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giraffedata

join:2009-07-11
San Jose, CA

Does AT&T throttle users when over capacity?

When AT&T's network beyond the DSLAM is saturated, does the system have some way of allocating the shortage among customers? Perhaps by what tier of service the user has purchased? Or what kind of usage it perceives by the user?

I ask because I have the 1.5 Mbps ADSL product and the modem consistently syncs at that cell rate. I often use nearly that entire bandwidth to stream a movie from Netflix, and it usually works fine without dropped packets.

But sometimes, (typically Sunday evenings), while streaming a movie, an IP ping to the router at the CO shows as much as 75% of packets lost. Also, the modem recycles the PPPoE connection repeatedly, complaining of excessive lost packets.

When in that state, if I stop the movie, things go back to normal almost immediately.

Since the only part of the network unique to me is a synchronous ATM connection, there's no reason any packet would get dropped there, so I want to conclude that AT&T is picking on me to solve a congestion problem in high-use times. But does it have such technology? And if so, would paying AT&T more money get it to stop?


David
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well essentially yes, upgrading will definitely make it stop. Why the packet loss is happening is because netflix on the mid tier takes between 1.5mbps up to 3mbps. So essentially you are choking out your modem to the point it's just dropping (the 75% packet loss you ee) them or timing them out due to the fact there is too may of them coming in.

Since I am a netflix subscriber I did some testing with an elite DSL circuit one of the first few nights I had netflix on a dd-wrt router watching the WAN port during a movie.

The basic setting or lowest quality setting you can get will typically stay rather steady at 1mbps up to 1.2mbps at times. I have also seen it go as low as about 512kbps a second.

the next (mid-grade tier) starts at a 1.5mbps average and goes up to 3mbps on average. Sometimes it goes as low as 1mbps but very seldom under this.

The HD or High end grade starts at 3mbps streaming and goes up to 5mbps (mine topped at 575kb/s), and seldom dropped below 2.5 to 3mbps.

You have 3 options typically

1.) upgrade your speed package

2.) downgrade your netflix package/picture quality

3.) Alternate ISP for service if you can't upgrade and still want HD or midgrade viewing.

I must close as least 10-20 tickets a week and I even copy netflix's own FAQ word for word including the link that explains the bandwidth speed requirements and put it right in the closing comments of the ticket. Only about 2-5% of the time do I ever really find any ATM level congestion.
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giraffedata

join:2009-07-11
San Jose, CA
I don't understand how my modem could be getting choked out or dropping anything. The link from AT&T to my modem is a 1536 Kbps synchronous ATM link. AT&T cannot send more than 1536 Kbps to it no matter what anyone wants to send me. Since the modem is capable of handling 1536 Kbps, there is no reason for it to drop anything based on too much inbound data.

That's why I believe these packets are being dropped further out in AT&T's network, and since it varies by time of day, I suspect congestion in a component shared with other customers. Could be an ATM switch, an IP router, or who knows what. Hence the question about what determines whose packets get dropped.


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reply to giraffedata
Well as you stated and I quote...

said by giraffedata:

When in that state, if I stop the movie, things go back to normal almost immediately.

typically if you can do that, it means you are flooding your connection or using all of it.

for gits and shiggles I can check your ATM and such, but my chances of finding back end overutilization is probably at most 10% as areas are getting converted to IPDSL and VDSL (Uverse internet).

I checked one today...

her DSLAM port: 22% peak for the day 25% for the whole month
her ISP connection: it's peak for the month was at 34%, it's daily average was at 19% it hit 34% on a saturday, three weeks ago.

Most circuits don't hit problems or "congestion" till they are well above the 70% mark.
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giraffedata

join:2009-07-11
San Jose, CA
The fact that the problem goes away when I stop the major stream of incoming data is consistent with lots of other explanations too, which is why I asked about the throttling.

You seemed to say before that the choke point was my modem (the one on my premises), which we can safely rule out. The connection might still be overtaxed in a number of ways, but the packets would be dropped before they ever started down my phone wire.

It's possible that at certain times Netflix or something else is sending 4 times my connection capacity to me, thus causing AT&T to drop 3/4 of my packets, but that seems unlikely, considering that the rest of the time, Netflix correctly detects my bandwidth and sends only what I can take. So it seems more likely to me that the variable is how much demand AT&T is experiencing at the time from other users.

But it could be any number of other things too, like an intermittently broken modem.

I don't remember if I tried IP-pinging the other end of the PPP connection when this happens. I guess that would shed some light on where the congestion lies.

How would I go about getting you or someone to look up the numbers for the DSLAM port and ISP connection?


