Communication and Information Systems
Network Security and Accounting
Data Communications and Standards
Communication and Information Systems
Centralised Processing Systems
Until the 1970s, organisations used centralised systems where all processing was done by a central mainframe. "Dumb Terminals" (machines with no processor of their own) allowed users access to the mainframe.
Centralised processing still exists e.g. ATMs and airline booking systems, still exist.
Dispersed Systems
Because the price of hardware has fallen, it has become more cost-effective to move the processing power to where it is needed, i.e. on desktop machines. Word processing and spreadsheet software has made desktop processing very popular. Standalone machines have now been replaced by networked workstations, to allow data to be shared.
However, there is now evidence of a move back from "fat clients" to "thin clients". Organisations are removing things like floppy and CD drives for security reasons. See http://www.thinplanet.com/
LANs - Local Area Networks
No telecommunication lines are needed because computers on one site are linked together.
Files, printers, scanners and disk space can be shared
Users can communicate using software e.g. Lotus Notes
Software on the server can be used by anyone
All users can access the same database
Backup can be done automatically across the network
Client-Server v Peer-to-Peer Networks
Most networks operate on a client-server system, except for small networks of not more than 10 machines. These days, clients are normally not "dumb terminals" because they have their own processor. Applications may be loaded into the client's RAM but printing tasks may be handled by the server. This includes managing print queues. Backup and security are also handled by the server.
Peer-to-Peer networks are usually small networks of not more than 10 machines. Software may be held on any of the computers and it is made available to any other computer. An office can share disk space, software and data.
WAN - Wide Area Networks
These are networks over a wide area. WAN networks are created by organisations for data transfer within that organisation or between organisations. Booking an airline ticket and paying for goods by credit card use WAN networks.
Distributed Processing
This means that computers have their own processing capabilities rather than all computers using a mainframe.
See case study p. 316-317
Distributed Databases
A distributed database is a database that consists of two or more data files located at different sites on the network.
Because the database is distributed, different users can access it without interfering with one another. However, the scattered data must be periodically synchronised to ensure data consistency.
Advantages: Can provide local autonomy, gives the advantage of being able to share data.
Disadvantages: Distributed systems are likely to be more complex and expensive to install and maintain. The need to transfer data increases the security risks.
Using Telecommunications for Competitive Advantage
The use of telecommunications has reshaped the way organisations work. They can increase efficiency and speed of operations, they can help make management more efficient and they can improve customer service.
Look at the examples on pages 318-319
See UPS (United Parcel Service) case study on pages 319-320
The Internet and the World Wide Web
The Internet started life as the ARPANET in 1969 and it consisted of four computers. It now consists of several million computers linked together by cables, wires and satellites. Data travelling from one computer to another is transmitted from one link in the network to another using the best possible route it can find. If some links are out of service, the data will be routed through different links. The major communication links that for the Internet are called the "backbone". A handful of network service providers (NSPs) e.g. BT, maintain a series of nationwide links. More links are being added as Internet use increases.
A home computer user connects to the Internet through an ISP, which is connected to an NSP.
The WWW is a part of the Internet, which consists of linked HTML pages.
You should also revise Network Topology
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Network Security and Accounting
To have a network, you need:
File Server(s) - a powerful computer that stores and distributes files across the network.
Network Adapter - each workstation needs a network card
Cabling - to physically connect the computers
Network Operating System
Network Accounts - each user has a user ID and password to access their space on the network.
There are advantages in making data available to people all over the world from a central location but it brings problems of security.
Employees should be aware of the security policy and of the risks to data held on networks. For example:
Typical levels of access are:
Access levels can be applied to both software and data.
Viruses
Use of floppy disks should be examined. Firewall software can be used to check all downloads for viruses.
Backup
The network manager has the responsibility of keeping files on the network backed up.
Encryption
Data sent across a wide area network can be encrypted (put into code).
This can be based on:
All these methods are less effective if users do not follow security procedures. Some systems can log off if left unattended e.g. for 10 minutes.
Firewalls
If the Internet is accessed through a LAN or WAN, there is a security problem because someone from outside the organisation could hack into it. There is also a problem of users inside the organisation, accessing inappropriate material e.g. a school might want to prevent children looking at pornography or using chat rooms.
Various types of firewall are:
Find out about the proxy server used on your school network.
Audit Controls
Audit controls track all activity on a network, for example:
Special monitoring software can also store statistics about what programs and data files each user accesses. The program can then detect statistically abnormal behaviour of users.
Audit software can also monitor attempted logons.
Performance Management
Network monitoring software keeps statistics on all aspects of the network i.e. down-time, response time, utilisation of hardware resources, utilisation of software, network traffic density, etc. This can help with the management and planning of a network. Bottlenecks and other problems can be detected.
Network Accounting
There might be a need to monitor print use (e.g. so that departments can be charged for printing).
Data Encryption
Data on a network is vulnerable to wire-tapping. Therefore, confidential data can be encrypted. This data can then only be read by an authorised person who has a "key".
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Data Communications and Standards
Speed of Transmission
Transmission speed is related to the bandwidth of the communications channel. This "channel" is the link between computers and it could be a telephone line, a microwave link, a fibre-optic cable, or something else.
Baseband Connection - carries one signal at a time. A bit value of 1 or 0 is sent depending on the presence or absence of a voltage in the cable. Such signals can be sent very fast but only over short distances, otherwise a booster is needed.
