WiFi ping times fluctuating

I can't tell what's causing the problem, mostly because I don't have a clue as to what you have for hardware, but the problem is obviously packet loss. Wireless routers work on two levels (layers). At the MAC layer, you only see the longer time delays caused by the packet loss. Packets are retransmitted transparently. So, at the IP layer, you get somewhat reliable delivery, but with the observed time delays. My guess is that you have a neighbor that just dragged home a new wireless router.

The standard fixes for interference problems are to change the RF channel or play with directional antennas. Putting your laptop next to the wireless router isn't going to do anything if either is hearing the interference. Not much I can suggest until you identify the source of the interference.

Hi Jeff, thanks for the suggestions. That's interesting that it would report packets as delivered when actually they were dropping, I didn't know that. What kind of hardware details would help?

There a couple of other wireless networks in the area, probably neighbours, but they're on channel 6 and I'm on channel 11. I've tried setting it to channel 1 as well and it's the same. What else could be causing interference? The router is quite near my TV and stuff, could that be causing the problem?

Layer 2 diagnostics (MAC layer) are very rare in commodity wireless. The IP layer never sees the retransmissions. All it sees are longer delays.

Maker and model of router. Hardware version. Firmware version optional. Maker and model of test client laptop. Some clue as to the topology, neighborhood, etc. Is the interference continuous or intermittent? Times?

Incidentally, go down this list of probable culprits and see if any look new.

Municipal wireless installation seem to be becoming a problem.

See list above. Also, you can't "see" a wireless network that doesn't broadcast its SSID. You can use Kismet to sniff these, or a spectrum analyzer:

There are also some MIMO (802.11n) networks that don't show up on a client utility or active scanner.

If your radios are near a window, try moving the access point and/or client away from the window. That's the most likely point of entry.

The router is buffalo whr-g54s, according to the web interface it is: WHR-HP-G54 Ver.1.40 (1.0.37-1.08-1.04)

My laptop is an apple macbook pro, just over a year old.

I live in a small city in the uk, I'm pretty sure there's no municipal wifi here.

The problem I'm experiencing is constant, every time I've pinged the router over the last two days I've seen the same thing.

I've got istumbler on my mac which I believe is similar to kismet.

The router is quite near a window, I've tried moving it away a bit (it's about 10 feet away now) and that doesn't seem to have helped.

Appreciate your guidance Jeff, thanks.

Not exactly. The WHR-HP-G4 and WHR-G54S are two different products. The "HP" for high power version has higher tx power output. I like these units and use them with DD-WRT firmware.

Well, muni wireless was just a guess. There's a long list of other sources of interference. The reason I asked about the timing is that many sources are intermittent in timing. For example, a microwave oven interferes for about 10 minutes, with long pauses in between.

That eliminates about half the list. A "small city" isn't very useful, but if you see any metro wireless security cameras, they may also be a source of interference.

Nope. Istumbler and Netstumbler are active sniffers. They transmit probe requests, and listen for responses. Kismet is also a passive sniffer. It listens for traffic but does not transmit. I stumbler will not show an access point that is NOT broadcasting its SSID.

Well, I think it might be useful to test this in an isolated location, known to be interference free, such as a basement. Just the Buffalo and the Mac laptop. If it screws up in the basement, then there's something wrong with the hardware.

Hmm, well unfortunately I don't have a basement.

I have tried kismac, but it doesn't seem to work well, I've heard it has compatibility problems with newer macbooks so maybe that's why.

Do you think trying a high-gain antenna would be a good idea? To try and overpower the interference?

Appreciate your insight Jeff, I feel like I understand the issues a lot better now, but I am starting to feel like I might just have to learn to live with the problem :-(

Do you have a shovel? Never mind. My humor skills are temporarily impaired.

I previously suggested. If you can't find anything that will work on the MacBook, then I was hoping that you would consider dragging your wireless router and MacBook to some isolated location know to be devoid of 2.4GHz interference or surrounded by sufficient quantities of dirt to be effectively shielded. What you're doing is determining if it's really interference, or if it's a weak signal to the wireless router, or a some configuration problem on the router or MacBook. You decide if it's worth the exercise.

Probably not. Lots of problems.

