Broadband slows to crawl late at night lately?

[John Masterson]

I have filed a formal complaint with Comcast.  An "IT manager" is supposed to call me to get more information, they promised.

During the last few nights my broadband slows to a C  R A  W  L sometime around 11:30pm.  In the morning it's OK again.

Here is the trace route I just did. Any idea what this could be?

A neighbor doing HUGE downloads at night?

Code: [Select]

C:\Documents and Settings\Admin>tracert comcast.net

Tracing route to comcast.net [76.96.38.12]
over a maximum of 30 hops:

  1     1 ms     1 ms     1 ms  192.168.1.1
  2     *        *        *     Request timed out.
  3     9 ms     *        8 ms  ge-9-1-ur01.smpls.mn.minn.comcast.1]
  4     9 ms     9 ms     9 ms  te-9-1-ar02.roseville.mn.minn.com.232.122]
  5     *        *        *     Request timed out.
  6     *        *        *     Request timed out.
  7    36 ms     *       36 ms  te-1-1-ar01.potomac.co.ndcwest.co6.72.58]
  8    37 ms    35 ms    39 ms  68.86.206.110
  9     *        *        *     Request timed out.
 10     *        *        *     Request timed out.
 11     *        *        *     Request timed out.
 12     *        *        *     Request timed out.
 13     *        *        *     Request timed out.
 14     *        *        *     Request timed out.

[DarkHumour]

You could be right.  It also could be:
* maintenence. 
* bandwidth throttling that they *swear* they are not doing.
* a neighbor on the same node has a wide open wifi connection near a public place.

Lots of things.

[The Gorn]

Use a speed measurement tool like those at the site http://www.dslreports.com/stest.

The tracert looks pretty bad but you need to establish with these people that you are seeing a real problem.

Hopefully Comcast has some technique for determining what is going on at your end.

[John Masterson]

Here's what the SpeedTest looked like this morning:




Last night is was as low as 0.4 mbps !!

And this was last night as well, at about 1:45am CST

[The Gorn]

Hey, it's better than dial-up. 

Seriously, the dodge that all cable providers use is that everyone is muxed onto the lines that go to each neighborhood, so your speed varies depending on demand in your trunk.

But OTOH, you probably pay for a certain level of service, like 10 mbs.

We have DSL from CenturyLink (was Sprint/Earthlink originally) and it is 3 MB/s. It never seems to vary much from that level. DSL is more deterministic than cable. The supposed advantage of cable is that your *average* speed will be much higher than similar priced DSL.

[John Masterson]

Last night when my computer was slow after 11:30pm, I went upstairs to my music studio computer and was floored when I did the speedtest there and found it was super fast!

It was blazing away at 11mbps to 28mbps!  And the DNS was finding websites in an instant.

So back downstairs I went and looked at my main computer.

When I tried to look at the router, even finding the ROUTER was slow, and going between pages on the router admin app was taking 20 secs each time!

Upstairs in the music studio the router pages were instant.  Same thing when I went to the cable modem page it was fine.

But downstairs it struggled to even *see* the cable modem, timing out looking for it.

I checked for some scheduled process like a scan or a backup.  Nothing.

I used process explorer to see what was running. Only 1% of cpu was being used and there was plenty of available memory. It's a 4GB machine.  A Core Duo CPU.

This morning all is well again!


This is a real puzzle.  Any thoughts?

[Richardk]

Well, it's the computer or not.

Same DNS?

Is it wireless? Do you have Dish or Direct TV with a DVR that starts updating at that time, that's also wireless?

Try a different port on the router if wired but that's a real long shot.

What we know is that between the "world" and your router, everything is OK. Odds are good that the router is OK but could you have some kind of throttling turned on your router for that computer?

Then you have the wired / wireless question.

Last is something on the computer itself but 1% cpu?

I'm betting you have a "toy" that's updating but regardless when this is going on, how much traffic is on the network? That will at least tell you where to look.

[John Masterson]

It's hard wired. Network traffic during the problem time is almost nothing.

I think a clue is that the affected computer cannot even find the router admin (192.168.1.1) very quickly, it even timed out once while looking for the cable modem admin page.

[John Masterson]

I may have found something.

I see the main computer goes through a switch. I plugged it directly into the router and things dramatically sped up.

Let's see what happens tonight.

[DarkHumour]

Hmm.  Wonder if you're 'double natted'.   

One symptom is that the WAN ip is 192.168.x.y and the LAN ip is 192.168.a.b. 

Also that "QOS" setting in some routers meant for optimizing voip or internet phone service can bugger regular traffic.

DarkHumour

[Richardk]

QoS or 'interference' but what about the timing? Even being double natted doesn't explain that.

What else is connected to that switch but you said that there was virtually no traffic?

[John Masterson]

There are no other computers connected to the switch any longer. So I disconnected the switch and plugged my main computer straight into the router.

Now it's pulling 23mbps, so that's great. But the test will be after 11:30pm.  I still can't figure our what would be happening then that clears up in the morning.

[John Masterson]

Well, putting the main computer directly into the router boosted it's daytime speed 400% to 23mbps, and eliminated the late night slowdown.

I have no idea what happens late the caused the "switch effect" to drop the speed so low. Must have been something deeper about networking that I don't have the knowledge to fathom.

[Richardk]

But saying "it's just the switch" doesn't address why at night.

[DG9]

The switch has to sleep too you know... At some point do you even care, as long as the the switch is not needed?