Subject: Re: can't raise in kernel pppoe0 with mtu > 1460
To: None <tech-net@NetBSD.org, port-i386@NetBSD.org>
From: Matthias Scheler <tron@zhadum.de>
List: tech-net
Date: 03/22/2005 18:15:04
In article <200503212111.j2LLBZc09092@eevee.engine.ca>,
	Alicia da Conceicao <alicia@engine.ca> writes:
> map pppoe0 192.168.1.0/24 -> 123.123.123.123/32 portmap tcp/udp 20000:40000 mssclamp 1420
> map pppoe0 192.168.1.0/24 -> 123.123.123.123/32 mssclamp 1420
> map pppoe0 192.168.1.0/24 -> 123.123.123.123/32

Please read this document ...

	http://www.netbsd.org/Documentation/network/pppoe/#clamping

... and use "mssclamp 1408" afterwards.

> I heard that Windows machines typically use an MTU/MSS value of 1480.

That's both wrong. They use the usual value MTU of 1500 bytes on ethernet
which leads to a MSS of at most 1460 bytes. The MSS will of cause be
smaller if TCP options are used on the connection (e.g. TCP SACK).

	Kind regards

-- 
Matthias Scheler                                  http://scheler.de/~matthias/