Subject: draft-ietf-megaco-ipphone-02.txt: hookswitch/ringer?

From: Bob Lukas <[email-masked]>
Date: Tue, 18 Apr 2000 20:39:54 -0700

I've been looking at draft-ietf-megaco-ipphone-02.  One thing that isn't
clear to me is in which termination would I expect to find the package that
supports the hookswitch and ringer?

In Megaco, Annex E Basic Packages define hook and ring only in the analog
line supervision package, which is a misnomer if nothing else for an IP
phone.
You could make an argument that each of the audio transducer terminations
has the equivalent of a "hook" event (e.g. hookswitch for handset and
spkr/release button for handsfree), or that hook and ring should be part of
the user interface termination, independent of transducer. Or, to be
extreme, you could even say hook is just another function key and ring is
just another tone applied to the speaker transducer.
And something has to figure out when I switch to handsfree and hang up the
handset that I'm not terminating the call - which argues either for more
intelligence in the IP Phone (if there is a single "onhook" event, or more
intelligence in the MGC (if each transducer has it's own "onhook" event).
It is certainly important that there is clear concensus for
interoperability.

Can anyone shine some light on this?

_____________________________________________________
Bob Lukas
Broadcom Canada
Richmond B.C.
[email-masked]
604-233-8665

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From: "Glasgow, George" <[email-masked]>
Date: Wed, 19 Apr 2000 08:59:19 -0400

Bob,
To the best of my knowledge, the task of distinguishing between hang-up and
switching to handsfree mode, has always been in the telephone. All of my
speaker phones at home and in my office work that way.

I don't see that it would be to our advantage to change this operation,
given that legacy systems will be expected to work identically in a
softswitch environment to the way they work now.

Consistency of operation is important here. Achieving this will mean that
someone can have a regular POTS or ISDN phone alongside an IP phone, and
they will all operate the same way.

I suppose I'm saying that, in my opinion, the "intelligence" should be in
the IP phone, not the MGC.

Regards,

George Glasgow
Senior Engineer - SRX-3000 Development
Unisphere Solutions,
900 Broken Sound Parkway, B12S,
Boca Raton, FL 33487,
USA
1-561-955-6555 Voice
1-561-955-6477 Fax

[email-masked] <mailto:[email-masked]>

Visit us on the web at: http://www.unispheresolutions.com

---

From: Jeff Ridley <[email-masked]>
Date: Wed, 19 Apr 2000 07:45:40 -0700

George and Bob,

I think there are conflicts in some features if the hook-switch were to be a
hard feature in the phone.  There are some cases where a system actually
wants the audio paths to turn on / off independently of the hook switch.  A
person using a headset for example is not using the hook switch but would
still like their headset to turn on/off based on their calls.

If there were local smarts to switch handset to hansfree, it would have to
be done in such a way as to avoid blocking the situations where the phone
needs to be controlled more directly.  Turning the hook switch into another
feature key seems to make it easier to get this level of control.

Jeff

Jeffrey Ridley, Sr. Product Manager
Phone: 408-331-3413, FAX: 408-331-3333
For Shoreline See: www.goshoreline.com

-----Original Message-----
From: Glasgow, George [mailto:[email-masked]]
Sent: Wednesday, April 19, 2000 5:59 AM
To: [email-masked]
Subject: Re: draft-ietf-megaco-ipphone-02.txt: hookswitch/ringer?

Bob,

Regards,

George Glasgow

---

From: Peter Blatherwick <[email-masked]>
Date: Wed, 19 Apr 2000 11:51:09 -0500

Bob, list:

You query is partly specific, partly philosophical, hence the
longish reply.

Specific answers to your queries:

- All user interface related packages (as opposed to audio),
including hookswitch and ringer, are found in the User Interface
termination.  Hookswitch is a well known name within the
Function Key Package, and Ringer is a well known name in
the Indicator Package (see Annex G).   Analog line
supervision is not used, nor is hookswitch attached to
an audio transducer.  See reasoning below.

- If you wish to model handset and handsfree invisibly to the MGC
application, you certainly can.  In that case it is up to the MG
implementation to model this and map to a logical hookswitch key.

- Normally, one would expect to see events from a handsfree key
to initiate a switch from handset to handsfree.  This feature level
mapping belongs at the MGC since it owns the user interface
application for Megaco IP Phone MG end devices.

Philosophically speaking, Megaco IP Phone takes full advantage
of Megaco/H.248's master/slave control model to remove as much
application intelligence from the end device as possible.  The
reason all these elements are kept separate is to allow us to
provide for a very high degree of user interface flexibility,
well beyond what fixed function telephones can do today.  Well
know names help identify the intended purpose of a particular
element on the physical device, removing the need for
device-specific knowledge at the MGC application.

