[openbeosnetteam] Re: PPP API
- From: "Nathan Whitehorn" <nathan.whitehorn@xxxxxxxxxxx>
- To: openbeosnetteam@xxxxxxxxxxxxx
- Date: Wed, 21 May 2003 22:16:30 -0400
> Nathan wrote:
> > What happens is that you declare yourself, say, ppp/ethernet. The
> > net
> > stack, which keeps a register of all active layers, then tries to
> > attach all ethernet/* devices underneath you, and to attach you to
> > all
> > */ppp devices. In the case of PPP, since the ppp protocol does
> > things
> > itself, pppoe would be something like ppptransport/ethernet, and
> > PPP
> > would be ppp/ppptransport.
>
> Oh, I see now.
> Don't ask, but first time I saw the layer names, I thought of MIME
> string :-)
>
> So, for a TCP connection sent over an ethernet card /dev/net/vt86c100
> /0
> (that's an example fitting well my home system :-) ) it will give
> these
> down linked layers:
>
> 1) socket[able]/tcp
> 2) tcp/ip
> 3) ip/ethernet
> 4) ethernet/vt86c100(/0?)
>
> where:
>
> 1) implement the TCP datagram(s) building and handling
> 2) implement the TCP datagram encapsulation into a IP frame (and
> handle
> fragmentation, retries, etc?)
> 3) implement ethernet framing of a ip datagram
> 4) implement an ethernet type interface link
>
> Am I right?
Yes. For generic IP tasks shared among IP protocols, you might have
iptransport/ethernet and ip/iptransport layers. It depends how much
shared functionality there is.
You might also have a sockets/socketable layer at the very top that
implements the sockets layer. This would allow us to have multiple
front-ends to the stack too, as well as removing network functionality
from the central stack entirely.
> For input, the Net::Layer::ParentType() give the layer name from
> which
> we accept (or is it only "expect" here?)
> input, like in your sample ppp/pppoe layer, which return ParentType()
> of "ethernet/*"?
This is an old version of the architecture, which let you supply, in
ParentType() a regex for the sorts of things you want under you. I
prefer the above-mentioned naming architecture to the way it exists in
the code I submitted.
> Overall, I like this way of auto-assembly of network layers, which
> suppress the protocols/interfaces classic split too.
Thanks!
> Fortune Cookie Says:
>
> Pohl's law:
> Nothing is so good that somebody, somewhere, will not hate it.
Interesting applicability. I wonder who will hate this? :P
-Nathan
--
Fortune Cookie Says:
Around computers it is difficult to find the correct unit of time to
measure progress. Some cathedrals took a century to complete. Can you
imagine the grandeur and scope of a program that would take as long?
-- Epigrams in Programming, ACM SIGPLAN Sept. 1982
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