IP
- Each packet consists of a structure header and data.
- The header helps route, fragment and process packets efficiently.
- Packet switching ensures interleaved and reliable data transmission.
TCP
- TCP runs on top of IP, ensuring lost packets are retransmitted.
- Establishes a connection-oriented communication model.
- Guarantees ordered, complete, and error-checked data transfer.
TCP Socket
- A TCP connection is defined by (Destination IP, Destination Port, Source IP, Source Port).
- The destination port depends on the service :
- Web (HTTP) → Port 80
- Secure Shell (SSH) → Port 22
- DNS → Port 53
- The source port is usually chosen randomly.
DNS
- DNS translates names into IP addresses via a hierarchical system.
- Requests first go to the ISP’s DNS resolver, then higher-level DNS servers.
- The authoritative DNS server provides the correct IP.