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FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast

1 edit
reply to FirebirdTN

Re: momentary internet issues-help.

Leave it to ME to find the most difficult problem imaginable. I should probably start a new thread, but I will try to keep it all in this one.

So after over a week problem free, I decided it was time to get Comcast to replace the DOCSIS 2.0 loaner with a DOCSIS 3.0. That was quite an experience in itself. I will spare those stories.

So finally after TWO full weeks problem free I *finally* get my DOCSIS 3.0 emta. This time an Arris TM822 (I had initially purchased a TM722 from Best Buy when I became a Comcast customer last year).

Within MINUTES of my wife using her iPad on the new TM822, the problem is BACK.

This is really starting to look like some issue with channel bonding, as I had ZERO problems when I was using the DOCSIS 2.0 emta, which looks like only used a single upstream, and a single downstream channel.

So....does anyone have any thoughts on where I go from here besides throw these emtas out my car window on the way to work?

-Alan

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast
Another update:

I think I have *finally* found the problem, but before I get into it:

I have a supervisory visit this coming Tuesday. Got a call from him yesterday. He is monitoring my connection, so we will see if he had any success in seeing these "outages". Unfortunately, his tester can only check it once every 5 minutes, so it may not be enough for him to see them. We will see.

Anyway, it really is starting to look like I am suffering from "Bufferbloat". Its just a SWAG, but my symptoms very much mimic bufferbloat's behavior, especially considering my outages always occur during high demand, and my pings get progressively higher.

Tonight I will set up my router to throttle my bandwidth *just* below my actual "shaperprobe" throughput levels, and test again. Last night, the wife got on her ipad, and I had over 10 45second outages in less than 1 1/2 hours.

Once I impletement traffic shaping on my router, if the issue goes away, then I will know for certain it is indeed bufferbloat, and I will update this thread accordingly for anyone stumbling on it from a search.

-Alan

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast
After three LONG months my issue is finally resolved. The problem was indeed bufferbloat in the emta. I wish I could find detailed technical specs on the three emtas I have had hooked up these past few months, but based on what I have seen, the newer the model, the worse the issue [the current Arris TM822g I have in operation now was actually suffering from even longer durations of packetloss].

A really good "one pager" is here:

»www.bufferbloat.net/projects/blo···calIntro

I set my router up to limit my bandwidth to just *slightly* under my measured throughput to keep from overloading the modem's upload buffer. I told my wife do her best to "break the internet". Not only did it work flawlessly with no outages or packet loss, but now even when she is on it, the maximum latency I have seen with pingplotter for the entire evening to the first hop has been 76ms, and that is even when she is on it, doing the exact same things that she was before when I suffered horrible latency [sometimes close to 3 full seconds] before it eventually started causing 100% packet loss.

I will need to give it another few days to be on the safe side, but I am now about 99.9% convinced that is what it was. After implementing traffic shaping in my router, everything is so much better, and I no longer get any dropouts.

I am still keeping my tech visit Tuesday, if nothing else just to see how to go about getting another customer owned emta, since I returned mine to best buy and can't find another.

But unless something radically changes, this will be my final post in this thread.

To those that offered constructive advice and pointing me in the right direction, you have my sincere thanks [Netfixer, switchman, and a couple others].

To those that suffered "tunnel vision", and completely ignored the logic of my test results-A piece of advice: Every problem is unique. Just because you have seen something before 99 times, does not mean its going to be the same thing the 100th time.

One last note regarding troubleshooting issues like this: I know its generally considered common practice to hook one PC directly to a modem for troubleshooting purposes; but alot has changed in the last 10 years. It is very difficult to duplicate an entire network's load on a modem with one PC, so just because someone doesn't experience any issues with a PC connected directly to the modem, doesn't necessarily prove anything. I believe its still a valuable troubleshooting aid, but depending on the issues and circumstances, I would not lay as much credence in the results of that test as I would have 10 years ago.

-Alan


NetFixer
Bah Humbug
Premium
join:2004-06-24
The Boro
Reviews:
·Cingular Wireless
·Comcast Business..
·Vonage
Glad to hear that you have tentatively found a solution.

I almost mentioned the possibility of buffer bloat, but I backed off because so many people don't believe that it exists (and I have to be careful in this forum about making controversial posts) . I have experienced some buffer bloat symptoms on my network, but not as severe as yours. On my network, the primary symptom I would see was poor quality VoIP.

One on-line test that can be run to check for buffer bloat (among many other things) is Netalyzr. Warning! This test requires Java, so anyone who doesn't want to run a Java app over the Internet should not bother to click the link.

