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Chapter 2 The Infrastructure Understand the structure & elements As a business student, it is important that you understand what the technology can and cannot do, when a particular technology is appropriate, and when it is not. If you recognize the potential, you can always get the necessary help. If you do not recognize the potential, your competitors probably will. Copyright © 2003, Addison Wesley Figure 2.1 This chapter introduces the technology that makes e-commerce possible. Applications The World Wide Web The Internet The global data communication network Copyright © 2003, Addison Wesley Figure 2.2 Communication requires five elements. Transmitter Medium Receiver Message Protocol: a set of rules for transmitting a message. Message Information/content Transmitter Source or sender Medium Path or pipe Receiver Sink or destination Copyright © 2003, Addison Wesley Media Types Cable Physical wire Twisted pair, coaxial, fiber optic Wireless No physical wire Cellular, digital cellular, satellite Copyright © 2003, Addison Wesley Connectivity Ability to operate over a connection Physical – medium Logical – protocol Line types Baseband – one signal at a time Broadband – simultaneous signals in parallel Example – cable TV Cable can be baseband or broadband Wireless can be baseband or broadband Copyright © 2003, Addison Wesley Figure 2.3 Plain old telephone service. Central office Source Long distance connection The cloud is a common way to visualize an infrastructure Central office Destination Copyright © 2003, Addison Wesley Figure 2.4 Wireless communication. BaseHub station Radio tow er Mobile switching center Trunk Alice Telephone Long distance network Both POTS and wireless use the same long distance infrastructure. Trunk BaseHub station Mobile switching center Radio tow er Bob Telephone Copyright © 2003, Addison Wesley Figure 2.5 POTS and wireless are alternative access paths to the long distance infrastructure. POTS Wireless service Long distance infrastructure Cable and satellite Internet services use the same long distance lines. Copyright © 2003, Addison Wesley Figure 2.6 Bandwidth. Amount of data a medium can transmit in a given time. Conventions B – bytes (8 bits) b – bits K – c. 1,000 M – c. 1,000,000 G – c. 1,000,000,000 Connection Type Bandwidth Local telephone line 56 Kbps Wireless 2G digital cellular 2.5G digital cellular 3G digital cellular Bluetooth Wi-Fi (802.11b) 19.2 Kbps 144 Kbps 2 Mbps 1 Mbps Up to 11 Mbps Home satellite service 400 Kbps DSL 1.44 Mbps Cable service 2 to 10 Mbps Leased line (T-1, T-3) 1.5 to 43 Mbps Fiber optic cable Up to 10 Gbps Copyright © 2003, Addison Wesley Networks Network: two or more computers or devices linked by communication lines. Each computer/device is a node Transmitter and receiver are nodes The network is the medium Communication rules are defined by a protocol Copyright © 2003, Addison Wesley Protocols Communication protocol An agreed-upon format or procedure for transmitting data. Implemented in hardware and/or software Key issues Deliver message efficiently Detect errors Correct errors Copyright © 2003, Addison Wesley Figure 2.7 An electronic message consists of a header, a body, and a trailer. Message Header The header carries delivery information Body Information about the message The trailer is often optional. Copyright © 2003, Addison Wesley Trailer Network Structures LAN (local area network) Links nodes in close proximity Point-to-point or broadcast WAN (wide area network) Links geographically disbursed nodes Typically utilizes common carrier Copyright © 2003, Addison Wesley Figure 2.8 Common LAN topologies. Bus Ring Star Topology Describes shape or form Defines interconnections Copyright © 2003, Addison Wesley Message Delivery Broadcast Every message sent to every node Node picks out messages addressed to it Bus and some star networks Point-to-point Message moves node-to-node Topology or routing determines path Copyright © 2003, Addison Wesley Collisions LAN traffic management problem Token passing (collision avoidance) Simultaneous transmission by two or more nodes Electronic token passed from node to node