Due to my new role, I have been thinking a lot about how modern network architecture has evolved over the years. \u00a0When I first entered networking it was the “cool” thing that we did so that we could play Doom in our fraternity house with a bunch of other guys. \u00a0That was the old 10Base-2 connectors. \u00a0I quickly graduated to a real job shortly after pulling and terminating cables and in some cases repairing the old baseband systems that we can thank IBM for in schools. \u00a0But really since the standardization of cable around Cat5 or Cat6 – haven’t we come a long way? \u00a0Yes I realize that things can interfere with cable such as electrical current, but for the most part if you have well terminated copper cable you can run at a minimum 100M without a problem.<\/p>\n
This got me thinking to why were networks ever built to plan for dropped packets. \u00a0Did it go back to the original ARPAnet design that we wanted to be able to survive a nuclear blast? \u00a0 Yes we all know that this rumor is not true, but in fact part of ARPAnet was to be able to work across an unreliable medium. \u00a0Is this why protocols were built on top to compensate for \u00a0this problem with reliable delivery? \u00a0Does that same problem with a reliable medium still exist today? \u00a0If not, how would we change our network architectures? \u00a0These questions plagued me for the last month or so and hence I decided to do some research.<\/p>\n
Here are a couple thoughts:<\/p>\n
Dropped Packets Suck in the Data Center!<\/strong><\/p>\n Whether it is from oversubscription or a microburst in the network, dropped packets in large suck. \u00a0This problem is only going to get worse as we increase the speeds of the networks. \u00a0Are you aware that on a 10Gb Ethernet link, that a single second of dropped packets will spew ~15M packets onto the datacenter floor. \u00a0Worse yet is that we are in an era of now 40Gb ethernet and soon to be 100Gb Ethernet. \u00a0Yes that math is correct that a single second of impediment on 100Gb ethernet would throw away 150 million packets (assuming the smallest frame size). \u00a0I don’t care what application you are using if you lose 150M packets, the user experience is going to be bad.<\/p>\n This makes me ask the question, why would you ever build a datacenter network that is massively oversubscribed? \u00a0You could suggest that you are playing the economics game…explain that to your CIO when the #1 revenue producing application is down. \u00a0You could also hypothesize that it is only oversubscription if everyone talks at the same time…which I understand. \u00a0The premise that I am suggesting is that we should never build a network that works “in a perfect world.” \u00a0Believe me I have seen some of the finest pieces of powerpoint engineering that in practice fail worse than Ben Affleck and Gigli did in 2003.<\/p>\n