Subject: RE: [Megaco] Comfort Tone?

From: "Kevin Boyle" <[email-masked]>
Date: Thu, 22 Nov 2001 11:51:13 -0500

Comfort tone is the white noise generated to keep people from thinking their
phone line is dead.  People seem to get very uneasy when met with the
absolute silence of the digital world, and much prefer the fuzzy silence of
the analog world.

The "little tones" that indicate that you are on hold are known as "held
tone".  While they may provide you comfort, they are not "comfort tone".

Kevin

 -----Original Message-----
From: 	Blatherwick, Peter [mailto:[email-masked]] 
Sent:	Tuesday, November 20, 2001 8:31 PM
To:	'Paul Long'; [email-masked]
Subject:	RE: [Megaco] Comfort Tone?

MY comfort tone is really really loud clashing guitars...   Oh, sorry, you
were probably looking for a standards kind of definition.  (Sorry, could not
resist.  ;-)   

Seriously, what "comfort tone" do you mean?  Do you mean the noise
intentionally put in by codecs to mask the uncomfortable sound of real
silence, do you mean those little tones on hold to tell you the call is
still alive?  What specific reference are you trying to resolve?  

-- Peter

-----Original Message-----
From: Paul Long [mailto:[email-masked]]
Sent: November 20, 2001 19:27
To: [email-masked]
Subject: [Megaco] Comfort Tone?

Anyone know what the aural characteristics of comfort tone are? IOW, what
the heck does it sound like? I know this could vary from region to region,
but I can't recall ever hearing it or seeing a description of it.

Paul Long
ipDialog, Inc.

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---

From: "Paul Long" <[email-masked]>
Date: Mon, 26 Nov 2001 10:52:58 -0600

RE: [Megaco] Comfort Tone?Kevin,

No, what you describe is comfort _noise_. I'm talking about comfort _tone_,
not comfort noise or tone-on-hold. To be fair, I've also seen comfort tone
mean many different things including comfort noise, tone-on-hold, ring-back,
and even dial tone, but more often than not it means the tone after dialing
while a call is progressing. It is apparently very locale-specific, and I
don't think it is very common in North American.

I found a South African (?) document
(http://satra.gov.za/satra/Telkom_comments.htm) that describes comfort tone
as a succession of beeps. Some signal generator
(http://www.hellosoft.com/products/hellovoice/cpt.html) provides a
continuous tone. With a help-desk system
(http://www.voxad.co.uk/easydesk.htm), "Every few seconds the caller hears a
comfort tone ..." A colleague in India said that they often hear a comfort
tone after dialing. Nortel even describes comfort tone as "a short burst of
two standard tones"
(http://www.nortelnetworks.com/products/01/centrex/library/isdn/g0035.html).

So I'm still looking for some sort of standard for comfort tone, which I'm
beginning to believe does not exist.

Paul Long
ipDialog, Inc.
  -----Original Message-----
  From: [email-masked] [mailto:[email-masked]]On Behalf Of
Kevin Boyle
  Sent: Thursday, November 22, 2001 10:51 AM
  To: Blatherwick, Peter; 'Paul Long'; [email-masked]
  Subject: RE: [Megaco] Comfort Tone?

  Comfort tone is the white noise generated to keep people from thinking
their phone line is dead.  People seem to get very uneasy when met with the
absolute silence of the digital world, and much prefer the fuzzy silence of
the analog world.

  Kevin

   -----Original Message-----
  From:   Blatherwick, Peter [mailto:[email-masked]]
  Sent:   Tuesday, November 20, 2001 8:31 PM
  To:     'Paul Long'; [email-masked]
  Subject:        RE: [Megaco] Comfort Tone?

  -- Peter

  -----Original Message-----
  From: Paul Long [mailto:[email-masked]]
  Sent: November 20, 2001 19:27
  To: [email-masked]
  Subject: [Megaco] Comfort Tone?

  Paul Long
  ipDialog, Inc.

---

From: "Paul Long" <[email-masked]>
Date: Mon, 26 Nov 2001 10:52:58 -0600

Paul Long
ipDialog, Inc.
  -----Original Message-----

  Kevin

   -----Original Message-----
  From:   Blatherwick, Peter [mailto:[email-masked]]
  Sent:   Tuesday, November 20, 2001 8:31 PM
  To:     'Paul Long'; [email-masked]
  Subject:        RE: [Megaco] Comfort Tone?

  -- Peter

  -----Original Message-----
  From: Paul Long [mailto:[email-masked]]
  Sent: November 20, 2001 19:27
  To: [email-masked]
  Subject: [Megaco] Comfort Tone?

