PPPoE and UDP fragmentation

[Charles Sprickman]

On Sat, 10 Sep 2005, Julian H. Stacey wrote:

>> -Are there any tunables at either end (both hosts are FreeBSD 4.11 p11) to
>> alter how fragmented packets are re-assembled?
>
> /usr/ports/net/tcpmssd
> An MTU adapter.  Apparently not needed on FreeBSD-5 but I mean to
> install it on my FreeBSD-4 DSL gateways when I find time to think if it might
> have any implications re ipfw & security.

I don't think that does anything to UDP, it just digs into tcp and "fixes 
up" the MSS by altering it on outgoing packets.  I'm looking to further 
understand UDP fragmentation and why a host might ignore fragments, and 
who along the way is actually doing the fragmentation.

My current "fix" is just to set the interface MTU on the sending box to 
1492, and that works well, but I'd really like to understand why it fails 
without that.

Thanks!

Charles

> -- 
> Julian Stacey.  Consultant Unix Net & Sys. Eng., Munich.  http://berklix.com
> Mail Ascii not HTML.          Ihr Rauch = meine allergischen Kopfschmerzen.
>