RE: Personal protocols: Where do they fit in the big picture?

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2 total messages Started by "Kees de Groot ", DEGROOT Mon, 24 Oct 1988 08:52

#872

Author: "Kees de Groot ", DEGROOT
Date: Mon, 24 Oct 1988 08:52

33 lines
2249 bytes

Hamed Nassar wonders:

>      ===  personal protocols: where do they fit in the big picture ===

> People have been asking me this question.  Personal protocols (such as
> kermit, xmodem, ymodem, <banana>modem, tlink, sealink, <banana>link,
>cis a, cis b, cis <banana>, etc..etc.(where banana = any thing)), where
>do they fit in the ISO reference model?

I would say they represent the application layer. There are two
applications at both sides communicating with each other, more or less
duplicating functions of the lower layers. If the lower layers provide
more functionality you can choose a more appropriate protocol. Eg. if
you use one of those ISDN-killing-modems which transport data
error-free at astonishing speeds then you can use a simpler protocol.
But if you have no error-handling what so ever then you should use a
protocol that handles this itself.
Modems as the Telebit trailblazer do 'protocol-spoofing'. They collect
packets ACKing each packet directly to the host and send them in one
long datapacket to the other modem which handles them one by one to
the receiving host. I have always thought you could see this as a
(confusing) implementation of the layers 1,2 and 7 (physical, data- and
application layer). Comments?

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DISCLAIMER:     My opinions are my own alone and do not represent
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Re: Personal protocols: Where do they fit in the big picture?

#869

Author: Stan Switzer
Date: Mon, 24 Oct 1988 17:59

31 lines
1820 bytes

Kees de Groot ( DEGROOT@HWALHW50) writes:
> Hamed Nassar wonders:
> 
> > People have been asking me this question.  Personal protocols (such as
> > kermit, xmodem, ymodem, <banana>modem, tlink, sealink, <banana>link,
> >cis a, cis b, cis <banana>, etc..etc.(where banana = any thing)), where
> >do they fit in the ISO reference model?
> 
> I would say they represent the application layer.

ISORM is just a model.  It is useful only to the extent that it helps
to clarify and organize understanding.  There is no sense
force-fitting things to this model when it only serves to confuse.

Knowing what "level" it is won't make it any more "standard" and it
won't make it interoperate any better either.

The protocols you mention have functionality assigned to several of
the ISO levels, and are layered differently.  So one answer is that
they don't fit at all.  When it comes down to using them with or over
"standard" protocols, you will have to make certain map-or-wrap
choices, though, and I suppose that you could say (if you must say it)
that the protocols are onel level higher than where you started to
"wrap" your protocol.  Nevertheless, I do not find this approach very
useful.

And anyway, it's the OSI reference model.

Speaking for myself,

Stan Switzer  sjs@ctt.bellcore.com

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