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Lag/connection spikes?

Last response: in Networking
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March 9, 2010 1:44:59 AM

Greetings!
I'm fairly decent with routers, but modems confound me, if that's even what this is. Now and then, every computer on my network will simultaneously get a spike of latency (or something that seems like latency) for 1-15 seconds, usually around 3 or 4 seconds, and then it will go back to perfectly normal. We play a lot of online games here, so it's a major nuisance. In-game, we won't see our latency get any higher, it will just behave strangely and we won't be able to control the game at all, or in some cases say we've disconnected, and then go back to normal. Any idea how I can go about fixing this?

More about : lag connection spikes

March 9, 2010 3:47:19 AM

You need to rule out possible causes... maybe start with something like this?:

1) Could be a switching problem (switch getting overloaded and not passing traffic to the router perhaps, or some <other> issue)

2) Router gets overloaded / otherwise jacked up and doesn't route traffic for a few moments.

3) Modem gets overloaded / otherwise jacked up and drop's connectivity or stops forwarding traffic.

4) Your ISP has some lags in their system and drops / slows down your traffic.

Really you gotta narrow it down. I've listed a couple possiblities but I wouldn't even say that I've scratched the surface of what COULD be going on here. Get packet caps while it's happening... see what your switch and router loads are. What does the traffic look like coming out of the router / firewall's external interface look like when this happens? Have you asked your ISP if they are experiencing any known issues in your area? Have you tried swapping out modems, routers, switches, etc to see if you can isolate the issue?
March 17, 2010 8:35:24 PM

Thanks for the response and ideas, Brian.
Can't find anything particularly funky coming out of the router, and the ISP says nothing strange is happening. They say the power levels are also within acceptable range, but they gave us a new modem to try out for a week. It's just a Surfboard SB5100, nothing fancy, but I thought for sure it would help since our modem is approximately 7 years old.
The power levels are more "safe" than the old modem somehow, I'm not really sure how that works, but now the lag spikes have gone to full-blown disconnects. Everything will be fine, and suddenly, no internet at all. The modem lights will all be on, and the Activity light will continue to blink, but we cannot reconnect or access 192.168.100.1 with anything short of a power cycle.
IN ADDITION... Switching back to the old modem does not help. What's happening since the first 20 minutes of trying the new modem is now what happens with the old modem. What the bloody hell is going on?
Very few people at our ISP know much more than how to read from scripts, and the people that do seem to have 8-hour lunch breaks. I have yet to speak to anyone that even remotely sounds like they know what they're talking about.
Any more ideas?

P.S. - I just had to power cycle to get this posted. RAGE!
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March 18, 2010 1:40:04 AM

What are talking about here, wire? Wireless? Both?

What happens if you remove the router and use a direct connection to the modem?
March 18, 2010 2:27:34 AM

Well... the fact that you can't access an internal (192.168.100.1 modem IP) ip address kinda makes me think that it might be something internal to your network, aka switch, NIC, etc.... When you say you're power cycling what components are you power cycling?
March 18, 2010 4:36:38 AM

Both wireless and wired have this problem.
Same exact things happen whether it's through the router or direct link (though obviously with direct link only one computer will be experiencing it).
We've tried direct link to 4 different computers with the new modem, and it always happens the same way. The modem lights will all say the modem is just fine, but we won't be able to access the modem IP without power cycling it.
When we're using the router, we power cycle the modem and router together, as individually, it has no effect on this situation.
March 18, 2010 4:42:22 AM

So power cycling the modem on it's own has no affect and power cycling the router on it's own has no affect either?

If the modem seems to be causing the problem I'd have the cable company look at the signal to noise ratio as well as the power... both play a big role in your ability to connect. With Comcast I'm currently at 37db signal to noise and it's currently doing about 21mbit down / 4mbit up...
March 18, 2010 4:44:40 AM

I should also note that I've got a Surfboard 5100 as well... and my "Downstream power level" is 6 dBmV and upstream powerlevel is "45 dBmV" with zero complaints / issues.
March 18, 2010 9:21:11 PM

Downstream: 13.3
Upstream: 31.0
Signal to Noise Ratio: 41.0

That's at the moment, but they stay pretty close to those numbers.
Something new in the modem's logs, though:

No Ranging Response received - T3 time-out

Got a bunch of these within the last 12 hours. Cabling issue?
March 18, 2010 9:51:53 PM

Yeah.... sure seems like something on your ISP's end there. I'd mention those errors to them and may ask your neighbors if they are having any similar issues too. If you know them well enough maybe compare your #'s to theirs on the modem.
!