  Paul Long
  ipDialog, Inc.

---

From: Al Varney <[email-masked]>
Date: Mon, 26 Nov 2001 16:28:45 -0600

At 10:52 AM 11/26/01 -0600, Paul Long wrote:
>Kevin,
>
>No, what you describe is comfort _noise_. I'm talking about comfort 
>_tone_, not comfort noise or tone-on-hold. To be fair, I've also seen 
>comfort tone mean many different things including comfort noise, 
>tone-on-hold, ring-back, and even dial tone, but more often than not it 
>means the tone after dialing while a call is progressing. It is apparently 
>very locale-specific, and I don't think it is very common in North American.
>
>(<http://satra.gov.za/satra/Telkom_comments.htm>http://satra.gov.za/satra/Telkom_comments.htm) 
>that describes comfort tone as a succession of beeps. Some signal 
>generator 
>(<http://www.hellosoft.com/products/hellovoice/cpt.html>http://www.hellosoft.com/products/hellovoice/cpt.html) 
>provides a continuous tone. With a help-desk system 
>(<http://www.voxad.co.uk/easydesk.htm>http://www.voxad.co.uk/easydesk.htm), 
 > "Every few seconds the caller hears a comfort tone ..." A colleague in 
>India said that they often hear a comfort tone after dialing. Nortel even 
>describes comfort tone as "a short burst of two standard tones" 
>(<http://www.nortelnetworks.com/products/01/centrex/library/isdn/g0035.html>http://www.nortelnetworks.com/products/01/centrex/library/isdn/g0035.html).
>

    Both the tone and the occasion for its usage are experientially 
described in E.182.  That is, first you have to determine WHEN (if ever) 
the tone is needed, and then you have to find one that avoids premature 
abandon by your callers.

    The 1994 version of E.182 Supplement 2 describes a standard arrangement 
for "comfort tone" only for South Africa.  The specifics are identical to 
your 'satra.gov.za' URL above.  Even they do not describe WHEN to apply the 
tone.

    The solution adopted by most administrations and public carriers is the 
reduction of post-dial delay to the point where artificial tones are no 
longer needed.  (SS7 may have carried this too far -- many folks now expect 
to hear audible Ring Tone within a second of dialing the last digit.)

    If your equipment and/or carrier(s) causes long post-dial delays for a 
class of calls, then one will need to experiment with typical users of your 
equipment to determine the tone most likely to keep them from early 
on-hook.  Anything repetitive is likely to be less effective than a 
"click/clunk" at random intervals.

    I suspect there is a class of user who will not be content with 
anything other than Ring Tone, because they have virtually no exposure to 
systems that produce "click-click" tones prior to Ring Tone.  And my 
experience has been that offering such tones prematurely on failed calls 
creates the opposite of the intended effect -- callers become less tolerant 
of post-dial delay.

    Since users are not "standardized" or trained in this aspect, an 
effective Comfort Tone would be difficult to standardize, as would the 
determination of when it should be used.

Just my opinion,
Al Varney  --  [email-masked]

---

From: Al Varney <[email-masked]>
Date: Mon, 26 Nov 2001 16:28:45 -0600

Just my opinion,

---

From: "Paul Long" <[email-masked]>
Date: Mon, 26 Nov 2001 18:19:43 -0600

Al,

post-dial delay - I agree that it should be as small as possible but, for
example, a colleague of mine is concerned about getting a response to a SIP
INVITE (yeah, I know this is the Megaco reflector, but the concern spans
protocols). He says that a response could take up to 75 seconds for TCP and
32 seconds for UDP. I'd personally say that if a call takes that long to set
up it probably won't be a viable call once established, but I suppose we
should do whatever we can...

random click/clunk - Yeah, this may ultimately be the best solution.

Ring Tone - But ring tone (as a comfort tone) followed by busy tone sounds
really weird. What do you think about this scenario?

Paul Long
ipDialog, Inc.

-----Original Message-----
From: Al Varney [mailto:[email-masked]]
Sent: Monday, November 26, 2001 4:29 PM
To: Paul Long; [email-masked]
Subject: RE: [Megaco] Comfort Tone?

At 10:52 AM 11/26/01 -0600, Paul Long wrote:
>(<http://www.nortelnetworks.com/products/01/centrex/library/isdn/g0035.html
>http://www.nortelnetworks.com/products/01/centrex/library/isdn/g0035.html).
>

Just my opinion,

---

From: "Paul Long" <[email-masked]>
Date: Mon, 26 Nov 2001 18:19:43 -0600

Al,

Paul Long
ipDialog, Inc.