Given node can transmit when it holds token Collision detection and recovery Let collision happen Sense and retransmit affected messages Copyright © 2003, Addison Wesley Figure 2.9 An Ethernet network. Wiring closet Server Wiring closet Copyright © 2003, Addison Wesley Figure 2.10 With point-to-point transmission, the signal is routed node by node. Router 1 Router 6 Router 8 Router 3 Source Destination Router 5 Router 4 Router 2 Router 7 Copyright © 2003, Addison Wesley Router 9 Figure 2.11 Internetworking. Process of linking two or more networks. Workstation Workstation Workstation Workstation Workstation Workstation Server Bridge Server A bridge links similar networks Workstation A gateway links dissimilar networks Workstation Server Gateway Copyright © 2003, Addison Wesley Workstation Workstation A router accepts a message at one of several input ports and forwards it to the appropriate output port. Router Routers are faster and less expensive than computers at performing the highly specialized task of routing messages. Out In Copyright © 2003, Addison Wesley Figure 2.12 A client/server network. Client Client Server Server Printer Controls resource Normally software Term sometimes applied to hardware Client Client Requests resource Workstation File system Copyright © 2003, Addison Wesley Client Figure 2.13 Most users access the Internet through an Internet Service Provider (ISP). Access network ISP Communication link Most ISPs offer Workstation E-mail, data access, chat rooms, site hosting, … Internet Workstation ISP Host or end system Runs server software http//thelist.internet.com Copyright © 2003, Addison Wesley Figure 2.14 The backbone. Major corporate network Major ISP Network Service Provider (NSP) Network Access Point (NAP) Network Access Point (NAP) Network Service Provider (NSP) Major corporate network Major ISP Regional ISP Major corporate network Local ISP Regional ISP Local ISP Regional ISP Local ISP Copyright © 2003, Addison Wesley The Backbone Network Service Provider (NSP) Network Access Point (NAP) National wide-area network Lease bandwidth to ISPs Place where NSPs meet and exchange data Chicago NAP Regional ISP Statewide of regional backbones Copyright © 2003, Addison Wesley Figure 2.16 Packet switching. Message A Objective: Efficiently utilize bandwidth Packet A1 Packet A2 Packet A3 Packet A3 Packet Packet Packet A1 Packet Open Packet Packet A2 Packet Packet Packet Open Open Packet Packet Packet Packet Packet Process Break message into packets Transmit packets independently Multiple messages share line Reassemble message at receiving end Packet A1 Packet A2 Message A Copyright © 2003, Addison Wesley Packet A3 Figure 2.17 A message’s packets can follow different paths. Router 1 Router 6 Router 8 Router 3 Router 4 Router 4 Router 2 Router 5 Router 5 Router 5 Router 7 Copyright © 2003, Addison Wesley Router 9 Figure 2.18 The TCP/IP model. Application layer The top two layers work with the message. Transport layer Internet layer The bottom two layers work with packets and control the network. Network access layer Copyright © 2003, Addison Wesley OSI layer Responsibilities The top four layers work with the message. Application Figure 2.19 The Open Systems Interconnect (OSI) model. Provides a logical link between an application program and the lower-level protocols. Presentation Performs necessary data representation and/or syntax conversions; e.g., encryption/decryption. Session Establishes, maintains, and terminates a connection. Transport Breaks the message into packets. Ensures error free, end-toend delivery of the complete message. The bottom three layers work with packets and control the network. A blueprint. Network Determines the best route for sending a packet from the source node to the destination node. Data-link Formats a packet for transmission to the next node. Physical Interfaces with the physical communication medium. Copyright © 2003, Addison Wesley Figure 2.20 The application layer protocols support application programs. From application program Application layer FTP telnet http SMTP POP SNMP Other DNS Transport layer Internet layer Network access layer To transport layer Copyright © 