Sluggish WiFi Connections Hurt Everyone 232
MindNumbingOblivion writes "Wireless technology has revolutionized access to local area networks when one can't always be close to an ethernet jack. But a recent research paper from the French Centre Nationale de la Recherche Scientifique tells how one slow user accessing a hot point can hurt the whole group. Apparently the very nature of CSMA/CD guarantees such anomalies. Here's the story, and here's the release from CNRS (in French)."
Taking bets on (Score:5, Interesting)
I say about 1 month, maybe less. Any takers?
Re:Taking bets on (Score:5, Informative)
"Wlan Jack" can send fake disassociation packets, which disconnects clients from an AP. As long as its running, nobody would be able to lock onto an access point.
I also imagine someone could do something that would just flood noise into the spectrum that would kill the connection better than somebody just hogging it at 1 Mbps.
Re:Taking bets on (Score:5, Interesting)
interesting,
I really, really hate Starbucks...
Re:Taking bets on (Score:5, Funny)
Yeah, or you could use a pair of wirecutters and cut their phone line, with less investment ($2) and chance of being busted. Or just throw rocks through their windows.
Re:Taking bets on (Score:4, Funny)
Re:Taking bets on (Score:5, Funny)
Re:Taking bets on (Score:2)
Yes, but taping the box under a table and leaving it there permanently isn't. Especially since it'll probably get you sent to Camp X-ray.
Re:Taking bets on (Score:2)
OT, but I have to ask.
Why? In some parts of the country it is the only place that serves decent coffee. I know several girls who went through HS and college working at Starbucks for better money than they could make elsewhere.
Re:Taking bets on (Score:4, Informative)
In the Australian context where we already have a thriving independent cafe culture, Starbucks is offering an inferior product and using marketting size and brand recognition to crush smaller players (plus wireless access).
If their coffee was better than the alternatives I wouldn't get so riled up,
Re:Taking bets on (Score:2)
Re:Taking bets on (Score:2)
Re:Taking bets on (Score:2)
Re:Taking bets on (Score:2, Insightful)
Re:Taking bets on (Score:2)
Re:Taking bets on (Score:2)
Re:Taking bets on (Score:3, Interesting)
You forgot a few options:
Re:Taking bets on (Score:2)
No. It's consumerism. Capitalism says something about better products and services rising to the top. Starbucks ain't got it.
What Starbucks does have is shitty coffee. Overroasted, nasty, burnt up coffee. That, and several layers of middle management straight from the ranks of Taco Bell and Burger King. Which is why many of the comapany's earliest employees left years ago. They realized that quality was being sacrificed in the name of profit and logo.
The proliferation of Starbucks has less to do wi
Re:Taking bets on (Score:2)
How do you know it's an inferior product? Do you even know what the product is? To me, Starbucks sells me an environment where I can study, plug in my laptop, and/or meet people for the price of a cup of coffee. To others, Starbucks means decent wages and benefits for their workers.
Re:Taking bets on (Score:2)
go drink your swill and support the corporate goliath, I'm not stopping you.
If there's no better alternative I suppose I'll end up there myself.
But make your own judgments instead of being offended, not by the subtance of others judgements, but that they make them at all.
Re:Taking bets on (Score:2)
No, I prefer to live in a world where each individual makes his/her own judgement.
"But make your own judgments instead of being offended, not by the subtance of others judgements, but that they make them at all. "
I am not offended. I am just worried that some of you would be willing to take away my own individual right to chose. Not that you all think that way. If you don't, then my apologies, my message wasn't directed at
Re:Taking bets on (Score:2)
also the exchange students, diplomatic community, international visitors, anyone who's new to town and doesn't know which cafe to go to but knows Starbucks is "safe"
same reason i end up eating breakfast at Macdonalds when I'm in tokyo.
Plus as others have mentioned big boys can rnu at a loss for a long time until they drive the competition out of the market.
most cafes can run at a loss anything from 1 week to a couple of months.
Re:Taking bets on (Score:2)
Took me a while to get used to Starbucks, but now I'm okay with it. So yeah, I call it decent.
