Re: Device Capabilities

[Mike Lake <mlake@xxxxxxxxxxxxxxx>]

At 11:36 16/05/97 -0700, you wrote:

>I think the email model requires capabilities - the UK proposal talks
>about using a minimal transmission until you know the capabilities of the
>recipient.

True, but just to be on the defensive for a moment.  Implementations could
elect to handle this in different ways.  After all, exactly what are we
trying to do with the exchange of capabilities?  We are trying to provide
the far end with our capabilities (so they can log them) and we are trying
to get theirs (so we can log them).  It would be simple to send a dummy
Email fax (rather like a "Fax Capabilities PING"! - now, there's a thought
.... no - I've rejected that - the far end may be a dial-up so a FAXPING
would be no use) specifically for the purpose of sending capabilities and
eliciting a response containing capabilities.

Like Email, most of the people I send faxes to I send to regularly so there
is no hardship sending/getting capabilities either in the first real
transmission or in a dummy.

>However, I don't believe it addresses the cases where the
>recipient's capabilities are upgraded or downgraded

Oh yes it does!  DIS is sent with every message and every response and
either end would be immediately aware of any change at the other - and log
it.  All automatic and all simple.  I admit that you might send one
transmission and receive one negative confirmation (along with the new DIS)
so your system could automatically adjust and re-transmit using the new
capabilities.  Swapping machines in and out does not happen that often
(except in our R&D lab!!) so I don't think this is a serious real-world problem.

>Futher, with vCard or the UK proposal, consider the case where two fax
>machines are connected to a hunt-group (where someone dials one number
>and can get the unoccupied fax machine), where the two fax machines have
>different capabilities.  If you store the capabilities along with the
>phone number you dialed (which is the only way I think such a database
>could be designed), you won't get the "correct" fax machine, thus you'll
>earn a bounce (not good) or some piece of software or firmware will have
>to downgrade the fax (which I believe is impossible with the UK proposal
>which includes T.30 data in the message itself, so an offramp couldn't be
>expected to understand all the NSFs that are possible).

True.  On the other hand I could think of implementations to get round some
of this.

>(Or is downgrading possible with the UK proposal?

Yes, after receipt of the DIS in the negative confirmation.  Obviously the
sender would then do exactly what we do for real-time fax - adjust the job
according to the capabilities of the receiver - it does not require any
manual intervention to do this.

>And if so, doesn't that mean the offramp understands all of the T.30
"stuff" encoded in
>the message and could transmit that stuff itself?)

I don't like the idea of intermediate intelligence because if I am attaching
files to my faxes and the off ramp finds the receiver can't handle files
there is no way it can adjust things accordingly.  I prefer everything to be
end-to-end - like real time fax.

>I view bounces to non-deliverable faxes due to incompatible capabilities
>as a workaround to the problem, not a true solution.

I true solution is real-time - no more, no less!  However, we are not (I
think) discussing real-time here.

>On (D), above, the client can:
>
>  1.  guess at the recipient's capabilities and send the message.  This
>      is what happens with email today.

Agreed.  You can always send fine resolution images first time and be sure
of getting through.

>  2.  determine the recipient's capabilities and send a message that
>      doesn't exceed those capabilities.
>      
>      First, this only needs to be done if the sender has capabilities
>      that exceed the minimum implementation requirements specified for
>      case (1), above.
>      
>      If the sender has capabilities that exceed the minimum
>      requirements, and:
>      
>        a. it cannot determine the capabilities of the recipient, the
>           sender should send the minimum required capabilities.  
>        b. it can determine the capabilties of the recipient, it can send
>           the message using those capabilities.

Total agreement.  This leaves freedom to do EVERYTHING or the minimum.  No
second-best here.
      
>  a.  the sender needs to never exceed the recipient's capabilities.
>      With the UK proposal that includes T.30 data in the message, I
>      think you can exceed the offramp's capabilities

I have a real hangup about this.  I don't see the need for an "onramp" or an
"offramp"  I just see two Email addresses sending faxes to one another - in
which case the T.30 frames hold everything we will ever need.

>or:
>  b.  the offramp needs to be able to transform the message into
>      something that will work for any recipient.  Perhaps this will
>      always fall into the "vender value-add", "implementation specific"
>      arena, and bounces are generated when this can't happen???

Again, I don't like any processing of the message between sender and
recipient.  The "vendors" I am interested in are the ones who generate the
Email fax in the first place and those who receive and decode it.  This
falls into two camps: PC software and fax-capable machines.

I hope I don't sound too grumpy but I have spent the day putting a second
hard disk into my home PC, cloning my office machine onto this disk for use
at home and trying to get all my hardware gadgets working under Windows '95.
6 hours of my life have gone out of the window thanks to Mr Gates!  Perhaps
I should send him a bill for my professional time!!!!  Does ANYONE really
believe that Windows '95 is "intuitive"?  Perhaps I am just getting old!

Best regards

Mike
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