Subject: [avt] SV: RFC2793bis and byte orders and other details

From: "Gunnar Hellstrom" <[email-masked]>
Date: Thu, 13 Nov 2003 21:44:27 -0600

In the avt meeting, the RFC2793bis RTP Payload for Text Conversation was
accepted as an avt workgroup item.
I promised to produce draft-avt-rfc2793bis-00 out of
draft-hellstrom-avt-rfc2793bis-02
The current version is found at:
http://www.ietf.org/internet-drafts/draft-hellstrom-avt-rfc2793bis-02.txt

When I do that, I want to include actions on the comments so far.

Therefore, I want to check the reaction on some suggestions.

1. Specify byte-order for the new T140block counter. ( motivation below from
Frank Shearar )
   I doubt that it is advicable to specify byte order for one little piece
of the packet.
   I assume that byte order issues are enough covered centrally in RTP.
   I would like to get comments on that assumption.

2. Open for other redundancy schemes than RFC2198, at least for the
audio/t140 format
   Especially for the audio intermixed packetization audio/t140, there might
be of interest to use any of the
   FEC mechanisms to gain reliability. It may for example be desirable to
use the same FEC mechanism for the
   audio stream as for the interleaved text. The requirement to use the same
clock frequency for text and audio in the audio/t140 medium may also make it
hard to use RFC2198, because the maximum offset will not be long enough to
cater for transmission only every 300 ms, when the clock frequency of the
audio packetisation is used. ( for text/t140 it is 1000 Hz, and that is a
suitable frequency to allow for redundancy. )
I recommend that I insert wording that for audio/t140 , any suitable FEC
packetisation can be used.

3. IANA considerations
The following IANA registrations shall be included in the draft:

register media types for MIME and SDP usage:

text/t140  - already done
text/red
audio/t140

register the main media type  for sdp usage
text

register the attribute parameter
cps=

Register the capability for capability registration.
text

Anything more?

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

-----Ursprungligt meddelande-----
Från: [email-masked] [mailto:[email-masked]]För
Frank Shearar
Skickat: den 12 november 2003 05:07
Till: [email-masked]
Ämne: RFC2793bis and byte orders

Hi all,

I noticed that the RFC 2793bis draft never speaks of byte ordering. Is it
assumed, since this is usually used in the context of RTP, that the byte
order of the T140block counter is the byte order defined in RTP, i.e.,
network order?

Wouldn't it be slightly better to specifically mention the byte order in the
draft, just to avoid any potential confusion?

frank

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---

From: Colin Perkins <[email-masked]>
Date: Fri, 21 Nov 2003 10:25:47 +0000

>    I would like to get comments on that assumption.

You need to specify the byte order for the payload header, the RTP spec  
only defines the byte order for the standard RTP header.

> packetisation can be used.

Yes.

> Register the capability for capability registration.

The "text/red" registration is now a separate draft, otherwise these  
look appropriate.

-- 
Colin Perkins
http://csperkins.org/