Re:Taking bets on (Score:2)
Not likely (Score:3, Interesting)
Jamming (Score:4, Interesting)
Re:Jamming (Score:2, Funny)
Lord Helmet: Rasberry! There's only one man who would dare give me the rasberry! Lonestaaarrrr!.
Re:Taking bets on (Score:3, Insightful)
Re:Taking bets on (Score:1)
That wouldn't do anything to them. Buy a dozen microwaves or 2.4GHz phones perhaps, but 900MHz isn't anywhere near the 802.11b spectrum.
I think you mean 2.4 Ghz phones (Score:2)
Re:Taking bets on (Score:2)
Why can't we make it so that the fast user gets 54 mbit and the slow user gets one?
plagiarist Re:Taking bets on (Score:2)
I foresee lynchings (Score:5, Funny)
"There he is! Get him!"
Re:I foresee lynchings (Score:1)
There he is! (Score:2)
Yeah but so does.... (Score:5, Funny)
Typing le courrier electronique or "courrier" instead of email also slows everyone down.
it's 'courriel' for email (nt) (Score:1)
Re:Yeah but so does.... (Score:5, Informative)
Thank you! The humor was playing off the French origins of the referenced article and was based upon the recent story of the French government banning the use of the term "email" in favor of "courriel". So....you...see......the humor...... references........Oh, if I have to explain it, I guess it's not that funny.
By the way, this should in no way be considered Francophobic. Vive la France! (especially the cuisine and the wine).
Re:Yeah but so does.... (Score:2)
Re:Yeah but so does.... (Score:2)
Re:Yeah but so does.... (Score:2)
Non. En Francais......it is courrier. With 2 r's
Re:Yeah but so does.... (Score:2)
Yes the world loves the wining industry of France
I'm not Francophobic either
Now we just need some way to kick slow users off (Score:5, Funny)
You are the slowest link. Goodbye!
I could have had first post, but nooo... (Score:5, Funny)
I could have had first post, but unfortunately, another user on this hotspot has caused the network to slow down for some reason.
There are solutions (Score:5, Interesting)
A solution would be to leave the 802.11b AP inplace and servicing the older 2 meg devices and put an 11a or 11g AP in next to it to service the faster devices. Alternitively you might be able to put the slower devices on channel 1 and put the faster one on 6 and 11 (they have to be 5 apart to avoid overlap, and in the US you only have a total of 11 unregulated channels)
Wireless is different than wired communication. People are just going to ahve to get used to it. More stuff to learn, more rules to follow, more work for people like me.
Its a good thing- especially in this economy.
Re:There are solutions (Score:5, Interesting)
802.11g is supposed to be both 54Mbps and backwards compatible to 802.11b. From my own experience with 802.11g, if there is even one person using an 11Mbps connection, the rest of the wireless nodes also slow down.
Just like driving on a one lane country highway behind a slow car doing only 11 mph in a 54 mph zone.
Re:There are solutions (Score:5, Informative)
Of three 802.11g AP's they tested, bandwidth was reduced by 15-50% for the entire wireless network when a single 802.11b card was present. It is also notable that WEP reduces bandwidth by ~30%.
Re:There are solutions (Score:1)
Re:There are solutions (Score:2)
The speed limit must have been originally posted in metric or something
Re:There are solutions (Score:3, Interesting)
certain speed ???
I do not know if any access points come with this feature,
maybe the high $$$ cisco does, I have not checked
Peace,
Ex-MislTech
Re:There are solutions (Score:2)
Obligatory RIAA joke (Score:5, Funny)
WiFi doesn't use CSMA/CD (Score:5, Informative)
Thus, each node must try to avoid causing the collision in the first place - hence such techniques as RTS/CTS protocol...
