Re: Path MTU and beacon
On Wed, Feb 09, 2005 at 12:47:24PM -0500, Marshall Eubanks wrote:
> On Wed, 09 Feb 2005 17:17:38 +0100
> Jean-Jacques Pansiot <pansiot@crc.u-strasbg.fr> wrote:
> > Marshall Eubanks wrote:
> Got you. However, this is the beacon, which can go who knows where. An MTU should be chosen to
> maximize the probability of working globally.
Mostly agree, but it depends a bit what you're measuring. If you want to
see how some specific multicast applications would work in your network,
then you may want to use same packet size as them?
> Remember, many I1 ISP's still use overlay networks for multicast. Other networks (I1 or I2) are
> likely to drop fragmented packets entirely.
[...]
> > What about using Path-MTU discovery ?
> >
>
> Unlikely to be useful or supported, alas :(
To my surprise I've found that this actually works with IPv6 multicast
on Linux. The Path-MTU is determined the usual way based on ICMP packet
too big messages.
For IPv4 I'm not so sure you're allowed to send such ICMP messages in
response to multicast. Not quite sure.
Stig