Chapter 2 The Infrastructure
Copyright © 2003, Addison Wesley 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.
Copyright © 2003, Addison Wesley Figure 2.2 Communication requires five elements. 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. The cloud is a common way to visualize an infrastructure
Copyright © 2003, Addison Wesley Figure 2.4 Wireless communication. Both POTS and wireless use the same long distance infrastructure.
Copyright © 2003, Addison Wesley Figure 2.5 POTS and wireless are alternative access paths to the 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
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. The header carries delivery information Information about the message The trailer is often optional.
Copyright © 2003, Addison Wesley 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. 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 Simultaneous transmission by two or more nodes Token passing (collision avoidance) 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.
Copyright © 2003, Addison Wesley Figure 2.10 With point-to-point transmission, the signal is routed node by node.
Copyright © 2003, Addison Wesley Figure 2.11 Internetworking. Process of linking two or more networks. A bridge links similar networks A gateway links dissimilar networks
Copyright © 2003, Addison Wesley A router accepts a message at one of several input ports and forwards it to the appropriate output port. Routers are faster and less expensive than computers at performing the highly specialized task of routing messages.
Copyright © 2003, Addison Wesley Figure 2.12 A client/server network. Server Controls resource Normally software Term sometimes applied to hardware Client Requests resource Workstation
Copyright © 2003, Addison Wesley Figure 2.13 Most users access the Internet through an Internet Service Provider (ISP). Access network Communication link Most ISPs offer , data access, chat rooms, site hosting, … Host or end system Runs server software http//thelist.internet.com
Copyright © 2003, Addison Wesley Figure 2.14 The backbone.
Copyright © 2003, Addison Wesley The Backbone Network Service Provider (NSP) National wide-area network Lease bandwidth to ISPs Network Access Point (NAP) Place where NSPs meet and exchange data Chicago NAP Regional ISP Statewide of regional backbones
Copyright © 2003, Addison Wesley Figure 2.16 Packet switching. Objective: Efficiently utilize bandwidth Process Break message into packets Transmit packets independently Multiple messages share line Reassemble message at receiving end
Copyright © 2003, Addison Wesley Figure 2.17 A message’s packets can follow different paths.
Copyright © 2003, Addison Wesley Figure 2.18 The TCP/IP model.
Copyright © 2003, Addison Wesley Figure 2.19 The Open Systems Interconnect (OSI) model. A blueprint.
Copyright © 2003, Addison Wesley Figure 2.20 The application layer protocols support application programs.
Copyright © 2003, Addison Wesley Figure 2.21 Some common application layer protocols.
Copyright © 2003, Addison Wesley Figure 2.23 The next layer down is the transport layer. The transport layer usually uses the TCP protocol.
Copyright © 2003, Addison Wesley Figure 2.24 TCP adds its own header.
Copyright © 2003, Addison Wesley Figure 2.25 The Internet layer uses the Internet protocol (IP).
Copyright © 2003, Addison Wesley Figure 2.26 IP adds its own header.
Copyright © 2003, Addison Wesley Figure 2.27 The network access layer adds another header.
Copyright © 2003, Addison Wesley 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. Domain: a set of nodes administered as a unit.
Copyright © 2003, Addison Wesley The parts of a domain name are structured as a hierarchy.
Copyright © 2003, Addison Wesley Figure 2.29 Top-level domain names.
Copyright © 2003, Addison Wesley Figure 2.30 An IP address. Wrong
Copyright © 2003, Addison Wesley Figure 2.32 The domain name system.
Copyright © 2003, Addison Wesley Figure 2.33 Well-known port assignments. Port: location at an IP address which services a particular application