--On Monday, 27 November, 2006 11:07 -0800 Dave Crocker
<dhc2(_at_)dcrocker(_dot_)net> 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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