02 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.