Internet Protocol Suite

The TCP/IP suite uses encapsulation to provide abstraction of protocols and services. Such encapsulation usually is aligned with the division of the protocol suite into layers of general functionality. In general, an application (the highest level of the model) uses a set of protocols to send its data down the layers, being further encapsulated at each level.

This may be illustrated by an example network scenario, in which two Internet host computers communicate across local network boundaries constituted by their internetworking gateways (routers).

The functional groups of protocols and methods are the Application Layer, the Transport Layer, the Internet Layer, and the Link Layer(RFC 1122). It should be noted that this model was not intended to be a rigid reference model into which new protocols have to fit in order to be accepted as a standard.

The following table provides some examples of the protocols grouped in their respective layers.

Application

DNS, TFTP, TLS/SSL, FTP, Gopher, HTTP, IMAP, IRC, NNTP, POP3, SIP, SMTP,SMPP, SNMP, SSH, Telnet,Echo, RTP, PNRP, rlogin, ENRP

Routing protocols like BGP and RIP which run over TCP/UDP, may also be considered part of the Internet Layer.

Transport

TCP, UDP, DCCP, SCTP, IL, RUDP, RSVP

Internet

OSPF for IPv4 was initially considered IP layer protocol since it runs per IP-subnet, but has been placed on the Link since RFC 2740.