--On Monday, 27 November, 2006 11:07 -0800 Dave Crocker
<dhc2@xxxxxxxxxxxx> wrote:
> John C Klensin wrote:
>...
>> I would add an observation to Dave's about possibly different
>> sets of needs by reminding everyone that considerable IM
>> functionality (other than presence) isn't new. We had
>> SEND/SOML/SAML from the beginning of SMTP, even though they
>> had,
>
> Just to nit-pick, since Internet history has become an
> important topic:
>
> By "beginning of SMTP" John actually means the mid-1970s, in
> the original Arpanet FTP-based mail service.
>
> And since I think it was a particularly clever option, I'll
> note that one of the commands John cites was "deliver to the
> recipient's screen if they are logged in and deliver it to
> their mailbox if they aren't."
Yes. I wanted to keep the note from becoming even longer, but
you are of course correct -- both on the substance and that
those things are important.
> Would be nice to have that in today's world, wouldn't it?
I think so. And I'm getting interested in the difference
between IM-ish systems for which the model is "if they aren't
online, it is lost" and "they aren't online now, but your
message will be held and delivered when they are".
>> None of these supported a presence mechanism in the sense that
>> we understand it today.
>
> There as a close approximation, as I recall, with the way the
> Finger mechanism was implemented at some sites. You would
> Finger a particular username at a host and the returned
> information would tell you if they were logged in.
Indeed. Or with, e.g., talk, one could try to set up a
connection and assume that failure meant "not present". Both
are approximations, but so are today's presence mechanisms.
>> As a result, one had to bind a user
>> identity to a target host in much the way SMTP does, rather
>> than having someone attach to the network at any point and
>> announce presence and, implicitly, location.
>
> Mumble. I'd claim that the current presence mechanisms do the
> same thing that was done originally.
>
> If I came in through an arpanet dial-up at some random place
> on the net, and telneted to my home system, then the finger
> for that home system would show me as 'present'. I am not
> seeing how today's presence systems are fudamentally different
> from that.
Subjectively and from my perspective, the present systems
"feel", and sometimes actually are, much more distributed. But,
yes, from the perspective you describe, we have advanced very
little in terms of basic functionality.
>> It is arguably those
>> presence and mobility mechanisms and not IM itself that is the
>> recent development. To the degree to which those mechanisms
>> are what caused IM to take off, perhaps that reinforces
>> Dave's view of different services serving different needs.
>
> I think it was Graham Klyne who pointed out to me that IM and
> Internet Mail also do tradeoffs in reliability vs. timeliness.
>
> An IM is not expected to survive a system crash, whereas an
> email is. That leads to very different software development
> decisions, such as whether to incur the cost of a
> write-to-disk for every message. In the aggregate, the cost
> difference can be huge.
Indeed.
john
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