Re:WiFi doesn't use CSMA/CD (Score:1)
Re:WiFi doesn't use CSMA/CD (Score:5, Interesting)
The users of WAFreeNet (Perth, Australia) have just released some open source software (frottle) to combat this. Essentially it provides a polled/token operation at the IP layer, virtually eliminating collisions. This is a similar application to WiCCP, and we've been helping/competeing with the WiCCP developers. The other alternative is Karlnet Turbocell - expensive proprietarty software, firmware and hardware, with poor linux support.
I cant post any url's now - the websites wouldnt appreciate the slashdotting. For those of you than can find the sites for yourself, it may be well worth your time.
Re:WiFi doesn't use CSMA/CD (Score:2)
It does look fairly restricted to more or less permanent links, however, since most (preferably all) of the clients have to run the software (linux only) for it to be effective.
2mbps is plenty (Score:5, Insightful)
nothing new (Score:3, Insightful)
In other words. (Score:5, Funny)
<ibm_thinkpad> omfg lag
<LEET_POWERBOOK_1400> hi does this map have the bfg ?
<dell_dimension> boot the lpb
<iBook> boot leet_powerbook_1400
* ibm_thinkpad has initiated a vote to kick LEET_POWERBOOK_1400
* Vote to kick LEET_POWERBOOK_1400 was successful (6 for, 1 against, 1 abstain)
* LEET_POWERBOOK_1400 has been kicked from server WIFI_POINT
<dell_dimension> ah much better
* dell_dimension was gibbed by iBook's rocket
Mainstream news, yes...slashdot, no. (Score:5, Informative)
Re:Mainstream news, yes...slashdot, no. (Score:1, Interesting)
Go back to your cave.
How much faster is wireless today then 5 years ago? A million percent? Do you think 802.11g is the end of wireless evolution? In ten years you don't think we will have gigabit wireless with 100m range?
I get nice wireless in my cave (Score:2)
I certainly don't think what we have now is the end all be all of everything, but lets be serious. Signal will always degrade the further you go away. Whether the technology lets you take advantage of this will be uncertain
Re:Mainstream news, yes...slashdot, no. (Score:2)
Re:Mainstream news, yes...slashdot, no. (Score:2)
What? (Score:4, Informative)
From the yahoo article: their research paper that anomalies in the IEEE 802.1x standard -- including 802.11a, 802.11g, and the most widely-used Wi-Fi protocol, 802.11b
I was under the impression that the IEEE 802.1x standard is solely a security standard and that it is not to be used as a generic term for the 802.11* wireless protocols. Anyone care to clear this up?
Re:What? (Score:4, Informative)
Human translation (Score:5, Informative)
--
A primary analysis of Wi-Fi network performance anomalies was done by four reserchers of the Institute for Information Technology and Applied Mathematics (IMAG)'s Software Systems Resources unit. Martin Heusse, Franck Rousseau, Gilles Berger-Sabbatel, and Andrzej Duda just published the surprising results of their study for the INFOCOM conference in San Francisco, on of the most prestigious in the domain of networks research. it reveals that in certain very --- circumstances, this type of wireless network produces a relatively penalizing slowdown: users with better connectivity, and thus with better data flow, are penalized by those with degraded connections.
Local wireless networks based on the "Wi-Fi" (IEEE 802.11b) standard are starting to be deployed in a relatively large number of locations, and many models of portable computers already come with a Wi-Fi network card. Attempts providing connectivity in public places, by way of what are called "hot spots", are becoming more common. The number of potential users are increasing rapidly, and the first hot spots are in wide use, but can Wi-Fi networks stand up to the needs of numerous users and increased bandwidth demands?
In their usual operating mode, Wi-Fi networks are built upon on a wired network infrastructure. Wireless access points rely on a local, high-bandwidth network, most commonly Ethernet, and create a link between wireless network equipment and the local wired network, as well as the internet. In practice, wireless network cards use four flow levels with different signal modulation techniques that can be selected according to the quality of the connection to the access point. More simply, a card close to an access point can get good bandwidth, nominally 11 megabits/second; as it gets farther away, the levels go to 5.5 Mbit/s, 2 Mbit/s, and finally 1 Mbit/s, as the signal gets weaker and degrades.
