Computer Networks & Hardware essentials

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 Network communication

  • 1kb/s = 1000 bits per second 
  • 1KB/s= 1021 bytes per second
 File size is always measured in kilo Bytes and download speeds are always calculated based on how many bytes per second are downloaded and hence kilobytes and kilobits are interchangeable. (512 kbps can never achieve a download speed of 512 KBps)

Components of networks
  • Network interface card (NIC):  a hardware component which is installed on a computer so it can connect to a network.
  • Network medium: A cable that plugs into the NIC and makes the connection between a computer and the rest of the network.
  • Interconnecting device: allows two or more computers to communicate on the network without having to be connected directly to one another.

Software components
  • Network client software: Requests information stored on another network computer or device.
  • Network server software: Allows a computer to share its resources.
  • Protocols: Defines the rules a computer uses when sending information across the network.
  • NIC driver: Receives data from protocols and forwards this data to the physical NIC.
Network Communication Process
1. An application tries to access a network resource.
2. Client software detects the attempt and passes the message to the network protocol.
3. The protocol packages the message in a suitable format and sends it to the NIC driver.
4. The NIC driver sends the data in request to the NIC card (converts it into necessary signals to be transmitted across the network medium).

  •  TCP/IP is the most common protocol (language) used on networks.
  • TCP/IP uses logical address (IP address) and physical address (MAC address) to identify devices.
Broadcast IP Address
It was designed to facilitate message broadcasting for all network devices.

How two computers communicate on LAN
  1. Comp A types ping 192.168.0.1 at command prompt.
  2. Network software creates a ping message.
  3. The network protocol packages the message by adding IP address of sending and destination computers and acquires the destination computer's MAC address.
  4. The network interface software adds MAC address of sending and destination computers.
  5. Comp B receives the message, verifies the message and sends a reply to Comp A.


Network Terminology: Internetworks
  • An internetwork is networked collection of LANs tied together by devices such as routers.
Reasons for creation:
  • Two or more group of users and their computers need to be separated but still need to communicate.
  • Number of computers in a single LAN has grown and is no longer efficient.
  • The distance between two groups of computers exceeds the capabilities of most LAN devices.



Personal area network (PAN):
It is a group of network devices that allow communication between various connected devices.

Local area network (LAN):
It is a group of network devices that allow communication between various connected devices.

Wireless LAN:
It is a wireless computer network that links two or more devices using wireless communication to form a local area network within a limited area.

Metropolitan Area Network (MANS):
  • It covers a larger area than LAN such as small towns, cities and many more.
  • Connects two or more computers that reside within the same or completely different cities.
  • It is expensive.
Wide area network (WAN):
  • It covers a large area than LAN as well as MAN such as country/continent etc.
  • It is expensive.
Internet:
  • It is a worldwide public internetwork.
  • Uses protocols such as TCP/IP and HTTP to transfer and view information.
Intranet:
A private internetwork in which devices and servers are only available to those users connected to the internal network.

Extranet:
Allows limited and controlled access to internal resources by outside users.

Difference between Private IP Address and Public IP Address

Packet and frames
Computer transfer information across networks in short bursts of about 1500 bytes of data.

Reasons data is transferred this way:
  • Pause between bursts allow other computers to transfer data.
  • Allows receiving computer to process received data.
  • Allows receiving computer to receive data from other computers.
  • Gives sending computer an opportunity to receive data from other computers and perform other tasks.
  • If an error occurs during the transmission, only chunks of data involved in the error have to be sent again.
Packet: A chunk of data with a source and destination IP address added to it.

Frame: A packet with the source and destination MAC addresses added to it.

Client:
The word 'client' is used in three contexts:
  • Client operating system: OS installed on a computer.
  • Client computer: Primary role is to run user applications and access network resources.
  • Client software: Software that requests network resources from server software on another computer.
Server:
The word 'server' is also used in three contexts:
  • Server operating system: OS installed on a computer designed to share network resources.
  • Server computer: A computer's primary role is to give client computers to access to network resources.
  • Server software: Responds to requests for network resources from client software.









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