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The Infrastructure Technologies

The Infrastructure Technologies. Communication. All communications require: Transmitters/Senders and receivers Transmission medium Rules of communication A message. Computer Data Communication. Transmitter/Receiver Combination of Hardware and software Physical Media Types Cable

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The Infrastructure Technologies

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  1. The Infrastructure Technologies

  2. Communication • All communications require: • Transmitters/Senders and receivers • Transmission medium • Rules of communication • A message . .

  3. Computer Data Communication • Transmitter/Receiver • Combination of Hardware and software • Physical Media Types • Cable • twisted pair • coaxial cable • fiber-optic cable • Wireless media • radio • microwave • cellular telephone • satellite • infrared

  4. Bandwidth Measure of a medium’s carrying capacity Measured in bits (bps) Two categories Baseband one line, one channel most local communication Broadband one line, simultaneous channels DSL, cable Data Communication Media

  5. The Message • Messages have header and trailer carry information for delivering and ensuring the integrity of the message • These are used by application and communication protocols • The electronic form of a message is a signal

  6. A precise set of rules for communicating A communication protocol defines: message format (header/trailer) communication speed How the message is encoded (e.g., ASCII, EBCDIC) filtering/error correction rules An implementation of standard rules for passing parameters between adjacent layers Protocols

  7. Signal Transmission (Fig. 13.14) Electromagnetic spectrum • Signals transmitted in the context of a Carrier Signal • Known frequency • Known amplitude

  8. Inside the computer must have discrete/digital Many existing communication lines are continuous/analog (especially in the last mile) Signal must be converted between digital/discrete and analog/continuous through modulation/demodulation. The function of a modem 1-bit 1-bit 0-bit 0-bit Signal Incompatibility

  9. Signal degrades or loses strength. Called attenuation Signal picks up noise. EMI - Electromagmetic interference Static If not addressed, noise can overwhelm signal These limit the distance of some communications As Signal Moves Over Line

  10. Analog contiguous signal amplify to boost signal noise amplified, too noise accumulates filter known or predictable noise tape hiss Digital discrete signal digits (0, 1) sample/retransmit boosts signal automatically filters most noise errors function of sampling rate Digital vs. Analog Both digital and analog data are transmitted in the context of a carrier signal.

  11. Networks • A network consists of two or more computers linked by communication lines. • Connectivity – the ability of a device or software to work with other devices and/or software over a network connection • Each connected device is called a node

  12. Local Area Network - LAN • Small geographic scope • Computers in close proximity • Local communications • no boosting or filtering • Workstations

  13. Wide Area Network - WAN • Network of networks • Computers geographically disbursed • Long-distance communication • common carrier • boost and filter signal • Enterprise networks • Intranet • Supply chain integration • Extranet • Global networks

  14. Use to connect multiple LANs or WANs Have intelligence to filter, route and do protocol conversion Examples Bridges - Similar Networks Gateways - Dissimilar networks Routers Switches Internetworking Hardware

  15. A bridge links similar networks. A gateway links dissimilar networks. Bridges and Gateways

  16. accept messages at one of several input ports and forward the message to the appropriate output port Routers

  17. Common Network Topologies

  18. Clients/Server Networks

  19. Peer to Peer Networks

  20. Client/server architecture LANs The system software runs on the server (The server’s operating system) Part of the NOS runs on each workstation Software that handles communication between the workstation and the NOS Agent process on client client’s link to network Examples Novell NetWare Windows 2000 Server Windows NT Peer to Peer Networks NOS is installed on each attached workstation Runs on top of the local operating system Server Client Network Windows ME operating system Network Communication software Network Operating Systems

  21. Each computer or terminal is a node Messages (signals) are either Broadcast to all nodes Or move from node to node (point to point) Topology or routing determines the route Protocols define the precise rules to follow for LAN access and message delivery (Many different protocol exist) Popular LAN Access control methods Collision detection Token passing Message Delivery

