linux-kernel - Re: [Patch] fix packet loss and massive ping spikes with PPP multi-link

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Message-ID: <4BACE918.7020508@workingcode.com>
Date:	Fri, 26 Mar 2010 13:04:24 -0400
From:	James Carlson <carlsonj@...kingcode.com>
To:	Richard Hartmann <richih.mailinglist@...il.com>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-ppp@...r.kernel.org
Subject: Re: [Patch] fix packet loss and massive ping spikes with PPP 	multi-link

Richard Hartmann wrote:
> Also, I am not sure if it would not be better to default to no
> fragmentation and enable it optionally. I am aware that changing default
> behaviour is always a bit of a problem but to the best of my knowledge
> enabling fragmentation is a bug in any and all real-world applications.

It worked well and was enabled by default on all the Bay Networks
equipment I used ~15 years ago.  And I know for certain that we tested
with other gear (Ascend and Clam, probably) that did it right.

If it works with the equipment you're using, it's a useful feature in
that it can balance out the latencies among the links, resulting in much
lower overall latency observed by higher layers -- especially so on
lower-speed links where MP is more likely to be used.  Without it,
you're left either waiting for the one slow link choking on a big packet
to catch up, or (worse) disabling the sequence headers altogether,
resulting in reordering unless you're really "clever."

It's a darned shame that lame implementations would force a change in
the default ...

-- 
James Carlson         42.703N 71.076W         <carlsonj@...kingcode.com>
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