structure (not 7!) ECE 766 Computer Interfacing and Protocols

  13. Application Application Presentation Not present in the model Session Transport Transport Network Internet Data Link Host-to-network Merged Physical OSI Model TCP/IP Model OSI Model vs. TCP/IP Model ECE 766 Computer Interfacing and Protocols

  14. OSI Model vs. TCP/IP Model ECE 766 Computer Interfacing and Protocols

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