Network interface Card (NIC) 

NIC is an electronic circuit board used to connect computer to a Local Area Network (LAN).

• Each NIC has a media access control address (MAC address).
• MAC address is unique identifier assigned by the manufacturer.
  Mac address stored in card's read-only memory.
• MAC addresses used as physical host address for IEEE 802 network technologies.
• When computers boots up the NIC broadcast it's MAC address

and obtain an IP from the Network Switch.

A wireless Network Card


Ethernet

Ethernet is the most widely installed local area network (LAN) technology.
and support IEEE 802.3 standard with higher bit rates and longer link distances.

Ethernet support 10BASE5 Ethernet (coaxial cable) and 10BASET (twisted pair) and fiber optic with hubs and switches.
Data transfer rates have been increased latest 100 gigabits per second (Gbit/s).

How Ethernet transmit data
Ethernet transmission divide data into frames. Each frame contains the source and destination addresses, and error-checking data. Error-checking data used to discard or accept messages.
Ethernet uses a 48-bit MAC address and frame format.


Computer  Network Diagram

Advantages of networks

• Sharing devices such as printers saves money.
• Site (software) licences are likely to be cheaper than buying several standalone licences.
• Files can easily be shared between users.
• Network users can communicate by email and instant messenger.
• Security is good - users cannot see other users' files unlike on stand-alone machines.
• Data is easy to backup as all the data is stored on the file server.
  
  

Network Disadvantages

• Purchasing the network cabling and file servers can be expensive.
• Managing a large network is complicated, requires training and a network manager usually needs to be employed.
• If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated.
• Viruses can spread to other computers throughout a computer network.
• There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.

INTERNET is a network of Networks