Networking & Connectivity

Mendelsohn

A Computer Network

• What is a network?– A system of two or more computing devices

that are linked together.

• Why are networks useful?– Share information (e.g. databases, software,

other data)– Share peripherals (e.g. printers)– Share access (e.g. internet)– Allow people to work together

Early Networks

• Telegraph• Voice (telephone)

Copyright 2008 M J Davidson

What type of information does a computer network typically carry ?

• Voice

• Data

• Both

Copyright 2008 M J Davidson

What type of signal does the network carry ?

• Digital

• Analog

Terminology

• Node: Any device on the network such as computers or peripherals (printers, routers, etc) is called a node.

• Nodes are typically connected to hubs (or sometimes switches).– Think of how you get your electronics on the electrical

“network” by plugging them into an outlet. – Similarly, to get devices onto a network, you need to

plug them into the network. Frequently this is done by connecting the node to a hub.

A Hub

Ethernet cable

A network can be as simple as two computers connectedto each other

• Most networks involve at least a few computers frequently with some peripherals (printer).• With multiple computers, the nodes need to be plugged into a hub.

Home networks

• Most people create a home network for the purpose of sharing an internet connection.

• However it is also possible to share peripherals such as scanners and printers.

A Home Network Sharing an Internet Connection

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Connecting a device to the network

• Wired– Various types of cabling are available

• Wireless– Requires the use of a shared or agreed-upon

standard such as WiFi

• Twisted Pair (shielded, unshielded)

• Coaxial

• Fiber-Optic

Wired – Types of Cables

Modems• One wired method of connecting to a network

– Increasingly obselete

• Networks such as telephone systems use analog signals (as opposed to digital)

• Before a computer can work with the data, it has to be “translated” into digital

• The process of converting an analog signal to digital is called MO-dulation.

• Converting digital to analog is called DEM-odulation.

• These days, modems are becoming less common as most people are networked digitally.– They don’t have to “dial in” using a telephone line.

Bandwidth• If your online experience seems slow and jerky—

particularly when dealing with multimedia (audio, video), your problem is likely a question of bandwidth.

• When talking about internet connections, bandwidth refers to the quantity of data that can be transferred from an ISP to your PC in a given period of time (e.g. each second).

• These days, is typically measured in megabits per second (mps).

Broadband• Broadband refers to a high-bandwidth connection.

– Typically several mps– That said, there is typically a large difference between your theoretical bandwidth and the actual bandwidth you get at home.

• Types of broadband:– DSL: uses standard phone lines – therefore, widely available– Cable: requires a cable line (same as TV cable)– Wireless: such as WiFi, Satellite, Infrared, Bluetooth– Fiber-Optic: far faster than any other technology. However, fiber-

optic wiring is still only available in a small number of locations.• 1 FO cable can transmit the equivalent of 10,000 copper (e.g. cable) cables

Broadband Penetration Worldwide

Wireless Technologies/Standards

• In terms of connectivity, wireless technologies include Satellite, Infrared, WiFi, Bluetooth, and others

WiFi (IEEE 802.11)• More and more people every day are connecting to networks

such as the internet using WiFi• Not surprisingly, WiFi is the fastest growing networking

technology.• The IEEE standard is known as 802.11

– Versions: 802.11a, 802.b, 802.11g, 802.11n– These versions have varying ranges and speeds

• Speed ranges from 10 mps to 100+ depending on the version (Version ‘n’ is the fastest, ‘b’ is the slowest)

• Very limited range: about 30 meters. – Version ‘n’ has a greater range – but still measured in meters

• Not as fast as Ethernet, but still quite fast and good enough for multimedia networking

WiMax (802.16a)

• A new wireless standard

• WiMax towers have a range covering about a 25 square mile area

Broadband Comparison

Bluetooth (IEEE 802.15)• Another wireless standard• Very low range (about 10 m)• Low bandwidth (about 1-3 mps

in practice)• Costs less – therefore popular

with manufacturers• Given low range and

bandwidth, not widely used for network connectivity

• Much more popular for wirelessly connecting two devices together– provided they are in close

proximity

Read this!!!

• There will be an exam question that comes from reading this article….

• http://dvice.com/archives/2006/08/shift_verizons_fios_and_sprint.php

Connecting a PC to a Network

• Wired– Requires a network

adapter or “network interface card” (NIC)

• Wireless– Requires a wireless

network adapter

A typical home cable/DSL broadband connection1. Pre-existing cable wires are

extended to the interior of your home.

• This cabling may already be in place (e.g. if you have cable TV)

2. Your internet service provider (ISP) provides a cable or DSL “modem” that establishes the connection between the cable wiring and the internet.

3. The cable/DSL modem is typically connected either directly to a PC or sometimes to a wireless router.

4. If a wireless router is in place, the internet signal to and from the wireless router is broadcast throughout the home.

Classifying networks

• By Distance (LAN, WAN), Relationship (e.g. client-server), Protocol (e.g. TCP/IP)

Copyright 2008 M J Davidson

Classify by Distance• PAN – personal

– E.g. a home network: • sharing one internet connection• sharing a printer

• LAN – local– Usually implies that the networked computers are in the same

building– E.g. a small business

• WAN – wide– A network spanning a wider area such as a city or even larger.– DePaul’s network on several campuses around the Chicagoland area– City-wide networks are sometimes referred to as ‘MAN’s

(metropolitan area networks)

Copyright 2008 M J Davidson

Classify by Relationship

• Client-server

• Peer-to-peer

Copyright 2008 M J Davidson

Classify by Protocol

• a set of rules for the exchange of data over a communications channel

• Examples– SNA– TCP/IP

• The internet is classified based on the type of protocol it uses (TCP/IP)– More on this in a later lecture

Wired Communication Ports

– Serial - single bit at a time– Parallel – eight bits at a time– FireWire (IEEE 1394 )– Universal Serial Bus (USB)– Ethernet– VGA– Etc

Parallel Port

– Parallel – eight bits at a time

• Before USB, was commonly used for printers. Many printers still come with cables to connect to a parallel port.

• Before faster and more efficient ports were developed, was also used for CD ROMs, Zip drives, etc

VGA Port

• These days, pretty much exclusively limited to connecting a monitor to a PC.

USB Port

– USB Universal Serial Bus• 1.0 (11 Mbps) or• 2.0 (480Mbps) - the current standard

– Developed to replace connections that previously were limited to serial or parallel ports.

• Printers• Keyboard• Mice• You name it….

IEEE 1394 (Firewire, i.Link)

– High-speed communications– Brand names:

• Firewire (Apple)• i.Link (Sony)

– Fast!– Popular uses: Devices that

require speedy transfer • external hard drives• Camcorders (transfer of large

data devices from camera to PC)

Ethernet Port• Ethernet wiring is far and away the

most popular (wired) method of connecting a computer to a network

• Pros:– Faster than wireless– More reliable than wireless– Easier to set up

• Cons– Wired!