Is a rare timeout from a ping on 5ghz normal?

[binarydad]

I might be obsessing, but I was looking into how well my wireless is performing. I have two 5ghz laptops on wireless-N. My AP is an ASUS rt-n66u (w/ merlin .40), WPA2, N-only, 40mhz only. I wrote a script that endlessly pings both laptops and records whether there's a timeout.

I let the script run pretty much all day yesterday, pinging from a desktop (wired) machine to one of my laptops (wireless). Pings were once per second and default settings (4000ms timeout, 128 ttl).

After many hours, it recorded only one timeout. All other pings were between 1-2ms consistently, except for just this one. Same behavior with the other laptop, where pings were about 1-2ms and there was only one timeout registered over several hours of pinging. The script was using the IP instead of the netbios name to alleviate lookup times.

The laptops weren't that far away - it was one floor above the AP. Signal is strong and there's no interference from other APs.

My question is, is this normal for an occasional ping timeout to slip by? I don't have anything to compare to. Thanks.

 

[L&LD]

I too would want it to be perfect; but 1 ping out of 36,000 (I assumed 10 hours of testing) is nothing to be worried about, is it?

 

[binarydad]

I too would want it to be perfect; but 1 ping out of 36,000 (I assumed 10 hours of testing) is nothing to be worried about, is it?

I guess I just don't have a baseline of "How many timeouts over X total is normal?".

 

[azazel1024]

Between 0 and some is normal.

Heck, I've run wired tests and I've managed to loose at least one on my LAN between wired machines. Honestly, 1 being dropped out of 36,000 on WLAN is pretty good performance.

 

[TonyH]

Hi,
I would rather worry about error rate on TX/RX per x-action than a missed ping. Even solid copper line can lose a thing or two on heavy traffic. That kinda things we are watching in syslog.

 

[binarydad]

Could even things like activity on the remote computer cause a ping to timeout? I just had one again within a few minutes, but hasn't done it since. I was running an update at the time it timed out.

 

[stevech]

Pings on wireless will fail. At some average rate. Something on the order of < 1% is to be expected.
If your chosen frequency/channel is busy with other users, other types of wireless, the rate will increase a lot.

Fear not. Ping has no retries. TCP does.

 

[binarydad]

Sorry to bring it up again, but I've noticed something. I've been letting my script run again, but noticed that the last two times a ping to a device timed out, it was on or right around the DHCP lease renewed.

So, even if the IP stays the same, when the lease is renewed, could it cause a tiny *blip* in the connectivity to cause a timeout?

 

[TonyH]

Hi,
Like getting off a bus and getting onto another one. BTW, tried to run dnsbench to see which DNS is best for you. Some times it's not your ISP provides.

 

[binarydad]

Hi,
Like getting off a bus and getting onto another one. BTW, tried to run dnsbench to see which DNS is best for you. Some times it's not your ISP provides.

Not sure if that applies to me, though. In my case, I'd be getting back onto the same bus.

Also, external DNS shouldnt be a factor here. I'm pinging internally only. Thanks.

 

[stevech]

So, even if the IP stays the same, when the lease is renewed, could it cause a tiny *blip* in the connectivity to cause a timeout?

Yes, depending on how manufacturers' implement things.
Easy to eliminate this if you wish: use a static LAN IP outside the DHCP range.

Ping failures on wireless will usually be common. Shared use spectrum. Ping/ICMP is an unreliable datagram by design, unlike TCP.

Don't worry unless ping failures get above 1% or so.

Pingplotter (freeware/shareware) can help you build stats.
If you see lots of ping failures to your own router's IP, on WiFi, change channels as there may be, on occasion, too much competition with neighbors' WiFi who are very active.

 

[binarydad]

Ok, so I'm off work and geeking out over my pinging here.

I set up my old 5ghz Linksys AP and connected one of the laptops to it. I downloaded PingPlotter, am running my script, and letting a ping.exe run all at the same time (crazy, right?).

I've noticed that even on a completely different wireless AP, I'm still getting these random timeouts. Also, the timeouts only happen when windows is scanning for networks every 60-70 seconds. It doesn't always happen every time, but sometimes, one of the three processes will pick it up right as the lag spikes. PingPlotter is reporting that every timeout so far is right on a ping spike when windows scans for APs. All three processes are indicating the same cause.

So, I'm coming to the conclusion that my timeouts were caused solely by windows scanning for networks periodically. So far, not a single timeout has happened outside of these 60-70 second intervals.

Thanks for the input. I learned a lot.