Here is the buffer bloat test segment result when I have minimal upstream rate limiting enabled:
said by Netalyzr :

Network buffer measurements (?): Uplink 360 ms, Downlink is good –
We estimate your uplink as having 360 ms of buffering. This level may serve well for maximizing speed while minimizing the impact of large transfers on other traffic.
We were not able to produce enough traffic to load the downlink buffer, or the downlink buffer is particularly small. You probably have excellent behavior when downloading files and attempting to do other tasks.

This is what I see from the same test if I disable upstream traffic shaping:
said by Netalyzr :

Network buffer measurements (?): Uplink 710 ms, Downlink is good –
We estimate your uplink as having 710 ms of buffering. This level can in some situations prove somewhat high, and you may experience degraded performance when performing interactive tasks such as web-surfing while simultaneously conducting large uploads. Real-time applications, such as games or audio chat, may also work poorly when conducting large uploads at the same time.
We were not able to produce enough traffic to load the downlink buffer, or the downlink buffer is particularly small. You probably have excellent behavior when downloading files and attempting to do other tasks.

Depending on network conditions, sometimes the upstream buffering for my connection is over a second.

I didn't bother to do it for this post, but if I use an old DOCSIS 2 modem (no channel bonding), the upstream buffering drops to ~60 ms.
--
A well-regulated militia, being necessary to the security of a free State, the right of the people to keep and bear arms shall not be infringed.

When governments fear people, there is liberty. When the people fear the government, there is tyranny.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
reply to FirebirdTN
How are you certain that it is the modem and not something farther upstream ?

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast

1 edit
Hmmm, by upstream I do not know if you mean further along the comcast network, or further along my home network?

But to try and answer:

Prior to implementing upload traffic shaping on my router, I ran some packet loss testing internally from my LAN headed toward the internet, and from the internet headed toward my LAN [tested from my office PC at work on a 20/20 fibre connection].

When total network failure occurred, internally I could get all the way from my PC to the modem itself, but no further. From the internet I could get all the way to my first hop, but no further. This isn't quite conclusive, as I don't have the ability to test to the modem *itself*, but...its the best I can do. [It will be interesting to hear the Comcast tech's results after monitoring my connection-I'll lay money down he did not see any drops at all. Unfortunately, I haven't heard from him since Thursday].

So, logically that would indicate an issue between the modem itself and the first hop. Cabling, signal levels, etc have all been eliminated as a source of the trouble. That only really leaves the modem itself.

When I swapped out for a D2 emta, the *packet loss* went away completely [but the high latency under load did not]. When I swapped out for a newer D3 emta than the one I originally had, the problem returned, but this time with even *longer* periods of total packet loss.

Now at this point, you *could* say its just a staggering coincidence and I actually had two defective D3 modems, BUT...to have two separate devices fail in the exact same manner would be extremely rare.

But I think the final nail in the coffin was after implementing traffic shaping [on the upload path only, the download path is set for full speed], not only did the loss disappear, but the accompanying high latency during my wife's iPad usage that always precipitated the 100% packet loss did as well, and that is while testing under the exact same load conditions prior to implementing the traffic shaping.

I ran pingplotter for over six hours last night under high load, and had not one single lost packet, and the highest latency to the first hop the entire time was 76ms.

-Alan

switchman

join:1999-11-06

1 edit
reply to FirebirdTN
Good to hear you think it is solved. I recently, within the last month, implemented QoS rules on my router. I can see the difference in my network. With multiple devices using the network I could experience slow downs/pauses in normal browsing. In my case, I could look at the link and see that I was saturating it so knew I needed QoS to solve my issue. After the QoS rules were put in place, no more issues. This goes to show that with properly implements QoS at the endpoint, possibly a lot of problems people have or appear to have with there internet provider could be solved. I am surprised that the service providers do not push a QoS profile down to the modem/routers they provide. But maybe some of them do. Obviously this would not help where the customer is only using it as a modem as you are.

Not to hijack your thread, but for anyone using Tomato and interested in QoS, Toastman has developed a very good set of rules that seem to work well. I am using his rules on a Shibby build. More information can be found here.

»tomatousb.org/tut:using-tomato-s-qos-system
and here
»tomatousb.org/tut:easy-toastman-qos-setup

After setting up these rules, I tweaked the the rates and tested it on a 30/5 link. During the testing I can download a file at ~20Mb/s, stream two Netflix streams in HD quality and do normal web browsing with no slowdown in performance.


workablob

join:2004-06-09
Houston, TX
kudos:4
Reviews:
·Comcast
reply to FirebirdTN
I too have been having this issue. I'll be surfing and the modem will reset.

It sometimes happens several times a day.

It's been happening for about the last month or so.

Dave
--
I may have been born yesterday. But it wasn't at night.

