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Why is a network switch like a post office?

by | Jul 30, 2020 | Blog

Register for our next webinar! Tuesday, August 4 | 10 AM

This installment of our networking education series will help you understand how a switch works, why packet size and buffering matters, and more. Featuring BCD’s Darren Giacomini and a special guest from the networking world, this webinar will expose technical concepts in an easy to understand format.

Imagine this post office is actually a network switch, sitting on your video surveillance network.

This Post Office – your switch – has one job. It is supposed to take packets of information that are sent to it from a sender (like an IP camera) and see to it that these packets are properly addressed and sent along the proper pathway for delivery.

As these packets arrive at the switch- letters at the post office- they are kept in a buffer, waiting for their turn to be sorted. Think of a buffer as a bag of mail that is full of letters; our Post Office can hold 1000 of these bags.

The internet, and many of the devices that run it and are seen and used each day, was designed for “bursty” traffic. Think of your old-school mailman; he would stop at the end of the street, grab his bag of mail for that spot, and trudge off to deliver the mail. When he was done, he’d drive off and do it again on the next street, and so on. When his mail truck was empty he would head back to base for more mail.

Video traffic of all kinds is rather constant…until it is not, and suddenly becomes bursty. Just like letters that have to be in order to make a word, video traffic has to be in order to make it easy to decompress and view. Imagine that our orderly delivery of letters, fitting so nicely through the mail slot, suddenly became a torrent of letters of all different sizes trying to squeeze through the slot at the same time.

Back at the post office, we now know that our “packets” of mail are streaming into the building non-stop. OK, not a problem, we have highly trained people on the job seeing that each incoming letter is routed correctly.

What happens when the volume of mail exceeds the space in the post office? What happens if the sheer volume of letters is too much for the guys to handle?

The size of the post office determines how many letters we can fit within and our Post Office can hold 1000 bags. When those 1000 bags are each filled to overflowing, our intrepid mail workers above start making mistakes. Eventually, they simply throw away all the letters and start fresh!

Not all Post Offices are the same size, of course. Some are small as is the one in our example, while others are simply huge and have hundreds of times the space of our little building.

To further complicate the whole situation, each letter may not be the same size. Indeed, some are not letters at all but as seen in the illustration above they are parcels, boxes, soft-sided envelopes, and more. Each one of these takes up space within a bag inside our office and reduces the overall total pieces of mail we can have waiting for sorting. These larger items are usually not a problem but if we suddenly find ourselves overwhelmed, those bigger parcels have taken up space normally reserved for our smaller letters which have no place to go. If we are lucky the mail carrier will just circle the block and wait for a chance to drop off the outbound letters. If the Post Office is truly stuffed those letters may be discarded.

The role of the switch in any network is important. In video surveillance, and in hHCI systems that purport to be video-centric it is perhaps the single most important part of the hardware decision.

Does the switch you chose have the proper buffer to deal with the things video surveillance can create?

If you are not sure, contact us and find out.