Very Computer

Okay, so I've been given this job to write something using sockets.  I start
into the documentation (Sun) and the first thing it says is (paraphrased):
"Don`t do that, you idiot -- use TLI".  Well, now I went back to my management
with the information that Sun says we shouldn't use Sockets.  The reply (a really
good one, I must admit): "Why?".

Well, I checked all the documentation I could round up and didn't find any
comparative info.  Why would one use Sockets (or TLI) versus the other?  Which
one provides more bandwidth?  Which is more reliable?  Which is easier to
program?

Thanks.

Wade Guthrie

However, if there were, the reason would probably have been that sockets
was considered to be an obsolete interface, which Sun wasn't planning on
making major improvements to in the future, while TLI is the newer, more
standard interface.  I don't think the choice between them would have
anything to do with the technical merits of the particular interface,
merely which one would get more attention by the development organization
in the future.

I'm not saying that Sun has or hasn't got such plans regarding where their
development resources will go; only that *if* they had such an official
recommendation, this would be why.

The actual performance and reliability should be pretty similar, since
sockets and TLI are both just programming interfaces to the same underlying
networking code.  In SunOS 4.x sockets should be slightly more efficient
than TLI, since the kernel implements those operations directly, while TLI
is a library layered on top of these system calls.  In SunOS 5.0, though, I
believe they will both be libraries layered on top of a completely new
network interface in the kernel.

--
Barry Margolin
System Manager, Thinking Machines Corp.

Oh, by the way, (for intra-system communication) are named pipes slower or
faster than TLI/Sockets?

Thanks (sorry for the dual post).

Wade

The major advantage it holds over sockets is protocol independence.
Sockets are very much bound up with TCP/IP.

I have used TLI to interface to TCP/IP, Lan Manager/X and AT&T StarGroup,
the only code changes I had to make were to deal with orderly disconnection
on TCP/IP (about three lines of code).

As regards reliability, I don't think there is much difference.
Most recent commercial implementations of both are based on the Streams
concept introduced in SVR3 and standardised in SVR4.

I would say that the TLI is a little easier to use, but I am sure long
term sockets users would disagree.

--harry

Workhorse Systems Ltd.
142 Terenure Road North
Dublin 6W
IRELAND

The easiest way to compare sockets and TLI is to get "Unix Network
Programming" by Stevens, and compare chapters 6 and 7.  In particular,
compare figure 6.2 with 7.1, and figure 6.3 with 7.2, and you'll see that
the general structure of sockets and TLI are similar.  Also, in the TLI
function descriptions in section 7.4, there are notes showing how the TLI
features compare to the corresponding sockets features.

Now, it *is* true that the sockets interface was prompted by the design and
implementation of TCP/IP (in NCP, the predecessor protocol to TCP/IP,
"socket" was the term for what TCP and UDP call "ports").  However, TLI was
just as much influenced by OSI.
--
Barry Margolin
System Manager, Thinking Machines Corp.

Quote:>While in System V, sockets are a library layered on top of TLI.

It's funny, in the POSIX 1003.12 draft they claim that a survey they took
showed equal usage of sockets and TLI, hence they're supporting both.
Yet in survey after survey (informal) that I take when I teach network
programming classes, I continually find 95% of the people use sockets,
5% use TLI, and half of the 5% are AT&T employees who don't have a choice.

        Which is more portable?
        Which is going to be supported in future releases?
        Which faces towards Sys V and which faces towards BSD when it prays?
                :-)

orville

--------------------------------------       **********************************
Orville R. Weyrich, Jr.                          Weyrich Computer Consulting
Certified Data Processor                       POB 5782, Scottsdale, AZ 85261
Certified Systems Professional                      Voice: (602) 391-0821

--------------------------------------       **********************************