Hi all,
I''ve tried to look for this info in previous messages but had no
luck.
I''ve a 2.4.20 kernel on an Intel arch., all TC is configured and it
seems to work. Anyway, I''ve had some troubles in configuring TBF via
tc:
1. when I configure burst or minburst to be, say, 1500b, when I peek the
configuration with "tc -s qdisc" the answer is that burst/minburst is
equal to 1499. Moreover, any other value I try to configure in "b"
unit is always decremented by 1 (3000->2999, and so on). Any clue about that?
2. I also have some strange behaviours about latency configuration - it is
always far from what I request. If, for example, I try to set 500ms, the most
probably I get something around 620ms. Note that if I configure the
"limit" parameter instead of "latency", I can manage to
reach values closer to what I need (e.g. 500ms). Is there something I''m
missing about latency configuration?
3. I''ve tried to configure peakrate/minburst, but I had to struggle a
bit to have them work. In particular, when I tried to set minburst equal to
interface MTU (100 bytes, ethernet) as suggested in the manpage I did not even
manage to set up an HTTP session. I had to configure a minburst equal to around
12000 to have some traffic pass arrive to the remote client. Is the manpage
wrong?
4. What I really need is to have a controlled bit rate for a unique HTTP session
from my PC (i.e. no other traffic during the tests I want to perform). I was
thus wondering what does it mean that there is a "drop" in packets
that are generated from my own machine. I thought that there could be two basic
models:
4.1 write-wait model, in which the rate is limited directly towards the
application that issues some "write" on the socket file descriptor,
thus limiting its rate - or
4.2 tcp-wait model, in which the application talks to TCP very fast, and some
packets from TCP are actually dropped if TCP tries to send them too fast.
What model is actually implemented?
Thank to you all for any bit of attention,
Flavio.
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