2003, Addison Wesley Figure 2.21 Some common application layer protocols. Acronym FTP HTTP POP SMTP SNMP Telnet Name File transfer protocol Function Download a file from or upload a file to another computer. Hypertext transfer protocol Request and download a web page. HTTP is the standard Web surfing protocol. Post office protocol Deliver accumulated mail from a mail server to the recipient's computer. Simple mail transfer Send an e-mail message from the originator's protocol computer to the recipient's mail server. Simple network Monitor the activity of a network's hardware management protocol and software components. Terminal emulation Log into a remote computer. System operators protocol use telnet to remotely control a server. Copyright © 2003, Addison Wesley Figure 2.23 The next layer down is the transport layer. From application layer Application layer Transport layer Other transport protocol TCP Internet layer Network access layer To Internet layer The transport layer usually uses the TCP protocol. Copyright © 2003, Addison Wesley Figure 2.24 TCP adds its own header. FTP request Application program FTP header Application layer Transport layer (each packet) TCP header FTP header Copyright © 2003, Addison Wesley FTP request FTP request Figure 2.25 The Internet layer uses the Internet protocol (IP). From transport layer Application layer Transport layer Internet layer IP ARP Network access layer To network access layer Copyright © 2003, Addison Wesley Figure 2.26 IP adds its own header. FTP request Application program FTP header Application layer Transport layer (each packet) Internet layer (each packet) TCP header IP header TCP header FTP header FTP header FTP request FTP request FTP request Copyright © 2003, Addison Wesley FTP request Application program FTP header Application layer Figure 2.27 The network access layer adds another header. Transport layer (each packet) Internet layer (each packet) TCP header IP header TCP header FTP header FTP header FTP request FTP request FTP request Network access layer Network header IP header TCP header Copyright © 2003, Addison Wesley FTP header FTP request Open standards TCP/IP is an example Promotes Platform independence Interoperability Open standards make the Internet a true public medium. Copyright © 2003, Addison Wesley Figure 2.28 A domain name consists of two to four words separated by dots. sbaserver1.sba.muohio.edu Top-level domain Miami University domain SBA sub-domain Server within SBA sub-domain Domain: a set of nodes administered as a unit. Copyright © 2003, Addison Wesley edu com org 134 The parts of a domain name are structured as a hierarchy. muohio 134.53 sba cas 134.53.40 134.53.54 sbaserver1 sbadata 134.53.40.2 134.53.40.4 Copyright © 2003, Addison Wesley Figure 2.29 Top-level domain names. Domain aero biz com coop edu info gov mil museum name net org pro Signifies Air-transport industry Business organization US commercial Coooeratives US educational Unrestricted US government US military Museums Individuals US network US non-profit Professionals Domain au br ca cn de fi fr gb in it jp ru za Copyright © 2003, Addison Wesley Signifies Australia Brazil Canada China Germany Finland France Great Britian India Italy Japan Russia South Africa Figure 2.30 An IP address. 134.53.40.2 Server within SBA domain SBA domain Miami University domain Top-level domain Wrong Copyright © 2003, Addison Wesley Figure 2.32 The domain name system. service.microsoft.com 1 2 sba DNS 5 service.microsoft.com 207.46.140.71 muohio DNS com = 207 service 207.46.140.71 6 7 3 service.microsoft 207.46 4 com DNS microsoft = 207.46 Copyright © 2003, Addison Wesley microsoft DNS service = 207.46.140.71 Figure 2.33 Well-known port assignments. Port 5 20 21 23 25 79 80 110 119 Used for: RJE (Remote Job Entry) FTP (File Transfer Protocol) data FTP (File Transfer Protocol) control TELNET (Terminal emulator) SMTP (Simple Mail Transfer Protocol) FINGER (Given e-mail address, identify user) HTTP (Hypertext Transfer Protocol) POP3 (Post Office Protocol, Version 3) NNTP (Network News Transfer Protocol) Port: location at an IP address which services a particular application Copyright © 2003, Addison Wesley