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Transcript
Chapter 11 Network Fundamentals Agenda • • • • • • Definition Classification Information Routing Connection Telecommunication software Architecture Definition • Network • Backbone network Classification • • • • Topology Ownership Geography Transmission Network Topology • • • • • • Star Hierarchical Mesh Bus Ring Hybrid Star Network • Circuits – Point-to-point, multipoint, or combination • Pros – Expand – Implement – No limit to no. and length of arms • Cons – Single point of failure – Overload of mater during peak traffic Hierarchical Network • Tree structure with a root • pro – No single point of failure – Divisional communications and processing Mesh Network • Web structure • Usage – Public telephone system • Pro – Alternative communication route – Virtually fail-safe • Con – Line cost Bus Network • Usage – High speed, short distance between nodes – Local area network • Pros – Independent between nodes – High reliability • Cons – Limited number of attached device – Hard to locate the problems Ring Network • Usage – Nodes are relatively close together • Pros – Less attenuation – Error control – Network management • Cons – Failing of a node • Two opposite direction channels Hybrid Networks • Usage – Connecting different networks • Pro – Communication between different networks • Con – Conversion device and costs Network Ownership • Private networks • Public networks • Valued added networks Private networks • Full control • Special needs • Expense Public networks • Controlled by carriers • Regulated by government • Inexpensive Valued Added Networks • Public network • Functions – Code translation – Speed conversion – Store message and delivery • Examples – – – – Telex SWIFT SITA (airline) IVAN (insurance) Networks by Geography • Wide area network (WAN) • Metropolitan area network (MAN) • Local area network (LAN) Wide Area Networks • Public Switched Telephone Network (PSTN) • Provided by carriers • Inexpensive • High quality service for infrequent users Metropolitan Area Networks • • • • • IEEE 802.6 Distance up to 30 miles High bandwidth for data, voice, and video T1, T3, or fiber optic cable Private own or dark fiber supplied by MAN provider Network Transmission Types • • • • Circuit Switching Packet data networks (PDNs) Frame relay Asynchronous transfer mode: ATM (Cell relay) Circuit Switching • Temporarily Dedicated communications line between two stations for transmission • Efficient for constant voice and video transmission • Inefficient for non-constant data transmission Packet Data networks (PDNs) - I • Packet – Less than 1,000 bytes – PAD (packet assembly/disassembly) – Address and control fields for error checking • Connection types – Switched virtual circuit: dial-in (switched) – Permanent virtual (leased) circuit: heavy & frequent traffic – Datagram: short message, no error checking Packet Data networks (PDNs) - II • Standard – ITU-T’s X.25 • Between terminal and PDN on public network – ITU-T’s X.75 • Interface between two PDNs • Examples – USA: APARANET, Telenet, Tymnet, General Electric Information Services (GEIS) Packet Data networks (PDNs) - III • Characteristics – – – – – Reliable service Nationwide service Lower error rates Variety of transmission speeds Cost-effectiveness Frame Relay • Acknowledge only by final node • Benefits – Variable-length frames (1- 64,000 bytes) – Reduce overhead – More efficient transmission • Problems – Circuit congestion – Committed information rate (CIR) & port speed for service guarantee & discarding frames ATM (Cell-Relay) • • • • Asynchronous transfer mode (ATM) Cells : fixed length packets of 53 bytes 45Mbps (T3) or higher speeds Pros – High throughput, low delay, transparency, flexibility, and high capacity • Con – Expensive ATM Services • Realtime service – Constant bit rate (CBR) for telephone and videoconference – Realtime variable bit rate (rt-VBR) for compressed video • Non-realtime service – Non-realtime variable bit rate (nrt-VBR) for airline reservation or financial transaction – Available bit rate (ABR) for LAN-to-LAN – Unspecified bit rate (UBR) for TCP-based traffic Routing Message • Connection-oriented routing & connection less routing • Broadcast routing • Centralized routing • Distributed routing • Static and dynamic routing Broadcasting Routing • CSMA/CD • Pros and cons – Simplest – For small network – Not for moderate to heavy traffic Centralized Routing • Star or hierarchical networks – IBM’s SNA networks • Using static routing table in one central computer • Pros and cons – Simple – Potential performance