Information & Communication Systems

These slides cover the following topics:

• Centralisation of control and data – mainframes

• Dispersed system – personal computers

• Dispersed + networking = distributed system

• Distributed storage

• Distributed processing

• Distributed control

• Telecommunications for competitive advantage

• Networking

• Network infrastructure for the World Wide Web

Mainframes• The earliest computers were

what we now call mainframe computers

• The first commercially available computers appeared in the 1950s (e.g. LEO, shown right)

• Mainframe computers centralise the processing and use dumb terminals, which are often text only – they do no processing, and are effectively just monitors and keyboards

• Centralised processing fell from favour in the 1980s as PCs became cheaper and smaller

• Centralised processing is making a comeback with the increased popularity of the internet, network computers (NCs) and systems such as Citrix Metaframe

Centralised Processing

• Terminals are cheap

• Expansion is easy – just add another terminal

• No software to configure on terminals

• Centralised resources – data and peripherals

• Fewer data integrity/redundancy issues

• Background processing can continue after logout

• Security issues – data can be accessed from anywhere

• Space – large computer room required!

• Permanent communication link required

• Speed – large bandwidth required for GUI

• Cost of maintaining link – phone/leased line

• Limited facilities – no local printers, disc drives, etc.

Dispersed Systems

• Everyone has their own PC – processing is dispersed throughout the organisation

• This changed working practices, as everyone had access to data processing facilities – e.g. managing directors could type their own letters!

• Lack of centralisation leads to problems:– No standardisation – e.g. shared templates– Data redundancy/integrity problems – multiple

copies of data could be changed separately– Communication between departments is not

possible

Distributed Systems

• When networking is added, dispersed systems become distributed systems

• Advantages and disadvantages as per networks:

• Shared hardware, software and data

• Easier to install applications, etc.

• Improved communications

• Centralised management of users, backups, etc.

• Dependency - server or cable failure affects all users (potentially!)

• Security issues - passwords, restricted access, viruses, etc.

• Performance - network slows down under load

• … to be furthered!

Centralised Storage

• Storing data centrally has big benefits in terms of redundancy - all users are using the same data which can easily be kept up to date

• The DBMS needs to be careful to maintain the integrity of the data through record-locking

• What happens if two users try to update a record at the same time?– prevent access to records in use?– make open records view only?– lock open records so that they can’t be changed?– lock related records? – lock the whole table?

Client-Server

Database

Server

Applicationor web-site

Client

Request for information

Results of query

• The database is centralised

• The application or web-site itself contains no data

• No redundancy• Can connect remotely -

e.g. from home• Improved security - data is

not stored by the client?• Less traffic as only subsets

of the data are transferred

• Less secure as users may connect remotely?

• Communication cost for remote connections

• Performance?

Distributed Databases

• Another approach is to distribute the database so that all users are not connecting at the same time over costly communication lines

• This can be done in one of three ways:– duplicate the entire database– split the database into sections– create a central index to local databases

• This can cause problems:– if the database is duplicated, how do you reconcile

changes made to one database with the other databases?

– if someone is editing a record, how can you lock that record or table in a database elsewhere?

Example

HeadOffice

North East South West

Ipswich NorwichKingsLynn

John Janet

• The head office has all the data for the whole company

• Each region stores only customers in that region

• Each branch will only store local customers

• Each adviser only has his/her own client records

Appointment

Appointment

HeadOffice

North East South West

Ipswich NorwichKingsLynn

John Fred

I’m off toKings Lynn!

• Such transfers might only occur once a day

Distributed Storage

• Better than dispersed systems?

• No dependence on central database or server

• Faster - the data is stored locally, so there are no communication bottlenecks

• Still dependent on communications

• There are security issues with remote connections

• There is quite a lot of redundancy - mismatches need to be reconciled

• Inability to lock records could cause integrity problems

Distributed Processing

• Processing of data can also be broken down - this is known as distributed processing…

• …or parallel processing

• This can take place on networked computers, or computers with multiple processors

• It is best suited to processor-intensive jobs with not much data (otherwise the overhead of transferring the data would outweigh the benefit)

• How do you split a job?

• Examples:– SETI (search for extra-terrestrial intelligence)– Oxford university screen saver

Distributed Control

• Control can also be distributed, e.g. network routing:

Source Destination

• When the message sets out, there is no pre-determined route

• Each node decides the best route, based on local traffic, etc.

