high packet loss despite good signals

D

diogo

Limp Gawd
Joined
Jan 29, 2006
Messages
450
I've been having issues with my internet connection. Severe lag spikes and packet loss that happen every few seconds. It is the type of stuff that is unnoticeable if just browsing the web, but very noticeable when playing games and streaming videos. Here's a few representative pingtests:

http://www.pingtest.net/result/69052706.png
http://www.pingtest.net/result/69041706.png
http://www.pingtest.net/result/68952623.png

Now, the thing is that this happens despite the fact that all signals seem to be within spec:
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 615000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK
Security Enabled BPI+

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 8 615000000 Hz 4.2 dBmV 39.9 dBmV 0 0
2 Locked QAM256 1 573000000 Hz 2.9 dBmV 39.4 dBmV 0 0
3 Locked QAM256 2 579000000 Hz 3.7 dBmV 39.8 dBmV 0 0
4 Locked QAM256 3 585000000 Hz 3.9 dBmV 39.6 dBmV 0 0
5 Locked QAM256 4 591000000 Hz 3.7 dBmV 39.8 dBmV 0 0
6 Locked QAM256 5 597000000 Hz 3.8 dBmV 39.8 dBmV 0 0
7 Locked QAM256 6 603000000 Hz 4.1 dBmV 39.9 dBmV 0 0
8 Locked QAM256 7 609000000 Hz 4.2 dBmV 40.0 dBmV 0 0

Total Correctables Total Uncorrectables
0 0


Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 7 5120 Ksym/sec 34800000 Hz 44.0 dBmV
2 Locked TDMA 8 2560 Ksym/sec 27900000 Hz 43.3 dBmV
3 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
4 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

I asked comcast's tech to check the usnr and the upstream receive power level and they are also within spec (31.7 and 0.0 respectively)


Now, I have replaced my modem, my cables, bypassed my router, used a different computer etc. etc. and I still have the same problem. I've had comcast technicians over twice and they couldn't find anything wrong with the signals or anything.

Would anyone have an idea of what this could be or what to do next? Only reason I haven't left comcast at this point is that the options in my area aren't much better.
 
Do you notice this on more than one computer in the house? Is the packet loss intermittent or constantly present?
 
Ehren8879 said:
Do you notice this on more than one computer in the house? Is the packet loss intermittent or constantly present?
Click to expand...

I have tried different computers connected directly to the 2 different modems I've used, and the issue is always the same. The packet loss happens in spikes every few seconds. That is, ping will be steady and low for 10-30 seconds, and then I will see a spike. As an example, here's what happens when I ping comcast's server:

bytes=32 time=9ms TTL=62
bytes=32 time=25ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=591ms TTL=62
bytes=32 time=44ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=8ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=8ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=1239ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=14ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=8ms TTL=62
bytes=32 time=11ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=11ms TTL=62
bytes=32 time=71ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=16ms TTL=62
bytes=32 time=8ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=9ms TTL=62
Request timed out.
bytes=32 time=15ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=10ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=8ms TTL=62
bytes=32 time=8ms TTL=62
bytes=32 time=9ms TTL=62
bytes=32 time=33ms TTL=62
bytes=32 time=8ms TTL=62
Request timed out.

Ping statistics for 68.85.91.149:
Packets: Sent = 50, Received = 48, Lost = 2 (4% loss),
Approximate round trip times in milli-seconds:
Minimum = 8ms, Maximum = 1239ms, Average = 50ms
 
This would appear to be an issue with your cable modem or your ISP.

I would have them change the cable modem and if that doesnt work have them run a full diagnostic from their demarc or whatever cable calls it all the way to your home.

See if your cable modem modulates a perfect signal that still doesnt rule out that the silicon or some process embedded is not funked up. The ASIC in the cable modem might be defective causing this or going bad, or there is a bad cap, or something else.

The issue might also be with Comcast's router on their end. It might be having some kind of issue.
 
Thanks for the suggestion. I've tried 2 different cable modems on my end (one of them brand new), but I've requested that the next comcast tech that is scheduled to come here bring one of their own, so that I can try a 3rd one out in the improbable but possible case I have 2 bad modems.
 
On your PC, start three cmd prompts, and in each, ping a different target (your default gateway on your LAN, your 2nd hop, your 3rd hop) and see where the latency/loss is coming from.

If you have zero loss to your gateway, and zero loss to your 2nd hop, but loss to the 3rd hop, you know the problem is between 2nd and 3rd hop, and can focus your troubleshooting there.
 
