Computer Networks and Hardware essentials

 Network Communication

  • In data communication, a Kilobit is one thousand bits.
  • It is used to measure the amount of data transferred per second.
  • Kilobits per second is shortened to kb/s, Kbps or kbps.
  • Lower case b is used to represent bits while the upper-case B is used for Bytes.
  • The "K" stands for 1024.
  • The "k" stands for 1000.
  • Download KBPS speed = (Kbps value*1000) /8)) / 1024.
 Components of Networks

  • A network interface card (NIC) is a hardware component, typically a circuit board or chip, 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. Network media can also be the air waves, as in wireless networks. 
  •  Interconnecting device—allow two or more computers to communicate on the network without having to be connected directly to one another.
Protocols—define the rules and formats a computer must use when sending information across the network (e.g. TCP/IP protocol stack).
NIC driver—receives data from protocols and forwards this data to the physical NIC.

  •  Each step required for a client to access network resources is referred to as layer.
How Two Computers Communicate on a LAN: Some Details 
• TCP/IP is the most common protocol (language) used on networks 
• TCP/IP uses 2 addresses to identify devices:
• Logical address (IP address) • Physical address (MAC address)
 • Just as a mail person needs an address to deliver mail, TCP/IP needs an address in order to deliver data to the correct device on a network.

Network Terminology: Internetworks
  • An internetwork is a collection of LANs tied together by devices such as routers.
  • Reasons for creation: 
  •   Two or more groups of users and their computers need to be logically 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.
PAN: Personal Area Network is a group of network devices that allow communication between various connected devices.
LAN: Local area network is a group of network devices that allow communication between carious connected devices.
  • Private ownership has control over the local area network rather than the public.
  • LAN has got a shorter propagation delay as compared to MAN and WAN because they only have to cover smaller areas such as colleges, schools, hospitals and so on.
Wireless LAN– A wireless LAN is a wireless computer network that links two or more devices using wireless communication to form a local area network within a limited area such as a home, school, computer laboratory, campus, or office building devices in a small geographic area.

Metropolitan Area Networks (MANs) – It covers a larger area than LAN such as small towns, cities, etc. 
  • MAN connects two or more computers that reside within the same or completely different cities. MAN is expensive and should or might not be owned by one organization.

Wide Area Networks (MANs) – It covers a large area than LAN as well as a MAN such as country/continent etc.
  •  WAN is expensive and should or might not be owned by one organization. PSTN or satellite medium is used for wide area networks.
Reserved for private networks. 
● The organizations that distribute IP addresses to the world reserves a range of IP addresses for private networks. 
○ 192.168.0.0 - 192.168.255.255 (65,536 IP addresses) 
○ 172.16.0.0 - 172.31.255.255 (1,048,576 IP addresses) 
○ 10.0.0.0 - 10.255.255.255 (16,777,216 IP addresses) 

The main difference between a private and a public address is how far they can reach and to what they are connected to.
A public IP address identifies you to the wider internet so that what you are searching for can find you.
A private IP address is used within a private network to connect devices within that same network.
Each device within the same network has unique private address.

When data leaves your computer, they are grouped into small chunks called packets.

Computers transfer information across networks in shorts bursts of about 1500 bytes of data (bursty – unlike video streaming) 
Reasons for transferring data as mentioned above are because:
  • Pause between bursts allows other computers to transfer data during pauses
  •   Allows the receiving computer to process received data 
  • Allows the receiving computer receive data from other computers at the same time 
  •  Gives the sending computer an opportunity to receive data from other computers and perform other processing tasks.
  •  If an error occurs during transmission of a large file, only the chunks of data involved in the error have to be sent again. 
Packets: a chunk of data with a source and destination IP address added to it.
Frames: a packet with a source and destination MAC address added to it.

The process of adding MAC and IP addresses to chunks of data is known as encapsulation.




 

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