Answer to Question #322688 in Computer Networks for Cubic

Question

1.      Suppose end system A wants to send a large file to end system B. At a very high level, describe how end system A creates packets from the file. When one of these packets arrives to a router, what information in the packet does the router use to determine the link onto which the packet is forwarded? Why is packet switching in the Internet analogous to driving from one city to another and asking directions along the way?

Answer 1

When sending large files from end system A to end system B, the file is first divided into chunks by end system A. Each chunk is then assigned a header by the same end system A thus creating a packet. The header in each packet contains the destination address.

The router uses the destination address in the IP header to determine where each received packet will be forwarded to and which network interface will be used when sending the packet.

Packet switching in the internet is analogous to driving from one city to another and asking directions along the way because of the packet’s nature of asking which outgoing link it should be forwarded on. As each packet contains a destination address, this specifies the outgoing link it should be forwarded on when it reaches the packet switch.