Subject: Re: [Simple] Pres Data Model Open Issue #3, UUID URN or something else

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 01 Oct 2004 01:01:38 -0400

inline.

Paul Kyzivat wrote:

>> I would propose approach (3). In particular, I think the data model
>>  should revert to being agnostic on the URN scheme, reference the
>> UUID URN as one possibility, document its problems. We should
>> develop a separate specification that defines guidelines for
>> choosing the URN for various devices in order to get the
>> correlation properties we want. I also think we should take a stab
>> at defining a few URN schemes that would be useful - MAC and ESN in
>> particular.
> 
> 
> I think it does make sense to leave the particular choice out of this
>  document.
> 
> I do think the problem with UUID can be dealt with in a couple of
> ways:
> 
> - for some kinds of "devices", like softphones and IM clients, it is 
> probably fine as-is. They can typically have multiple instances per 
> device, so they must construct and instance id and save it 
> persistently as part of the instance configuration.

I think softphones are PC-based devices are a candidate where we want to
be able to correlate service information with device information learned
from network elements like an 802.11 AP. Thus, I do think this problem
applies to things besides phones.

> 
> - for a dedicated device, like a phone, that can't or doesn't want to
>  use the above technique, a cannonical mac-based uuid can be 
> constructed by using a fixed time (e.g. zero) along with the mac.

I thought about that, but wasn't able to convince myself that it was
allowed in the UUID URN spec. Do you find words that allow you to set
the time to zero?

Henning wrote:
> As discussed previously, a device may not even have a MAC or may have
> several (if it is a composite or a multi-homed device). Thus, this
> seems inherently difficult. We went through this whole discussion
> before, I believe.

Right. We talked more about it during the design team meeting in San 
Diego. We did in fact reach conclusion on a few things:

a. there isn't a universal URN that is going to solve this problem, due 
to the fact that different devices will be identified in different ways

b. using an interface address or an esn works ok, but is likely that for 
devices which have both (like my palm treo 600, which has Internet 
access and is a phone), an app which tries to djin the device ID may 
choose the wrong one. Thus, the presence server will think that services 
on the same device are running on different devices. THe ultimate 
solution to this is that determination and handing out of a device ID 
needs to be an OS function. That is now documented in the model draft.

c. Ideally, with a bunch of URNs under our belt, if there was a "well 
known" algorithm for computing a sensible URN for different devices, it 
would improve the chance of being able to correlate presence information 
from different sources together. We could at least cover the common case 
(single homed PC) with the recommendation of a mac address, and cover 
more complex cases later. Thus the recommendation in the model draft of 
using UUID URN.

Thanks,
Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
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---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 01 Oct 2004 12:27:35 -0400

> applies to things besides phones.

Yes, I guess you are right. I was still thinking of "instance id", 
rather than specifically "device id".

> allowed in the UUID URN spec. Do you find words that allow you to set

Well, it probably does require some mental gymnastics to justify it. It 
is a matter of saying you are using the UUID generated with this mac at 
"the beginning of time".

Would it work? yes.

Is it ideal? Probably not.

Is it a valid usage? Debatable.

Could we recommend it? I don't know.

Could we say "you might be able to find a creative way to use this form 
of uuid"? Why not?

	Paul

---

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 01 Oct 2004 22:08:44 -0400

inline.

> Could we say "you might be able to find a creative way to use this form 

I think at this point the help of one of the authors of the UUID draft 
is needed. One issue is that, if someone develops a UUID implementation, 
it may have no way of allowing an app to set the time to zero, since its 
not really something one would think to do based on that spec alone. I'd 
hate for folks to be forced to write a UUID URN implementation from 
scratch just because of this.

-Jonathan R.