It is known that the boundary between the router and its link is called as interface. Also, the boundary between the host and the physical link is also called an interface.
Consider that there are three routers between source host and destination host as shown below:
• The numbers in the above diagram represents the interfaces.
• Since the fragmentation functionality is ignored, there is no need to split the IP datagram into fragments.
• Source forwards the IP datagram to link interface 1.
• First router(R1) receives the datagram from interface 2 and outputs the datagram to interface 3.
• Second router(R2) receives the datagram from interface 4 and outputs the datagram to interface 5.
• Third router(R3) receives the datagram from interface 6 and outputs the datagram to interface 7.
• Destination host receives the IP datagram from the link interface 8.
Thus, the original IP datagram that is sent from source to destination will travel over the all eight interfaces that are exist between source and destination.
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