As Wi-Fi networks are created, some users get the best flow (11 Mbit/s) in the access point's coverage area because they're close to the access point. A user enters in this coverage area and, being relatively far away, is connected at 1 Mbit/s. When this user communicates over wireless channels, that is, when he transmits data, it causes a drop in bandwidth for all the others, leaving them at a bandwidth apparently identical to his, 1 Mbit/s. No matter which bandwidth levels the original users are connected at, the weakest will be observed by all hosts.
This anomaly, inherent in networks relying on CSMA/CA (Carrier Sense Multiple Access / Collision Avoidance) which is defined in the Wi-Fi standard and revealed by the CNRS research team, penalises the network users. Despite a good connection, their apparent performance can become strongly degraded in a completely unforseeable manner, due simply to the activity of a third party connected to the same wireless access point at a lower bandwidth level.
However, though it will be observed on any network of this type, the impact of this anomaly should be more or less moderate for two reasons. First, most equipment today connects to the network in a sporadic and non-continuous manner; periods of activity, like downloading a web page, are relatively short compared to the time spent reading it. Conversly, if a long communication takes place - downloading a large video, for example - it will continuously penalize all users. A second mitigating factor comes from higher-level protocols, especially TCP, which perform some sort of flow-control that creates an effect on apparent bandwidth.
The researchers are currently working on solutions to limit or suppress this anomaly, which could become extremely limiting with the development of new communication applications, notably audio and video over the Internet.
It's the nature of the system, but... (Score:4, Interesting)
jeff
Configure the AP properly then... (Score:1, Informative)
I hate slow traffic. (Score:1)
slow? (Score:2)
Milwaukee has this issue (Score:5, Interesting)
Taking into consideration that Milwaukee is a city of ~600,000 people, that not many are going to have wireless laptops and even fewer are gonna spend time in a park surfing the web, it still seems like 20-40 users clogging a public WI-FI is a bit odd.
I suppose they can't complain, though, since the city paid less than a couple of hundred dollars for the setup. Still, it just seems somewhat pointless if it's gonna be clogged all the time.
Don't get excited about the obvious (Score:3, Informative)
http://www.karlnet.com/Documents/WhitePaper/Turbo
Even better is that it details a superior system (albeit pricey per node). It's based on military technology and military technology is light years ahead of what most of us are using on a daily basis.
Blue skies...
Just use a phased-array wireless switch. It's easy (Score:5, Informative)
Re:Vivato "developed" no such thing (Score:2)
Question to clarify (Score:3, Interesting)
If I'm the only one on an 11mbps network and sitting right next to the station, I'd expect all the bandwidth. If somebody else joins the same network, in fairness my bandwidth may be halved. But do I really care whether the other guy is getting 1mbps or 11mbps during his timeslice? I'm still getting half the bandwidth as if I had it all to myself, right? I would only consider it strange if a single user joining with a weak connection cut my bandwith by > 1/n.
Re:Question to clarify (Score:2)
Basically, the way CSMA/CA works, when I want to transmit, I send a jamming signal. If I don't receive a jamming signal in some small amount of time, I can assume with some degree of safety that no-one else is trying to transmit at the same time. So, I go ahead and do my business, during which time no-one else can transmit.
Now, let's say you and the other person on the network are trying to send some large file. Say your networking implementation sends a jamming signal, transmits one TCP pa
Re:Question to clarify (Score:2)
Re:Question to clarify (Score:5, Informative)
Hmm? That's roughly how Ethernet works (and it's
With 802.11* communication, you typically transmit at ~20dBm and receive at ~-60dBm. The difference in signal strength is ~10^8, so it is pretty much impossible to detect someone else transmitting at the same time. Instead, 802.11* use Collission Avoidance. In short - listen before transmit, and explicit ACK.
The worst case scenario will end up with simple alternation: you send a packet, the other person sends a packet; you send a packet, the other person sends a packet; etc.
Yup. That's pretty much how the 802.11 MAC layer works if several wireless stations are trying to communicate at the same time. All stations have roughly the same chance of sending a packet, and the client @1Mbps will use 11 times more air time per packet than a client @11Mbps.