For example, consider group listening (1 person talking on handset
or headset, others listening on handsfree with mute on).  If the real
transducers were hidden behind a single termination this feature
needs to be added to the phone, while if the MGC can "see" each
transducer separately an application running at the MGC can pretty
much do whatever it wants.  Similarly, keeping the various function
keys, indicators, etc separate, the MGC application has complete
control over the user interface.  There are many, many applications
which can be easily modeled in this way, and provide an extremely
flexible and cost-effective system.  This is good for innovation on a
master/slave controlled device.

I believe the above is actually spelled out in the Megaco IP Phone
document, though it may be a bit terse in places.  If it is unclear
in some way, please suggest what I can to make it clear, and I
will certainly do so.

Before the religious war starts (yet again), I would like to make it
very clear that I do not see Megaco/H.248 master/slave as being in
conflict with peer approaches such as SIP or H.323.  On the contrary,
I believe master/slave and peer approaches are complementary in the
marketplace and are both extremely helpful, even necessary, in
creating truly useful and flexible Internet communication systems.
Certainly, the two models are fully compatible at the system level.
Its NOT about one "versus" the other.

-- Peter Blatherwick

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From: Peter Blatherwick <[email-masked]>
Date: Wed, 19 Apr 2000 13:07:35 -0400

See reply just sent to Bob.  Additional comment in line below.
-- Peter

-----Original Message-----
From: Glasgow, George [mailto:[email-masked]]
Sent: Wednesday, April 19, 2000 08:59
To: [email-masked]
Subject: Re: draft-ietf-megaco-ipphone-02.txt: hookswitch/ringer?

Bob,

[PB] Yes, this is generally the situation now.  However it is not nearly as
flexible as separating the elements and allowing full control by the MGC
application.  With separated elements, the MGC application can make the end
device behave as phones do now, but can also easily implement a very much
wider range of applications as well.

[PB] This is beyond legacy.  We can do much better, and still map to legacy
where we want to.

[PB] If you want lots of intelligence in the end device, use a peer approach
such as SIP.  Its the other valid model.  Or, you could use Megaco IP Phone
and choose to hide some aspects in the implementation if you want to.  As
long as they are logically organized (in the protocol sense) as a Megaco IP
Phone, interoperability will be good.

Regards,

George Glasgow

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From: Bob Lukas <[email-masked]>
Date: Wed, 19 Apr 2000 16:20:43 -0700

Peter,
Thanks for the reply. I agree with your philosophy.
I think the source of my problem is the missing Annex G.
It's not part of MegacoH248v16.doc, nor  draft-ietf-megaco-protocol-07.txt.
I guess you are referring to draft-ietf-megaco-otherpkgs-00.txt?

-----Original Message-----
From: Peter Blatherwick [mailto:[email-masked]]
Sent: Wednesday, April 19, 2000 9:51 AM
To: [email-masked]
Subject: Re: draft-ietf-megaco-ipphone-02.txt: hookswitch/ringer?

Bob, list:

<snip>

---

From: Peter Blatherwick <[email-masked]>
Date: Thu, 20 Apr 2000 09:54:32 -0400

I guess this is one of those problems of working in two standards bodies at
once.  Annex G is currently in TD form available in ITU, but does not
currently exist in the form of an IETF I-D or RFC.  I'm very glad to see the
2 bodies working together so closely, but it is a pain sometimes.  Tom is
currently trying to figure out process for the package documents in general,
on a different thread in this e-list.

I've attached the latest Annex G TD I have (UI package TD.doc), output from
the Geneva ITU meeting in Feb, but not sure it will make it through the
reflector (I think not).  I will get it posted in the Megaco repository
(oops, should be there).

The user interface related packages detailed as part of
draft-ietf-megaco-otherpkgs-00.txt (Display, Keypad, Function Key,
Indicator, Soft Key, Ancillary Input) are very close to the Annex G TD, but
not quite the same and missing a few details found in review.  Explanatory
text is also improved in Annex G.  Certainly the general form is the same
between the two.

-- Peter

-----Original Message-----
From: Bob Lukas [mailto:[email-masked]]
Sent: Wednesday, April 19, 2000 19:21
To: Blatherwick, Peter [CAR:AT14:EXCH]; [email-masked]
Subject: RE: draft-ietf-megaco-ipphone-02.txt: hookswitch/ringer?

Peter,

-----Original Message-----
From: Peter Blatherwick [mailto:[email-masked]]
Sent: Wednesday, April 19, 2000 9:51 AM
To: [email-masked]
Subject: Re: draft-ietf-megaco-ipphone-02.txt: hookswitch/ringer?

Bob, list:

<snip>