Unit 4: Computer networks
- Most computer systems are now connected together in some way to form what is known as a network.
- To large networks such as the internet which effectively allows any computer connected to it to communicate with any other computer similarly connected.
- Most networks are controlled by the user of servers. There are different types of servers:
+ file servers, which allow users to save and load data/files.
+ applications servers, which deal with the distribution of applications software to each computer.
+ printers servers, which ensure printing from devices on the network is done in a queue
+ proxy servers, which are used as a buffer between WANs and LANs.
- To large networks such as the internet which effectively allows any computer connected to it to communicate with any other computer similarly connected.
- Most networks are controlled by the user of servers. There are different types of servers:
+ file servers, which allow users to save and load data/files.
+ applications servers, which deal with the distribution of applications software to each computer.
+ printers servers, which ensure printing from devices on the network is done in a queue
+ proxy servers, which are used as a buffer between WANs and LANs.
##What is LAN and WAN?##
LAN (local area network)- the connection of all computers in a small area like a room or a building.
WAN (wide area network)- the connection of all computers in a large area like over a building.
WAN (wide area network)- the connection of all computers in a large area like over a building.
* ADVANTAGES OF USING LANs:
+ the sharing of resources
+ communication between users
+ a network administrator to control and monitor all aspects of the network
* DISADVANTAGES OF USING LANs:
+ easier spread of viruses
+ the development of printer queues, which can be frustrating
+ slower access to external networks, such as internet
+ increased security risk when compared to stand-alone (no internet connection) computers
+ if the main server breaks down, in most cases the network will no longer function
+ the sharing of resources
+ communication between users
+ a network administrator to control and monitor all aspects of the network
* DISADVANTAGES OF USING LANs:
+ easier spread of viruses
+ the development of printer queues, which can be frustrating
+ slower access to external networks, such as internet
+ increased security risk when compared to stand-alone (no internet connection) computers
+ if the main server breaks down, in most cases the network will no longer function
There are four common types of LAN network topologies: ring, bus, star and tree networks.
RING NETWORKS
Advantages:
Advantages:
- Ring networks work well under heavy loading
- It is possible to create very large networks by using this topology
- If there is fault in the wiring between two computers then the whole network will fail
- It can be very difficult to add a new device or computer
BUS NETWORKS
Advantages:
Advantages:
- Easy to add a device or computer
- One device/computer fails, it won't affect the rest of network
- It doesn't need a hub/switch and also requires less cabling
- It is difficult to isolate any fault on the network
- If the central line has a fault, the whole network fails
- Increasing outdated topology
- When added more devices/computers, the network will become worse
STAR NETWORKS
Advantages:
Advantages:
- One device /computer fails, it won't affect the rest of network
- The problems are easy to identify and carry out
- It is easy to expand the network
- If the central hub breaks down, the whole network crashes
TREE NETWORKS
Like bus and star network
Like bus and star network
Wireless LANs (WLANs) are similar to LANs but there are no wires or cables.
Access points (APs) are connected into the wired network at fixed locations
receive and transmit data between the WLAN and the wired network structure
Modem is a device which converts a computer's digital signal into an analogue signal for transmission over an existing telephone line
is used to allow computers to connect to networks
Network hubs are hardware devices that can have a number of devices/computers connected to them
Switches are similar to hubs but they are more effective in the way distribute data
Bridges are devices that connect one LAN to another LAN that uses the same protocol
Routers are often used to connect the LANs together and also connect them to the internet
Access points (APs) are connected into the wired network at fixed locations
receive and transmit data between the WLAN and the wired network structure
Modem is a device which converts a computer's digital signal into an analogue signal for transmission over an existing telephone line
is used to allow computers to connect to networks
Network hubs are hardware devices that can have a number of devices/computers connected to them
Switches are similar to hubs but they are more effective in the way distribute data
Bridges are devices that connect one LAN to another LAN that uses the same protocol
Routers are often used to connect the LANs together and also connect them to the internet
What is the advantages and disadvantages of WLANs?
ADVANTAGES:
- All computers can access the same services and resources
- There is no cabling so safety is improved
- The system is more flexible
- Adding new computers/devices is very easy and costs are reduced
- Security is a big problem
- The data transfer rate is slower than in a wired LAN
- There may be problems of interference which can affect the signal
Understand more about the network
The computers will catch the network such as internet by access point (AP). The AP will move the wireless to modem which is connected to hubs/switches.
Hubs/switches distribute data from four types of server included: files servers, printers servers, applications servers and proxy servers.
We will use the bridges to connect a LAN to another LAN
Hubs/switches distribute data from four types of server included: files servers, printers servers, applications servers and proxy servers.
We will use the bridges to connect a LAN to another LAN
modem
the difference between hub and switch
The connection of network
Accessing the internet
An ISP is internet service provider
There is 3 ways of accessing the internet:
There is 3 ways of accessing the internet:
- Dial-up internet access: the slowest type of connection
- Cable internet access: the users can access to the internet through the cable networks by using cable modem
- Broadband modem: we can have the fastest download speeds by using DSL broadband connections
Intranets
An intranet is as well as the internet and an intranet is usually used by the company
The reason why we use an intranet:
The reason why we use an intranet:
- It is safer
- It is easy to prevent the employees from accessing websites that we don't want them to see
- Companies can make sure that the employees can find the specific information they need
- An intranet has limit of finding the information and the internet doesn't have.
- It is possible to prevent certain internet sites by using an intranet but this is much more difficult by using internet
- An intranet has a firewall. To do this with an internet is more difficult
Network security
Network security is included:
- User ID: when we log on to any network system, it will ask a user ID
- Password: password and user ID go together
- Encryption: is the converting of data into a code by scrambling it
- Authentication techniques: is the ways that you prove who you are, like by something you know, something belonging to you, something unique to you.
Communication methods
Communication methods are included fax, email, video conferencing and VOIP
Email
ADVANTAGES:
- Faster when sending and receiving replies
- The low cost
- Not needed to leave home to send the email
- Virus and hackers
- When we send a mail, the email address must be completely correct
- We cannot send another objects like a table by the email
Video conferencing
This is a method of communication between people at two separate locations
VOIP
VOIP ( voice over internet protocol) is a method used to talk to people using the internet and it converts sound too.
The most important of security issues are:
The most important of security issues are:
- Viruses and malware
- Junk mail
- Phishing attacks (the activity of defrauding)