AT&T Midwest → [Speed Problem] Downloads pause constantly

I am having problems where downloads will pause for several seconds. Most of the times it will resume but sometimes the downloads will timeout and never restart. This has also been getting worse with downloads timing out, especially it seems during evening hours (6-9pm). Most of my issues seem identical to the ones in the following thread from another user:

»[Speed Problem] Can't figure out why downloads like to pause for

I've attached a couple of my own screenshots from the bandwidth monitor on my router. They look similar to those in the above thread.

I've had this DSL installation for over 6 years now, and it just became a problem around February/March of this year. It has been doing this constantly ever since.

I had a Westell MSTATEA modem. I replaced this with a Actiontec GT701D to make sure the modem was not causing problems. I tested both of these modems outside the house at the NID and they both still have problems. I have DSL filters on all phones in the house, except for the security system. The phone connection for this uses a RJ45 jack instead of a RJ11, and I don't have an adapter. It's been like this for years though so I doubt this is now causing problems, and even at the NID there is problems.

I just last month contacted technical support. The phone tech contacted someone who said there was line trouble. They said they did something to fix the line over the phone, but the problem was not corrected. I had them send a tech out. He came out and checked the lines. He said the signal was ok. He left with no resolution to the problem. There is no DSL filter on the security system. He claimed this was the problem even though the problem persists at the NID, and I've had the house connected this way for 6 years with no problems before.

In addition to download pausing my modem occasionally trains at lower speeds. I have 1.5M down / 256k up. The modem will occasionally retrain at lower speeds, sometimes as low as 384kbps. This is on the Actiontec. Before I switched out the Westell it would occasionally lose DSL sync all together.

These are the current stats from my Actiontec after having reset the counters a few days ago. It seems like there are a lot of CRC and FEC errors. I don't know if this pointing to a line problem.

DSL Status
VPI: 0
VCI: 35
DSL Mode Setting: MMODE
DSL Negotiated Mode: G.DMT
Connection Status: Showtime
Speed (down/up): 1536 / 384 Kbps
ATM QoS class: UBR
Near End CRC Errors : 0/118
Far End CRC Errors : 0/21871
Near End CRC(Within last 30 mins) : 0/0
Far End CRC(Within last 30 mins) : 0/0
Near End RS FEC : 0/8577
Far End RS FEC : 0/0
Near End FEC(Within last 30 mins) : 0/0
Far End FEC(Within last 30 mins) : 0/0
Discarded Packets(Within last 30 mins): 0
SNR Margin (Downstream/Upstream): 1/18
Attenuation (Downstream/Upstream): 39/31

Downstream SNR=1.0 dB? Was that a C&P, or transcription? Because nothing DSL works reliably with such a low margin.

I think the Actiontec reports downstream SNR incorrectly. This is what others have said as well.

These are the statistics from my Westell.

ADSL Information
Line State Up
Modulation G.DMT
Data Path FAST

To Modem To Internet
Max Allowed Speed (kbps) 1536 384
SN Margin (dB) 13 18
Line Attenuation (dB) 56 31
Loss of Signal 0 -
Loss of Frame - -
CRC Errors 1 1

ATM Information
VPI / VCI 0 / 35
Protocol PPPoE

In Octets 36587
In Errors 0
In Unicast Packets 222
In Non Unicast Packets -
In Discard Packets 0

Out Octets 41224
Out Errors 0
Out Unicast Packets 213
Out Non Unicast Packets -
Out Discard Packets 0

It also appears that the Actiontec reports the download attenuation incorrectly as well. That high attenuation from the the Westell would cause you to first suspect possible high CRC error rates as causing the slowdowns.

Keep the Westell on your line for a day and then check and post the CRC error counter results.

One other question, do the download pauses occur through the day or only at certain times of the day?

The pauses happen all throughout the day. Although it seems worse during peak hours. The first screenshots were taken around 11pm on a weekday. I've attached one I took just now around 4pm on a Saturday. The pauses are much more frequent, and when it is downloading the speed seems much more jittery.

