Path: utzoo!utgpu!attcan!uunet!husc6!mailrus!ames!pasteur!agate!ucbvax!LARRY.MCRCIM.MCGILL.EDU!philipp
From: philipp@LARRY.MCRCIM.MCGILL.EDU ("Philip A. Prindeville")
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: Sharing Interfaces
Message-ID: <8808050336.AA06496@Larry.McRCIM.McGill.EDU>
Date: 5 Aug 88 03:36:07 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 40


	of the list. But having MAC/Vector demux the packet between 
	protocols based on a type field can get pretty complex when you 
	consider how the offset, values, and size of the type field can 
	vary. Putting this burden above the Vector layer allows things 

But what are SAPs for, anyway? The driver should know the offset
and size of the SAP, as well as how to interpret it.  And you can't
argue about Ethernet vs. 802.3 because...

	like two IP stacks co-existing, or a single driver processing 
	Ethernet and 802.3 packets. It would generally be easier to 

It is possible for a single driver to "register" multiple interfaces.
(Just as under DOS a single driver can register multiple device
headers).  There is even a differentiation amongst the various
types of Ethernet in the documentation (it is at home right now,
but I remember there were "802.3", "802.3+DIX" [?], "Ethernet",
etc).  An protocol stack, such as IP, must be aware of whether it
is binding to 802.3, ethernet, token ring, pronet, arcnet, etc.

Indeed, since it doesn't have to worry about driving the device,
it can transfer the complexity (conservation of complexity) to
speaking multiple MAC flavours (a protocol stack, that is).

	     One of the benefits of any packet driver spec becoming a 
	standard is that hardware makers hopefully will release 
	conformant drivers with their hardware products, freeing software 
	companies of the burden of coding new drivers. If MAC/Vector 

Yes, even if MAC/Vector isn't a *great* spec, it still beats having
to write device drivers over-and-over...

Lastly, supporting DOS 3.X wasn't worth the trouble.  There isn't
enough memory to make having multiple applications resident
feasible, so why restrict yourself to it?  The same with real-
memory mode.  Is anyone *really* going to both?  If I have a
386, I'm going to damn well use it like a 386...

-Philip