David
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reply to giraffedata
Send me the DSL number via IM (click on my name "david" in blue and you should see a yellow box on that page that pulls up) put in the number and press send.


David
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reply to giraffedata
I got your number and I am checking on your circuit as of tonight. So far sync-wise it appears fine from best I can see. I don't see any errors or retransmits or nothing. I am still doing some more checking. So far the DSLAM capacity is at about 47% average and it's peak for the last 90 days was 68% max (68% only lasted for 2.5 hours).

I plan on checking the ISP side of things tomorrow as time permits I ran out of time tonight.
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David
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reply to giraffedata
I checked the ISP side of the circuit tonight, ISP circuit was ok. I went ahead and changed it for gits and shiggles. Should take effect by 1/15/13 11:59:59.

The one I moved it to in the last 90 days had a peak of..... get this.... 25%, and a nightly average of 14%. OUt of 150mbps available that means peak it used 37.25mbps and averaged 20.86Mbps. Your circuit will be the only one in this location.

Hopefully that helps, short of that I heard out there you can request a Netflix tech.
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giraffedata

join:2009-07-11
San Jose, CA
Hey, thanks. For the information as well as the reconfig.

What is a "nightly average"?

And can you expand on "Your circuit will be the only one in this location"?

I was actually thinking something in the ISP component of my AT&T Internet service might be prioritizing traffic based on the service level I'm paying for, but that really seems far fetched. I think the total extent of the difference between the HSI product tiers is the ATM sync rate between my house and the CO.

There are a bunch of things I can do to investigate further; I was just starting by focusing on the question of what could be different between days when everything is fine and days when most packets get dropped whenever a movie is playing.


David
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said by giraffedata:

What is a "nightly average"?

the nightly average or I should say daily or day average. that average was like 14% (very low).

said by giraffedata:

And can you expand on "Your circuit will be the only one in this location"?

You are the only AT&T DSL circuit out of 1000 slots available in this location. There is nobody else here on this level, and everyone else like t1's, Other ISP's, VDSL's, and other ATM circuits total only 25% peak/14% average for this entire path/connection/box.

For the car analogy... you are pretty much the only car on this level in a rather empty parking lot. 1st level probably has 1/2 the lot open, level 2 probably has a few cars, level 3 probably has like 2-5 cars and you are on level 4 by yourself.

You might even be sharing this box with smart phones, coffee shop wi-fi's, etc. Anywho, it's a very light traffic box.
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giraffedata

join:2009-07-11
San Jose, CA
Just before this change, I also changed the ATM cell rate (by buying the higher tier product) from 1536 Kbps to 3008 Kbps, and the problem seems to have disappeared.

It's kind of a pity; there were various tests I could have done to isolate the problem, and now we'll never know. My leading theory now is that something is broken in the Netflix server or the Netflix client running on my Wii game console that causes Netflix to monopolize the connection occasionally on slow connections. I note that even during these extended 75% packet drop episodes, the movie never stopped playing (not even while the DSL modem recycled the connection due to its own packet drops). So Netflix was getting its packets through; it's just everyone else who had practically no connection.

With the 3008 Kbps line, I have measured the Netflix stream at 1.6 Mbps in ethernet octets (so maybe 2 Mbps in ATM sync) averaged over 10 minutes, and I've never seen more than 2% packet drops (measured with separate IP pings).


David
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join:2002-05-30
Granite City, IL
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said by giraffedata:

My leading theory now is that something is broken in the Netflix server or the Netflix client running on my Wii game console that causes Netflix to monopolize the connection occasionally on slow connections.

As a wii owner and has the elite tier on a rather underutilized element (such as your new one) I am thinking it's more the wii software. Ever since I recently upgraded/updated it, it seems to tell me quite frequently that it's not connected to the internet. Though at the same time (and since I have a dual-wan router which is attached to a charter cable of 11/3 and dsl of 6/768) I can be surfing on the laptop, wife can be on her iphone, and my son watching netflix just fine on his iphone. So I am not exactly sure as to why the wii has so many problems. In a bit of irony my homebrew apps don't have any inet problems at all on the same wii. So I agree something is up with the netflix software on the wii.

For you the additional bandwidth is probably what did it. I did hear recently that there were "netflix techs" that were going to customer homes and from what we learned they are telling end users you need a 2mbps or greater connection now. I heard that from a tech in this center recently.
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If you have a topic in the direct forum please reply to it or a post of mine, I get a notification when you do this.
Koetting Ford, Granite City, illinois... YOU'RE FIRED!!