1. An omnidirectional antenna will increase the signal strength of both the interference and the MacBook.
2. A directional antenna will help, but only if you know what direction the interference is coming from.
3. You still don't know if it's really interference, or something in the router or MacBook.
4. You don't know if the interference is entering the system at the router end, or the MacBook end. The resultant packet loss will be similar.

Once you've determined the source of the interference, only then can you take remedial action. However, it might be useful to try a directional antenna at one or both ends. If you can see the interference as an increase in "noise level" reported by the wireless client, you might be able to determine the direction of the source.

Incidentally, someone once wrote that their local source of interference turned out to be their new wireless doorbell receiver.

Perhaps the shovel wasn't such a bad idea.

Ok, I think I will take my router over to my girlfriend's house and try it out there, at least then I'll know if it's a hardware problem or not. I can try connecting to it from her computer as well and see if I have any success.

I've tried taking the macbook to the other end of the house, but no difference. Would it be worth plugging the router in in a different room?

Then if it turns out it is interference-related, do you reckon it would be possible to use tin foil instead of dirt to achieve much the same effect? Can I improvise a directional aerial from a wok or something?

On Aug 6, 4:45 pm, Mark wrote: (trimmed...)

Well, if you're going to do that, you might want to try doing some benchmarking over the wireless link. See IPerf at:

If you search this newsgroup for my postings on IPerf, you'll find instructions and sample output.

Dunno. I was looking for a location that was guaranteed to have no interference sources at either end. That means moving both the MacBook and router. I don't think it will be worth the effort.

Sure. See home made reflectors at:

However, the problem will be where to aim the antenna. If you can't identify the source, some tinkering and trial and error will probably suffice.

Well, this morning I happened to turn off my computer and when I turned it on again this evening, I noticed the problem had resolved itself. In hindsight I probably should have thought of restarting my computer before...

I'm now hoping that it's actually fixed and doesn't come back, or I might have to break out that shovel!

Anyway, I wanted to thank you Jeff for your patience and knowledge, I've found your pointers helpful in understanding this technology better, which I'm sure will come in useful in future!

Cheers!

Sigh. So much for the interference theory. I sorta assumed that you had power cycled everything. I think you can safely put away the shovel.

However, I do have a solution. Just run Windoze XP as your primary operating system. It has to be rebooted far more often than OS/X so you won't see such problems.

I love that answer. I'll save it as a response whenever anyone asks me "why should I run Windows". Is it trademarked, or just copylefted?

Larry

should I run Windows".

Neither. It's all yours. I'm a bit jealous of the stability of OS/X machines. I've seen them go for months without a reboot. I can almost do that with Windoze, but nowhere nearly as long or as well. My background is mostly SCO Xenix and Unix systems. I had systems that had uptimes of over a year without a reboot. That includes CAD workstations and some desktops. However, the current plague of security updates and patches has largely prevented long term uptime testing. Mean time between updates that require a reboot is about a month and dropping.

At one point, there was a bug fix for Windoze 98 that involved a timer counter overflow and subsequent crash after something like 60 days. I couldn't find the reference, but it's real. The joke was that nobody had experienced this bug because Windoze systems just didn't stay up that long.

Someone always asks why I deal with Windoze when there are better alternatives. Well, I have to make money, and I don't make money repairing systems that work well. So, I do Windoze, which offers me the maximum revenue flow and largest customer base. The company motto is "If this stuff worked, you wouldn't need me".

I would be negligent if I didn't offer some light Mac bashing. I don't have a problem with the Mac hardware or software. Unix is good no matter how it's packaged and buried under a GUI. It's the customers that drive me nuts. Apple makes it sound like running a Mac is so easy and reliable, that if something goes obviously wrong, it's probably the customers fault. The result is that customers blame themselves all too often and simply don't seek help until they're over their heads. Since I'm in the business of providing help, this is a bad thing for business.

I had a Linux machine functioning as a file and print server and as a router between 22 Windows computers and the Internet in a computer lab. It and the DSL modem were plugged into a UPS with enough capacity to ride out the interruptions that happened in Phoenix in the summer and was up for

I heard it was 180 days. However long, someone had to find it from analyzing the code, not a crash dump.

Clearly Windoze is a good deal for the repairers and Bill Gates.

Some users can be awful. In the old days, before OS X, I had one guy that managed to blow away the OS on his Mac regularly - about once a month. Tragically, he died and the person that inherited that machine never had the problem. I have no idea what he was doing, but I had to keep the CD handy.

Larry