MTU

Problem

A packet travels through physical networks. But each network has a maximum packet/frame size it can carry. For example, Ethernet commonly allows an IP packet around: 1500 bytes What happens if you try to send something larger?

Solution — MTU

Each link has a Maximum Transmission Unit defining the largest IP packet it can carry without fragmentation at that link. Ethernet MTU = 1500

Core idea: MTU is the size limit imposed by the network carrying the IP packet.