What VPN and private network are ? - Part of ICT system

To understand what a virtual private network is, let's first think of what we mean by a private network. Many large organizations are geographically widespread. Think for instance of large chains of shops supermarkets or banks. Very often each shop, supermarket or bank will have its own LAN. Typically a large organization needs to join up its LANs for data communications. If the only data that needed to be transmitted were emails, then using the internet might be a satisfactory way to do this, however, large organizations have more complex data requirements than that. They may have servers holding files that need to be accessed by people throughout the organization, but which need to be inaccessible to people outside  the organization. Ideally, then the organization would have a private network which is a data network for the exclusive use of the organization.

ADSL & DSL technologies

Digital Subscriber Line is a technology that links all telephone wires connecting most homes to their local switching center. DSL  technologies achieve high data rates by reducing the effects of noise, used advanced error detection and correction, in addition to supplying broadband to the home. DSL technology may be a component of large institutional networks, such as NHS network.

Denial of service attacks - Know about exploiting weaknesses in software

Denial of service attacks is an attack on a computer which disables the computer to such an extent that normal work cannot be carried out on it. For example the internet worm effects a computer by executing simultaneously on each infected computer and so slowing down other programs to the point where useful results could not be obtained from them. There are a number of ways that denial of service attacks can be made.

First, a program can be inserted into a computer which consumes amounts of some resource. This program could for example be an attachment to an email, it could masquerade as a software update issued by the supplier or it could enter the computer because of a weakness in the software that controls the computer. These types of attacks are relatively easy to guard against.

What spam can cost ?

 Spam is junk email ( sometimes referred to as unsolicited commercial email or UCE ) that is sent automatically to thousands of recipients at once. it is currently estimated that between 40 and 60 per cent of email received in organizations spam. Once your email address falls into the wrong hands, you are likely to become the target of spam. Note that if you subscribe to a service that sends email notices of new product or a regular newsletter, whether or not you realize it, solicited them by subscribing to the service.

Signals ( waves ) in ICT systems

It is important to know that in ICT system we must represent message or data in signals to convey data from one to another location, this process is the same with radio waves which enable to manipulate, store and convey data where this data travels along through other related means. You can think about more examples for signals like wires between telephone and local exchange, pulses through wires underground for bell house and many other things.Generally a signal full oscillation called wave cycle which is the frequency of the numbers of signals measured in Herts or (Hz).

Personal Area Network (PAN), AD hoc and Bluetooth in types of LAN networks

 PAN or Personal Area Network which is the smallest type of networks and can cover a small area. Bluetooth depends on this type that enables devices that connected to can form ad hoc ( Ad hoc is type of networks enables devices to communicate with each other without central control ) to establish the same network PAN ( sometimes called piconet ).

Each device has its own MAC address ( similar to that one the computer uses when connect to network (LAN) ). In PANs networks devices join in a group of 8 devices all them called slaves, and a master that controls commands and slaves respond to these command because that helps to organize data in the order to avoid sending data from each devices in the same time.

Database and database server - ICT system components

There is a different between databases and database server, because any new changes or more details can be updated in databases, for example in government departments about citizens or in airport about flight reservations. That all can be held in databases to organize new events. Database server which enables users to get information from database itself, but limited depending on a policy or purpose of the services. If individuals want to check out about flights in airport that stored in databases, then users should use database server to give them information about that.

Government departments, airports or even big supermarkets may have more then a database. We describe database server as a connector between database and user instead of access to database directly, that is.

ICTs systems components and radio waves

ICT  is a network that contains means of communications and can convey, manipulate and store data, each one of ICTs systems should have these principles. For instance convey a message through radio waves when a computer is connected by network only that can show us a clear example about an ICT system, because you have to be connected through network that enables to convey manipulate and store data. Also whether these ICTs systems have various types such as at home LAN, public services or even the big supermarkets that linked all computers in a network to a database to provide price and the type of goods.Network implements various operations because it works as a communication channel to manipulate, store and retrieve data to be delivered to the recipient from a transmitter or sender ( any type of data ).