Where is that UDP dword?

m-v-b · Post by **m-v-b** » Thu Apr 28, 2016 4:29 am

Hi guys you mentiond here http://www.speedguide.net/articles/adva ... eaking-156
That the dword for UDP packet size is to be found here.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters
MaximumUdpPacketSize=512

But it wasnt there under WIN7 and its not there under WIN10

I searched with google everywhere and in the registry but cant find anything.

Cheers from Switzerland and thanks for the TCP Optimizer!

johnathonm · Post by **johnathonm** » Thu Apr 28, 2016 8:50 am

May I ask an a novice question for purely informational purposes - under what circumstances would I want to change the size of the udp packet?

Post by **Philip** » Thu Apr 28, 2016 9:56 am

In general, when an entry is not present in the Registry Windows assumes some default value. For that particular setting, the default is 1280. Keep in mind that it was documented by Microsoft for XP, Windows Server 2003, but not later, so it is unclear whether it will work in Windows 7/8/10. Maybe one can test with a UDP stream and packet sniffer.

Johnathonm - one may want to use smaller packets if latency is a big concern (smaller packets travel slightly faster), at the expense of somewhat reduced total speed and some additional packet header overhead.

Wahnond · Post by **Wahnond** » Thu Apr 28, 2016 10:47 pm

I cannot even see a "DNS" folder. Should I create it myself?

Post by **Philip** » Fri Apr 29, 2016 10:06 am

You can create one, it wont do any harm. The only question is whether it works in newer OSes.

m-v-b · Post by **m-v-b** » Tue May 10, 2016 3:05 am

Just wanted to give feedback, after checking with Wireshark, i found that like 99% of UDP packets are between 100-500 in size.
I tried to create the path and set udp packetsize to 128 but it had zero effect (Win10). Maybe i did something wrong, but as the packets are small anyway it dosent really matter.

Cheers

Post by **Philip** » Tue May 10, 2016 7:23 am

Thanks for testing it m-v-b

tobiaslk · Post by **tobiaslk** » Wed May 11, 2016 10:49 am

Hey

I was browsing the internet and saw this article.
http://stackoverflow.com/questions/1898 ... er-windows
and this
http://stackoverflow.com/questions/2031 ... -so-sndbuf
I uthought maybe this cold be the answear to changing the UDP packet size. I am kinda curious since I have looked into this tweak aswell. Anyways I dont know if these tweaks in the articles I linked are worth something but since I cant really understand them i'll leave them to you philip to see if they are valid. Hopefully they can help.

best,
Tobias

Post by **Philip** » Wed May 11, 2016 8:16 pm

Those two articles are about buffering, about the TCP Window. The second one is about setting it in Linux.