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Standard User simonbratt
(newbie) Thu 14-Apr-11 12:00:47
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CN21 really messed up our internet


[link to this post]
 
CN21 really messed up our internet.

Since the upgrade from ADSLMax(CN20) to ADSL2+ (CN21) when ever we upload data we get very high latency (ping speeds) typically from 800ms to 2000ms which causes any users to have exceptionally slow webpages.

This has been ongoing since july 2010, and still BT cant find the problem. It took them about 3 months to acknoledge there even was a problem as all their tests showed no problem. It wasnt until BT's ITSM agreed to remote logon to a laptop connected to a router (had 2 different routers) and saw the bad pings and tracerts while uploading was happening that they admintted there was a problem.
Anyway anyone else with CN21 problems?
Administrator MrSaffron
(staff) Thu 14-Apr-11 12:17:29
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Re: CN21 really messed up our internet


[re: simonbratt] [link to this post]
 
if you saturate the upstream on most connections the latency rises a lot, i.e. the data being sent out can make getting ACK and page requests out difficult.

Did you change any hardware at your end?

With 21CN the upstream is usually faster, and it may be that the existing hardware has trouble doing much beyond handling this busier upstream data.

Which ISP is it?

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User simonbratt
(newbie) Thu 14-Apr-11 12:30:24
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Re: CN21 really messed up our internet


[re: MrSaffron] [link to this post]
 
hi

ISP is BT line is with BT, existing Draytec vigor 2800 is ADSL 2+ compatible (after firmware upgrade) have 2 of these routers + BT sent out one for us to test... all give the same bad results when uploading.

Its so bad, sometimes webpages wont even load, let alone be very slow


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Administrator MrSaffron
(staff) Thu 14-Apr-11 13:25:19
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Re: CN21 really messed up our internet


[re: simonbratt] [link to this post]
 
On an ADSL2+ IP network that is NOT 21CN I see the same, high latency/packet loss if I saturate the upstream

20CN line (same computer) it is still higher latency but not as bad.

When you consider how TCP works this is to be expected, and the solution is to throttle back the upstream of uploads by the application to the point where it does not saturate the upstream, leaving some room/time for HTTP requests and TCP ACK's to be sent in a timely manner.

The higher upstream of ADSL2+ I think just make the issue more apparent.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User simonbratt
(newbie) Thu 14-Apr-11 13:36:19
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Re: CN21 really messed up our internet


[re: MrSaffron] [link to this post]
 
well on all the networks ive tested, i can upload as much as i like and always the ping times are below 100ms, usually below 50ms

We used to have no problem on the old service, and the above was true.

Well BT have installed a new line, back on the old cn20 network (as it used to be) and that is also now having the same problems as the CN21 line.

And by saturate the upstream i assume you mean by uploading anything ie one 5 mb picture.
Upstream will always try and run as fast as it can no matter how large or small the file uploading (assuming no forced restrictions in use)

i wonder if i can throttle uploads in the draytek router, i will see.

Edited by simonbratt (Thu 14-Apr-11 13:38:14)

Administrator MrSaffron
(staff) Thu 14-Apr-11 13:43:02
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Re: CN21 really messed up our internet


[re: simonbratt] [link to this post]
 
The 20CN test I did was on a Zen line at an exchange with no WBC, and people have complained about the issue before. I was only uploading 2-3MB to get the effects I did.

With small uploads people often don't notice.

Most complaints were from people using torrents and letting them run flat out. I also if sending large files generally go make coffee rather than try and carry on with web browsing.

NOTE: if you do a flat throttle of all uploads that won't help, you need to be intelligent, e.g. throttle only certain types of upload traffic. It is why QoS has started to appear in some devices, which allow you to give priority to TCP ACK packets.

With 21CN being all IP based it may be more noticeable, i.e. it is worse with a big IP Backbone, but the effect is there with 20CN, just not as harsh.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User simonbratt
(newbie) Thu 14-Apr-11 14:03:48
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Re: CN21 really messed up our internet


[re: MrSaffron] [link to this post]
 
i appreciate your replies.

Well in our experience, Cn20 upload throttling wasnt noticable, then CN21 upgrade came, and was so noticable it was not possible to live with it. then an additional CN20 line was installed, but with the exact same problem as the Cn21 line.

I have just set the draytek TX rate to 100kb to see if that throttles the max upload speed to100kb

i have QoS on my router but to be honest not sure of what to put in it.
Administrator MrSaffron
(staff) Thu 14-Apr-11 14:09:45
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Re: CN21 really messed up our internet


[re: simonbratt] [link to this post]
 
http://www.openbsd.org/faq/pf/queueing.html some background reading, to show I am not talking from my behind.

In the draytek see if you have something like "QoS Outbound TCP ACK Prioritize"

To add, the 20CN connection, is with an ISP that uses 21CN, you might actually have something that looks like 20CN i.e. ADSL but its actually using the 21CN IP Backhaul.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk

Edited by MrSaffron (Thu 14-Apr-11 14:10:54)

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User simonbratt
(newbie) Thu 14-Apr-11 14:16:29
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Re: CN21 really messed up our internet


[re: MrSaffron] [link to this post]
 
im sure your not talking from there, dont take my replies the wrong way, i am grateful.

yes i see the TCP ACK prioritize?
Administrator MrSaffron
(staff) Thu 14-Apr-11 14:23:50
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Re: CN21 really messed up our internet


[re: simonbratt] [link to this post]
 
If you select that what will do is speed up TCP ACK's for material that you have downloaded.

In essence for each TCP packet you download there is a small ack sent back, and the next packet is not sent to you until the server sees this. The effect is to improve download performance when the upstream is busy.

Web pages comprise of many small elements usually, so by making the ACK'ing better it should improve the visible performance when the upstream is busy.

This may not solve all the problems, but am hoping it will return some of your performance.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
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