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The Joys of Microwaves And Wireless
Simone Paddock pointed me to the article on O'Reillynet about some quick and dirty testing of WEP, wireless, microwaves, ovens and all sorts of fun stuff. The article is entertaining and informative - my favorite kind.
Last month I had a vasectomy. Now I've got wireless rocks.
I also have a 802.11 setup and a microwave :) and thrown into the mix, an x10 dvd anywhere 2.4 Ghz audio video sending unit which I use to play radio from a satellite reciever on my stereo. I use the 802.11 setup to play mp3's off of an NFS mounted file system on a laptop also on the same stereo.
Here is what I see.
1) If I am playing the radio through the x10 setup and turn on the microwave, it practally destroys my speakers. This is true on all of the 4 channels that the x10 supports. It is impossible to use the X10 and the microwave at the same time.
2) If I am playing an mp3 on the laptop and switch the stereo over to the x10 receiver, i will here the laptop accessing the file system as a series of fuzzy zip sounds.
3) If i am playing mp3's through the laptop and run the microwave. I see and hear no noticable difference. Also the 2.4 GHz broadcast from the X10 equipement does not seem to affect the laptops's disk access in anyway.
Now I realize that this is not an itensive network application, nor or is very scientific. It is however a real world application of the technology and my take is that if you are using an 802.11 device to do downloads or serious network intensive applications, sure you will suffer from interference from other 2.4 Ghz devices (including microwaves which by the way happen to fall exactly in that spectrum). Go do these things on your PC. If on the other hand, you are using your wireless network for more low key applicatioins such as surfing the net, checking email, simple file access. You will not notice any problem at all, it is simply not a problem.
The difference between Canada and the USA is that in Canada healthcare is a right and gun ownership is a privilege.
A few cans of strategically placed Mountain Dew next to your wireless card helps reflect the microwaves, allowing a fast connection with no interruptions.
Pie tins work wonders too.
While browsing around source code, I see that the wvlan_cs module out of the latest pcmcia-cs package, originally designed to work with the Lucent cards, supports the PrismII chipsets as well, at least nominally. And in any case, it supports ad-hoc where the linux-wlan does not.
So what's the deal? 2 different drivers supporting the same card, I guess? Will prismII support continue in wvlan_cs? I'm so confused.
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I would claim that you sir, have "no fucking clue" when it comes to 802.11b. Let's look at your claims: DSSS has a maximum theoretical thruput of 4-5Mbps? I don't think so. I have personally run performance tests of Aironet and Lucent 802.11b cards, and have acheived thruput of 7.6Mbps. 50% higher than your "maximum". Results are right here.
You also claim that WEP adds zero overhead becuase it is a "hash" done in hardware. WEP is not a hash. It is RC5 encryption, a stream cipher not a hash. Moreover, many products do not implement the cipher in hardware. Specifically, Lucent uses software and takes a 20% performance hit when WEP is enabled. The Aironet cards use hardwar and take no performance hit. See the above URL for details.
The reason DSSS is marketed above FHSS is because it is faster. The fastest FHSS 802.11 hardware runs at 2Mbps, and is in fact cheaper than DSSS hardware. 802.11b is winning because it is flat out the fastest afordable wireless ethernet technology on the market.
So, I ask, if we are "fucking stupid idiots" for buying 802.11b, what would you recommed? 2Mbps FHSS gear? Non-existant HomeRF that even Intel abandoning? Please, o wise one, enlighten us "fucking stupid idiots"
Ah, got it. He meant all the little bits of protocol data that got sent along in addition to the 11,000,000 bits of payload data getting sent across the stream. Thanks.
--Brogdon
This tagline is umop apisdn.
Well, most digital cordless phones seem to be either 900MHz or 2.4GHz. 802.11 runs at 2.4-2.4835MHz in the US, and bluetooth runs at 2.4GHz as well. Both the phones and, AFAIK the wireless data technologies, use frequency hopping so they should be able to coexist peacefully.
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So now I can heat up pizza in my car, right?
Got Rhinos?
Thought: If your microwave messes up your wireless LAN then get the oven professionally tested. An oven with a faulty seal can be dangerous.
I recall one office that was over a metal shop, where alot of the RFI came from the Arc Welders.
Very nasty stuff, messed with the desktops big time, even though they were on separate power systems.
Being located directly over the stop didn't help.
Check out the Vinny the Vampire comic strip
"It is a greater offense to steal men's labor, than their clothes"
If you take a florecent (sp?) light bulb and put it up near a CB antenna and Key the mic the bulb will light up.
If you take a regular light bulb and throw it up in front of powerful enough microwave transmitter it will go offlike a flash cube.
But the thing about interference is a matter of frequency, that of interference being within the same frequency range.
