Oz – Foundations of Electronic Commerce© 2002 Prentice Hall

Essentials of Telecommunications

2 Oz – Foundations of Electronic Commerce© 2002 Prentice Hall

Learning Objectives Compare and contrast network

topologies Explain the basic functions of the TCP/IP

protocols Evaluate the limitations of the various

classes of Internet addresses Select the best Internet link service

according to organizational or individual needs

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Network Topologies A network is made up of nodes

and communication lines Network topologytopology refers to the

physical layout of the network Star Ring Bus

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Star

Ring Bus

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Peer-to-peer vs. client-server networks Peer-to-peer: each computer has

equal capabilities Client-server:

Servers offer services to clients Predominant on the Internet

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Switching Techniques Switches – devices that direct the

flow of signals and route communication traffic

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Circuit switchingCircuit switching The entire communication path is

reserved for the duration of the session

Typical of voice communication Inefficient for data communication

Resources are being wasted while reserved, but not in use

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Packet switchingPacket switching Data divided into packets Each packet travels independently

through the network Upon arriving at the final destination,

packets are reassembled Efficient solution for data

communication

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Network Protocols A set of rules that governs the flow

and processing of information in a network

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TCP/IP: IP:IP:

Addressing Packet reassembly Multiplexing Operates between hosts

TCP:TCP: Controls flow of information from client to

server

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LANs and WANs Local Area Network (LAN) – serves

a building or a campus of adjacent buildings Owned by an organization Used for internal purposes Typically linked to the Internet

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Wide Area Network (WAN) – cover large areas Employ different types of

transmission media Ex.: telephone networks, Internet

backbone, etc.

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IntranetIntranet - an internal network based on TCP/IP

ExtranetExtranet - an intranet that can also be partially accessed by customers and/or suppliers Often, LANs of two or more partners

linked through the Internet

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Virtual private networks (VPNs)Virtual private networks (VPNs) SecureSecure internal networks connected

to the Internet To be covered in more detail later

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Internet Addressing Each device connected to the

internet must be assigned a uniqueunique IP number Also called Internet address or IP

address The IP number may be temporary (just

for the duration of the connection) The IP number is made up of up to four

blocks

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StaticStatic vs. dynamicdynamic IP numbers An IP address consists of two parts,

identifying the Network, and The node within the network

IPv4 vs. IPv6

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Five network classes Class A – very large networks Class B – medium-sized networks Class C – small networks Classes D and E are currently not

assigned

Oz – Foundations of Electronic Commerce© 2002 Prentice Hall

Bandwidth, bandwidth, and more bandwidth

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Integrated Services Digital Network (ISDN) International standard Transmits voice, data, and video

over digital lines 64Kbps and 128Kbps Service offered by phone

companies Already outdated

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Cable modem Permanent connection to the

Internet Shared resource

Actual speed depends on the number of subscribers sharing the same cable

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Digital Subscriber Line (DSL) Service offered by phone companies Several standards and technologies Permanent connection Speed deteriorates with distance Most common: asymmetric DSL

(ADSL) High download speed Low upload speed

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T lines T1:

1.544Mbps Point-to-point

Not switched Dedicated Digital

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T2: A combination of four T1 lines

T3: A combination of 28 T1 lines

T1 and T3 lines form the basis of most private networks

T lines (continued)

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Asynchronous Transmission Mode (ATM) Very high speed, fiber optics

based, standard Cell switchingCell switching

A cell = 53 bytes All cells use the same route from

source to destination

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Wireless Communication Mobile communication

PDAs Wireless Internet connections

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Business considerations in telecommunications Scalability – the ability to easily

augment a network Three types of costs:

The one time investment in lines Monthly fees for leased lines Maintenance costs

Security issues

Oz – Foundations of Electronic Commerce© 2002 Prentice Hall

Essentials of Telecommunications