By Art Reisman
CTO – APconnections
Have you ever been on a shared wireless network, in a Hotel , or Business, and noticed how your connection can go from reasonable to completely unusable in a matter of seconds, and then cycle back to usable ?
The reason for this , is that once a network hits its bandwidth allocation, the providers router usually just starts dropping the excess packets. Intuitively, when your router is dropping packets, one would assume that the perceived slow down, per user, would be just a gradual shift slower.
What happens in reality is far worse…
1) Distant users get spiraling slower responses.
Martin Roth, a colleague of ours who founded one of the top performance analysis companies in the world, provided this explanation:
“Any device which is dropping packets “favors” streams with the shortest round trip time, because (according to the TCP protocol) the time after which a lost packet is recovered is depending on the round trip time. So when a company in Copenhagen/Denmark has a line to Australia and a line to Germany on the same internet router, and this router is discarding packets because of bandwidth limits/policing, the stream to Australia is getting much bigger “holes” per lost packet (up to 3 seconds) than the stream to Germany or another office in Copenhagen. This effect then increases when the TCP window size to Australia is reduced (because of the retransmissions), so there are fewer bytes per round trip and more holes between to round trips.”
In the screen shot above (courtesy of avenida.dk), the Bandwidth limit is 10 Mbit (= 1 Mbyte/s net traffic), so everything on top of that will get discarded. The problem is not the discards, this is standard TCP behaviour, but the connections that are forcefully closed because of the discards. After the peak in closed connections, there is a “dip” in bandwidth utilization, because we cut too many connections.
2) Once you hit a congestion point, where your router is forced to drop packets, overall congestion actually gets worse before it gets better.
When applications don’t get a response due to a dropped packet, instead of backing off and waiting, they tend to start sending re-tries, and this is why you may have noticed prolonged periods (3o seconds or more) of no service on a congested network. We call this the rolling brown out. Think of this situation as sort of a doubling down on bandwidth at the moment of congestion. Instead of easing into a full network and lightly bumping your head, all the devices demanding bandwidth ramp up their requests at precisely the moment when your network is congested, resulting in an explosion of packet dropping until everybody finally gives up.
How do you remedy outages caused by Congestion?
We have written extensively about solutions to prevent bottlenecks. Here is a quick summary of possible solutions
1) The most obvious being to increase the size of your link.
2) Enforce rate limits per user. The problem with this solution is that you can waste a good bit of bandwidth if the network is lightly loaded
3) Use something more sophisticated like a Netequalizer, a device that is designed to specifically counter the effects of congestion.
From Martin Roth of Avenida.dk
“With NetEqualizer we may get the same number of discards, but we get fewer connections closed, because we “kick” the few connections with the high bandwidth, so we do not get the “dip” in bandwidth utilization.
The graphs (above) were recorded using 1 second intervals, so here you can see the bandwidth is reached. In a standard SolarWinds graph with 10 minute averages the bandwidth utilization would be under 20% and the customer would not know they are hitting the limit.”
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The excerpt below was a message from a reseller who had been struggling with congestion issues at a hotel, he tried basic rate limits on his router first. Rate Limits will buy you some time , but on an oversold network you can still hit the congestion point, and for this you need a smarter device.
“…NetEq delivered a 500% gain in available bandwidth by eliminating rate caps, possible through a mix of connection limits and Equalization. Both are necessary. The hotel went from 750 Kbit max per accesspoint (entire hotel lobby fights over 750Kbit; divided between who knows how many users) to 7Mbit or more available bandwidth for single users with heavy needs.
The ability to fully load the pipe, then reach out and instantly take back up to a third of it for an immediate need like a speedtest was also really eye-opening. The pipe is already maxed out, but there is always a third of it that can be immediately cleared in time to perform something new and high-priority like a speed test.”
Rate Caps: nobody ever gets a fast Internet connection.
Equalized: the pipe stays as full as possible, yet anybody with a business-class need gets served a major portion of the pipe on demand. “
Are those rate limits on your router good enough?
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Together We Can Put an End to Pop Up Advertisements
October 5, 2016 — netequalizerNormally I would not advocate something like I am about to propose, but those pop up video advertisements are just killing me. Especially when I am using my wireless device as a hot spot, these unwanted annoyances add insult to injury by draining my precious data usage. Yes, I have ad blockers on my browsers, but it is only a matter of time before they are subverted with some new technology. There is a better way to put an end to Pop up Advertisements but it will take a village to make a difference.
Believe it or not, the best way to put an end to unwanted advertisements is to click on them and then quickly abandon the resulting web page. Abandonments are the bane of the Marketing world. Here is why…
In traditional media a marketing team plays an advertisement/commercial for a known demographic at a fixed price, whether it be Television, Newspaper, Magazine, etc. They then measure the effectiveness of the advertisement by the increase in leads or sales over the period of time that the advertisement runs.
Digital pop advertisements are a bit different. It is a pay-for-click scheme where the advertiser gets charged by the click. They blast these annoying advertisements to perhaps a million people with no real cost consequences, (other than fraud, but that is another story) because they do not pay unless people click on their ad. As the people who click on the advertisements are very likely their target audience, this model is very efficient. Advertisers love this model, as it allows them to essentially only pay advertising dollars to a self-qualified audience. After all, who clicks on an advertisement unless they have some level of interest in the product to start with?
However, if we consumers and web users rise up and just simply click on one or two web pop up ads a day that we have no interest in, the practice of bombarding us will come to end.
Why? Because the cost of these extra clicks will make their advertising campaign much less efficient. The advertiser is looking for a return on investment, and the more clicks with no follow through sale that happen, the more unpalatable pop up ads will become.
If you too are annoyed by pop up ads, please share this article. Let us see if we can drive these advertisers back into the margins of our web pages, and get them out of our faces. I cannot do this alone.
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