Subject: docs [was: Re: 802.1Q & ETHER_MAX_LEN[
To: Manuel Bouyer <email@example.com>
From: Hubert Feyrer <firstname.lastname@example.org>
Date: 10/02/2000 18:25:21
It would be cool if someone could write up some docs on VLAN for out web
* what it is
* how to configure it
* example of interaction
See IPsec etc. for examples. No novells required, but some docs that we
could point people to would be highly appreciated.
On Mon, 2 Oct 2000, Manuel Bouyer wrote:
> On Sun, Oct 01, 2000 at 12:48:04PM -0700, Matt Thomas wrote:
> > > [...]
> > >There are several issue here:
> > >- hardware: does the ethernet adapter supports frames of 1522 bytes ?
> > > I looked quickly at the tulip and smc83c170 sources and found no way to
> > > change this, it looks like the 1518 bytes values is hardcoded in hardware.
> > > Does anyone know if there are (10/100) ethernet chips that can send/receive
> > > frames bigger than the standart len ?
> > The tulip can. For receive, you just need to ignore the frame length error.
> > the de driver has code to do that.
> Ok, I ignored the frame length error and now I can talk 802.1q with the
> cisco without troubles (using NFS, etc).
> > >- software: assuming there are adapters that can do something else than 1518
> > > (gigabit adapters can), we need a way to advertize this to the vlan layer.
> > > For now the vlan layer uses the MTU advertised by the ethernet driver.
> > > We can't change this (from 1500 to 1504) because non-802.1Q packets would
> > > be too big. So we may need a new field in the if_data struct (maybe
> > > ifi_rmtu)
> > > to advertise the real MTU the interface can do, and which can be used by
> > > pseudo-interfaces like vlan.
> > Personally, I'd rather have a IFF_ flag that indicates this instead. Not
> > all 802
> > media is ethernet.
> I don't understant this. All interface have an MTU, rigth ?
> I can't see what a IFF_ flag would give us. To enable/disable the "long frame"
> feature ?
> Anyway we have 2 things: the MTU we want to advertize to protocol layers,
> and the MTU the interface can really do. We need a way to advertize both and
> this, independantly from a IFF_ flag.
> Manuel Bouyer, LIP6, Universite Paris VI. Manuel.Bouyer@lip6.fr
Hubert Feyrer <email@example.com>