[AVT] RE: One more change to draft-ietf-avt-rfc2833bisdata

["Gunnar Hellstrom" <gunnar.hellstrom at omnitor.se>]

I can agree that if you want to shorten off the document, you could cut the V.18
description in 2.6.2 before the sentence:

" The rest of this section sketches the V.18 calling sequence."

You have correctly said that the implementor anyway must go back to the original
Recommendation to get full detail.

I would also suggest that you preserve a description of the XCI signal, that is intended
for stimulation of V.23 (Minitel ) textphones to respond

So, this part should be rescued from deletion and modified:
" 3.  Play out the XCI signal, a three second string of V.23 bit
       patterns defined in clause 3.13 of Recommendation V.18 and using
       the V.23 1200 bits/s upper channel.  The calling end gateway
       SHOULD send the V23Main event defined in Section 2.6.1 to
       indicate the nature of the content."
It seems that the V23Main does not contain details on the data bit contents that is
critical for the use of the XCI signal. XCI is designed so that a V.23 modem will perceive
it as a carrier, while a V.18 terminal should detect the XCI bit pattern and understand
that it is from another V.18, so that two V.18s in contact do not end up in V.23 mode.

So, for XCI, I suggest that you allocate an event code to the central part of it called
XCI marker in V.18. Call it XCIMark here and add it to the table in section 2.6.1.
including this description:

XCIMarker:  A signal in the V.23 upper channel by sending two bytes XCI marker containing
the data pattern (0) 1111 1111(1)(0)1111 1111(1) sent at 1200 bit/s.

XCI: A signal transmitted in high-band V.23 modulation to stimulate V.23 terminals to
respond and to allow detection of V.18 capabilities in a DCE.
The 3-s XCI signal uses the V.23 upper channel having periods of "mark" (i.e. 1300 Hz)
followed by the XCIMarker. The full definition is found in V.18 section 3.13.
The XCI signal SHOULD be sent by using the the V23Main and XCIMarker events to indicate
the nature of the content.


Gunnar
-------------------------------------------
Gunnar Hellström
Omnitor AB
Renathvägen 2
SE 121 37 Johanneshov
SWEDEN
+46 8 556 002 03
Mob: +46 708 204 288
www.omnitor.se
Gunnar.Hellstrom at Omnitor.se
--------------------------------------------


>-----Original Message-----
>From: Tom Taylor [mailto:taylor at nortel.com]
>Sent: Thursday, March 03, 2005 10:10 PM
>To: avt at ietf.org
>Cc: gunnar.hellstrom at omnitor.se
>Subject: One more change to draft-ietf-avt-rfc2833bisdata
>
>
>While digging requirements out of draft-ietf-avt-rfc2833bisdata-01.txt, I
>discovered a couple of typos in the section on V.18 terminals.  This led to
>reflect that after the general introduction to V.18 the section is really an
>extended example, and not one that's particularly needed.  I will propose on
>Monday that the detailed description of the V.18 probing be deleted, leaving only
>the general description.
>
>Tom Taylor
>


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