Unit 28 - D1

TCP/IP protocols map to four layers. These four layers are; application, transport, internet and network interface. Each layer in the model links to one or more layers of the seven layer open systems interconnection model. The seven layers are the; application layer, presentation layer, session layer, transport layer, network layer, data-link layer and physical layer.

Internet Layer - This is responsible for addressing, packaging and routing functions. The protocols for the Internet layer are IP, ARP, ICMP and IGMP.

The Internet Protocol (IP) - This is the routable protocol responsible for IP addressing, routing and the breaking up and reassembly of packets.

The Address Resolution Protocol (ARP) - This is the resolution of the internet layer address to the network interface layer address such as a hardware address.

The Internet Control Message Protocol (ICMP) - This provides problem solves and reporting errors due to the unsuccessful delivery of IP packets.

The Internet Group Management Protocol (IGMP) - This is for the management of IP multicast groups.


Transport Layer
This provides the application layer with session and datagram communication services. The protocols of the transport layer are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).

TCP
This provides a connection oriented and reliable communications service. The sequencing and acknowledgment of packets sent, and the recovery of packets lost during transmission.

UDP
This provides many connectionless and unreliable communications service. UDP is used when only small amounts of data are transferred. When the overhead of establishing a TCP connection is not wanted or when the upper layer protocols provide good delivery.

Application Layer
This gives applications the ability to access other layers and defines the protocols that applications use to exchange data. There are many application layer protocols and new protocols are always being created. The most popular application layer protocols are those used for exchanging user information. These are HTTP, FTP and SMPT.

The Hypertext Transfer Protocol (HTTP)
This is used to transfer files that make web pages for the internet.

The File Transfer Protocol (FTP)
This is used for the interactive file transfer.

The Simple Mail Transfer Protocol (SMPT)
This is used so the transfer of mail messages and attachments work.