Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!decwrl!ucbvax!FTP.COM!jbvb
From: jbvb@FTP.COM ("James B. Van Bokkelen")
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: ODI?
Message-ID: <9008161321.AA06910@ftp.com>
Date: 16 Aug 90 13:21:25 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: jbvb-pd@ftp.com
Organization: The Internet
Lines: 40


    From: Russ Nelson <nelson@sun.soe.clarkson.edu>
    
    geoff@hinode.East.Sun.COM (Geoff Arnold @ Sun BOS) writes:
    
       Why not adopt PD instead? Because in principle I think that NDIS does
       demultiplexing "right" and ODLI and PD do it "wrong".
    
    If *that*'s your only objection to the PD, then we can bash jbvb@ftp.com
    over the head until he changes the spec to allow multiple drivers to be
    upcalled with the same packet.  Then your application can just ask for all
    packets.

The problem is of course the slow, DMA-based boards.  The Packet Driver
spec doesn't prevent a given driver from allowing simultaneous "match all"
and "specific packet" handles.  Our own NDIS-to-Packet-Driver doesn't (and
won't) support multiple driver upcalls primarily because the NDIS spec
doesn't guarantee that an NDIS driver can deliver the same packet to more
than one stack, and we needed to minimize size.

Version 1.10 of the packet driver spec is in the works.  A revision of
the as_send_pkt() function has been implemented and tested by Drew
Perkins.  Since Drew proposed the original version, and I don't know
of anyone who implemented it, I am moved to include this in the new
spec.  However, I have seen requests for gather-mode on output.  I am
soliciting people to propose (write up and hopefully test) extensions
to Drew's mechanism.

As far as "look at the packet before it is copied to my buffer" goes,
there are certainly a lot of free registers on the first 'receiver()'
upcall.  The 'get_parameters()' function allows the stack to
determine the PDS revision the driver conforms to.  Suppose that with
v1.10 of the spec, if the DX register is non-zero on the 'AX == 0'
upcall, it is the length of a 'look-ahead' buffer pointed to by
register pair ES:DI.  If the stack doesn't want the packet after all,
it can just return an empty buffer pointer.  One could also guarantee
a minimum length of 60 bytes in Class 1, possibly larger in Class 3.

James B. VanBokkelen		26 Princess St., Wakefield, MA  01880
FTP Software Inc.		voice: (617) 246-0900  fax: (617) 246-0901