The TCPIP Model

The TCP/IP Model

The TCP/IP model layers are

• Network interface ” Assembles data packets into Ethernet frames , handles the transmission across the physical network, and detects errors using a CRC. Uses Ethernet (or MAC) addresses at this layer. Protocols are Ethernet, SLIP, and PPP.

• Internet ” Responsible for routing of data packets (IP datagrams) and fragmentation. Uses IP addresses at this layer. Protocols are IP, ICMP, ARP, and RARP.

• Transport ” Responsible for end-to-end delivery through sequencing, acknowledgements, and flow control. Uses port numbers at this layer. Protocols are TCP and UDP.

• Application ” Interacts with running processes, such as email and Web browsers. Handles data format, presentation and session connections. Protocols are Telnet, SMTP, HTTP, DNS, DHCP, and FTP.

The model uses peer-to-peer communications ”each layer communicates with only its peer on the remote host. Encapsulation occurs on the sending host, where each layer adds header information to the data before passing it to the next layer. At the receiving end, each layer interprets the control information for the relevant layer (known as decapsulation).