RE: [Sipping] draft-ietf-sipping-ToIP-00 - Section 8.4

["Peter Ridler" <[e-mail]>]

Gunnar,

Thanks for the reply.

If indeed the 1000 is the clock rate, how is this value derived at?

The negotiation of the transmission interval is where I was thinking that
each end MAY suggest a timeout value that it is willing to accept (default
would be the 300ms).  The application I have in mind is the case a TDD
device is communicating via a PSTN gateway to a SIP IVR/ITR where it can
handle a longer delay of text packets (say 500 - 1000ms range).  This would
reduce the number of RTP packets going across the network.  BUT, I am quite
happy with the fixed 300ms interval.

Regards

Peter


 

> -----Original Message-----
> From: Gunnar Hellstrom [mailto:[e-mail]] 
> Sent: Wednesday, December 29, 2004 3:48 AM
> To: IETF Sipping; Peter Ridler
> Cc: Toip list
> Subject: RE: [Sipping] draft-ietf-sipping-ToIP-00 - Section 8.4
> 
> Peter,
> I am glad you are looking at details of sipping-toip.
> 
> The figure 1000 in the sdp line
> >      a=rtpmap:98 t140/1000
> is indeed a clock rate.
> 
> You can read more about it in:
> http://www.ietf.org/internet-drafts/draft-ietf-avt-rfc2793bis-09.txt
> Where some requirements are stated for handling the timestamps.
> 
> Even if it has little meaning for a text packet where text 
> characters are stored at the moment they are created rather 
> than by being sampled, we did not want to deviate from normal 
> RTP usage of that parameter.
> 
> The clock is used for setting the timestamp of the text 
> packets, and for calculation of time offset for redundant 
> text, and can thus be used if there is a desire to time the 
> display of characters.
> 
> ------
> 
> Do you see a need for negotiation of the transmission interval?
> 
> Regards
> 
> Gunnar
> 
> -------------------------------------------
> Gunnar Hellstrom
> Omnitor AB
> Renathvagen 2
> SE 121 37 Johanneshov
> SWEDEN
> [phone]
> Mob: [phone]
> www.omnitor.se
> [e-mail]
> --------------------------------------------
> 
> 
> >-----Original Message-----
> >From: [e-mail] [mailto:[e-mail]]On
> >Behalf Of Peter Ridler
> >Sent: Tuesday, December 28, 2004 6:08 PM
> >To: IETF Sipping
> >Subject: [Sipping] draft-ietf-sipping-ToIP-00 - Section 8.4
> >
> >
> >Hi,
> >
> >In section 8.4 of this draft states::
> >
> >--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--
> >
> >Text capability SHOULD be announced in SDP by a declaration in line 
> >with this example:
> >
> >      m=text 11000 RTP/AVP 98 100
> >      a=rtpmap:98 t140/1000
> >      a=rtpmap:100 red/1000
> >      a=fmtp:100 98/98/98
> >
> >Characters SHOULD BE buffered for transmission and transmitted every 
> >300 ms.
> >
> >--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--.--
> >
> >On SDP line 2 (a=rtpmap:98 t140/1000) what does the 1000 stand for?
> >
> >Nominally it is the clock rate.  If just a filler, could it be the 
> >Timeout value i.e. 1000 = 1000ms or better yet (a=rtpmap:98 
> t140/300) 
> >300 = 300ms timeout value?
> >
> >Thanks
> >Peter
> >
> >
> >
> >_______________________________________________
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> >This list is for NEW development of the application of SIP Use 
> >[e-mail] for questions on current sip Use 
> >[e-mail] for new developments of core SIP
> >
> 
> 


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