-----Original Message-----
From: Al Varney [mailto:[email-masked]]
Sent: Monday, November 26, 2001 4:29 PM
To: Paul Long; [email-masked]
Subject: RE: [Megaco] Comfort Tone?

Just my opinion,

---

From: Al Varney <[email-masked]>
Date: Mon, 26 Nov 2001 19:45:52 -0600

>should do whatever we can...

    Typical callers abandon calls that appear to be "dead" very 
quickly.  Let's say 10 seconds without any tones, and perhaps 20 at the 
outside if you offer some tones that indicate something useful is 
occurring.  Try it yourself -- pretend to dial a call and then wait 20 
seconds.  Do it again and wait 32 seconds.  Ask yourself why a non-telecom 
person would be willing to do either repeatedly, without complaint.

    In SS7 ISUP networks, the "awaiting address complete" timer (T7) has 
values in the range of 20-to-30 seconds.  This represents fairly closely 
the SIP INVITE-to-audio-response time.  If T7 times out, the call is not 
re-attempted on another circuit, even though a major reason for such 
timeout is a lost IAM.  Why?  Because it's unlikely there is anyone still 
listening at the calling end.  The timer exists primarily to clean up a 
failed call and protect the network from the occasional caller (or 
mechanical device) that never hangs up.

    Now, if a call might take 75 seconds and you want to keep the caller, 
you COULD announce that your network is rather busy and is still working on 
the call.  But offering that advice too often is a good way to lose 
customers to faster networks.

    If such long calls represent a tiny fraction of all call attempts, 
perhaps it would be better to let the caller hang up and re-attempt the 
call.  But the re-attempt had better have a good chance of quick success, 
or the caller will be mightily perturbed.

>really weird. What do you think about this scenario?

    Sorry, I was not clear.  I was not suggesting Ring Tone AS comfort tone 
-- I was suggesting some users would not be persuaded to continue waiting 
by ANY tone.  They want "real" Ring Tone quickly.  Unless you offer your 
callers something of value in exchange for their time, they will be unhappy 
(and perhaps ex-) customers.

Al Varney

---

From: Al Varney <[email-masked]>
Date: Mon, 26 Nov 2001 19:45:52 -0600

Al Varney

---

From: "Paul Long" <[email-masked]>
Date: Tue, 27 Nov 2001 10:39:02 -0600

Al,

Thanks a lot for your input. I suppose my one comment to what you have said
is that, as the manufacturer of equipment and not the owner of the network,
I have no control over the performance of the network and ultimately the
call setup time--I can't assure "'real' ring tone quickly." Therefore, I
need to build equipment that performs well under all conditions.

Paul Long
ipDialog, Inc.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Al Varney
Sent: Monday, November 26, 2001 7:46 PM
To: Paul Long; [email-masked]
Subject: RE: [Megaco] Comfort Tone?

Al Varney

---

From: "Paul Long" <[email-masked]>
Date: Tue, 27 Nov 2001 10:39:02 -0600

Al,

Paul Long
ipDialog, Inc.

-----Original Message-----

Al Varney

---

From: Al Varney <[email-masked]>
Date: Wed, 28 Nov 2001 16:12:37 -0600

>need to build equipment that performs well under all conditions.

    I understand -- since Nortel wrote the H.248-based spec that "requires" 
comfort tone, and also built it as a switch feature, it's too bad they 
aren't adding to this discussion.  I worked on 3 generations of switching 
equipment that never included such tones.  The only delays requiring such 
tones in non-IP networks (that I know of) are with complex call handling 
scenarios involving multiple IN database queries.  In such scenarios, IN 
can be used by the "network owner" to add "comfort announcements".  The 
content and timing of such announcements are determined by the network owner.

    It seems to me this is true for H.248 as well; the spec indicates the 
tone and duration are in the gateway.  Would asking the purchaser of such 
equipment to program the tone (prior to deployment) be a possibility?  If 
not, and some default tone/duration MUST be provided, then who could object 
to you providing whatever seems reasonable to you, the manufacturer?  Maybe 
the phrase "buy ipDialog", whispered in a sultry voice, would preclude an 
early on-hook.  It would certainly pique my interest in holding on, and 
isn't that the intent?  :)

    So, which pattern are you going to use for "held tone"?

Al Varney

---

From: Al Varney <[email-masked]>
Date: Wed, 28 Nov 2001 16:12:37 -0600

Al Varney