lecture 2 web page design

8/14/2019 Lecture 2 Web Page Design

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Web Page Design and Development CT130

Lecture 2

Connecting to the Internet

At the end of this lecture you should be able to explain the factors affecting a connection to the

Internet. These include:

• the technical factors affecting the server-side of a connection

• the technical factors affecting the client-side of a connection

• the telecommunication factors involved

•

the factors affecting the choice of Internet Service Provider.

Internet Service Providers (ISPs)

‘Connect with us! Cheap Internet service! Free Emails! Free hosting! Fast connections’

A typical advertisement from an Internet Service Provider (ISPs). With so many home users and

so many commercial ISPs touting for business, we need to know what is involved in connecting to

the Internet.

It is difficult to escape from the many ISPs telling us how easy it is to sign up with them and to

connect to the Internet but just what is involved? Is one ISP any better than another?

We are confronted with terminology such as clients/servers/links/access etc. but how do we know

what terms mean and can we select and use them properly?

Some large companies and organizations can afford to set up as their own ISP but most

individuals and small businesses connect to the Internet through a commercial ISP. You pay such

an ISP to be part of its network and to get access to Internet services. The ISP provides servers

to which client computers will log on to gain access to the global Internet.

For the purpose of this unit, a server is any computer that is (almost) permanently connected to

the Internet to which other computers, clients, will log on. Access to the services available on the

Internet is through a server. A server is a computer that receives, stores and forwards



communications data. The range of services available on the Internet (WWW, ftp, e-mail, news

etc.) and the demand for them have led to ISPs providing dedicated server(s) for each service.

A Web server (updated to Application or Information server) stores HTML documents, which

can be accessed using a web browser . An HTML document is a page of text and graphics,

which are viewed using a special piece of software called a web browser. Some of the text or

graphics will actually be links to other documents stored on other servers. Clicking on these links

will download that new document from its server to your computer.

A mail server is a computer dedicated to serving mail for subscribers to the ISP’s network. This

type of server stores any incoming e-mail messages in a mailbox for each subscriber. When you

log on to the mail server, any new mail cam be downloaded form the server to your client

computer. The mail server also deals with any outgoing messages you may send, sending the

message to the mail server specified in the e-mail address. For example,subscriber@company_name.com

Newsgroups are a popular feature of the Internet and a news server is dedicated to managing

these on-line ‘discussions’. A newsgroup is like a bulletin board system. Users will log on to the

news server and can see any postings (messages/questions/replies) that have been made.

These postings to a newsgroup are called articles. Anyone who accesses the newsgroup will see

the articles previously posted and can reply to these. Contributions to a newsgroup can be made

by anyone. The server will store the titles of each posting so that users do not have to waste time

and money downloading content which they may not want.

The titles will be stored as links to the actual posting, which may be on a server from across the

world. Client computers can download only the postings they wish to read.

Another popular feature of the Internet is file transfer. An ftp server is similar to a newsgroup in

that it stores links to files stored elsewhere on the Internet. Program or data files can be

downloaded onto a client computer via an ftp server. The server will store a list of all the available

files on that server. This list will consist of a series of hyperlinks to each file.

The ISP provides the servers and through these allow users to access other servers in other

networks and other countries. The servers at the ISP provide the software necessary to create

these links to other servers and networks. There are, however, some requirements for the client

computer.



Hardware

First of all we need to know what hardware is required.

A typical home user will own a computer system which includes:

• a processor capable of running the necessary communication software

• a keyboard

• a monitor

• a mouse

• a modem

The first four items you should already be familiar with. A modem is a vital piece of hardware in

electronic communication. A modem converts outgoing computer data (digital data) into a form

that can travel over the standard telephone network (analogue data). It also coverts incoming

analogue data into a form that that computer understands. The speed at which a modem can

send/receive data is one of the most important factors in the success of on-line communication.

At the time of writing, a standard modem will operate at 56K bits per second (bps), although much

faster ones are available. Some modems are connected externally to the computer. However, it is

becoming very common for computers to come with an internal modem installed – all that is

needed is a connection to a telephone line.