  22. Distributed Access Control Token passing Circulating electronic token prevents collisions Must possess the token to transmit a message Random Access Control Eliminates collisions CSMA/CD (collison detection) “Listen” for quiet line (carrier signal); then send message Collision occurs with simultaneous messages Must wait and resend Three major standard protocols for LANs Ethernet - (CSMA/CD, Star or Bus) Token-Ring - (Token passing, Ring) ARCnet - (Token passing, Star or bus) Network Access Control Methods

  23. Most popular type of message delivery Break message into packets Transmit packets independently Multiple messages share line Reassemble message at receiving end Packet Switching

  24. Packets can follow different routes to reach destination Error handling is important Packets can arrive out of order Individual packets may be lost Objectives Deliver the message accurately Efficient utilization of available bandwidth Efficient error recovery Packet Switching

  25. The Open Systems Interconnect (OSI) Model

  26. Sending computer Receiving computer Message Flow Each level “talks to” the equivalent level on the other node. Transmission errors call for retransmission of affected packet or packets. Display and manipulate worksheet Excel worksheet created Application Decrypt and decompress worksheet Worksheet encrypted and compressed Presentation Drop connection on completion Establish connection Session Reassemble packets Verify delivery of entire message Divide into packets and create messages Transport Determine packet routing Reroute if necessary Network Transmit one packet to next node Accept packets Data link Medium of transmission Medium of transmission Physical Physical Medium

  27. The TCP/IP Model • TCP/IP is the standard packet switching protocol for the Internet

  28. Application layer corresponds to OSI Application and Presentation layers protocols that directly support application programs protocols such as telnet, FTP, SMTP, DNS, POP, and HTTP Transport layer corresponds to OSI Session and Transport layers TCP (Transmission Control Protocol) creates packets and reassembles messages guarantees delivery Receiving end acknowledges each packet Sending end re-sends unacknowledged packets TCP/IP Layers

  29. Internet layer corresponds to OSI Network layer IP (Internet Protocol) routes and delivers individual packets Network access layer corresponds to OSI Data-link and Physical layer This is where Ethernet, Token ring and other network access protocols reside TCP/IP Layers (continued)

  30. TCP/IP Layers (continued)

  31. IP address 32 bit number dotted decimal format 134.53.40.2 Standards IPV4 – current IPV6 – proposed Internet protocol communication requires IP address IP Address

  32. All computers attached to the Internet must have an IP address. Static allocation IP address established at installation linked to specific computer’s Media Access Control (MAC) address (ie. Ethernet address) Dynamic allocation IP address allocated dynamically at login time Must use a protocol such as Dynamic Host Configuration Protocol (DHCP) Assigning an IP Address

  33. Domains

  34. Accepts domain name Converts to IP address Network operating system routine on each host each server each Internet service provider (ISP) each network service provider (NSP ) Domain Name System (DNS)

  35. Domain name and IP address cached by all participating Domain Name Systems. Subsequent references use cached IP address. Business student uses cob Caching

  36. 1960s Started as ARPANET (Advanced Research Projects Agency) 1986 NSFNET became internet Backbone (56Kbps) 1989 NSFNET upgraded to T1 1.44 (Mbps) 1991 NSFNET upgradet to T3 45 (Mbps) 1991 - First commercial traffic 1994 - First Web browser introduced 1995 NAPs Replaced NSFNET 1995 - Control turned over to independent governing bodies Internet History

  37. Interconnect Level Any means for bandwidth providers to interconnect Network Access Points (NAPS) MAEs, FIXs and CIX (pseudo NAPs) Network Service Providers NSPs (National Backbone Providers) Replaced NSFNET (old backbone network) high-speed lines or series of connections that form the major pathways of the internet Regional Networks connect up to one or more national backbone providers Local Internet Service Providers (ISPs) Consumers and Businesses Servers - Contain information and are located on independently owned networks Internet Terminology

  38. Internet Architecture

  39. Access via local point of presence (POPs) by local call broadband access into the home ISPs provide access (the “on-ramp”) POPs connect up the network hierarchy to an interconnect point Phone is most common for individuals Broadband (Cable and ADSL) are coming fast...and competing for market share. Internet Access

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