Path: utzoo!attcan!uunet!mailrus!tut.cis.ohio-state.edu!ucbvax!yuba.UUCP!hwajin
From: hwajin@yuba.UUCP (Hwa Jin Bae)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: UDP bind question
Message-ID: <9002161947.AA12497@yuba.WRS.COM>
Date: 16 Feb 90 19:46:47 GMT
References: <9002151527.AA03143@dcrocker.pa.dec.com>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 46

>Well, there certainly is a difference between TPI and TLI, and I did
>miss your reference in the original note, but I'm afraid that I don't
>think it helps the issue much.

There are not just one, but *many* differences between TPI and TLI.
I'm afraid you're confusing the comment about "mapping" between TLI to 
TPI as the "difference" between TLI and TPI.  This is a trivial issue;
they're called differently because they are different (but similar, as
the similarity in the name suggests).  What "issue"?

>TPI is the in-kernel interface.  TLI is the application level mapping
>to TPI, as you describe.

Redundancy.

>Unfortunately, the mapping between TPI and TCP (or UDP) is NOT
>subject to inherent or even universal definition.  Basically, the
>TLI and TPI interfaces assumed a TP4 environment.  (Yes, I know that
>they claim to be protocol independent.  So did sockets.)  But there
>still are places where a TCP implementor has choices of how to
>make some of the functionality available.  The acid test is to
>see the continued need for IOCTL within common applications.

The reality is that there is no single universal definition of 
anything anyway.  But TPI/TLI interfaces did *not* assume a TP4 
environment; it assumed *any* OSI Transport Protocol (i.e. TP0,TP1,
TP2,TP3 and TP4) environment.  That's why the TPI STREAMS message 
types are modeled after the IS 8072 Transport Primitives.  If you 
have the TPI spec you can find a table which maps each of the 
TPI message types to corresponding IS 8072 Transport Primitives, 
although there are several TPI extensions that don't have 
corresponding ISO T Primitives.  It is all matter of "degrees";
sockets *are* protocol independent to a certain degree (IMHO,
to a very satisfying degree) -- it currently provides interfaces
for the following protocols: TCP, UDP, IP, ICMP, VMTP, XTP,
XNS (SPP, PE, etc.), TP4,  and several others.  TPI and TLI
are protocol independent to the same (arguably more) degree --
not at all perfect but pretty reasonable.  They're reasonably
useful for me and I can build useful stuff on top of them.  And
they're not really that bad to implement.  That's the bottom line.
What's your point anyways?

hwajin
--
hwajin@wrs.com (uunet!wrs!hwajin)   "Omnibus ex nihil ducendis sufficit unum."
Hwa Jin Bae, Wind River Systems, 1351 Ocean Avenue, Emeryville, CA 94606, USA