Very Computer

I am in need of a text to read.  I ask if you can read these questions,
and my statements, and, after discerning the level of my ignorance, to
please recommend a text.  I am a mechanical engineer desiring to learn
network communications.

I am aware that there is an ISO-OSI seven layer standard which
describes a data communications model.  I am aware that TCP/IP is
another comm. model which, while not adhering to the seven layer
standard, basically does most of the things of that standard.

I am aware the UDP/IP is a sister suite of protocols.

Next, it seems that, upon reading IRIX documentation, that there is a
layer called the Transport Layer Interface (TLI) which is the
recommeded interface to use to allow IPC.  It seems that TLI lives
between the Transport and Session Layers, and, thus, partakes of the
full seven layer standard.

IRIX seems to dissuade me from using sockets -- which I will use anyway
-- because sockets (it seems to me) is a 'kind of' transport layer
interface (notice the lower case) which adheres to the TCP/IP suite (as
opposed to the ISO-OSI suite).

Next, I have this compulsive need to 'substantiate' this knowledge by
actually coding.  So, I learned about how to open, close sockets, how
to get server names, how to read/write to sockets, etc.

This is good for me because I can, then, write a client and server code
for two different machines, and using sockets, exploit the TCP/IP
suite, and allow for IPC.  Naturally, the codes are VERY simple.

OK, so far so good!  I am learning.

Next, throw ATM into the picture.  And now I am lost!!!

I think!! that ATM is a kind of sister to UDP/IP, however it strictly
adheres to the ISO-OSI standard stack.  But I do not know this.

Also, suppose I have ATM.  Big deal!  for me, I need to know how to use
it, not only in the abstract sense, but also how to implement it.
WHile it may be true that different machines implement ATM in different
ways, the texts I look at all describe things in the abstract, and this
is difficult for me to learn: I need some simple examples even if they
are written in C, for a UNIX environment.

I would like to know where ATM fits into the ISO-OSI standard stack.
Further, if I write two codes which simply send data back and forth,
what do I do to enable communication?  Will the standard sockets be
useful? (assuming that IRIX manual is correct in dissuading use of
sockets, I still would like to substantiate things with an example).
In fact, if I choose, can I use sockets OVER ATM OVER IP?
Is this even a correct sentence?

Basically, I think I have a toe-hold on the TCP/IP, UDP/IP, ISO-OSI,

And

TLI vs Sockets.

But Now I need to know:
1) where does ATM fit into this picture
2) How can I substantiate this with a small code example which does IPC

Does this make sense?
Can someone suggest a book?

Thanks,
Tom