hi
i want to ask is data link layer only used on LANs?....as i read in a book that when a packet is transfered from one router to another it is in network packet format. and when it reaches a LAN on which the destination computer is attached, the router encapsulates it in a data link layer frame
The meaning is come from a fact that: Switch, can encapsulate the data up to layer 2 "DATA Link Layer" Router, can encapsulate the data up to layer 3 "Network Layer"
and so,
on the level of the LAN, the only needed is "switch", which means that the devices in the LAN will read from Layer 1 up to only Layer 2. which yields to usage only of the first two layers in the OSI model in the LAN.
The data link is the second layer in ISO-OSI (Open System Interconect) and egsists in every communication systems, not just 802.3 lans.
Actualy not all of the 7 layers of the osi have to egzist in a communication system but the lower layers allmost allways egzist.