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast
workablob-

I think you might have a different issue. In my case, my modem NEVER reset. Signal levels never waivered. And modem indicators never changed. As far as looking as all aspects of the modem, it was all well and perfectly happy, even during my service disruptions. Its a shot in the dark based on very limited info, but if your modem is resetting under load, it may just be going bad.

Since I'm posting back in here, I can happily report I was problem free ALLLLLLL WEEEKKKEND LOOOONGGGG whooHOO!!!!

-Alan


workablob

join:2004-06-09
Houston, TX
kudos:4
Reviews:
·Comcast
said by FirebirdTN:

workablob-

I think you might have a different issue. In my case, my modem NEVER reset. Signal levels never waivered. And modem indicators never changed. As far as looking as all aspects of the modem, it was all well and perfectly happy, even during my service disruptions. Its a shot in the dark based on very limited info, but if your modem is resetting under load, it may just be going bad.

Since I'm posting back in here, I can happily report I was problem free ALLLLLLL WEEEKKKEND LOOOONGGGG whooHOO!!!!

-Alan

I see.

I started the Netalyzer tool and it almost finished but now the netalyzer site is down.

»www.downforeveryoneorjustme.com/···u/,d.aWM

Dave
--
I may have been born yesterday. But it wasn't at night.

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast
reply to NetFixer
Click for full size
I did lose a little speed in this whole process. When I swapped to a D2 emta I lost 10dn/3up. I shrugged it off as an older device. Once I got a new D3 I never got my speed back, and lost my upstream channel bonding.

I'm still problem free, but this is the only reason I decided to keep the tech visit. 800Xfinity wasn't able to help me get my speed back.

Anyway, while I wait for the tech, I thought I might upload a screenshot of the newest D3 modem PRIOR to traffic shaping. Much more horrid if you compare it to the D2 and my initial [older] D3 shots on the previous pages.

-Alan

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast
I'm still problem free since the traffic shaping, but I wanted to give an update:

Although I still don't see how it could have caused the packet loss, I just found a stuck email with video attachment in my wife's outbox in her iPad. Its been there since Dec 26th, which is EXACTLY when my problem started! Still don't understand how that could have created loss. Creating LAG I get, but loss, I don't...

I still am keeping the traffic shaping in place though because my internet feels more "responsive" when multiple people are on it.

-Alan


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
iPads are great at crashing wireless equipment with issues like that.

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Reviews:
·Comcast

4 edits
said by beachintech:

iPads are great at crashing wireless equipment with issues like that.

I can definitely see how that could happen!

I still don't get how it could have caused packet loss between the emta and 1st hop though [and all successive hops] but ONLY with DOCSIS 3 equipment. I did not have the loss or momentary internet outages with DOCSIS 2 equipment, only the lag when the upstream was saturated as you would expect.

I guess it doesn't really matter as the issue has long since been resolved, but a stuck email should NOT have caused this, no matter how large it was. It just raises an eyebrow that it only caused issues with DOCSIS 3 devices [well, two different Arris emta models anyway].

During the later course of this process, I fired off an email to Jim Gettys [the person who coined the term "bufferbloat"], and he understands the lag generated when the upstream is saturated, but even he is at a loss as to why I was seeing 100% packet loss on D3 equipment. As he put it, the D3 equipment must "behave very badly" when its upstream buffer is full. But keeping the traffic shaping in place will prevent it from ever happening again.

-Alan


workablob

join:2004-06-09
Houston, TX
kudos:4
Reviews:
·Comcast
reply to workablob
Well, I had a tech visit yesterday and he noticed I had no ground box on the line outside.

He installed one.

He replaced the part that joins the Comcast coax with my home coax.

This shortened my cable enough that he had to put it a new cable from the pole to the house to make up the missing length from cutting the end off of my coax.

Before he did the work I was getting (on a good test) 2-3Mbps up but usually it would be less than 1 Mbps.

When my system was stable I was getting between 3~4 Mbps up.

Now I am getting 5~6.

And he said Houston will be getting the tier upgrade but no details on a schedule.

Dave
--
I may have been born yesterday. But it wasn't at night.


workablob

join:2004-06-09
Houston, TX
kudos:4
Reviews:
·Comcast
In my case the modem was the culprit. Over the past month it has been resetting more and more. Yesterday it would not boot up and just kept resetting.

I took it to the Comcast center and got a brand new Cisco DOCSIS 3 and my troubles are over.

Solid internet connection and over 5Mbps UP.

Dave
--
I may have been born yesterday. But it wasn't at night.

FirebirdTN

join:2012-12-13
Brighton, TN
kudos:1
Glad to hear your issues are resolved as well. I know it can be frustrating at times!

-Alan