Re: TCP capture effect :: estimate queue length ?

Re: TCP capture effect :: estimate queue length ?

[Joerg Pommnitz]

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> Pathchar, yet another Van Jacobsen toy does this. Unfortunately the old
> and rotten pre-version you can find in ftp.ee.lbl.gov/pathchar/ is afaik
> the last one. In the past it served me well you find about how ISPs are
> lying ... 100mbit backbone = fast ethernet in their computer room ...

clink and pchar are reimplementations of pathchar that
come with sources:
http://www.employees.org/~bmah/Software/pchar
http://rocky.wellesley.edu/downey/clink

Regards
Jörg

=====
-- 
Regards
       Joerg


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Re: TCP capture effect :: estimate queue length ?

[Ralf Baechle]

On Mon, May 14, 2001 at 11:49:16PM -0400, God wrote:

> > Packets are dropped when a device queue
> > fills, and when one sender is much faster than the other the faster sender
> > often wins the race, while the packets of the slower one get dropped.
> 
> [.....]
> 
> Speaking of queues on routers/servers, does such a util exist that would
> measure (even a rough estimate), what level of congestion (queueing) is
> happening between point A and B ?  I'd be curious how badly congested some
> things upstream from me are......   I know I can use ping or
> traceroute ... but they don't report queueing or bursting.  Both measure
> latency and packetloss ... short of stareing at a running ping that is
> ... <G>

Pathchar, yet another Van Jacobsen toy does this.  Unfortunately the old
and rotten pre-version you can find in ftp.ee.lbl.gov:/pathchar/ is afaik
the last one.  In the past it served me well you find about how ISPs are
lying ...  100mbit backbone = fast ethernet in their computer room ...

  Ralf

Re: TCP capture effect :: estimate queue length ?

[God]

On Mon, 14 May 2001, David S. Miller wrote:

> God writes:
>  > Speaking of queues on routers/servers, does such a util exist that would
>  > measure (even a rough estimate), what level of congestion (queueing) is
>  > happening between point A and B ?
> 
> Not that I know of, but it is funny you mention this because this is
> basically the kind of calculation the TCP Vegas congestion avoidance
> scheme attempts to make.  At it's core, it is trying to estimate the
> size of router queues from local machine to remote machine based upon
> "congestion events" (packet drop, etc.).


Really? .. hmmm... might just have to go read up on it.  I have my own
ideas of how to go about doing it (pretty simple I think .. unless I'm
missing something other then coding ability .... heh). 

 My basic reason for wanting such a beast was to
convince one internet provider (who shall remain nameless), that from
at home *cough* to the gateway, was under extreame congestion.  After
finaly speaking with a tech who knew the difference between him and
a dip switch, he agreed there was a serious problem (queues
were exceeding 190/255 tx/rx, logs were showing the link upstream
from the gateway was loosing sync multiple times per hour .. etc etc).

The path to that however was long and very frustrating.  Trying to explain
that
although you can ping me fine and I can ping you fine, you still have a
serious problem; can be very confusing to some.


Thanks for the pointer :)

Re: TCP capture effect :: estimate queue length ?

[David S. Miller]

God writes:
 > Speaking of queues on routers/servers, does such a util exist that would
 > measure (even a rough estimate), what level of congestion (queueing) is
 > happening between point A and B ?

Not that I know of, but it is funny you mention this because this is
basically the kind of calculation the TCP Vegas congestion avoidance
scheme attempts to make.  At it's core, it is trying to estimate the
size of router queues from local machine to remote machine based upon
"congestion events" (packet drop, etc.).

Later,
David S. Miller
davem@redhat.com

Re: TCP capture effect :: estimate queue length ?

[God]

On Mon, 14 May 2001, Andi Kleen wrote:

[.....]

> Packets are dropped when a device queue
> fills, and when one sender is much faster than the other the faster sender
> often wins the race, while the packets of the slower one get dropped.

[.....]

Speaking of queues on routers/servers, does such a util exist that would
measure (even a rough estimate), what level of congestion (queueing) is
happening between point A and B ?  I'd be curious how badly congested some
things upstream from me are......   I know I can use ping or
traceroute ... but they don't report queueing or bursting.  Both measure
latency and packetloss ... short of stareing at a running ping that is
... <G>