Broadband Connection - Can send multiple signals on a fixed carrier wave. Data, video and audio transmission can take place simultaneously.
Modems
Telephone lines were originally designed for speech, which is transmitted in analogue or wave form. Modems convert data from analogue to digital form.
Direction of Transmission
Simplex - data flows in one direction only e.g. electronic notice board at a railway station that displays train times.
Half-duplex - data flows in both directions but not at the same time e.g. CB Radio
Full-duplex - data flows in both directions simultaneously e.g. a telephone where two people can talk at once.
Serial and Parallel Transmission
Serial - each bit is transmitted one at a time over a single channel.
The two types of serial mode transmission are synchronous and asynchronous. Synchronous transmission (where blocks of data are sent in timed sequences is much faster).
Parallel - several bits at a time are "sent in parallel". Parallel transmission is, therefore, much faster than serial transmission. However, parallel transmission is suitable for communications over very short distances e.g. between a computer and a printer.
Telecommunication Standards and Protocols
Protocols allow the use of "open systems" i.e. systems that are independent of the manufacturer and the platform. Therefore, the user is not restricted to equipment from one manufacturer.
Even if an organisation buys all its hardware from one manufacturer, it may still end up needing to communicate with another organisation with incompatible hardware.
In order to allow different types of computers to communicate with each other, standards have to be established that govern all aspects of communication.
There is a difference between a standard and a protocol. Protocols are standards but not all standards are protocols. Standards are not binding.
De Facto standards - these are established by the fact that a certain manufacturer dominates the market e.g. Intel processors and Microsoft software.
Examples of De Facto standards:
ACSII
Betamax v VHS video recorders (betamax machines were useless because nobody produced tapes for them)
QWERTY keyboards (why don't we adopt a different layout?)
Light switches (down is on in Britain but off in America)
Windows and DOS (see case study p.328-329)
De Jure standards - these are defined by industry groups or governments. The ISO (International Standards Organisation) lays down the standards. Example: the standard for compressing JPG images was laid down by the ISO.
Advantages and Disadvantages of Standards
+ There is a wider marketplace for computers that comply with standards.
+ Standards allow the development of "open systems".
- Some major manufacturers have the power to dictate "de facto" standards.
- Standards can slow down technological advancement because standards have to be agreed before changes can be made.
The OSI Model
The OSI (Open Systems Interconnection) model was developed by the ISO (International Standards Organisation). OSI was developed as a guide to developing standards between computers of different origins. The OSI model is not a standard or a protocol itself. It is a guideline for developing standards.
If a manufacturer ensures that their products obey a set of standards based on the OSI model, they can be connected to another manufacturer's machines relatively easily.
There are seven layers in the OSI model because the task of controlling communications across a network is too complex to be defined by one standard. Layer 7 (the application layer) is the highest level because it is through an application that the user will interact with the network.
(7) Application Layer - is used to interact with the user. It is through this layer that all the other layers are accessed. In this layer, the user is presented with features that make the actual running of the network invisible.
(6) Presentation Layer - Translates instructions from the form the computer uses to the form used by the network and vice versa. This ensures that data in different formats can be exchanged.
(5) Session Layer - This allows applications being run to share a connection, also called a session. It deals with requests from users for network services.
(4) Transport Layer - This makes sure that packets of data arrive at their destination in the right sequence. It deals with data transmission between computers.
(3) Network Layer - This determines which route data packets will take if they are more than a single link away. It deals with the routing of information around a network. It deals with network accounting.
(2) Data Link Layer - Physical transmission media is subject to interference and this layer will handle the subsequent data transmission errors.
(1) Physical Layer - This layer is responsible for the sending of bits (i.e. binary digits 1 and 0) from one part of a network to another. It deals with the mechanical and electrical connections of devices.
Internet Protocols
On the Internet, there is every kind of computer, even WAP phones and cable TVs. The Internet would not work without protocols.
TCP/IP is the de facto standard for allowing different computers to communicate over the Internet.
HTTP is the standard for requesting and receiving HTML pages
FTP allows files to be transferred over the Internet
POP3 allows e-mail to be transferred.
Addressing Mechanisms on the WWW
IP Addresses - every host has a unique IP address of 4x3 numbers e.g. 123.456.789.987
Domain - because the IP address is difficult to remember, they are translated into a domain name, which identifies the organisation at which the computer is located - e.g. bbc.co.uk
URL (Uniform Resource Locator) - is a web page address e.g. http://www.bbc.co.uk
The first part of the URL specifies the protocol to be used for connection to the server. Protocols include:
http:// - Hypertext Transfer Protocol
https:// - HTTP for web sites with secure servers (used for e-commerce sites)
ftp:// - File Transfer Protocol (allows access to FTP sites, where files can be downloaded/uploaded)
www - indicates the part of the Internet to be used, in this case the World Wide Web
bbc - this is the first part of the domain (called the sub-domain)
co - this is the top level domain. There are many top-level domains and these are being added to, to cope with the increasing demand for domain names:
.co.uk - British commercial
.com - commercial (mainly US or international)
.org (non-profit organisation)
.edu (American University)
.ac.uk (British University
.sch.uk (British school)
uk - this is the country identifier. All countries (except the US) have one. For example:
.uk - UK
.jp - Japan
.de - Germany
.fr - France
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