The 60hz audio hum caused by improper grounding in audio equiptment is within the range of the audio equiptment subceptability. I'm sure wireless transmissions and reception interference is as well constrained within the specified range of the equipment.
3 S.E.A.S - Virtual Interaction Configuration (VIC) - VISION OF VISIONS!
Furthermore, the FCC is supposed to ensure that the two devices not cause interference with each other. I'm quite sure there is an FCC sticker on your microwave oven.
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A feeling of having made the same mistake before: Deja Foobar
Incidentally, the tea was delicious (although a bit too hot.) Mmmm ... Yerba Buena Maté
I'd name that microwave Eddie.
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A feeling of having made the same mistake before: Deja Foobar
I'd like to see this test repeated with a Ghz (1.2? 1/5?) cordless phone in the room. :)
I'm hesitant to buy one in case it interferes with my future bluetooth devices
(same goes for 802.11 I guess)
/..sig file not found - permission denied.
The key lengths are 40 bits and 128 bits as advertised but the effective strength is not 128-24 bits it is 24 bits.
There is a fixed version of the protocol being worked on by the IEEE.
Looking for an Information Security student project suggestion?
Try http://dotcrimeManifesto.com/
Bzzzzttt!! if the guy had read the litterature he would have mistakenly thought the encryption protocol works.
There is no substitute for checking this type of stuff out for real. Just because the marketroid who wrote the manual claims there is no effect does not mean that the statement is true.
Believe it or not, marketting people often use a sophisticated technique to sell faulty products, it is called lying. Other prominent exponents of the technique are to be found in politics (no new taxes, no more greenhouse gases).
In my day research meant going into a lab and doing an experiment like the article describes. Going into the library to read up second hand research claims is not the same thing, nor is it superior.
Looking for an Information Security student project suggestion?
Try http://dotcrimeManifesto.com/
The "mbit" rating on physical layers is the raw cycle rate of the bit symbols in the stream. That is, 10BaseT, in the middle of a packet, is sending bits at 10 mbps. But you're not always in the middle of a packet. You're forming packets, detecting the carrier, backing off collisions, sending preamble bits, sending header bits, doing it in two directions at once, etc., etc...
A moderately loaded TCP/IP/10BaseT network with well-behaved and responsive nodes on it will usually appear to have 3 mbps of user-data throughput, or roughly 300 kilobytes-per-second download rates in ftp.
In order to advance technology, I will now make a rash generalization that will in the future be looked upon as shortsighted and embarassing:
Nobody will ever really need more than 300 KB/s anyway.
--Blair
They missed one test case I'd love to see- laptop in the running microwave.
--WH--
just how many of these do I need to keep my beverages warm next to the PC?
Similar to the observations above, I have a home setup with:
:)
- 2.4 GHZ video/audio child baby monitor (Safety 1st brand).
- 2 laptops with Lucent Orinoco gold PC wireless card w/128 bit encryption (as in the article) talking to a Lucent AP 500 base station.
- An X10 2.4 GHZ wireless video camera array (3 cams).
- A microwave oven in close proximity to all.
It took me quite some time to figure out how to get any of this to work simultaneously. It turned out that all I had to do was set the X10 cameras to the fourth channel instead of the default, and suddenly they all worked simultaneously without any noticable problems. Sometimes you can see individual ethernet packets warp the screen of the baby monitor, but that seems to only happen sometimes. I don't know why. Otherwise, good to perfect throughput on the ethernet, nice clear screen on the baby monitor and good pictures on the X10 cameras. And my food tastes cooked.
I'm thoroughly amazed that it all works as well as it does. I am afraid of what will happen if I get any other microwave devices, though. There's clarity somehow in the cacophony, and I don't want to disturb that ordered chaos.
Microwaves are one thing, but let's look at something that operates in the same band. On my wireless lan, if I get on my 2.4GHz cordless, I have no more network, WEP or not.
If you read the literature, you'll notice that a conventional microwave has little or no effect on an 802.11b transfer.
Only a commercial microwave, with more than one magnetron will make a significant impact. Please, do your research before linking to such unsubstantiated fluff, and please correct them as well.
(does anyone even read technical literature anymore?)
Also, the original reports made it seem like an attack would be "hard" to do and would require alot of traffic to analyze. Is a current installation with low traffic usage vulnerable to real-world haX0rs today?
