cable technology, upstream limits and acks

Chrysalis · 11-06-2010, 18:58

I think I have discovered something.

I noticed when downloading at full speed I use around 2/3rds of my upload limit, this is on 20mbit.

So I decided to try with delayed acks disabled, which doubles the upstream requirement for ack packets.

I was expecting to not able to hit max download speeds but instead I still got max speed but using around 1mbit of ack packets (120kB/sec). Above my upload limit.

It would seem ack's are not subject to the upload limit set on the cable modem config, or that the tiny period of time they are sent is too short for the limit to apply.

Ignitionnet · 11-06-2010, 19:52

http://focus.ti.com/general/docs/bcg...contentId=4048

TurboDOX - you are talking to your cable modem at 1Mbit, it is TCP proxying and dealing with the Acks itself at a significantly lower rate.

EDIT: Just remembered you're on 20Mbps using one of the Ambit 256s or below. You'll be using Broadcom's equivalent, Propane.

pip08456 · 11-06-2010, 19:59

I think Chrys this would appear as FAIL on a certain website.

Chrysalis · 11-06-2010, 20:47

not got an ambit 256 got the cisco.

ignition is it the case the modem will be overiding the pc setting then and delaying the ack's? those docs just blurt on about performance boost's without been specific.

Peter_ · 11-06-2010, 22:16

All Virginmedia modems are locked down by Virginmedia so if you try to unlock a modem or use software to try override internal settings in the modem then you would be in breach of the Terms and Conditions.

You can use any software on your computer to improve the connection.

Ignitionnet · 11-06-2010, 22:23

Quote:

Originally Posted by Chrysalis

not got an ambit 256 got the cisco.

ignition is it the case the modem will be overiding the pc setting then and delaying the ack's? those docs just blurt on about performance boost's without been specific.

Still a Broadcom chipset so Propane enabled, and kinda.

Chrysalis · 11-06-2010, 23:38

Quote:

Originally Posted by Masque

All Virginmedia modems are locked down by Virginmedia so if you try to unlock a modem or use software to try override internal settings in the modem then you would be in breach of the Terms and Conditions.

You can use any software on your computer to improve the connection.

rest easy my friend, I am not tampering with the modem.

Peter_ · 12-06-2010, 06:09

Quote:

Originally Posted by Chrysalis

rest easy my friend, I am not tampering with the modem.

I did not expect that you were but it is good to post about the T&C's and cable modems as not everyone would be aware of that and the are illegal ways and means to use software on the modem.