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Calculating Total Network Capacity
New submitter slashbill writes "MIT's working on a way to measure network capacity. Seems no one really knows how much data their network can handle. Makes you wonder about how then do you calculate expense when building out capacity? From the article: 'Recently, one of the most intriguing developments in information theory has been a different kind of coding, called network coding, in which the question is how to encode information in order to maximize the capacity of a network as a whole. For information theorists, it was natural to ask how these two types of coding might be combined: If you want to both minimize error and maximize capacity, which kind of coding do you apply where, and when do you do the decoding?'"
This is a synopsis of the first of two papers on the topic.
Didn't read the article, but I imagine that part of the difficulty is that network capacity isn't reducible to an individual scalar number, but rather looks like an N-dimensional graph. There are many points of failure and bottleneck depending on how each node behaves relative to other nodes.
It was a program by one Robert Tappan Morris, as I recall.
That didn't go over so well with everyone.
Best way I've found to measure growth is to have a running history of traffic on each router. You don't need a $billion to do it. There are some decent enough FOSS tools out there to do it. MRTG or Cacti will work nicely and integrate with SNMP.
For a smaller network, you could run a span port and graph your own data with a shell script, or hook up NTOP. which will give you real-time views of traffic but you would need to implement something to save those reports daily.
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From TFS: "Makes you wonder about how then do you calculate expense when building out capacity?"
They're not talking about "not knowing" the capacity of a given network like (e.g. what you buy in the pipe from the datacenter to your ISP. They're talking about the overall bandwidth between 2 points across all possible routings. It's the difference between knowing Ohm's law and computing the net resistance between 2 adjacent nodes on an infinite grid of 1 ohm resistors.
Seems no one really knows how much data their network can handle
Doesn't that shoot a hole in the ISP's anti-bittorrent arguments?
"If any question why we died, Tell them because our fathers lied."
You reduce network capacity, but now your routers need to be smarter, so they're taking longer to encode-decode or you're spending more on hardware to keep throughput the same.
I swear to God...I swear to God! That is NOT how you treat your human!
I dont really think coding is the real bottleneck breaker for getting to the Shannon limit of these channels. I believe a better routing mechanism would be a better approach.
Its not in the box.... Its in the band.
What goes around comes around, kid.
It sounds like they are studying the effect of having intelligent nodes in a network that not just forwards a packet, but also performs error correction, has some basic path intelligence, and sends the packet out multiple interfaces. The end node then receives these hybrid packets from different directions, some coming faster, some later, developing a map with the most efficient path.
One could argue that this could be used, for example, in a mesh MPLS cloud when a path through a specific hop (i.e. office) may be more efficient, because of network conditions, than going straight to the end node. However, this would require each node to have enough bandwidth to support the added traffic, over and above the normal location traffic. Which means requiring a larger budget for bandwidth that is only used in certain degraded conditions.
Basically, it's a study of the Internet and, in my opinion, would have little application in a corporate LAN. The reason why I say this is because a Corporate LAN is more deterministic in path selection and is limited by cost.
and the answer is "It Depends". The traffic, the routing, the overall bandwidth (you never get 100% usage) all have factors. The easiest way is to look at your pipes (each segment is separate) and see the error rates, back pressure (QOS, Ethernet, etc.), average throughput breakdown (types of traffic), and usage percentage. This will give you a clear picture. Take those numbers and watch them over time, and you will get a clear picture of your network.
You cannot answer a question such as this truthfully if you take one sample size, and assume that is fact. Many sample sizes make the true picture, and then you can also see trends to determine if things are getting out of control.
...how to encode information in order to maximize the capacity of a network as a whole...
I always send my data as a series of 0s and 1s. I tried using 2s, but they took up too much bandwidth.
It must have been something you assimilated. . . .
"MIT's working on a way to measure network capacity. Seems no one really knows how much data their network can handle. Makes you wonder about how then do you calculate expense when building out capacity? From the article: 'Recently, one of the most intriguing developments in information theory has been a different kind of coding,
Different from what? Compared to what, and on what context? The sentences preceeding that remark do not make any reference to any coding scheme whatsoever.
called network coding, in which the question is how to encode information in order to maximize the capacity of a network as a whole. For information theorists, it was natural to ask how these two types of coding might be combined: If you want to both minimize error and maximize capacity, which kind of coding do you apply where, and when do you do the decoding?'"
Two? Which is the other? There only mention (in the summary) of the newly proposed coding.
YES, I can infer that, for the most part (and then confirmed from reading the article) that the other coding the summary refers to is error-correcting coding. But it shouldn't be necessary to neither rely on prior knowledge (which varies from person to person) nor read TFA to find EXTREMELLY IMPORTANT information that is missing from a summary. A summary cannot leave crucial pieces out. Moreover, there are other types of coding related to information transmission (compression coding for instance) so at worst (and without having to rely on TFA), the summary is not just incomplete, but ambiguous.
I'm not trying to be mean or being a gramm3r nazi. Just remember to proof read your summaries.
Just right size individual components right from storage to client level...check the average bandwidth used at all levels and allocate accordingly. Its like asking how many molecules of water in a glass..when you know you only need to drink one glass of water ... And wouldnt traffic/second increase or decrease with the choice of medium and communication protocol used over same distance.
I come to Slashdot only to read sigs. One you are reading is mine.
That ideal encoding method isn't XML.
Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats. -HLM
Microsoft's Baseline Analyzer doesn't cut it anymore? ;-)
OPNET- great tools, horrific price...
Dave
Release Diablo III...
Not one Nerd dare crack open the CAFR?
Not one Nerd dare wear a badge and go after the banks?
Not one Nerd dare restore the US Constitution?
What's your fucking excuse?