Chapter 3 Internet Architecture

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall2 Overview What is a Network? IP Addresses Networks Information Transfer Cable Types Key Components of a Network Factors in Designing a Network Network Management System

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall3 What is a Network? A connection between at least two computers for the purpose of sharing resources Types: –Local Area Networks (LANs) –Wide Area Networks (WANs) –Metropolitan Area Networks (MANs)

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall4 Peer-to-Peer Network Computers linked together as equals No centralized control Share resources on the same network in any way and any time Promotes institutionalized chaos < 10 computers

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall5 Peer-to-Peer Network (Cont’d) Benefits –Easy to install/configure –Inexpensive –User is able to control their own resources –Independent from a dedicated server –No need for a network administrator Drawbacks –Security problems –Performance suffers when a computer is accessed –Difficult to have backup –Decentralized logon passwords –No centralized data management

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall6 Client/Server Network Server – designed to address a client’s request Client – any computer connected to a server within a network A cluster of computers (called clients) connected to one or more servers to form a network Allow authorized user to access any programs/application resided on the server

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall7 Client/Server Network (Cont’d) Benefits –Centralized security control –Simpler network administration than peer-to- peer network –Centralized password –More scalable –Ideal for computers are apart Drawbacks –Network failure - clients are helpless –Specialized staff are needed –Higher costs

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall8 IP Address A host number that identifies itself to other hosts Consists of strings of 32 bits E.g = Host Name –Human-friendly internet addresses –E.g. ema3z.mcintire.virginia.edu

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall9 Networks Network vs. Local Networks are classified by three sizes ClassBeginning Bit Bits in remainder of network part # of bits in local part Max. # of networks Max. # of hosts in network A million B ,00065,000 C million254

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall10 Networks (Cont’d) Zone –Three-letter kind (com, gov, edu) –Two-letter kind (ca, uk, jp) –New general-purpose zones (firm, store) –Last (rightmost) part of a domain name preceded by a dot

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall11 Information Transfer Packet –Grouping of data for transmission on a network –Large messages are split into a series of packets for transmission Protocol –A rule governing how communication should be conducted between two parties, two computers, or a sources and a destination –Internet Protocol Set of rules used to pass packets

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall12 Information Transfer (Cont’d) Open Systems Interconnection (OSI) –A layered approach to networking –Each layer handles a different portion of the communication process

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall13 OSI Reference Model LayerInfo TransactedTCP/IP Protocols ApplicationApplication messagesHTTP, FTP, SNMP PresentationCompressed data SessionSession messages TransportMultiple packetsTCP NetworkPacketsIP Data LinkFramesEthernet, PPP PhysicalBitsWiring, cables

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall14 OSI Reference Model (Cont’d) Application Layer –Defines requests and response formats –Standard: HTTP Governs requests and response between browser and Web server application program Other standards: SMTP, POP HTML-compatible –File Transfer Protocol (FTP), Simple Network Management Protocol (SNMP), Domain Name Service (DNS)

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall15 OSI Reference Model (Cont’d) Presentation Layer –Converts data into a format the receiving application can understand Session Layer –Exchanges data for the duration of session –Keeps track of the status of exchange –Ensures only designated parties are allowed to participate in the session –Enforces security protocols for controlling access

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall16 OSI Reference Model (Cont’d) Transport Layer –Manages the transmission of data across a network –Transmission Control Protocol (TCP) Specifies how two host computers will work together Flow control Sequence assurance Reliability and integrity

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall17 OSI Reference Model (Cont’d) Internet Layer –Routes messages across multiple nodes for delivery –Handles network congestion to minimize performance problems –Internet Protocol (IP) Standard for routing packets

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall18 OSI Reference Model (Cont’d) Data Link Layer –Packages data into frames for delivery –Point-to-point (PPP) Framing – mark boundary between packets Error detection –Ethernet Physical Layer –Converts bits into signals for outgoing messages and signals into bits for incoming messages

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall19 Cable Types Twisted-Pair Cable Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Optical Fiber Coaxial Cable Wireless Technology

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall20 Twisted-Pair Cable Consists of two pairs of insulated copper wires twisted around each other Advantages –Protect against cross talk and interference –Easy to add computers to network –Well understood technology –Less expensive Disadvantages –Susceptibility to noise –Least secure –Distance limitations –Requires more expensive hubs

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall21 Unshielded Twisted Pair (UTP) Pair of wires do not have the shielding against electrical interference Advantages –Less expensive –Easy to install Disadvantages –Vulnerable to electromagnetic interference and crosstalk –Subject to attenuation

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall22 Shielded Twisted Pair (STP) An electrically grounded woven copper mesh wrapped around each twisted pair Advantage –Reduces electromagnetic interference (EMI) Disadvantage –Makes the wiring thick and is difficult to maintain

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall23 Optical Fiber Uses light rather than voltage to indicate one and zeros Advantages –High speed transmission –High security –Smallest in size –Supports voice and video data Disadvantages –Expensive –Difficult to install –Require two cables to transmit & receive data –Require special connections

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall24 Coaxial Cable Copper center shielded by a plastic insulating material Advantages –Transmits up to 10Mbps over 500m –Easy to install –Low maintenance –Good resistance to noise over long distances Disadvantages –Inflexible –Low security –Limited distance

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall25 Wireless Technology Microwave –Connect LANs in separate buildings Radio waves –No distance limitations –Susceptible to atmospheric and electronic interference –Subject to government regulations Infrared transmissions –Interference from bright light

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall26 Key Components of A Network Network Interface Card (NIC) Hubs and Switches Routers Gateways

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall27 Network Interface Card Installed in a slot with a cable plugged into the back Plugged into a wall jack connection or into the hub/switch directly Modem –Converts digital signals into analog form for transmission and incoming analog signals into digital signal across the telephone line

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall28 Hubs and Switches Hub –Operates at Physical Layer –Acts as a connecting point –Passive, active, and intelligent hubs Switch –Offers direct connection to a particular PC –Available for almost every OSI level

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall29 Routers Operate at Internet Layer Evaluate network traffic and stop local traffic from causing congestion Filter out packets that need not be received Expensive and difficult to operate

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall30 Gateways Special-purpose computer allowing communications between dissimilar systems on the network Operate at Application Layer primarily Difficult to install and configure Expensive

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall31 Factors in Designing a Network Location Capacity Distance limitations Cost Potential growth Security

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall32 Factors in Selecting Network Architecture Hardware requirements Software requirements Disaster recovery and fault-tolerance requirements Corporate culture and organizational factors

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall33 Network Management System Manager Managed Nodes Objects Management Information Base (MIB) Requests and responses

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall34 Large-Scale E-commerce Issues Financial exposure IP exposure Legal security Packet sniffing

Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall35 Ensuring Corporate and Information Security Firewalls IP Security Intrusion detection systems

Chapter 3 Internet Architecture