From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Subject: Re: 6to4/SIT and IP DF Date: Wed, 15 Oct 2003 22:27:12 -0700 Sender: netdev-bounce@oss.sgi.com Message-ID: <20031015222712.18d1434f.davem@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: pekkas@netcore.fi, r.venning@telstra.com, nate@thebog.net, netdev@oss.sgi.com Return-path: To: David Stevens In-Reply-To: Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Wed, 15 Oct 2003 22:21:37 -0700 David Stevens wrote: > That doesn't sound terrible, but won't it have to drop a minimum of > 2 packets per tunnel on an MTU change (or initial probe with a large > packet)? Welcome to the real world where most routers don't quote enough information. :) What we do is the only sane way to handle this problem. All of our ipv4 tunnels work this way due to that quoting size issue. The "fragment but tell me about it" isn't such a great idea. You'll run into all kinds of difficult decisions about behavior in the cases where a too-big packet overruns multiple hops on the path. This is why the original implementors didn't put this into the RFCs.