4) Sending an HTTP URL. Alice calls Bob, a sales guy; Alice asks for
more info or a datasheet and Bob sends a URL for Alice to open with
her web-browser. -One could also argue this is just making SIP the
new SMTP, or this should be sent using MESSAGE (which really is the
new SMTP).
Well, here we already have something defined - REFER with an http URL.
See draft-ietf-sipping-app-interaction-framework.
5) Sending a session traceroute. Alice calls Bob, Bob answers, Alice
does a sip-traceroute to figure out the path to Bob, by sending Info
with an incrementing max-forwards type header starting at 0 (but not
really max-forwards),
Max-FOrwards but not really Max-Forwards??
with a sip-frag type response body or some
such. -It's debatable if certain types of B2BUA's (ie, SBCs) would
ever allow this type of thing to happen, due to security concerns,
but I think they may do it at domain boundary hops. I think this is
a reasonable use for INFO though, maybe.
I'm much less convinced here. This would require handling at proxies and
we haven't been discussing usage of INFO at proxies like this. Only e2e.
6) Sending geo-location information after call establishment. Alice
calls Bob, a hotel receptionist. Alice asks for directions to hotel,
clicks button and sends him location info of her phone (or Bob clicks
button and sends her his location). -The location conveyance draft
specifically calls out INFO as acceptable for geo-loc info. Whether
this is a real use-case is debatable, and obviously it could be done
with a sub/not.
SUB/NOT seems a bit better here, I think, since the recipient knows that
they want it.
7) Sending softkey-labels (not digit-match maps, but rather softkey
button labels). Alice calls her vmail server. Vmail server sends
softkey-labels for the menu items available in the response, Alice
presses softkeys and sends them in INFO. -This could (and maybe
should) be done with sub/not, a la KPML, where the vmail server sends
the softkey labels in the Subscribe, UA sends buttons pressed in
Notifies. But this is similar to the DTMF use case so may well have
the same benefit of lower overhead since buttons are rarely pressed.
Rarely pressed yes, but this is an application specifically looking for
them. This is squarely in the territory of
draft-ietf-sipping-app-interaction-framework and is better handled by
those mechanisms.
8) Sending a screen-pop-up message, e.g., "Do you want to continue
with this session?" -There is a patent for doing screen pop-ups using
INFO. I guess Alert-Info could be used for this, but it's not clear
it should?
See discussion on indirection above. I think this is reasonable for INFO
also.
/***************** * Use-cases which have been proposed by others or
even implemented, * which are dubious for INFO (IMHO):
*****************/ 1) Sending RTP/RTCP statistics during call. -There
is an implementation of this, and the rationale is the signaling
plane box that wants this info is not actually the media plane box
that gets RTCP. Again this could (and IMO should) be done with
sub/not, so it can get stats after the call is over, and since it
will probably want periodic reports the overhead of the Subscribe
should be dwarfed by the number of Notifies.
Agree SUB/NOT is better. Its already been defined that way.
2) Sending access-location information after call establishment.
-There is a P-Access-Network-Info header, and some have proposed to
send an update for it as a phone roams access points or cells. But I
think this is an odd thing to do inside an Invite session, vs. in a
sub/not or Register (and besides half the time the network inserts
this header, not the UA).
3) Sending media-control indications (ie, remote-control
"play/pause/etc.") -This is done today by at least one vendor, but is
debatable if it's the right model. The argument is it's like SDP
re-Invite for hold, except at a media content layer above RTP, so not
done in RTCP nor SDP.
I think this is much better done via a media-plane session. There is a
requirement for low latency here and there will be a lot of these that
get sent.
4) Sending video fast update command -This is an informational draft,
which documents what has been implemented, but states it should
really be done in the media plane.
Agree.
5) Sending peripheral control commands (ie, USB commands) -There is
actually a patent on this, amazingly. Someone thinks it makes sense
to create a SIP session to your laptop, or vice-versa, and then send
USB commands inside MIME in INFO messages. Methinks this should be
media-plane, if anything.
Agree.
-Jonathan R.