From: Karl Jeacle (karl at domain jeacle.ie)
Date: Wed 11 Sep 2002 - 18:06:01 IST
On Wed 11 Sep 02, 17:46:29 +0100, Paul Kelly wrote:
> As I understand it that won't protect them from braindead sites that
> firewall off PMTU discovery and send oversized DF packets anyway. Or
> am I mistaken?
I think you're mistaken!
A PPPoE client with an MTU of 1492 will open all TCP connections
with MSS advertisements of 1452. The TCP stack at the other side
will honour this MSS, and will never send an IP packet larger
than 1492 bytes.
So unless a link along the path is <1492 bytes, PMTUD won't take
place. And if a link along the path is indeed <1492 bytes, it will
affect everyone with an MTU of 1500, not just PPPoE people.
Karl
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