Subject: RE: [Simple] RE: [Sipping] RE: text/T140 and audio/t140 was: [avt]Comments/questions on draft-ietf-avt-rfc2793bis-04

From: "Arnoud van Wijk" <[email-masked]>
Date: Thu, 24 Jun 2004 11:48:19 +0200

I as another Interactive text user fully agree with Gunnar.
Dean, RTP in RFC 2793 excellent for text transport.
It works like a gem..
I will show you at the upcoming IETF if you like. But trust me. It works!
Interactive text is a real-world application, used by more and more people. 

I also want to stress the uses for IM and Interactive text (T140/RTP). 
IM is a wonderful application. I am using it and I will always use it. But
in situations where you prefer to use IM instead of calling the person
directly. In my case, when you want to use the telephone to place a voice
call the other person directly, I will use Interactive text (t140/RTP).
Because for me as a deaf person, this is the most close I can get to a real
conversation. And in that case, I do not mind the slow typing, corrections,
changes in the story in real-time. Since you don't mind the changes in the
dialogue, stutters, hickups, mispronounciations, distractions because the
baby is crying etc in a voice phone call. That is part of a phone call..it
is normal.

So, what do we have? You can put the use of Interactive text (t140/RTP) as
follows, from Real-time to non real-time:

Interactive text (t140/RTP, RFC 2793)**** Instant Messaging**** E-mail

They are all 3 different ways for text communication. They all have their
strong and weak points. Just use them for the best situations.

I encourage the IM people to use the same application for Interactive text!
Some interface changes perhaps, but then you have 1 application that can
switch between IM and text/t140.

And to people who say that IM is enough for communications and that
Interactive text is not necessary. Please e-mail me. And then promise never
to touch a telephone and use IM to communicate.
I guarantee that you will get crazy. Welcome in my world then!

Greetz

Arnoud

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Gunnar Hellstrom
Sent: woensdag 23 juni 2004 23:11
To: Dean Willis
Cc: Cullen Jennings; 'Toip list'; [email-masked]
Subject: RE: [Simple] RE: [Sipping] RE: text/T140 and audio/t140 was:
[avt]Comments/questions on draft-ietf-avt-rfc2793bis-04

Dean,
Thanks for explanations.

You say:
"Sure, it's straightforward. But I still feel that RTP is just not
suitable for text, no matter HOW much forward error correction you
apply. It doesn't detect and react to congestion. It gets delivered
out-of-order. It gets discarded by busy routers, and not resent. You
might do a lightweight UDP protocol with in-order delivery and
incremental acknowledgement, but that wouldn't be RTP. It would be more
like ntalk, which has been around for a while."

Our experience with a couple of generations of RFC2198 redundancy is very
good. Remember,
if you have 10% loss, already by one repetition you are down to 0.1*0.1 = 1%
loss. If you
repeat once more, you get 0.01*0.1 = 0.1 % loss. That is far better than any
typist
already with only two generations. Takes very little space.

I just started up an installation where we happened to get 40% loss because
of some
network configuration problems. Video was lousy, audio sounded pling
scratch, but text got
through beautifully without problems.

Bringing packets back to order in case of misordering is a simple procedure
normal for
RTP.

One good thing is that the medium gets through where the other media gets
through. No
extra protocol compatibility needed in the routers, just plain SIP RTP
compatibility.

Also the multiparty meeting arrangements gets so familiar because they are
similar to
video.

SIMPLE has no ambitions to carry real time audio and video. So, why real
time text when
there is already one acknowledged way to transmit text that has been
standard since 2000,
and is entered in a number of higher level documents?

Gunnar

-------------------------------------------
Gunnar Hellstrom
Omnitor AB
Renathvagen 2
SE 121 37 Johanneshov
SWEDEN
+46 8 556 002 03
Mob: +46 708 204 288
www.omnitor.se
[email-masked]
--------------------------------------------

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