The Joys of Microwaves And Wireless 67
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.
Re:In other wireless news... (Score:1)
In other wireless news... (Score:1)
But I guess it's not /. news until they can be sure to be the LAST to report it! Hmm.. Ya, but those wireless microwaves... Wooo doggy, uber geek, but... Ah, nevermind, it is sort of cool, just a bit more pointless. Just glad there are at least one [i4u.com] or two [kuro5hin.org] other sources of Geek news than slashdot...
Re:author doesn't know how to benchmark (Score:1)
Use ttcp or netperf.
Re:Other sources of RFI (Score:1)
All of those items operate at a different frequency than the wireless network. They should not have an effect, only devices that output noise in the 2.4 Ghz band should cause a problem.
Re:Fire up your cordless (Score:1)
Microwaves do operate in the same band. They run at 2.4 GHz. This may have something to do with why the 2.4 GHz band is unlicensed.
Re:Small technicality... (Score:1)
Re:It's a 104-bit encryption (Score:1)
The WEP encryption works like this (assuming 128 bit version)
- every station has a 104 bit secret key
- every packet has a 24 bit IV (initialization vector) in the header.
The 24 bit IV and the 104 bit key are combined into a 128 bit key, which is used to seed a pseudo random generator based on RC4. The resulting stream of random numbers is then XOR-ed with the payload. To avoid tampering with the contents, there's also a 32 bit ICV (integrity check vector appended) which is a CRC on the plaintext.
Now, the short IV is vulnerable to attacks because if you ever find two packets with the same IV (and the same secret key), you know the contents have been XOR-ed with the same stream.
However, if all the packets you receive use different IV, your only way to find the contents is to crack the 104 bit secret key.
The proposed changes to WEP include a larger IV, that's not appended to the secret key, but XOR-ed.
This will still result in a total 128 bit key length to seed the RC4 engine, so this will be a firmware-only upgrade on most (all ?) hardware vendors.
The next 802.11 and Ultra Wide Band (Score:1)
At 5GHz, walls attentuate the signal even more than at 2.4GHz, the 802.11b standard, so it remains to be seen how close you will get to the 54MBs signalling rate. With the MAC protocol overhead, even in the best enviroment, you'll loose between 30-50%. This is not just a wireless feature, 100 MBs Ethernet also gets a MAC penalty, just not as much as wireless.
What will really impress the geek in all of us is a new wireless products utilizing Ultra Wide Band [uwb.org] (UWB) techniques. A UWB radio tranmits its signal using gaussian monocycles instead of sine waves. With ultra-low power emmisions and over 2GHz of spectrum, conventional narrow-band systems are not disturbed and UWB signals appear as white noise making UWB very hard to detect. Highspeed bandwith, precise precision and location, and RADAR capabilities are being demonstrated today. A leader in the field is Time Domain [timedomain.com]. The FCC is expected to rule on legalizing UWB this fall.
Re:What about Ghz cordless phones? (Score:1)
Microwave Ovens and wireless backbones (Score:1)
We know for a fact it's the microwaves since turning them off cleans up the link and turning them on kills it. We've tried changing their positions and replacing some of the older microwaves. It still seems to be a problem. Strangely the micorwave we brought in has no problems but another of the same brand causes problems. Using a spectrum analyzer has also shown the microwaves to be a problem.
Can anyone suggest a way to shield a microwave or otherwise elminate the source of interference?
Re:That isn't the point (Score:1)
I'm using the Lucent stuff in my home. I've got the RSG-1000 gateway hooked to my cable modem, then I've got a tower PC with a PCI-to-PC card adapter, my laptop with it's PC card and my Jornada 720 gets a card too.
I've been able to download file at 400kps from the 'net, but that doesn't tell me whether the speed limit is the card or the broadband (my guess is the latter).
I'm running Windows on all the machines (I know, I know, but I make a living writing stuff for Windows) - if someone can suggest a compatible benchmark for peer-to-peer speed testing I'd be happy to give it a whirl.
On the topic of Windows... great glubb almighty, is SMB the slowest fscking thing in the word or what? I do better using Zip disks to transfer files!
Fugedaboudit (Score:1)
Based on my experience, you do not want to use a 2.4Ghz phone if you're running 802.11b.
I've got Lucent/Orinoc stuff. Bought a Siemens coordless, ran it in the same room as the wireless gateway (which is always on). The coordless would not see the base station if it were farther than a foot away.