bottleneck – Single point of failure Distributed Routing • Routing tables on several nodes • Pros and cons – No single point of failure – Routing table update problem – Complicated to implement Static and Dynamic Routing • Static routing – Predetermined route – Simple but inflexible • Dynamic routing – Use routing algorithms to evaluate traffic volumes, error rates, and other conditions for the best path – Flexible but high overhead and complicated to implement Interconnecting Networks • Transmission control protocol/ internet protocol (TCP/IP) • Internet • Intranet & extranet Transmission Control Protocol • OSI transport layer • Connection oriented • Functions – – – – Assemble and reassemble message packets Reliable & error free message delivery Urgency or priority Security (encryption) Internet Protocol • OSI network layer • Routing & addressing messages to other networks • Connectionless operation • IPv6 – 128 bits for addressing – Quick and efficient TCP/IP Application protocols • • • • File Transfer Protocol (FTP) Tenet Simple Mail Transfer Protocol (SMTP) Multipurpose Internet Mail Extensions (MIME) • Remote Procedure Call (RPC) • Simple Network Management Protocol (SNMP) Internet • Usages – Electronic mail, remote log in to various computers, discussion groups, information search and retrieval • Electronic mail (e-mail) – Edu, com, org, gov, mil, net • • • • • Web servers & web browsers Hypertext Markup Language (HTML) Uniform Resource Locator (URL) Home page Internet service provider (ISP) Intranets & Extranets • • • • Intranets Extranets Benefits: fast information transmission Problems: security & privacy Connect Network to Computer • Methods – Direct connection between circuit and computer • Small network • Low cost • Cycle stealing – Network interface card – Use a front-end processor: telecommunication control unit or transmission control unit • Large host computer • Better utilize computer resources Front-end Processors (FEPs) • Types – Hardware (interface or port): speed – Software ( network control program NCP): flexible FEPs - Functions • • • • • Circuit control Assembly messages Message queuing or storing Error control Administration functions Functions of Telecommunication Software in Host Computer • • • • • • • • • Security Buffer management Routing a message to a program Queuing messages Scheduling application program Providing continuity between part of a transaction Message formatting Checkpoint/restart Preventing messages from lost or duplicated Software for Network Management • Control and monitor the network status – Start/stop network, terminal, and line – Performance • Log network operation • Display network data Manufacturers’ Architectures • IBM’s System Network Architecture (SNA) • Digital Equipment Corporation’s Digital Network Architecture (DNA) IBM’s SNA Concepts • • • • • • Physical units Logical units Sessions Network addressing units (NAUs) Data link protocols SNA software – Network Control program (NCP) – Virtual Telecommunications Access Method SNA Physical Units • • • • Terminals (1) Cluster controllers (2) Front-end processors (4) Host computers (5) SNA Logical Units • People • Application programs SNA Sessions • Types – Terminal-to-terminal – Terminal-to-program – Program-to-program • Modes – Interactive – Batch – Multiple simultaneous SNA Network Addressable Units • Physical units • Logical units • Address: 24 bits SNA Data Link Protocols • Synchronous Data Link control (SDLC) • Binary Synchronous Communications (BISYNC or BSC) • X.25 System Network Architecture • Physical control – Physical and electrical connections – Transmission codes – Voltages • Data link control – Format – Reliability • Path control – Routing information • Transmission control – Security & compression • Data flow control – Flow control • Presentation services – Format • Transaction services – Coordinating application software Digital’s DNA -I • Protocols – Digital Data Communication Message Protocol (DDCMP) – X.25 – Ethernet • DECNET Layers – – – – – Application Network service Transport Data link control Physical link control Points to Remember • • • • • • Definition Classification Information Routing Connection Telecommunication software Architecture Discussion • Does CSUS need a backbone network? • What type of backbone do you think that CSUS needs (give your justifications)? • What type of network does CSUS needs in terms of topology, ownership, geography and transmission technology? • What type of network does a grocery chain store needs in terms of topology, ownership, geography and transmission technology?