From: James Carlson <carlsonj@workingcode.com>
To: linux-ppp@vger.kernel.org
Subject: Re: ppp_async: ioctl to set MTU needed
Date: Tue, 13 Jan 2015 22:22:47 +0000 [thread overview]
Message-ID: <54B59AB7.9060901@workingcode.com> (raw)
In-Reply-To: <54B556D0.5090204@mirix.org>
On 01/13/15 16:56, Christoph Schulz wrote:
> Hello!
>
> James Carlson schrieb am Tue, 13 Jan 2015 16:31:29 -0500:
>
>> Not so much "wrong" as "pointless." Why bother to ask for less? You
>> don't have to pad the packets out to the full MRU, so why do you care
>> what the peer has advertised as a maximum? All that matters is that (by
>> acking the value) you've promised not to send anything bigger. By
>> adhering to a smaller limit, you're certainly in compliance with the
>> peer's limitations.
>
> Yes. However, the problem lies in the mechanism the Linux kernel
> determines the MTU of a link in a multilink bundle: It simply takes the
> peer's MRU we ACKed. Obviously this is not correct if we are bound to
> use a smaller (channel) MTU due to other constraints (tunnel overhead).
> But there is currently no possibility to tell the Linux kernel what
> channel MTU to use.
Ah, ok. Are you referring to the individual link MTU rather than the
bundle's overall MTU?
If so, then, yes, that does look like a problem. It should be possible
to limit individual link MTU values as desired, but I don't see a good
way to do it.
But, for what it's worth, running MP over a tunneled link sounds like
extreme weirdness to me. Unless you're trying to set new records for
packet loss and link latency, why would you do that?
--
James Carlson 42.703N 71.076W <carlsonj@workingcode.com>
next prev parent reply other threads:[~2015-01-13 22:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-13 17:33 ppp_async: ioctl to set MTU needed Matthias-Christian Ott
2015-01-13 20:30 ` James Carlson
2015-01-13 20:57 ` Christoph Schulz
2015-01-13 21:31 ` James Carlson
2015-01-13 21:56 ` Christoph Schulz
2015-01-13 22:22 ` James Carlson [this message]
2015-01-13 22:56 ` Christoph Schulz
2015-01-13 23:04 ` Christoph Schulz
2015-01-13 23:24 ` Matthias-Christian Ott
2015-01-13 23:39 ` Matthias-Christian Ott
2015-01-14 0:10 ` James Carlson
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