You'll need to run tracert to confirm- try tracert www.google.com looking for unreachable nodes or long delays.
Issue is more than likely due to congestion on your ISP's system
 
Using pingplotter, the bulk of the packet loss happens between my house and comcast's server (the 1st hop outside my lan). Though it could indeed be congestion, since just now is one of the first times i've been able to test in the morning and the problem seems quite a bit better (but still far from perfect - 1 to 2% packet loss, as opposed to 4-6)
 
Would simple congestion explain these issues? More precisely, if the problem was congestion would I see something like this (good pings and speeds, but intermittent lag spikes/packet loss?)
 
diogo said:
Would simple congestion explain these issues? More precisely, if the problem was congestion would I see something like this (good pings and speeds, but intermittent lag spikes/packet loss?)
Click to expand...

Yes. When network equipment reaches capacity, it typically starts dropping packets. Dropping packets in a network is extremely bad, as it actually exacerbates a problem- both sides know packets were lost, so both sides request/send missing packets, which leads to more congestion, which leads to greater packet loss, which leads to...
ANY packet loss is bad because it contributes to congestion

Packet loss is typically very tough to see on most of the speed test sites, in my opinion. You can actually get awesome pings and speeds to most sites, because the test will just fail if not enough packets make it. From a user perspective, pages will load slower than normal, and intermittently not load at all. Online video will be buffering constantly and playing at low quality. All in all, you will see a very frustrating experience while most speed tests will show good results. Sometimes it will show-up by testing alternate/further test servers- latency will increase, but speeds should stay in the ballpark.

The toughest part is getting the issue addressed, as most 1st, second, and third-level techs don't even know what packet loss is (they'll think you mean latency), Good Luck.
 
RocketTech said:
Yes. When network equipment reaches capacity, it typically starts dropping packets. Dropping packets in a network is extremely bad, as it actually exacerbates a problem- both sides know packets were lost, so both sides request/send missing packets, which leads to more congestion, which leads to greater packet loss, which leads to...
ANY packet loss is bad because it contributes to congestion

Packet loss is typically very tough to see on most of the speed test sites, in my opinion. You can actually get awesome pings and speeds to most sites, because the test will just fail if not enough packets make it. From a user perspective, pages will load slower than normal, and intermittently not load at all. Online video will be buffering constantly and playing at low quality. All in all, you will see a very frustrating experience while most speed tests will show good results. Sometimes it will show-up by testing alternate/further test servers- latency will increase, but speeds should stay in the ballpark.

The toughest part is getting the issue addressed, as most 1st, second, and third-level techs don't even know what packet loss is (they'll think you mean latency), Good Luck.
Click to expand...

Thanks. I understand the effects of packet loss, but was just unsure if congestion would manifest itself that way.

And I could go on a pages long rant about dealing with lower level techs regarding this issue. The best examples I can think of are of the one who pinged my modem with 1 packet of data and then claimed that there wasn't any packet loss, since his test showed 100%, and another who said that maybe if I upgraded to their faster package the issue would go away.
 
It took me MONTHS, if not over a year to get CenturyLink to recognize the issue for a good part of Central Kansas. They're only going to see it by looking at logs on their routers or equipment- something anyone who gets paid to primarily answer a phone and invent excuses is kept far, far away from. I was able to get in touch with the KS area director and work from the top down. I sense some frustration in your future.
 
If your issues are node congestion related then you are unlikely to experience the packet loss between the hours of 3-5am, with the problem potentially being bad between 6-8pm and the worst between 8-11pm. This is based on the typical usage pattern we see day in, day out on our cable plant in residential areas.
 
Looking at my test history on pingtest.net, I almost certain that it is caused by congestion. Up to about 10% packet loss between 6 and 10 pm, and generally between 0 and 3% between 12am and 3am.

Now for the uphill battle in getting comcast to recognize this.

Thanks, everyone.
 
Ehren8879 said:
If your issues are node congestion related then you are unlikely to experience the packet loss between the hours of 3-5am, with the problem potentially being bad between 6-8pm and the worst between 8-11pm. This is based on the typical usage pattern we see day in, day out on our cable plant in residential areas.
Click to expand...

So spend money and deliver a better product?
 
tangoseal said:
So spend money and deliver a better product?
Click to expand...

Haha, no no no... You misinterpreted what I was trying to say.

We don't suffer from network congestion whatsoever. What I was saying that if the OP's area was exhibiting congestion then based on the usage profile I'm familiar with, those.are the time periods to expect it.

Our network kicks ass, trust me.
 
Last edited:
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