Philipp Leusmann wrote:
Hi andy,
I reset the ceiling to 600kbit and get same same bad results as before. Also
I set all classes to use the same quantum which is mtu (it is 1488 here).
Here is the output you requested:
class htb 1:103 parent 1:1 leaf 801b: prio 2 quantum 1488 rate 250000bit
ceil 600000bit burst 1724b/8 mpu 0b overhead 0b cburst 1899b/8 mpu 0b
overhead 0b level 0
Sent 27111784 bytes 28505 pkts (dropped 0, overlimits 0)
rate 286232bit 34pps backlog 2p
lended: 12193 borrowed: 16310 giants: 0
tokens: -83395 ctokens: -41934
That is strange - assuming that upload is tcp, there are no drops and
only a backlog of 2.
When uploading you are somewhat dependant on the size of the window
advertised by the far end - also loss, which in this case is not by htb,
will make your cwind small.
I think what you need to do is tcpdump -s 100 -w dumpfile the connection
from the start and have a look/ post what's going on.
Another way to see if it's external loss is on the sender do a few
netstat -s | grep retrans
and look at the counter.
Small chance there could be some window scaling mismatch caused by a
broken router in the way.
The loss could be isp/target server dropping or -
You mentioned a nominal upload rate of 1mbit which you don't reach. If
you are synced at a low target SNR margin then some modems will doggedly
hold the line and take the loss - others will drop and resync (often at
a similar rate as the extra noise that causes the resync is gone when it
retrains). I have to limit my downrate to 75% of 6db speed and it still
drops sometimes. My up is solid, though, as it's limited to 50% due to
the product I am on (448/up to 8128 - horribly asymmetric if I could
sync at 8128)
As to why shaping on/off makes such a difference - I am not sure, you
are backlogged so there is some limiting happening, so maybe the higher
speeds achieved without htb rely on being able to burst out full speed
whenever loss is low.
Andy.
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