John C Klensin wrote:
--On Friday, 24 November, 2006 10:30 -0500 Eric Burger
<eburger(_at_)cantata(_dot_)com> wrote:
Or, the reality that with (at the time) a single dominant
network provider made the inter-networking point moot.
Eric, you are being a little cryptic, perhaps unintentionally.
What do you mean about a single dominant provider and at what
time?
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."
Would be nice to have that in today's world, wouldn't it?
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.
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.
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.
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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