Points to Remember

• Connection-oriented protocols ensure that the sequence of data packets is the same at the source and destination nodes. These protocols are also called reliable protocols.

• Connectionless protocols do not send data packets in the same sequence at the source and destination nodes. These protocols are called unreliable protocols.

• Examples of connection-oriented protocols are Type 2 service of IEEE 802.2, ATM, TP0, TP1, TP2, TP3, and TP4, and TCP.

• Examples of connectionless protocols are Type 1 and 3 services of IEEE 802.2, CLNP, IP, and FST.

• The Data-link layer uses three types of protocols: PPP, SDLC, and HDLC.

• The primary protocol used on the Network layer is IP, which routes data packets from the source to the destination node in a network.

• The Transport layer of the OSI model uses TCP and UDP protocols for transferring data through the network. TCP is responsible for the connection-oriented data transfer, whereas UDP provides connectionless data transfer.

• The Session, Presentation, and Application layers are concerned with the applications accessed by end users. Examples of protocols residing on these layers are RIP, IGRP, and EIGRP.