1. 03 - Winter 2006ECE 766 Computer Interfacing and Protocols 1 Protocol Hierarchies First networks: hardware comes first Increased complexity  network architecture becomes more important file Network Service Network file Network Service

2. 03 - Winter 2006ECE 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

3. 03 - Winter 2006ECE 766 Computer Interfacing and Protocols 3 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 Layer N Layer N Peer Protocol

4. 03 - Winter 2006ECE 766 Computer Interfacing and Protocols 4 Layered Protocols Layer 5 Layer 5 Protocol Layer 4 Layer 4 Protocol Layer 3 Layer 3 Protocol Layer 2 Layer 2 Protocol Layer 1 Layer 1 Protocol Physical Medium Host 1Host 2 Interface M MH4H4 H3H3 M1M1 H4H4 M2M2 H3H3 H3H3 M1M1 H4H4 M2M2 H3H3 H2H2 H2H2 T2T2 T2T2 M MH4H4 H3H3 M1M1 H4H4 M2M2 H3H3 H3H3 M1M1 H4H4 M2M2 H3H3 H2H2 H2H2 T2T2 T2T2 Host 1Host 2

5. 03 - Winter 2006ECE 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

6. 03 - Winter 2006ECE 766 Computer Interfacing and Protocols 6 OSI Layers Application Application Protocol Presentation Presentation Protocol Session Session Protocol Transport Transport Protocol Network Network Layer Host-Router Protocol Host 1Host 2 Interface Data Link Interface Physical Interface Data Link Layer Host-Router Protocol Physical Layer Host-Router Protocol Network Layer Host-Router Protocol Data Link Layer Host-Router Protocol Physical Layer Host-Router Protocol Network Data Link Physical Network Data Link Physical Internal Subnet Protocols Communication Network

7. 03 - Winter 2006ECE 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

8. 03 - Winter 2006ECE 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

9. 03 - Winter 2006ECE 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

10. 03 - Winter 2006ECE 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

11. 03 - Winter 2006ECE 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

12. 03 - Winter 2006ECE 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!)

13. 03 - Winter 2006ECE 766 Computer Interfacing and Protocols 13 OSI Model vs. TCP/IP Model Application Presentation Session Transport Network Data Link Physical OSI Model Application Transport Internet Host-to- network TCP/IP Model Not present in the model Merged

14. 03 - Winter 2006ECE 766 Computer Interfacing and Protocols 14 OSI Model vs. TCP/IP Model OSITCP/IP DeveloperISODARPA PlanningModel first (Proactive)Protocol first (Reactive) Layers74 StrengthWidely used to classify protocol stacks Interoperable, widely used protocol implementation WeaknessNo widely accepted protocol implementation Model fits no other protocol stack