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On Monday 10 February 2003 16:25, Mark Baker wrote:
> On Mon, Feb 10, 2003 at 04:03:09PM +0000, Alaric B. Snell wrote:
> > No, they don't, despite both being protocols used to fetch stuff. Neither
> > do HTTP, LDAP, ODBC, IMAP, POP3, finger, ftp, tftp, fsp, etc.
> > interoperate; yet all of them are based around the concept of fetching
> > something. They were all designed to be too specific, trying to limit
> > their horizons in the hope of spending less effort on design, but that
> > cost was paid later in the effort of expanding the design...
>
> Not that I agree, but your point is what? That we need a generic "fetch
> stuff" layer 6 protocol?
>
> The problem with that - if that is indeed what you mean - is that
> layer 6 isn't where you define "fetch stuff"; that's for layer 7.
*scratches head* layer 6 is presentation, the mapping from abstract
information to strings of bits... XML and ASN.1 and MIME and so on are layer
6.
> So what's needed is not a common layer 6 protocol on which new "fetch
> stuff" protocols can be constructed, but a generic layer 7 protocol that
> can provide a network interface to those protocols.
Hmmm, I sense much confusion.
I'm talking about what, in the ISO 7-layer model, is called a Service Element.
Layer 6 defined ASN.1.
Layer 7 defined applications like email and file transfer, but on top of a
kind of toolkit (why not another layer? because the interrelationships start
getting complex and nonlinear; it doesn't stack neatly, I gather) of Service
Elements.
ROSE - Remote Operations Service Element - was your general 'request/response
protocol for making applications with'.
ACSE - can't remember the acronym; Assocation Control Service Element IIRC -
does something to do with managing long-term connections.
There's stuff to do with transactions and so on too.
And on top of that sat the actual application protocols; the SEs are not
protocols themselves, they are more like protocol toolkits. More like the
convention in most IETF protocols of single line commands and three-digit
response codes, found within SMTP and POP3 and others. But they allow the
actual applications to be built on top of something higher-level than raw TCP
or UDP!
> MB
ABS
--
A city is like a large, complex, rabbit
- ARP
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