VDSL Performance & Tuning

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841 posts

Ultimate Geek

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Reply # 655218 13-Jul-2012 19:07
Ok, TCPCongestionControl was set to 1. Yeah, it's possible that there is no autosizing in 2k3. In any case, something I've done today seems to have made a difference, I'm getting a bit more speed out of it now; 90% of full speed, up from 80. This is after manually setting the TCP Window to 1meg, 2meg didn't make any difference to speed.

mercutio

781 posts

Ultimate Geek

Reply # 655222 13-Jul-2012 19:19
SamF: Ok, TCPCongestionControl was set to 1. Yeah, it's possible that there is no autosizing in 2k3. In any case, something I've done today seems to have made a difference, I'm getting a bit more speed out of it now; 90% of full speed, up from 80. This is after manually setting the TCP Window to 1meg, 2meg didn't make any difference to speed. testing how far away? roughly... 1megabyte window size at 333.3 msec latency should allow 3megabytes/sec download speed. so it should generally be fine... you're also limited by window size at each end, and window size decreasing due to congestion / packet loss.

SamF

841 posts

Ultimate Geek

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Reply # 655223 13-Jul-2012 19:24
Auckland, 22ms latency. I get 35megabit on other computers, 32 on the 2003 machine. I'd be happy with that, but other downloads are much slower; ~20megabits.

mercutio

781 posts

Ultimate Geek

Reply # 655225 13-Jul-2012 19:34
SamF: Auckland, 22ms latency. I get 35megabit on other computers, 32 on the 2003 machine. I'd be happy with that, but other downloads are much slower; ~20megabits. what's performance like to/from and from to 2k3/w7 vm's? ie to each other.

SamF

841 posts

Ultimate Geek

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Reply # 655616 14-Jul-2012 17:27
hmm, good point, it's crap! There may be some more systemic issue going on here...

SamF

841 posts

Ultimate Geek

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Reply # 655766 15-Jul-2012 00:16
Actually... yes, it is crap, but I was reading the speeds wrong, I'm getting 15-25megaBYTES per second to them, so 4megaBYTES per second shouldn't be an issue...

mercutio

781 posts

Ultimate Geek

Reply # 655775 15-Jul-2012 01:19
SamF: Actually... yes, it is crap, but I was reading the speeds wrong, I'm getting 15-25megaBYTES per second to them, so 4megaBYTES per second shouldn't be an issue... it could still be if you're getting packet drops. make sure you're using proper virtual network drivers. that's over 100 megabit. but even on an older computer you should get at least 600 megabit on local network.

SamF

841 posts

Ultimate Geek

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Reply # 655776 15-Jul-2012 01:24
Yeah, definitely have the VMWare NIC drivers installed & connecting at 1gbit... It's running the AMD virtual NIC, but I don't think you can upgrade this to the Intel / VMX NIC with 2003...

mercutio

781 posts

Ultimate Geek

Reply # 655777 15-Jul-2012 01:28
SamF: Yeah, definitely have the VMWare NIC drivers installed & connecting at 1gbit... It's running the AMD virtual NIC, but I don't think you can upgrade this to the Intel / VMX NIC with 2003... don't think that's the vmxnet3 driver. have you got vmware tools installed? maybe take a look at this link: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1007195 Although I think that's from older versions of vmware esx.

SamF

841 posts

Ultimate Geek

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Reply # 655779 15-Jul-2012 01:36
Yeah, vmware tools installed and up to date. The driver is called 'VMWare Accelerated AMD PCNet Adapter'. Will give that article a go.

SamF

841 posts

Ultimate Geek

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Reply # 655853 15-Jul-2012 10:27
Ah, MUCH better with the enhanced VMX adapter!! I'm now getting pretty much full line speeds on my VM! Thanks for your assistance on this mercuito!! Edit: Oh, bum, that's only on speedtest, file downloads still seem to be limited to ~80% of full speed or less :( Edit 2: Ok, this now seems to be an issue with general networking. Previously I was saving the file to the VM Host, saving to the guest's local drive has resolved that issue. Due to a bug with VMWare Server 2, I've previously had to disable 'Large Send Offload v2' on the Host's NIC, which may account for this problem. Edit 3: I've changed some NIC buffer settings on the host & guest which has improved the LAN networking considerably, but I'm unfortunately still limited while downloading. It's interesting, when I first start the download it ramps up to full line speed almost immediately, but then drops down to low speed after a few seconds (now ~33% of full speed). Seems like a buffer effect to me.

Napster

202 posts

Master Geek

Reply # 657286 17-Jul-2012 22:45
Here is a rough SNR guide for you guys. ( Fritzbox only ) Sam will refine this if need be and post it up on the main page. . Start by enabling Telnet on the Fritzbox by connecting a phone up and dialing ( #967 ) Telnet into the Fritzbox, you will be asked for password. This is the same password to login to the Web interface. Should now look like this after you have entered your password. Type : nvi /var/flash/ar7.cfg and hit enter. As you see below. This list will appear. Scroll down by using ( Page up, Page down, or you arrow keys ) You will need to look for ( DownstreamMarginOffset = 0 ) So this is how it works. Your Target noise margin by default should be 12dB If you set DownstreamMarginOffset = -60; this will drop your SNRM by 6dB Setting DownstreamMarginOffset = -100 will drop your SNRM by 10dB and your new Target Noise Margin will be 2dB 0 to -100 is the current valid range. To edit the value you need to use your arrow keys and then press the ( INSERT ) key on your keyboard to allow the value to be changed. When done press ( ESCAPE ) and type ( :wq! ) to save the changes. When you have the( # ) symbol appear type ( Reboot ) and enter. To see what your new training margin is, open telnet again and enter your password. When done type VDSL and hit enter. You should now see a list like this. Now type ( 11 ) and look for Downstream Training Margin. If this value has changed to what you have set then your all done.

_Allan

142 posts

Master Geek

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Subscriber

Reply # 657505 18-Jul-2012 11:15
Napster, This is interesting stuff and easy to follow, but can you give us some explanation why we would want to do this? What is the problem you are trying to resolve? _Allan (my blog, my tweets, company tweets, company web site) Geekzone Speedtest - Download: 16.28 mbps Upload: 5.86 Mbps

quakeguy

79 posts

Master Geek

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Reply # 657550 18-Jul-2012 12:00
That will probably give you better sync rates, because you're telling your modem to 'treat less of the signal as noise' (lower the noise margins). However, on a bad line, it might cause framing loss, which will cause resyncs. Since I'm ~300m off the cab, I'll be doing this. Nice 17a, btw. Tim.

SamF

841 posts

Ultimate Geek

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Reply # 657566 18-Jul-2012 12:24
Just be aware that doing this may disable DLM from functioning correctly. Napster tried this hack but was unable to get back to the DLM-1 profile until he reset it back to defaults.

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