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Date:      Tue, 15 Jun 1999 20:51:33 -0700
From:      "Justin C. Walker" <justin@apple.com>
To:        freebsd-net@freebsd.org
Subject:   Re: Multiple ethernet frames for IPX
Message-ID:  <199906160351.UAA00707@walker3.apple.com>
In-Reply-To: <199906160120.SAA00645@walker3.apple.com>

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Boris,

Thanks for the response; I have a few more questions:

> From: Boris Popov <bp@butya.kz>
> Date: 1999-06-15 19:28:08 -0700
> To: "Justin C. Walker" <justin@apple.com>
> Subject: Re: Multiple ethernet frames for IPX
> Cc: freebsd-net@FreeBSD.ORG
> In-reply-to: <199906160120.SAA00645@walker3.apple.com>
>
> On Tue, 15 Jun 1999, Justin C. Walker wrote:
>
> > > 	Yes, it is really works now. This is first public release of  
> > > if_ef driver which extends current functionality of existing  
ethernet
> > > drivers.
> >
> > I have a couple of questions:
> >
> > How does this handle the problem of getting a forwarded packet back   
> > into the wrapper it needs (e.g., 802.3/SNAP)?
>
> 	Packet sended/forwarded to interface. Since frame type
> determined from the interface it is not a problem for ether_output() 
> rotine to select appropriate frame to wrap in.
  I should be clearer.  What I meant to ask is: given that you have  
a packet in the routing layer to forward, and that its incoming  
framing has been stripped, how does the routing layer decide what  
framing (E-II, 802.3/SNAP, ..) to use when sending it?

> > Why is this better than, e.g., having stacks register for
> > packet-type reception?  I'd think this would perform better than  
the
> > "virtual device" scheme.  A (minor?) drawback is updating both  
stack
> > and "driver family support" (e.g., ether_input()) to handle this. 
>
> 	No, you will also need to rewrite route* procedures. And changes 
> required to protocol stack(s) aren't "minor" in this case.
  I don't understand this.  If the route* procedures need rewriting  
in this case, why not in the "virtual device" case?

Also, I don't see why the stack changes are a big deal.  For each  
configured interface, the stack has to "register", which can be  
handled in the same "piece" of the stack that deals, e.g., with ARP  
and addressing issues.

I'm trying to get a better handle on the issues, since we're trying  
to deal with this at Apple now.

Thanks,

Justin

--
Justin C. Walker, Curmudgeon-At-Large *
Institute for General Semantics       |
Manager, CoreOS Networking            | When crypto is outlawed,
Apple Computer, Inc.                  | Only outlaws will have crypto.
2 Infinite Loop                       |
Cupertino, CA 95014                   |
*-------------------------------------*-------------------------------*


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