I don't think CRC errors are a direct cause of the pauses. The pauses happen constantly and when I check the CRC errors after each pause they are not increasing. The CRC errors just seem to happen at times, but the pauses happen all the time.

If the CRCs aren't causing the throughput pauses, then you can use the Wireshark thoughput test: »SBC DSL FAQ »How to measure throughput speeds on individual packets? to investigate possible causes. Post your results if you try the test.

I've attached a stream graph of a Youtube video download and the 16MB download test file linked in that FAQ article. They both just stop downloading for a bit and resume. The Youtube one is much worse.

OK. That's a new one on me. The packets simply stop during the slowdowns. There is no TCP/IP slowdown and gradual recovery. Nor is there any sudden slowdown and then near instantaneous speed resumption that can be symptom of ATM layer problems.

Could you have a malware, a virus or trojan, stealing some of your throughput?

I doubt it. It does this on multiple PCs, and if something was hijacking bandwidth it should still show on the bandwidth monitor from the router. Instead it still shows just pauses even at the router. It still shows pauses even if I telnet to the router and download straight from the router with wget.

My home network is pretty simple. Modem is hooked to a WRT54GL running DD-WRT. A couple PCs connected to the router via wireless and a wired connection to a DVD player for Netflix. The pauses happen on multiple PCs even if I connect straight to the modem and have the modem at the NID. I'm pretty certain it's a problem outside my house.

How is your ping time to your AT&T gateway?: »SBC DSL FAQ »How do I do a gateway ping test?

If I do just the ping from my PC with nothing else going I get this.

Ping statistics for 108.69.183.254:
Packets: Sent = 100, Received = 100, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 9ms, Maximum = 11ms, Average = 9ms

If I run the ping test when I am downloading the ping time is much worse and I start getting packet loss. I also get high ping times and packet loss if I do the ping from the router, so it is not just something on my PC.

Ping statistics for 108.69.183.254:
Packets: Sent = 100, Received = 96, Lost = 4 (4% loss),
Approximate round trip times in milli-seconds:
Minimum = 9ms, Maximum = 184ms, Average = 89ms

I get a weird graph for the jitter/loss with big packets from the line quality test. Although I'm pretty sure I've done this test before and it has looked normal so I don't know if this is related to the pauses.

I am getting the same problem. Anything that needs data to be constantly downloading like Skype will just stop and resume. There are gaps seen in my bandwith monitor. This just started to happen without any hardware changes. Any ideas?

»/pingt ··· /2934307

I checked his circuit, he rides the same path to collinsville, IL as I do. I know I haven't been having any download problems I can find and netflix streaming has been working good for me. just for kicks and grins I rebuilt the circuit at the DSLAM. SO far it's clean syncwise and to the ISP.

The Wireshark throughput was just strange -- no packets passing for extended time intervals and then almost instantly returning to full speed.

he has a 1.5/384 circuit, I can see upload saturation doing that. at 384kbps up it wouldn't be difficult to accomplish.

P.S. forgot to mention- the original guy that had this problem the only thing I found was he was on the interleaved profile. So far I haven't heard back from him and that was 6 days ago. This guy here in this thread never was on interleaved.

only thing I found in common so far is they are both running ddwrt on wrt54gL or GS boxes. I know those only have a max memory of like 8mb methinks. I have ddwrt but I have the x86 version with 256MB main memory and a 1.1Ghz amd xp processor. If any of my downloads have paused I can't tell. I have been netflix streaming like a mad deamon.

Another thing that I also just thought of I have a wrt54g v5 that also has 8MB memory as well. I tried replacing my dd-wrt x86 box for this unit, and this unit just wouldn't hold up. I suspect the number of devices and traffic has a lot to do with it. Netflix streaming didn't work worth a damn either. Part of my theory thinking is these units with 8MB memory did much better as 1 or 2 device routers and or access points only.

