RE: [ILUG] [Kinda OT] Bizare behaviour from ftp

From: Padraig Brady (Padraig.Brady at domain digital.com)
Date: Fri 03 Sep 1999 - 10:58:41 IST


The problem I think depends on the networks used
between you and the site you're downloading RH from.
At the IP level it's OK as these "connections" are point to
point and will be set up correctly for each hop (across PPP,
ATM, PPP etc.).
The problem therefore is at the TCP level where the connection
has an end to end context, which doesn't run well across
the networks in the middle. The problem I had before was
with an IP router we made which ran fine in all configs
but wouldn't over an ISDN connection over 2 satellite
hops (due to the delay).
The factors which in combination force the TCP connection into
"throughput deadlocks" are a large maximum segment size, asymmetry
of the socket buffer sizes, use of Nagle's algorithm, the delayed
acknowledgment strategy, the sequence of actions on acknowledgment
reception, and at last the socket layer optimization for
efficient memory management. TCP/IP is defintely not plug & play.
As you can see to get optimum performance involves a lot of
working out etc. but you can mess around with the "MTU" like
I said before which should get it out of the deadlock situation.

Padraig.

> -----Original Message-----
> From: John Mc Donald [mailto:johnmcd at domain cs.may.ie]
> Sent: 02 September 1999 10:36
> To: Paul Jakma
> Cc: 'John.McDonald at domain may.ie'; Kevin Dobey; ilug at domain linux.ie
> Subject: Re: [ILUG] [Kinda OT] Bizare behaviour from ftp
>
>
>
>
> Paul Jakma wrote:
>
> > > The only explanation I could think of was that a certain
> > > stream of bytes could
> > > be
> > > causing some dodgy router to break the connection.
> >
> > it kept breaking on Korean HOWTO for John didn't it? that'd
> certainly have
> > funny characters in it.
> >
> > it's unlikely to be hardware imo, cause people have
> reported seeing it on so
> > many different connections. which leaves software, either
> broken servers or
> > client. Do people only get this during the RH install? or
> does it happen
> > with a regular ftp client aswell?
>
> I originally spotted it using a regular ftp client.
>
> John.
> --
> ==================================
> John Mc Donald,
> Dept. of Computer Science,
> National University of Ireland,
> Maynooth,
> Co. Kildare,
> Ireland.
>
> Email : johnmcd at domain cs.may.ie
> Phone : +353 -1 - 7084589
> Fax : +353 -1 - 7083848
> http://www.cs.may.ie/~johnmcd
> ==================================
>
>
>
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