Subject: [Sip] SIP and distribution of context information

From: Egil Østhus <[email-masked]>
Date: Thu, 09 Jun 2005 16:34:15 +0200

Hi,

I'm looking into ways to distribute general context information, and 
have some questions connected to SIP Events.

SIMPLE is used to transport presence information to a watcher. In the 
introduction of RFC 3856 it is argued why SIP Events is an appropriate 
way to distribute presence information. I agree in the arguments given 
in the RFC, but there are some details that still is not clear to me. 
Presence status is a special kind of the more general Context 
Information. What I'm uncertain about, is whether SIP Events should be 
used for distribution of other kinds of context information as well? 
Arguments that support this approach is that it is convenient to have 
only one protocol taking care of distributing all sorts of context 
information (e.g. Temperature, Light level, geographical location and so 
on). Also, the arguements given why SIP Events is a proper way for 
presence info distribution goes for many of the other kinds of context 
information. Technically speaking, it is not any problem using SIP 
Events for this matter, what I belive is the problem is that this 
approach is in conflict with the "Guidelines for Authors of Extensions 
to the Session Initiation Protocol (SIP)" internet draft 
(http://www.ietf.org/internet-drafts/draft-ietf-sip-guidelines-09.txt). 
Section 3.1 defines SIPs solution space, and I have a hard time 
convincing myself that distribution of general context information is 
within the solution space of SIP, in other words SIP is not an 
appropriate protocol. Then again, it seems kind of strange to me to 
define one protocol per each kind of context information type. (e.g. one 
for geographical location, one for temperature and so on). Should SIP 
Events  be used to distribute all kinds of context information (i.e. 
breaking the sip guidelines draft)? Should presence be distributed by 
SIMPLE, and other kinds of context information distributed by other 
protocols, i.e. creating a great number of context distribution 
protocols? Or should a general protocol for context information be 
designed, taking care of all sorts of context information including 
presence status, i.e.dropping SIMPLE?

Any comments helping to clarify this matter is highly appreciated!

Cheers,
Egil C. Østhus

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---

From: "Dale Worley" <[email-masked]>
Date: Thu, 9 Jun 2005 11:18:12 -0400

> From: Egil Østhus
> on).

I would think the question is the context of the context information, so to
speak.  If the purpose is to present, display, or distribute information
about one person/agent so that another person/agent can decide whether it
wants to communicate with the first one, then it would seem to be reasonable
to use SIP events to distribute it.

Dale

---

From: "Brijesh Kumar" <[email-masked]>
Date: Thu, 9 Jun 2005 11:55:14 -0400

----- Original Message ----- 
From: "Dale Worley" <[email-masked]>
To: <[email-masked]>
Sent: Thursday, June 09, 2005 11:18 AM
Subject: RE: [Sip] SIP and distribution of context information

>Dale

Hi Dale and Egil:

Yes, you are right.

We have taken the similar approach to monitor device status and
learn about about device context information in our draft: A Session
Initiation Protocol (SIP) Event Package for Device Information
(http://ietfreport.isoc.org/idref/draft-rahman-sipping-device-info/).
A revised version will be submitted to sipping group in a few days.

We have used a event package mechanism (device-info) in the above draft,
however during presentation of the draft to Sipping group in IETF in
Washington
DC, we  mentioned in the future we will introduce the idea of device
presence to
learn the device status and the context in future revision of the draft.

regards,

--brijesh

---

From: Egil Østhus <[email-masked]>
Date: Thu, 09 Jun 2005 19:58:09 +0200

>to use SIP events to distribute it.
I totally agree about this, but I belive that context information could 
be used to other applications than those of (human) communication. 
Examples could be various tourist guides (using geograhical location for 
information delivery). For this application I find it hard to argue for 
using SIP, on the other hand in certain cases SIP applications could 
benefint for using location information (for instance a intelligent 
screening service, rejecting all work related calls when I'm at home). 
Should the same information (in this case the geographical location) be 
carried by to different protocols (requiring two or more implemented 
protocol stacks at the sensor), or should the same protocol be used 
(i.e. should each application use a context protocol in addition to 
other needed protocols)?

Cheers,
Egil Østhus