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From: dougm@ICO.ISC.COM ("Doug McCallum")
Newsgroups: comp.protocols.tcp-ip
Subject: Re: TLI, NLI, DLI - Request for information
Message-ID: <9008301422.AA26854@violet.ICO.ISC.COM>
Date: 30 Aug 90 14:22:44 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 67

In reply to your message of 30 Aug 90 06:45:51 GMT
-------

> TLI - Transport Layer Interface.

This is part of V.3 and V.4 UNIX.  X/Open's XTI interface in XPG3 is based
on TLI.

> NLI - Network Layer Interface

There isn't a current NLI.  There is a draft of NPI (Network Provider
Interface) that is currently being updated by UNIX International (OSI
Working Group). NPI will become the network protocol interface for V.4.

> DLI - Datalink Interface

DLPI (Data Link Provider Interface) is currently undergoing revision within
the same UI working group.  There is no user level interface defined at
present.

> I believe they were defined by AT&T for Unix environments and perhaps proposed
> in industry standard forums (UI?).  However I would like to know (particularly
> for NLI and DLI):

AT&T did the original specifications.  The refinement has been picked up by
UI in the OSI Working Group.

> What is there acceptance status?

They will exist for V.4 UNIX.  TLI/TPI appears to be done.  The others are
being finalized within UI.

> Where are the specs available from?

UI or AT&T.

> What implementations are available?

TLI has been around for several years in the UNIX System V Release 3.  It
was refined and adopted by X/Open in XPG3.  UNIX V.4 also comes with TLI.
Ultrix 4.0 is supposed to have an XTI (X/Open TLI) interface in it but I
don't have that version yet.

I don't know of any NPI implementations other than possibly AT&T's OSI
implementation which I suspect uses NPI but don't have any concrete proof
of.

DLPI implementations (to earlier drafts) are in the V.4 system and are used
by the TCP/IP that is part of the V.4 source release.

> Are they applicable to non-Unix environments?

No reason they couldn't be but they do assume a STREAMS type of structure
for the provider level interface since the provider is defined in terms of
STREAMS.

TLI definitely isn't restricted to UNIX.  TLI is the user level interface.
TPI is the STREAMS level interface for implementing protocols that can be
used by TLI.  A TLI implementation doesn't need to have an exactly TPI
conformant protocol implementation under it as long as it has the same
semantics from the programmer's perspective.

Does this help?

Doug McCallum
Interactive Systems Corp.
dougm@ico.isc.com