I didn't bother checking my throughput with the phone on, I just took the phone back. My old 900Mhz phone works just fine, no interference.
If anyone knows a 2-handset capable 900Mhz phone, give a shout.
Testing methods and incorrect assumptions (Score:1)
First let me express my bias: I do not believe that the 802.11b standard utilizing Direct Sequence Spread Spectrum (DSSS) technology suits mobile or last-mile usage. Ideally this technology suits point to point (PtP) or as a controlled point to multipoint (PtMP) involving less than an half dozen receivers. Now taken with a grain of salt, let us continue.
1. There is no baseline.
There are many variables involved in the transmission of data between two computers, and while the author made a valid attempt to remove some by eliminating disk I/O operations, interface delays (PCMCIA/Cardbus), protocol overheads (802.11b, 802.2, TCP), and signal quality (retransmissions/bad packets) were ignored. The simple addition of a test utilizing 10baseT PCMCIA cards and running the same test would have accounted for the TCP and 802.2 overheads, leaving only the 802.11b (wireless) protocol and retransmissions as variables which is what he was testing for.
2. Method of comparision flawed. Assuming that a 1Mbit radio link will provide 1,048,576 bytes/second is incorrect. The 1Mbit number refers to the maximum RADIO speed possible, not throughput that could be seen. The transmission process tested was SSH --> O/S --> TCP/IP --> Ethernet --> Wireless and reversed on the receiving side. Since this computer is probably used day to day with 100baseT ethernet and sees higher transmission rates than 4Mbit for this comparision it can be ignored in the lack of a valid baseline (see #1 above). SSH encapsulates the raw data provided with its own headers, TCP/IP adds packet headers, Ethernet adds MAC headers, and Wireless adds 802.11b headers. Depending on the packet size being utilized by the SSH implementations, this overhead can result in a packet overhead of 20% to 60%. In this case based on the times published, it is probably in the 20-30% range.
After deploying a real network supporting 10,000 desktops in 16 communities I can safely say that DSSS technology is being deployed and used incorrectly as it is not well suited to either office mobile, last-mile or roaming mobile deployments. The large overheads involved in the 802.11b protocol reduce actual throughput and the congestion that results from colocating cells in unacceptable outside of a small office or home environment.
The industry as a whole needs to take a hard look without the spin created by the large manufacturers pushing their own products at the true capabilities of both DSSS and FHSS technologies. DSSS has an excellent application in providing network backbone, and high-rate point-to-point communication it is not suited for outdoor point-to-multipoint deployment or in-office roaming between access points, let alone mobile roaming like a cell phone. Frequency Hopping technologies should be deployed in the busy office, are perfectly suited for outdoor deployment, are extremely resistant to interference and support high-speed roaming between cells at 60 mph for in-vehicle applications that will start to appear shortly.
Re:300W Microwave? (Score:1)
Re:What about Ghz cordless phones? (Score:1)
Actually, almost all of the 802.11b (definitely anything with a WiFi logo) uses Direct Sequence, rather than Frequency Hopping. Another thing to note is that _anything_ operating in the 2.4GHz band has the potential to interfere. I've seen a Frequency Hopping radio punch holes through a Direct Sequence radios throughput, because it's hopping happened to correspond to the same frequency at times (the frequency hopper also had a 100mW transmitter compared to a 35mW transmitter on the Direct Sequence radio).
Wireless Rocks (Score:1)
latency (Score:1)
Re:hehe (Score:1)
3 S.E.A.S - Virtual Interaction Configuration (VIC) - VISION OF VISIONS!
Re:The real question is (Score:1)
(Diet Coke or other soft drink may be substituted for 'Dew if applicable)
No problem for me (Score:1)
In fact, I've had more problems with the phone itself -- it dials too fast for my phone company and I have to put in a 1010xxx prefix in order to get it to work and not give a fast busy.
Re:The real question is (Score:1)
If not, I could use the excuse that all those cans laying around are to "optimize" my network connection
It's a joke. Laugh!