The graph pattern didn't look like the ACK starvation patterns that I'd managed to intentionally induce during Wireshark testing. Even during ACK starvation,a throttled stream of packets will get through, albeit at greatly reduced speeds. I never saw complete cessation of download transmissions.

Rebuilding the circuit didn't help. My SNR increased to 19 from around 13, but the pauses still happen.

I don't think the router has anything to do with it. I've tested straight from the modem before and it still pauses. I'm testing straight from the modem right now and it still pauses.

The other consistent symptom I get is high ping time and packet loss from the gateway when I start downloading. It is normal if I am not downloading anything, but when I start downloading ping times jump up and I start getting high packet loss.

I hooked my Actiontec back up. I telneted directly into the modem and started a download with wget while doing the gateway ping from the modem. It still does it even in this case. This is straight from the modem with the router not even hooked up. I don't think any PC or router on my network has anything to do with it.

Some increased ping during a download or during streaming is normal. Packet loss isn't.

That increase in SNR would help eliminate CRCs, so CRCs as a cause of the packet loss can pretty much be dismissed.

I think your Wireshark graphs looks like there is no buffering during the delays. I've always thought that the buffering delay occurred at/in the gateways. Maybe the problem lies in your DSLAM before the ATM transmission to the gateway, but that's just a guess.

I know me and him share the same ISP router se1.colvil port 4/1. He is on vp6 where he is at and I am on vp7 for granite city il. We both ride circuit 902 out of collinsville, IL.

only thought is I could change the port in the office, when I looked at his line on the DSLAM I didn't see any packet discards or dropped cells from the port itself.

I can initiate that change Monday, as the office to do that today is in maintenance/surveillance only mode for the weekend.

I ordered the port change today.

Well tried the office port change which didn't yeild any results and the problem still happens.

I have one last idea, which I am waiting on a confirmation if that did it or not.

And that was... lol sorry you left us hanging with that clifthanger

Pretty much in a nutshell it's pausing because he is using all his bandwidth. Essentially the only way to fix this problem is upgrade the DSL speed.

So he changed my bandwidth to 3Mbps for a day. I was able to download without pauses during this time. He changed it back to 1.5MBps and it started pausing again.

Sorry but this doesn't make any sense to me. I've had this installation for over 6 years. I've had 1.5Mbps this whole time and never have had problems downloading until early this year, even though my downloading habits haven't changed.

Looking back at the thread from the other guy and the Youtube video from another user it looks like they were all on 1.5Mbps from their download meter. Looks like this is just something happening to people with 1.5Mbps speeds.

The more I think about it I think the download degradation is an intentional ploy to force people to upgrade. Why would I not have problems maxing my bandwidth at 3Mbps and not 1.5Mbps?

I can't sustain a 3Mbps link where I'm at anyway as the SNR is too low. They've told me before it's not available at my house. I guess my next step is switching to Charter.

Noise margin wasn't that low when I checked it. It was holding at about 7-8db ( occasionally you would hit 9db with a max of 3680 and that was the fast profile, not interleaved, and it took no errors!). The reason why the 3mbps/512 worked because you had 33% more upstream to use, and 95.8% more downstream to use. The modem is timing out and discarding the packets because it says "Hey, there is too much here! and discarding." We used to have modems that would kick down (retard) your upstream and your downstream when this happened. It kept you going but it slowed your line down to accomplish it and keep you from flooding the modem. With the modems out there today, it just drops it, thus you see "pauses" and packet loss.

One final thought: it doesn't have to be 1.5mbps only, you can reproduce this problem with 3mbps, 6mbps, 12mbps, 18mbps, 20mbps, 50mbps or any other variation of broadband speed you buy. You can also reproduce this problem on dial up, dsl, cable, fiber or any other media as well. Even I am not immune as I can cause my modem to drop it's connection if I push it too hard with logmein and the wife is making a voip call at the same time. I fixed this problem for me with a dual-wan router with another connection, a little slower than my elite dsl, but still enough to make voip successful all day long.