The Network Layer

   Introduction

The Network Layer is Layer 3 in the OSI reference model. It is responsible for transmitting data packets between source and destination nodes that may not be connected by the same physical link.

If the source and destination nodes are not directly connected, the message must pass through a third node, called an "intermediate node." The Network Layer's job is to use intermediate nodes, when necessary, to transmit a packet to its destination.

   Objectives

At the end of this lesson you should be able to:

1.

Explain how a packet address differs from a frame address

2.

Describe how the Network Layer transmits a packet over multiple links

3.

Explain the difference between circuit-switched and packet- switched networks

4.

Explain the difference between connectionless and connection-oriented networks

Key Point
The Network Layer deals with packets. Network Layer addresses are symbolic computer addresses.