Software

On subscribing to an ISP, they will usually provide you with the specialist software, which is

required in order to connect to the Internet. The various different Internet services normally

require a specialist piece of software. This will typical include a browser, which can view

WWW pages. An e-mail program is also a specialist piece of software required for the

sending and receiving of e-mail messages. File transfer software is also necessary.

Developments in this area led to the emergence of browsers that brought together the

different software for all the different services. This is advantageous since only one

program is needed but the program is very large and uses a lot of memory. The simple

sending of an e-mail still requires that you load the whole browser if separate software is

not available.

You should already be aware of the diverse range of hardware and software available, all of

which must be capable of sharing information with different platforms, operating systems etc.

used in the client/server model.



(Please note that client/server concepts will be dealt with in another course- Web

programming)

Server-side factors

Since any type of server is the means by which connection is made to the Internet for a huge

number of clients it must operate at a very high speed and be able to handle multiple users

simultaneously.

There are obvious running costs associated with maintaining a server. In an attempt to reduce

these costs an ISP has the option of using one server to provide more than one service.

For example, a single server could provide both file transfer and e-mail. This will obviously reduce

the efficiency and speed of the server. As users log on for further service, traffic through this

single server increases are there more users to deal with, but also the actual operations that have

to be carried out by the server are different. It is no longer a dedicated server to one task but it

must now multi-task between different processes.

The ratio of modems to users accessing an ISP’s server is also an important factor. Several

hundred clients all demanding access to a server, with their messages having to filter through 10

server modems, can cause bottlenecks.

Client-side factors

The performance of the services available on the Internet is heavily dependent on the client

computer. For the purpose of this unit, a client computer will be assumed to mean a

microcomputer system although there are developments in network computers.

The client computer system must have a fast enough processor to deal with the software used in

transferring data to and from the Internet. There must be enough memory to run the necessary

software, for example browsers, mail programs etc. the hard disk must be large enough to store a

series of download files, mail messages etc.



For more advanced features like on-line radio, the hard disk must be fast enough to cope with

transferring batches of data at regular intervals to the processor. The operating system on the

client computer must support the different types of communications software used. The operating

system must also support any ‘plug-ins’ that is loaded from the Internet to add functionality to the

browser, for example for audio or video image handling. If different types of communication

software are going to be used for different purposes, for example, Internet Explorer for browsing,

Outlook for mail, then these applications must be able to run simultaneously and compatibly.

Types of connection

With the two parties ready to link up, the final piece of the puzzle is the actual connection itself.

This can be done in a variety of ways but before discussion of these methods, it would be useful

to define a term that is central to any discussion of connection speed – bandwidth. The

bandwidth of any communication line determines how much data can be carried on that line.

Obviously, the broader the band, the more data can be carried.

A dial-up connection is often used for home users of the Internet. This is where the client

computer’s modem is connected to an existing telephone line. This is the slowest form of

connection available for a number of reasons. The speed of the modem obviously places limits on

the speed of communication, but very often, the advertised speed of the modem, which at the

time of writing this is typically in the region of 56Kbps, is never reached. The telephone network

that is used to dial into the server is also the telephone network that people use for their phone

calls. Quite simply, it gets too busy for available bandwidth. Once a connection has been

established to server, subsequent connections from that server may be made using high speed,

broadband links. The speed of any system, however, is determined by the speed of the slowest

part – in this case, the normal telephone connection from the server to the client.

Another consideration is the cost of being on-line. As with phone calls, any computer using a

phone line will be charged accordingly for the duration of the connection. With on-line sessions

ranging from 1 minute to send e-mail to 4 or 5 hours browsing, on-line cost can vary remarkably.

“Surfing” the net, in particular, can clock up enormous phone bills.

The good news about dial-up connection are that most ISPs will provide a local call number to

access their server so regardless of where you may be browsing (Tobago, Japan, Australia etc.)



you are only paying for the call to the server at local call charges. The ISP absorbs the onward

costs to the rest of the world.