Anyway.. I don't quite understand why you have to be a researcher to 'discover' that a client that is associated at 1Mbps can drag an entire 802.11 segment down the drain. This has been known for a long time.
Oh, and by the way. (Score:2)
Re:Oh, and by the way. (Score:2)
Kind of. Except that you can't have both 10Mbps and 100Mbps NICs connected to a hub. They all have to use the same modulation speed, so the hub is locked at either 10 or 100.
But the theory is sound - if you have a shared medium that supports different modulation sp
CSMA/CD or CSMA/CA ? (Score:2)
http://aqua.comptek.ru/test/HiddenNode/hidden_n
Thanks,
Ex-MislTech
Time for Token Ring wireless... (Score:2, Interesting)
Cordless Phone Attack (Score:2, Interesting)
Re:Cordless Phone Attack (Score:3, Funny)
Re:Cordless Phone Attack (Score:2, Informative)
I really don't get it I guess.... (Score:2)
If I find myself in the "wet spot" I will gladly give it up to other users...
This is news? (Score:4, Informative)
The problem will occur in any shared multiple-access radio network when users are at different distances from the base station. Those far away from the base station use spectrum less efficiently than those close to the base station because they're forced to put more RF energy into each data bit to close the link.
The same thing happens in 1xEV-DO. As in 802.11, a wide range of data rates is available to adapt to varying channel conditions, and the lower data rates use the channel less efficiently.
Digital radio designers work hard to make their modulation, coding and multiple access techniques as efficient and adaptive as possible. But at some point, you have no alternative but to add more base stations so that each need serve only a reasonable number of users.
CD? (Score:3, Informative)
In wireless, we don't have this... instead you re-transmit packets that get lost, and you try to avoid collisions in the first place.
I don't buy it (Score:2)
I don't think this is the Apocalypse for WiFi. The important thing to remember here that this is radio...Only one conversation can happen at a time, and the 11mbps is shared across all nodes. This is similar to a hub, but the difference is all the nodes can run at different speeds.
The folks close to the AP will still be going 11mbps, but although the laggard out in BFE will be going 1mbps, he will not drag the others down to his level. W
Translation (And not Babelfish either!) (Score:2)
-uso.
First analysis of performance anomalies of Wi-Fi networks
A first analysis of performance anomalies of Wi-Fi networks (1) was completed by four Network System Software integrators at CNRS's Institut d'Informatique et de Mathematiques Appliquees de Grenoble (IMAG). Martin Heusse, Franck Rousseau, Gilles Berger-Sabbatel, and Andrzej Duda have published the surprising results of their study, on the occasion of the INFOCOM conference in San Fransisco, on
Is it just me, or... (Score:4, Funny)
Huh? (blush) Oh yeah. They actually are. Excuse me for the lack of controversy in my opinions. Next time I just might offend you. ;-)
802.11b ~= ethernet. Read Oreilly 802.11 book! (Score:2)
Out of the box most access points are configured for maximum throughput. 802.11b is CSMA/CA - collission avoidance. The CA features are disabled unless you turn on maximum fragment size and some other stuff so that the clients ask the AP for permission to transmit.
802.11 by design assumes that two transmitting clients can see each other. When remotes can't see each other, say in an outdoor access scenario, as soon as the cell gets busy you have to be all over the tuning parameters to keep the compl
Simple Fix. Lock your spped on the access point (Score:2)
Re:We've known about this since it's inception.. (Score:2)
Wireless switches? (Score:1)
Re:Easy enough to solve this problem (Score:2)
Re:Easy enough to solve this problem (Score:2)
If client A and client B send traffic to AP at the same time, they will still collide.
Re:Hmmm? (Score:2)
Re:Hmmm? (Score:2)
Re:Hmmm? (Score:2)
well, as much as I hate to tempt fate by saying this, but I think it depends on your area, I've been using adsl for a couple of years now and I rarely get dumped offline. I leave my computer on 247 and I don't often have problems.
dave