Re:It's a 104-bit encryption (Score:1)
Re:Useless test. (Score:1)
I should forward this to those people I left my old Litton commercial grade nuker with. It's...uh... near the computer center. :)
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Re:Other sources of RFI (Score:1)
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Someone mod this down, please? (Score:1)
Nevermind. Someone did. (Score:1)
That isn't the point (Score:1)
4 Megabits (Score:1)
I have noticed this as well, and with various types of equipment. At the time I wasn't sure if this was a limitation of the cards with respect to TCP connections, or just due to a lot of collisions. Does anybody have explanations or similar experience?
It would seem that this is relatively unimportant, considering a lot of people can't get 4 megabits to the net anyway. However, as this bandwidth is shared in a peer-to-peer network, I would worry that things would start to get ugly when the number of peers is > 2.
Yes, but (Score:1)
Re:I think this guy did his math wrong... (Score:1)
In addition to calculations and disk access, there's also overhead that is dependent on the line speed; specifically, the link access times (avoiding collisions with the other end accessing the medium) and the transmission time for checksums and the other minutia that make up headers. It may have been this to which his calculations referred.
Re:It's a 104-bit encryption (Score:1)
Re:4 Megabits (Score:1)
Network testing... (Score:1)
And yes, it's probably the broadband.
SMB is often faster than some distributed filesystems, but it also doesn't do as much. However, compared to a local hard drive, it's painful.
My point... (Score:1)
Similarly, people will wonder if this will cause cancer, but they would have much greater risk from their cellphone (say, almost nil), and similarly, much greater risk from their microwave, (which is to say, not much) when both of which are far safer than The Sun! (which people don't even think about, blah, blah, sunscreen, blah blah blah...)
My point is that a little research and correct information could have saved us all from this garbage, ad-hockery, and mockery of what used to be science. Apparently I was born in the wrong era, or came to the wrong place.
The test case microwave is too modern. (Score:1)
Modern microwaves are too well shielded and run on too tight a frequency band to really give interesting data in an experiment like this.
I want to try this with my grandparents' microwave. It's really old, but that carries with it a few "advantages". It's massively overpowered (it browns out the kitchen lights when turned on), inadequately shielded (I think the housing is bakelite), and runs just fine with the door open (I don't think they had product safety regulations when this thing was built). I've offered to buy them a brand new microwave in exchange for this beast, but no luck.
Now that I think about it, when I say "I" want to try this experiment with my grandparents' microwave, I actually mean I want a "research assistant" to try this experiment.
No (Score:1)
Re:Wireless Rocks (Score:2)
My observations (Score:2)
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.
Re:The real question is (Score:2)
Pie tins work wonders too.
Only slightly related... (Score:2)
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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You sir, are misinformed. (Score:2)
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"
Re:I think this guy did his math wrong... (Score:2)
--Brogdon
Re:What about Ghz cordless phones? (Score:2)
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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Microwaves and Wireless? Sweet! (Score:2)
Its the seal that matters (Score:2)
Thought: If your microwave messes up your wireless LAN then get the oven professionally tested. An oven with a faulty seal can be dangerous.
Re:Other sources of RFI (Score:2)
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 [clik.to] comic strip
CB and light bulb test (Score:2)
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!
Re:Useless test. (Score:2)
Re:Wireless Rocks - Um why I don't have my HW... (Score:2)
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Other sources of RFI (Score:2)
Incidentally, the tea was delicious (although a bit too hot.) Mmmm ... Yerba Buena Maté
I'd name that microwave Eddie.
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What about Ghz cordless phones? (Score:2)
I'm hesitant to buy one in case it interferes with my future bluetooth devices
(same goes for 802.11 I guess)
Re:It's a 104-bit encryption (Score:2)
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.
Re:Useless test. (Score:2)
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.
Uh-oh, is that a new boy-band? Re: "4 Megabits" (Score:2)
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
Let's hear it for testing to failure (Score:2)
The real question is (Score:2)
Similar observations (Score:2)
- 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.
Fire up your cordless (Score:2)
Useless test. (Score:2)
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?)
Will fix be in firmware? (Score:2)
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?
This guy knows nothing about 802.11. (Score:3)
Fucking stupid idiots buying 802.11b DSSS.
I think this guy did his math wrong... (Score:3)
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
300W Microwave? (Score:3)
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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Small technicality... (Score:3)
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?
It's a 104-bit encryption (Score:3)
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!
A few nitpicks (Score:4)
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).
Hmm... Good bandwidth... (Score:4)
"I pray that I never suffer an internal burn" - Nicolai Tesla