An alternative dial-up connection involves the use of an ISDN (Integrated Switched Digital

Network) line, which is much faster than the standard telephone exchange, with a bandwidth in

the order of 128000bps. The rental of the line, however, will cost much more and calls still have to

be paid for. The benefit of an ISDN line lies in the fact that the much faster rate of data

transmission means that you are not on-line for as long, and so the call does not cost as much.

There is a way to avoid paying for the actual on-line time using a leased line connection. It is

possible to lease a line from a telecommunications company. This means that you pay for the use

of high-speed digital line, which nobody else can use. With the previous types of connection, the

data that is being transferred from the server toy your computer or vice versa is divided into

streams of packets which may all arrive at their destination by various routes. This can take time.With a leased line, the connection is direct to the server there is no traffic which can delay

transfer. The obvious drawback is the cost. Most telecommunication companies will charge a lot

of money for the privilege of a leased line. It is not a viable option for a sole user requiring access

to pay for a leased line. A large organization or institution with internal networks may wish all the

users to have easy access to the Internet. In this case investment in a leased line that offers

continuous, open connection to the Internet is a good idea.

A DSL line is an "always-on" connection provided through your phone line. It uses different

frequencies and can thus bypass the 52 kbps limit. DSL speeds vary depending on the package

but are typically around 384 kbps for download and 128 kbps for upload.

A cable modem is similar to a DSL line but it is provided via the same coaxial cable that provides

Cable Television service. Cable Modem speeds vary depending on the provider and the number

of users in the neighborhood, but typically max out at 1450 kbps for download and 225 kbps for

upload.

An ethernet LAN is used by corporations and universities and provides access to the internet via

an ethernet cable connected to your computer. Speeds vary depending on the server being

connected to but can be as high as 15000 kbps for remote servers or 100000 kbps for local

servers.

Frame relay is packet-switching protocol for connecting devices on a Wide Area Network (WAN).

Frame Relay networks in the U.S. support data transfer rates at T-1 (1.544 Mbps) and T-3 (45



Mbps) speeds. In fact, you can think of Frame Relay as a way of utilizing existing T-1 and T-3

lines owned by a service provider. Most telephone companies now provide Frame Relay service

for customers who want connections at 56 Kbps to T-1 speeds. (In Europe it is called E1 to E3

and have speeds that vary from 64 Kbps to 2 Mbps).

On your Own – Research Satellite and ATM forms of connections

Configuring your computer

Regardless of the way you choose to connect, there remains the task of configuring the hardware

and software. An incorrectly configured client computer can result in inefficient use of the Internet.

For example, a client machine may have an internal modem, capable of operating at 56Kbps. If,

on configuring the communications software, a speed of 28800bps is entered as the rate of data

transfer, there is an obvious inefficiency in terms of the modem and therefore the speed at which

you can receive and send data.

Another common problem in terms of configuring an Internet connection is the choice of server to

which you log on. It is not unheard of from a user in Kingston to be dialing into a server in the

USA, simply because that was default setting on the installation program, rather than dialing into

a local server in Half way tree. ISPs will usually provide client pre-configured software.

Choosing an Internet Service Provider

In choosing how to connect you will also have to think which Internet Service Provider you are

going to subscribe to. You need to investigate the following issues.

Does the ISP provide the basic services that you are looking for and software to use them?

(WWW, e-mail, newsgroup access etc.)

What value-added service does the ISP provide? (Free web spaces on their server for your own

website, private network services, on-line support, technical support, number of email accounts

etc.)

Of course, generic considerations must be taken into account. These include:

• Cost



How much will an account cost? Is it a monthly payment? Are there additional charges

for on-line time as well as phone charges? Is there a local access number?

• Speed

What sort of access speed is being offered. Some ISPs have a ratio of twelve

subscribers per modem. This is a ration where wait time is unlikely. Others may have asmany as fifty subscribers per modem. Imagine turnstyles at a football match – with more

turnstyles, more people get through; fewer turnstyles and bottlenecks occur.

• Reliability

How reliable is the server? Is the access to the server 24 hour, or is it frequently off-line?

Consider of these questions should lead you to an informed choice of Internet Service Provider.

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