Obviously, this man has no fucking clue about the technology he is reviewing. Does he realize how Direct Sequence Spread Spectrum works? Does he realize that ANY DSSS 11Mb link will result in an absolutel MAXIMUM throughput of 4-5Mbps because of the radio overhead (30%) and the asyncronous nature of radio communication? Does he know the frequency and spread of the channel he is on? Does he know that that particular DSSS channel probably doesn't overlap with the frequency of his microwave oven, since, if it did, he would have probably seen somewhere in the range of a 30-80% drop in bandwidth? Microwave ovens appear as almost a tall vertical line usually centered at 2450MHz with a maximum of +/- 1MHz spread on a Frequency/Power graph, while DSSS radios have a spread of almost 7MHz. Does he know how WEP operates? Does he understand that WEP adds absolutely zero overhead to the actual radio data because it boils down to a SIMPLE KEYPAIR HASH THAT IS DONE IN HARDWARE? Does he realize that if he got a "2.4 GHz" cordless phone that operated with a frequency hopping radio as most of them are that he'd get almost 50% data rate reduction despite his phone working wonderfully? Does anyone seem to understand that DSSS sucks and is only marketed above FHSS because it is CHEAPER?
Fucking stupid idiots buying 802.11b DSSS.
"Before we get to the numbers, I'd like to point out that even with the above fancy command, there was still a small amount of system overhead in actually getting the packets sent. As the exact amount is difficult to calculate but non-trivial, I decided to weigh the figures like this:
At 1 Mbps, it should take 11.00 seconds to transmit my 11 Mbit file, in the best possible case. On average (each test was sampled five times and averaged), it took 14.91 seconds to complete.
So, we have 3.91 seconds of unaccounted-for overhead (or 35 percent of the total transmission time.) For purposes of argument, we'll assume that the 1 Mbit speed is optimal, and deduct 35 percent from all transmission speeds (chalking it up to system overhead.) And so we are grading on a curve.
I may be crazy here, but why does the amount of non-transmission overhead vary indirectly with the speed of transmission? He mentions early in the article that there is a small amount of overhead in generating the bytes he's sending and timing the process, etc. because of CPU time and accessing the hard disk. Why then does he scale the overhead percentage-wise with each of his tests? That overhead time shouldn't disappear just because you're using a faster connection, it should stay exactly the same - the rest of the time should vary with the transmission speed. If you redo his calculations without scaling the overhead, the results look a lot more logical for the bandwidths he's using (bandwith and transfer time vary more correctly with each other, that is).
--Brogdon
This tagline is umop apisdn.
If one's to perform such a silly test (see earlier post about FCC regs and devices that need to be able to deal with EM interference) then at least test it with something more than a cupwarmer.
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This essentially means "Take these 11 million random bits, copy them over the network using no encryption, just dump them into the bit bucket on the other end, and tell me how long it took you." I did this to try to minimize the impact of disk usage and CPU crunching, and just try to make the bits fly as fast as possible.
Umm... well, if he used ssh in order to make a connection to his other computer, wouldn't he still be technically using encryption? Or is the algorithm used to encrypt WEP connections really that much more taxing on the CPU?
Friends don't let friends use multiple inheritance.
I admit that 104-bit encryption is as hard to break as 128-bit encryption now, but Lucent is exaggerating the card's cryptographic strength by a factor of 2**16=65536. Not good!
As an engineer who works on 802.11 radios, I have a few issues with these tests.
First, the author performed only one test for each configuration. You can never come to a valid conclusion about performance from a one-shot test.
Second, the author doesn't really know much about RF, otherwise they'd realize that Microwaves are shielded to prevent from cooking the person operating the thing. While the shielding doesn't stop everything, it stops enough to let most 802.11 traffic get through without too much difficulty. As others have pointed out, the way to go is to operate other devices that communicate at 2.4GHz, such as certain cordless phones, Bluetooth devices, etc.
Third, the author doesn't appear to have read much on 802.11, or the author would realize that some amount of the overhead involved in 802.11 is used up in wireless headers that a simple application is never going to know exist.
Fourth, the author used tests on one vendor's radio to come to a conclusion about all 802.11 radios, and I can tell you that not all radios are created equally.
On the other hand, the author's results aren't actually terribly off from the performance seen in most 802.11b radios. Most 802.11b radios actually get a final throughput of about 3-5Mbps when running at "11 Mbps." Some of this is due to bus speed limitations (PCMCIA is slow), and some of it is due to the radios themselves (hey, you try getting a nice fast processor in there and maintain the price points), but whatever the limitation, no radio gets much more than 5Mbps in the best-case scenario (at least, of the radios currently on the market).
In the meantime, I'm looking forward to 802.11a, which will operate in the 5GHz band (hopefully, there will be less interference there) and should have a throughput of about 54Mbps (if they can ever finalize a standard, that is).
But I keep getting these festering lesions on my arms and chest when I try play EQ or Q3A. Must be 'line noise'.
"I pray that I never suffer an internal burn" - Nicolai Tesla
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