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- 1. 1 COMPUTER NETWORKS Network layersand protocols Lecture.1 Assis.lect.Arwa sahib By: Dr.Eng.Mohammed i.Shujaa 2020-2021
- 2. Application By:Dr.Eng.Muhamed.Shujaa 2 Physical Source 1. ComputerNetworks, AndrewS. Tanenbaum 2. www.cisco.com 3. www.novell.com 4. www.rad.com 5. www.3com.com Data Link Network Transport Session Presentation
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- 4. NETWORK GOALS By:Dr.Eng.Muhamed.Shujaa 4 1Physical 7 Application The two main benefits of networking computers are… Communications Information can be distributed very quickly, such as email and video conferencing. Saving Money Resources such as information, software, and hardware can be shared. CPUs and hard disks can be pooled together to create a more powerful machine. 2 Data Link 3 Network 4 Transport 5 Session 6 Presentation
- 5. NETWORK ARCHITECTURES By:Dr.Eng.Muhamed.Shujaa 7 Application 1Physical 5 A set of layers and protocols is called the network architecture. .1 Protocol Hierarchies Networks are organized as layers to reduce design complexity. Each layer offers services to the higher layers. Between adjacent layers is an interface. Services – connection oriented and connectionless. Interface – defines which primitives and services the lower layer will offer to the upper layer. Primitives – operations such as request, indicate, response, confirm. 2 Data Link 3 Network 4 Transport 5 Session 6 Presentation
- 6. NETWORK ARCHITECTURES By:Dr.Eng.Muhamed.Shujaa 6 Application 2.Design Issues for the Layers(functions( • Mechanism for connection establishment • Rules for data transfer • Error control • Fast sender swamping a slow receiver • Inability of processes to accept long messages • Routing in the case of multiple paths Network Data Link Physical Transport Session 6 Presentation
- 7. Network Protocols By:Dr.Eng.Muhamed.Shujaa 7 •Protocol: is a format order of messages sent and received among the net entities and action takenon msgs transmission receipt. Protocol process: • The format or structure of themessage • The process by which networking devices shareinformation about pathways with othernetworks • How and when error and systemmessages are passed between devices • The setup andtermination of data transfer sessions
- 8. Layering In Networked Computing By:Dr.Eng.Muhamed.Shujaa8 • OSIModel (open system interconnection) • TCP/IPModel • Protocols at eachlayer
- 9. Learning outcomes • Understandthe need of layeringin Networkedcomputing • Understand the OSImodel and the TCP/IPmodel – Understand the function protocols and their role at each layer. • TCPprotocol • UDPprotocol • Understand the role of header in communication betweenlayers • Understand how data sent from one host arrive to thetarget host. By:Dr.Eng.Muhamed.Shujaa 9
- 10. What is Layeringin Networked Computing? By:Dr.Eng.Muhamed.Shujaa 10 – Breaksdown communication into smaller, simplerparts.
- 11. Why alayered model? By:Dr.Eng.Muhamed.Shujaa 11 –Easierto teach communicationprocess. – Speedsdevelopment, changesin one layer doesnot affect how the other levelsworks. – Allows different hardware and software towork together. – Reducescomplexity
- 12. What is “THEMODEL?” By:Dr.Eng.Muhamed.Shujaa12 • Commonly referred to asthe OSIreferencemodel. • TheOSImodel – is atheoretical blueprint that helps usunderstandhow data gets from one user’s computer toanother. – It is also amodel that helps develop standards so thatall of our hardware and software talks nicely to eachother. – It aids to provide an organized structure for hardware and software developers to follow, to insure there productsare compatible with current and future technologies.
- 13. 7 LayerOSIModel • Q.Whyuseareference model? – Servesasan outline of rules for how protocols canbe used to allow communication betweencomputers. – Eachlayer hasits own function and provides support to other layers. • Q.What are Other reference models are inuse. – Most well known is the TCP/IPreferencemodel. – Wewill compare OSIand TCP/IPmodels • Ascomputing requirements increased, the network modeling hadto evolve to meet ever increasing demandsof larger networks and multiple venders. 13 • Problems and technology advancesalso added to the demandsfor changesin network modeling. By: Dr.Eng.Muhamed.Shujaa
- 14. Evolution of the7-Layers By:Dr.Eng.Muhamed.Shujaa 14 • SingleLayerModel - First Communication Between Computer Devices – Dedicated copper wire or radiolink – Hardware & software inextricablyintertwined – Singlespecification for all aspects ofcommunication 1 DEVICEA DEVICE B Hardware & Software Hardware & Software
- 15. Evolution of the7-Layers By:Dr.Eng.Muhamed.Shujaa 15 • Two LayerModel – Problem: Applications were being developed torun over ever-increasing number of media/signalingsystems. – Solution: Separateapplication aspects from technical (signaling and routing) aspects – Application Layer:Concerned with user interface, file accessand file transfer Application Technical Standards Application Technical Standards
- 16. Evolution of the7-Layers By:Dr.Eng.Muhamed.Shujaa16 • Four Layer Model - Network connectivity inherently requires travel over intermediate devices (nodes) • Technical Standards Level divided into Network, Data-link and Physical Layers 1 Application Network Data-Link Physical Application Network Data-Link Physical
- 17. Evolution of the7-Layers By:Dr.Eng.Muhamed.Shujaa17 Physical Layer –Describes physical aspects of network: cards, wires, etc –Specifies interconnect topologies and devices Network Layer –Defines a standard method for operating between nodes –Address scheme is defined (IP) –Accounts for varying topologies Data-Link –Works with Network Layer to translate logical addresses (IP) into hardware addresses (MAC) for transmission –Defines a single link protocol for transfer between two nodes(DLC protocol) DLC:Data link controlprotocol
