Chapter 3 Internet Architecture. Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall2...

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Chapter 3

Internet Architecture

2WWWWWW Awad –Electronic Commerce 2/e© 2004 Pearson Prentice Hall

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


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)


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


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


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


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


IP Address

• A host number that identifies itself to other hosts• Consists of strings of 32 bits• E.g. 10111111010101010100000000001100 =

191.170.64.12 • Host Name

– Human-friendly internet addresses

– E.g. ema3z.mcintire.virginia.edu


Networks

• Network vs. Local

• Networks are classified by three sizes

Class Beginning Bit

Bits in remainder of network part

# of bits in local part

Max. # of networks

Max. # of hosts in network

A 0 7 24 136 16 million

B 10 14 16 16,000 65,000

C 110 21 8 2 million 254


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


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


Information Transfer (Cont’d)

• Open Systems Interconnection (OSI)– A layered approach to networking– Each layer handles a different portion of the

communication process


OSI Reference Model

Layer Info Transacted TCP/IP Protocols

Application Application messages HTTP, FTP, SNMP

Presentation Compressed data

Session Session messages

Transport Multiple packets TCP

Network Packets IP

Data Link Frames Ethernet, PPP

Physical Bits Wiring, cables


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)



• 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



• 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



• Internet Layer– Routes messages across multiple nodes for

delivery– Handles network congestion to minimize

performance problems– Internet Protocol (IP)

• Standard for routing packets



• 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


Cable Types

• Twisted-Pair Cable

• Unshielded Twisted Pair (UTP)

• Shielded Twisted Pair (STP)

• Optical Fiber

• Coaxial Cable

• Wireless Technology


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


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


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


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


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


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


Key Components of A Network

• Network Interface Card (NIC)

• Hubs and Switches

• Routers

• Gateways


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


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


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


Gateways

• Special-purpose computer allowing communications between dissimilar systems on the network

• Operate at Application Layer primarily

• Difficult to install and configure

• Expensive


Factors in Designing a Network

• Location

• Capacity

• Distance limitations

• Cost

• Potential growth

• Security


Factors in Selecting Network Architecture

• Hardware requirements

• Software requirements

• Disaster recovery and fault-tolerance requirements

• Corporate culture and organizational factors


Network Management System

• Manager

• Managed Nodes

• Objects

• Management Information Base (MIB)

• Requests and responses


Large-Scale E-commerce Issues

• Financial exposure

• IP exposure

• Legal security

• Packet sniffing


Ensuring Corporate and Information Security

• Firewalls

• IP Security

• Intrusion detection systems

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Chapter 3

Internet Architecture

Chapter 3 Internet Architecture. Awad –Electronic Commerce 2/e © 2004 Pearson Prentice Hall2...

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