Telecomms for Competitive Advantage

• ICT is used to speed up or simplify business processes - e.g. mail order, customer management

• For example:– customers can order goods via a web-site, a

confirmation e-mail is sent, and the goods are dispatched from the warehouse - no money needs to be sent, or order forms filled in and posted.

– sometimes the goods can even be downloaded directly from the web-site, e.g. software, video clips.

– customers can view their account activity on-line and track orders, and there is less paperwork for the company - they could even have automated “pickers”

Case Study - Guardian Royal Exchange

• Old “manual” system:– an advisor visits the customer, completes forms

outlining cover requirements and budget and posts them to the head office

– actuaries at the head office produce the “illustration” (quotation) and send it to the advisor

– the advisor returns to customer with the illustration– if the customer agrees, the “proposal” form is

completed and the paperwork is sent off to the head office

• There was a 60% rejection rate due to proposals being completed incorrectly, or illustrations being done for ineligible customers, etc.

Case Study - Guardian Royal Exchange

• New “computerised” method:– The advisor visits the customer with his laptop and

enters the customers personal details– The software suggests suitable products and

performs “illustrations”– If the customer chooses to buy, the “proposal” is

completed on the laptop and printed out for the customer

– Back at the office, the advisor plugs the laptop into a phone-line and transmits the data to head office.

• Using this method, the advisor can complete the sale in one visit, and use of cross-field validation, etc., reduced the rejection rate to less than 2%!

Social Implications

• There can be resistance to using new technology– this can lead to systems lying unused– in the GRE example, so few advisors wanted to use

the laptops that they introduced a higher commission rate for policies transmitted electronically

• The workforce will need to be trained to use new systems

• Sometimes companies introduce new ICT systems with the intention of reducing the workforce - in the GRE example they would have been able to get rid of head office actuarial staff

• See also e-commerce on the intranet

Networking

• Local Area Network (LAN) - a number of computers on the same site, sharing a common electrical connection

• Can share hardware, software and data

• Easy to administer centrally, e.g.– users– backups– applications

• Improved communication

• There is dependency on the system - e.g. power or cable failures affect all users

• There are security issues - hackers, viruses, etc.

• Performance degrades under load

Networking Terminology

• A gateway is used to link two different networks together, e.g. to connect a LAN to the internet

• A bridge links together two similar networks

• A client-server network is one that has one or more file servers storing data and applications and print servers - this is the most common type for anything but very small networks

• A peer-to-peer server has no server:– files and peripherals (e.g. printers) are shared

between workstations on the network– all workstations may need to be switched on– suitable for small networks due to reduced cost

Client-Server or Peer-to-Peer?

• Choose client-server if:– you have a large network that can absorb the cost

of the server– you want centralised management of users and

resources– users are mobile and/or don’t always have their

PCs turned on

• Choose peer-to-peer if:– the network is small and you can’t justify the

expense of a dedicated server– you have a workforce that generally uses the same

PC and works the same hours so that all workstations are on at the same time

Wide Area Networks

• Some large organisations are national or multi-national, and data might need to be exchanged globally

• Large wide area networks (WANs) therefore exist to make this data transfer:– possible– secure

• Examples of WANs include:– airline booking systems– credit card payment systems– national lottery machines– Police National Computer

The Internet and the World Wide Web• The internet and the world-wide web are not the

same! The internet also supports:– e-mail

– newsgroups

– IRC chat

– FTP - file transfer

– telnet - for logging into other computers remotely

• Through a variety of protocols, e.g.:– TCP/IP - transfer control protocol/internet protocol

– POP3 (post office protocol) and SMTP (simple mail transfer protocol)

– HTTP - hyper-text transfer protocol

– FTP - file transfer protocol

Connecting to the Internet

• PSTN (public service telephone network)– connect using a modem– allows speeds up to 56kbps

• ISDN (integrated services digital network)– digital phone line - dialling of number required– 64kbps per channel - usually 2 channels = 128 kbps. – Connect using an ISDN or terminal adapter

• ADSL (asymmetric digital subscriber line)– connect using a terminal/network adapter– “always on” - no need to dial connection– faster to download than to upload (asymmetric!)– not charged per minute (unlike PSTN and ISDN)

Internet Infrastructure

• Consumers connect to Internet Service Providers (ISPs), e.g. Freeserve, AOL, Tiscali

• ISPs connect to Network Service Providers (NSPs), e.g. BT

• The links between the NSPs is the internet backbone

Consumers

ISP

ISP ISPOther ISPs

NSP NSP

NSP

NSP

Internet backbone