Ethernet Delivers the Internet


Think back now to our first movie in our Ethernet series, the Ethernet Tutorial. You’ll remember that that tutorial revealed that a lot of the design for Ethernet is based on the behavior of telegraph operators. Remember that as telegraph operations matured, the format for messages became standardized. As telegraph operators sent a message, the first part of each message was a description of the destination telegraph office: the destination address to receive the telegram. After the destination address, the telegram included the source address. In essence, each telegram started with a preamble that said something like, “Telegram to Salt Lake City, from Denver”. After those sections of a telegram identifying the receiving station, and the sending station, the main body of the text was transmitted.



Take a closer look at this telegram text.

You’ll see it contains a street address. This is a message within the telegram: a message within the message. And this additional addressing is necessary because telegraph addresses didn’t go everywhere; every home did not have a telegraph receiver. A telegraph operator could address the city and get to an area, but ultimate delivery of the telegram contents to a person’s home required an additional address. A boy on a bicycle would sometimes carry a hard-copy printout of a telegram to a person’s house using the addressing information contained inside the telegram.

 

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