[clug] upload speeds on transact
Andrew Smith
andrew at coolchilli.com
Wed Oct 22 09:08:20 GMT 2008
80-85% is a reasonable average for most xDSL products and PPPoE
framing. The declared speeds are the ATM rate, so you have to take out
ATM headers (5/53 bytes or ~10%), then 8 bytes of PPPoE framing (for
every 64-1500 byte frame), then TCP/IP overhead (16 bytes from memory
for every 64-1500byte frame). You're left with speed at the Application
layer.
xDSL is a killer on the TCP ACK side of things when downloading and
using PPPoE. RFC's require 1 ack per 2 packets, each ack is a minimum
Ethernet packet in size (about 64bytes with padding), which is larger
than 1 ATM packet, so it goes over 2. I've seen quite a few ADSL links
congest the upstream well in advance of the downstream.
If your routing allows it, a switch to PPPoA framing should see a bit of
an increase.
Andrew
Paul wrote:
> I've just upgraded to the transact rapid (8Mb/450k) and from using the
> http://speedtest.velocity.net.au/ I can't get Upload speeds to get
> anywhere near 450kb the closest I've got is 330kb .
>
> Is there a problem with upload bandwidth on transact? or is it my
> location etc...?
>
>
> Thanks
More information about the linux
mailing list