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Chp 15
Transferring data around
WELCOME
Data transmission medium
The material (or medium) that carries the signal passes on it’s journey from one computer to another .
There are three types of data
transmission media :
1)Metal cable
2)Fibre optic cable
3)Wireless media
Fibre optic cable Metal cable
It travels in the form of light It travels in the form of current
It is fast It is slow
It is expensive It is cheap
The difference between the metal cable and fibre optic cable are :
Wireless media Electromagnetic wave provides the medium into which data travels in the form of signals
Types of wireless media
1) Radio waves
Data are transmitted in the form of radio waves example:
Broadcast of t.v channels
2) Infrared
Data can travel in a short distance
Example :
Remote control of television
3) Microwave Data are transmitted in the form of microwaves Examples: mobile systems ,satellites
Advantage of wireless:1. No need for wire2. Cheap3. Faster
Disadvantage of wireless:1. Less security2. Limited range
Password:
• It is used to authenticate the user to the system.
• Advantage of password:
• It doesn’t allow anyone to access your data or files.
User Id:
• Tells the operating system that a certain person is using the terminal.
• Advantages of user id:
• Used to permit users to access certain files.
The differences between a user id and :a password
user id :
Tells the operating system that a certain person is using the terminal
Password:It is used to authenticate the user to the system
Access rights:
• They enable certain rights to be allocated to the files and users .
Example:For a particular user some files can be viewed only
not altered but for other it is for view and for altered and some can't be accessed at all.
Monitoring all attempts to access the system
• A system that is used to monitor the person who is allowed to access the files.
•We have to monitor all attempts to access the system because:
1. To find out who altered a file .2. To discourage fraud.3. To protect privacy of files.4. To know which file have been looked at.
IntranetInternal Restricted Access Network
IntranetsAn intranet is a private network that uses the same technology as that used by the intranet for the sending of messages around the network.
Intranet Internet
It stands for Internal Restricted Access Network.
It stands for International Network.
Hard to access by hackers.
Easy to access by hackers.
Private. Public.
Limited Open for ever.
The advantages in using an intranet:
Intranets are behind firewalls.Intranets are ideal in schools.Its more secure.It access the more relevant information to the organisation.
telecommunications
Can be used to link up to many online data bases
Message sending
Is a standard for the connection of pcs which enables communication between all the components This is called open systems interconnection (OSI)
PROTOCOLS , HAND SHAKES AND GATE WAY.
PROTOCOLS
Is a set of rules that we use to access data
Hand shake
It is an exchange of signals which establishes the communication between the devices .
Gateway
It translates the protocols between computers so that different computers are able to communicate with each other
Data compression
it is a technique used to reduce the size of the file.
Advantages of data compression
1)It is fast to upload files
2) It is fast to download files 3)It is fast to transfer as an email attatchment
4)It is fast to load files
Disadvantages of data compression
1)Images are not at a high quality
2)Sound is not clear
3)Thing could be transferred illegaly because of high speed of transferring data
4)The reciever may not have the software to receive data
Speed of accessTHE SPEED WITH WHICH YOU CAN SURF THE WEB OR VIEW DATA
OVER A WIDE AREA NETWORK . IT DEPENDS ON A COUPLE OF FACTORS. THESE FACTORS ARE:
•The speed of your modem.•The speed of the receiver modem.•The speed of the overall link.•Different types of cabling.
Bandwidth
• Bandwidth determines how fast the connection will be .
Smaller bandwidth means data will travel slowly.Bandwidth is determined by the medium
through which the data are transmitted.
Cost of installation :
1)Terminal cost 2)Server cost 3)Cabling cost 4)Software5)Back up devices6)Modem cost 7)Internet service provider8)Telephone or communication cost9)connectors
