Network Architecture ModelsLearning ObjectivesData Networks operationWhy Packet Switching & Multiplexing?How computers make sense of incoming packets?Network Architecture Model?Slide 7Network Architecture ModelOSI Reference ModelPrinciples guiding OSI developmentSlide 11Slide 12Slide 13Slide 14Slide 15The Internet Model (TCP/IP Model)The Internet ModelApplications/Protocols Use in Internet ModelIEEE’s DL and Physical layer standardsProtocolsProtocols and webservicesSummary QuestionsInternet and OSI Model comparedNetwork Architecture ModelsSchool of BusinessEastern Illinois University © Abdou Illia, Fall 2014(September 10, 2014)2Learning ObjectivesDiscuss the OSI reference ModelDiscuss the Internet ModelCompare OSI and Internet Models3Data Networks operationPacket Switching–Large messages are broken into small pieces called packets (or frames)Multiplexing–Packets from many conversations are mixed (multiplexed) over each trunk lineMultiplexing onTransmission LinePacket Switching4Why Packet Switching & Multiplexing?Switches, routers, bridges handle short messages efficientlySending a file all in one single string of data:–Other computers couldn’t use the Network during transmission–Not be appreciated by other users–If error, the entire file has to be sent again5How computers make sense of incoming packets?By using rules of operation defined through:–Network Architecture Models and their associated protocols, i.e.:Protocols = rules for communications between 2 computers (or other networking devices) implemented in hardware or in software.6Network Architecture Model?Definition 1: A communication model that defines specific tasks that together allow applications on different computers to communicateComputer 1Task 1Task 2Task 3Task 4Task 5Task 1Task 2Task 3Task 4Task 5Computer 27Network Architecture Model?Definition 2: A communication model that describes how data from a software application in one computer moves through a medium to a software application in another computer.Computer 1Task 1Task 2Task 3Task 4Task 5Task 1Task 2Task 3Task 4Task 5Computer 2RulesRulesRulesRules8Network Architecture ModelTwo main components:–Layers (representing groups of tasks to be performed for data comm.)–Protocols (representing rules to be followed)Examples of network architecture models:–OSI Reference Model–Internet Model (or TCP/IP Model)–Hybrid TCP/IP-OSI Model9OSI Reference ModelDeals with connecting Open Systems:–Systems opened for communication with other systems–Non-proprietary systems (e.g. IBM’s Systems Network Architecture )First step toward international standardizationThe other network architectures roughly follow the OSI structure10Principles guiding OSI developmentCreate a layer when a different level of abstraction is neededEach layer should perform a well defined functionChoose function of layers with an eye toward defining international protocolsChoose layers’ boundaries in order to minimize information flow across interfaces.11OSI Reference Model7 layersEach layer communicates with its peer layer, and with layer above and below it.Different protocols at each layerUpper layer deal with application issues, and are implemented in softwareLower layers handle data transport issues, and are implemented in software and hardwareApplicationData transport12OSI Reference Model7. Application6. Presentation5. Session4. Transport3. Network2. Data Link1. Physical13OSI Reference ModelLayers RoleApplication• Represent user interface between the application sofware (e.g. Eudora) and the Network• Provides services like: Identification of the intended communication partner, determining resources availability for communication, etc.7Presentation• Performs code conversion and data reformatting (syntax translation) incluing encryption and compression if required.• Uses coding & conversion schemes: Common Data Representation Formats, Common Data Encryption Schemes, EBCDIC, ASCII, etc.6Session• Responsible for establishing, managing & terminating communication sessions between computers.• Communication sessions consist of service requests and service responses between applications • Session layer’s protocols coordinate request & response sessions.514OSI Reference ModelLayers RoleTransport• Makes sure the data arrives at the destination exactly as it left source (in case of connection-oriented communication)• Provides error checking before transmission, and error recovery in case of failed delivery.4Network• Responsible for creating, maintaining and ending network connections. • Provides logical address (IP address) to messages• Provides routing services: determining routes for sending. If router can’t send large packets, break data into smaller units.3• Subdivided into 2 sublayers (Logical Link Control and Media Access Control)• Provides physical address (MAC address) to messages• Combines bits into bytes, bytes into a frames with header, address information, error detection code, and trailer2DataLinkLLCMAC15OSI Reference ModelLayers RolePhysical• Handles the transmission of bits over a communications channel.• Defines characteristics such as voltage levels, connector types and maximum transmission distance.• Places signal on the cable. Responsible to move bits between devices.116The Internet Model (TCP/IP Model)Created by the Internet Engineering Task Force (IETF)Named after its two most widely known protocols:–TCP (Transmission Control Protocol) and –IP (Internet Protocol)TCP/IP refer to the model, while TCP and IP are individual protocols17The Internet ModelApplicationPresentationSessionTransportNetworkData LinkPhysical4 layersInterface layer - equivalent to the OSI’s Physical and Data link layersNetwork layer - roughly equivalent to the OSI’s Network layerTransport layer - performs same function as OSI Transport layerApplication layer - equivalent to the OSI’s Presentation and Application layersApplication TransportNetworkInterfaceOSI InternetFigure 1-14 (White 2007:20)18Applications/Protocols Use in Internet ModelLayers Applications/ProtocolsApplication- Webservice: HTTP- E-mail: SMTP (Simple Mail Transfer Protocol), POP (Post Office Protocol), IMAP (Internet Message Access Protocol)- Telnet applications: Terminal Emulation Protocol- File transfer: FTPTransport- TCP (Transmission Control Protocol). - Required in