- 18. Evolution of the7-Layers By:Dr.Eng.Muhamed.Shujaa18 1 • Five Layer Model – Increase Quality of Service(QOS) •Variable levels of data integrity in network •Additional data exchanges to ensure connectivity over worstconditions •Became the Transport Layer Application Transport Network Data-Link Physical Application Transport Network Data-Link Physical
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- 20. Evolution of the7-Layers By:Dr.Eng.Muhamed.Shujaa 20 • The Seven Layer OSI Model - Addition of Management andSecurity – Standardizing notation or syntax for application messages (abstract syntax) 1 – Set of encoding rules (transfer syntax) – Became the Presentation Layer Application Presentation Session Transport Network Data-Link Physical Application Presentation Session Transport Network Data-Link Physical
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- 25. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa25 7 Application The Open Systems Interconnection is the model developed by the International Standards Organization. Benefits-Advantage • Interconnection of different systems (open) • Not limited to a single vendor solution Negative Aspect (disadvantage( • Systems might be less secure • Systems might be less stable 1 Physical 2 Data Link 3 Network 4 Transport 5 Session 6 Presentation
- 26. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa26 Application 1. Physical Layer a)Convert the logical 1’s and 0’s coming from layer 2 into electrical signals. b)Transmission of the electrical signals over a communication channel. Main topics: • Transmission mediums • Encoding • Modulation • RS232 and RS422 standards • Repeaters • Hubs (multi-port repeater) Physical Data Link Network Transport Session Presentation
- 27. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa27 Application Physical 2. Data Link Layer a)Error control to compensate for the imperfections of the physical layer. b)Flow control to keep a fast sender from swamping a slow receiver. Main topics: • Framing methods • Error detection and correction methods • Flow control • Frame format • IEEE LAN standards • Bridges • Switches (multi-port bridges) Data Link Network Transport Session Presentation
- 28. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa28 Application Physical 3. Network Layer a) Controls the operation of the subnet. b) Routing packets from source to destination. c) Logical addressing. Main topics: • Internetworking • Routing algorithms • Internet Protocol (IP) addressing • Routers Data Link Network Transport Session Presentation
- 29. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa29 Application Physical 4. Transport Layer a) Provides additional Quality of Service. b) Heart of the OSI model. Main topics: • Connection-oriented and connectionless services • Transmission Control Protocol (TCP) • User Datagram Protocol (UDP) •ACK Data Link Network Transport Session Presentation
- 30. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa30 Application Physical 5. Session Layer a)Allows users on different machines to establish sessions (dialogue) between them. b)One of the services is managing dialogue control. c) Token management. d) Synchronization. Data Link Network Transport Session Presentation
- 31. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa31 Application Physical 6. Presentation Layer a)Concerned with the syntax and semantics of the information. b) Preserves the meaning of the information. c) Data compression. d) Data encryption. Data Link Network Transport Session Presentation
- 32. OSI REFERENCE MODEL By:Dr.Eng.Muhamed.Shujaa32 Application Physical 7. Application Layer a) Provides protocols that are commonly needed. Main topics: • File Transfer Protocol (FTP) • HyperText Transfer Protocol (HTTP) • Simple Mail Transfer Protocol (SMTP) • Simple Network Management Protocol (SNMP) • Network File System (NFS) • Telnet Data Link Network Transport Session Presentation
- 33. SERVICES By:Dr.Eng.Muhamed.Shujaa 33 Physical Application Each layerprovides services to the layer above it. 1. Terminologies (scientific words means) Entities – active elements in each layer (e.g. process, intelligent I/O chip). Peer Entities – entities in the same layer on different machines. Service Provider – Layer N. Service User – Layer N + 1. Service Access Points – places where layer N + 1 can access services offered by layer N. Data Link Network Transport Session Presentation
- 34. SERVICES By:Dr.Eng.Muhamed.Shujaa 34 Physical Application 2. Connection-Orientedand Connectionless Connection-Oriented – before data is sent, the service from the sending computer must establish a connection with the receiving computer. Connectionless – data can be sent at any time by the service from the sending computer. Q: Is downloading a music file from the Internet connection-oriented or connectionless? Q: Is email connection-oriented or connectionless? Data Link Network Transport Session Presentation
- 35. SERVICES By:Dr.Eng.Muhamed.Shujaa 35 Application 4 Transport 4Transport 3. Service Primitives Request – entity wants the service to do some work Indicate – entity is to be informed about an event Response – entity responds to an event Confirm – entity is to be informed about its request Sending Computer Receiving Computer 1. request 4. confirm 2. indicate 3. response 3 Network 3 Network Physical Data Link Network Transport Session Presentation