School of Business Eastern Illinois University Network Architecture Models September 10 2014 Abdou Illia Fall 2014 2 Learning Objectives Discuss the OSI reference Model Discuss the Internet Model Compare OSI and Internet Models Data Networks operation Packet Switching 3 Large messages are broken into small pieces called packets or frames Multiplexing Packets from many conversations are mixed multiplexed over each trunk line Packet Switching Multiplexing on Transmission Line 1 Why 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 again How computers make sense of incoming packets 4 5 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 Network Architecture Model 6 Definition 1 A communication model that defines specific tasks that together allow applications on different computers to communicate Computer 1 Computer 2 Task 1 Task 1 Task 2 Task 2 Task 3 Task 3 Task 4 Task 4 Task 5 Task 5 2 7 Network 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 1 Computer 2 Task 1 Task 1 Rules Task 2 Task 3 Rules Task 2 Rules Task 4 Task 3 Task 4 Task 5 Task 5 Rules Network 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 Model OSI Reference Model 8 9 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 structure 3 Principles guiding OSI development 10 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 11 Data transport Application OSI Reference Model OSI Reference Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical 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 hardware 12 4 OSI Reference Model 7 Layers Role Application Represent user interface between the application 13 sofware e g Eudora and the Network Provides services like Identification of the intended communication partner determining resources availability for communication etc 6 Presentation 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 5 Responsible for establishing managing terminating Session communication sessions between computers Communication sessions consist of service requests and service responses between applications Session layer s protocols coordinate request response sessions OSI Reference Model 4 14 Layers Role Transport 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 3 Network 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 2 Subdivided into 2 sublayers Logical Link Control and Data Link LLC Media Access Control Provides physical address MAC address to messages MAC Combines bits into bytes bytes into a frames with header address information error detection code and trailer OSI Reference Model 1 Layers Role Physical Handles the transmission of bits over a communications channel 15 Defines characteristics such as voltage levels connector types and maximum transmission distance Places signal on the cable Responsible to move bits between devices 5 The Internet Model TCP IP Model 16 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 protocols 17 The Internet Model OSI Internet Application Presentation Application Session Transport Transport Network Network Data Link Physical Interface 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 layers Figure 1 14 White 2007 20 Applications Protocols Use in Internet Model Layers Applications Protocols Application 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 FTP Transport TCP Transmission Control Protocol 18 Required in webservice when HTTP is used Required in Mailservice when SMTP is used SMTP messages are encapsulated in TCP segments Connection oriented Establishes and maintains connections before sending Close connections after transmission Correct errors in TCP segments UDP User Datagram Protocol Connectionless Don t open connection Simply sends Discards incorrect UDP datagrams no retransmission Network IP Internet Protocol Interface PPP Point to Point Protocol V 90 for 56 Kbps modems 6 19 IEEE s DL and Physical layer standards 802 2 defines Logical Link Control sublayer 802 3 is the standard for Ethernet networks 802 4 is the standard for Token Bus networks 802 5 is the standard for Token Ring networks http grouper ieee org groups