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Networking Concepts

TCP/IP Model​

  • TCP / IP Models contains the following 5 layers.
    • Physical Layer
    • Link Layer
    • Internet Layer
    • Transport Layer
    • Application Layer
      • Combines 3 layers (Application, Presentation and Session) into a single layer.

IP Address​

  • Find ip address using the command
    • ipconfig - Windows
    • ifconfig or ip address show or ip a s - Linux
  • There are two types of IP addresses.
    • Private
    • Public
  • RFC 1918 defines the following three ranges of private IP addresses: 
    10.0.0.0 - 10.255.255.255 (10/8)
    172.16.0.0 - 172.31.255.255 (172.16/12)
    192.168.0.0 - 192.168.255.255 (192.168/16)

Subnets​

  • Subnet mask of 255.255.255.0 can also be written as /24.
  • /24 means that the leftmost three octets are the same across the whole subnet.
  • In this case the subnet range would be 192.168.66.1 to 192.168.66.254.

Ports​

  • IP address identifies the host.
  • Port determine the sending and receiving process.
  • Port numbers ranges between 1 to 65535 (2^16 - 1).

UDP and TCP​

  • UDP is fast but unreliable.
  • TCP is reliable but slow.
  • TCP connection is established using a three-way handshake.
    • Client intiates a connection by sending a SYN packet to the server.
    • Server responds to the SYN packet with SYN-ACK packet.
    • Client acknowledges the reception of SYN-ACK packet by sending an ACK packet to the server.

Encapsulation​

  • Process of adding the header at each layer and forwarding it as a unit.
  • At transport layer, TCP adds the header information and creates a TCP segment.
  • At transport layer, UDP adds a header information and creates a UDP datagram.
  • At the network layer, header is added to get an IP Packet.
  • At the link layer, Header and trailer is added to get a wifi or ethernet frame.

Telnet​

  • Telnet (Teletype Network) is a network protocol for remote terminal connection.
  • Telnet allows the user to connect and ommunicate with the remote system.