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Re: PPP for Hurd requirements

On Sun, Aug 06, 2000 at 08:10:28PM -0400, Roland McGrath wrote:
> > Why not unify all the different kind of link level devices with a "tun"
> > interface as suggested before. That way pfinet need know nothing about
> > what kind of device it's receiving frames from. And there should be a
> > translator that sits on top of the eth and ppp intefaces translating the
> > incoming frames into tun frames. Then once pfinet is fixed and stabilised
> > there is no need to update the code in order to support other protocols.
> You are missing the fundamental point of the design.  The very purpose is
> to have the clean and flexible layering you describe without necessarily
> requiring the overhead of passing data through multiple translator
> processes.  If you are not clear on the analog to libstore, please take a
> look at how that works.

I understand the analogy to libstore, i.e. creating an common API for eth,
ppp and others that pfinet could use transparently. I also think that's a
good idea. However in a previous message you also suggested that pfinet
would have to be aware of the format of ppp and ethernet frames and be able
to distinguish between then. This however seems the wrong way to go about

My main idea was that pfinet should treat all network interfaces the same. The 
question of whether this normalization of ppp and ethernet frames should be
done by a translator or a common API is a detail of implementation. If a
translator involves too much overhead then it might not be a good idea. You
must forgive that slip on my part, afterall, like Marcus says "everything
is a translator." :-)

I must admit I don't know much about link level communication protocols so
I'm not really sure what ethernet and ppp frames look like and how they
could both be passed in the same form to pfinet. But that again is an
implementation detail.


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