TCP/IP Network Stack

TCP/IP is the most commonly used network model for Internet services. Because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP) were the first networking protocols defined in this standard, it is named as TCP/IP. However, it contains multiple layers including application layer, transport layer, network layer, and data link layer.

Application Layer

  • The application layer includes the protocols used by most applications for providing user services.

  • Examples of application layer protocols are Hypertext Transfer Protocol (HTTP), Secure Shell (SSH), File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).

Transport Layer

  • The transport layer establishes process-to-process connectivity, and it provides end-to-end services that are independent of underlying user data.

  • To implement the process-to-process communication, the protocol introduces a concept of port.

  • The examples of transport layer protocols are Transport Control Protocol (TCP) and User Datagram Protocol (UDP).

  • The TCP provides flowcontrol, connection establishment, and reliable transmission of data, while the UDP is a connectionless transmission model.

Internet Layer

  • The Internet layer is responsible for sending packets to across networks.

  • It has two functions:

    • 1) Host identification by using IP addressing system (IPv4 and IPv6);

    • 2) packets routing from source to destination.

  • Examples of Internet layer protocols are Internet Protocol (IP), Internet Control Message Protocol (ICMP), and Address Resolution Protocol (ARP).

Link Layer

  • The link layer defines the networking methods within the scope of the local network link.

  • It is used to move the packets between two hosts on the same link.

  • A common example of link layer protocols is Ethernet.

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