Re: [LARTC] pfifo_fast doesn't seem to use bands

Re: [LARTC] pfifo_fast doesn't seem to use bands

[Stef Coene]

On Tuesday 27 May 2003 14:09, Balazs Miklos wrote:
> Hi,
>
> I have a Redhat Linux 7.2 box with stock 2.4.7 kernel and I'm trying to
> do some bandwidth management with tc..
> I have created a CBQ class-hierarchy, and I have a class which is
> limited to 16Kbit and it can grow up to 32Kbits if there is available
> free bandwidth in the other classes. This class hasn't got any qdiscs
> attached to it, so (as I understood) it should have the pfifo_fast qdisc
> by default. But I have made a little test: I've mangled the TOS field of
> the router's outgoing ICMP packets to be 0x10 (minimize delay), and I
> checked with tcpdump that they are actually getting mangled.
>
> The problem is, that it doesn't seem to make any difference... the ping
> is fine if the class is empty, but if I'm doing a download and pinging
> the router at the same time, I experience delays in ping replies in both
> cases (either if the ICMP headers are mangled or not). Shouldn't the TOS
> mangled ping replies arrive with no delays at all, while the class is
> full with bulk traffic?
Why not doing the test after you add a pfifo_qdisc to that class?  Just to see 
if it makes any difference.

Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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[LARTC] pfifo_fast doesn't seem to use bands

[Balazs Miklos]

Hi,

I have a Redhat Linux 7.2 box with stock 2.4.7 kernel and I'm trying to
do some bandwidth management with tc..
I have created a CBQ class-hierarchy, and I have a class which is
limited to 16Kbit and it can grow up to 32Kbits if there is available
free bandwidth in the other classes. This class hasn't got any qdiscs
attached to it, so (as I understood) it should have the pfifo_fast qdisc
by default. But I have made a little test: I've mangled the TOS field of
the router's outgoing ICMP packets to be 0x10 (minimize delay), and I
checked with tcpdump that they are actually getting mangled.

The problem is, that it doesn't seem to make any difference... the ping
is fine if the class is empty, but if I'm doing a download and pinging
the router at the same time, I experience delays in ping replies in both
cases (either if the ICMP headers are mangled or not). Shouldn't the TOS
mangled ping replies arrive with no delays at all, while the class is
full with bulk traffic?
Or did I misunderstood something?

Thanks in advance,
-- 
Balazs Miklos <mbalazs@n-soft.net>

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