Re: [AVT] Comments on draft-boyaci-avt-app-sharing-00

[Colin Perkins <csp at csperkins.org>]

On 14 Nov 2008, at 19:52, Cullen Jennings wrote:
> I like the idea of an applications share protocol that can be set  
> up over SIP and glad to see this submission.
>
> Few comments
>
> At a high level, why not just standardize something like VNC. It  
> seems like this would be better than inventing something new.
>
> I also wondered about why run it over RTP vs just be it's own  
> protocol. It was not clear that RTP was a good match.

This was the main issue raised back at IETF 62 when this was last  
discussed. The minutes from the AVT meeting back then state:

   draft-lennox-avt-app-sharing-00.txt
   draft-schulzrinne-mmusic-sharing-00.txt

   Henning Schulzrinne discussed some work his group has done on  
protocols
   for application and desktop sharing. This is not a work item of  
AVT but
   was presented for information, to determine if it might be  
appropriate
   to adopt as a future work item.

   The motivation for this work is to allow remote viewing and  
access of
   unmodified applications, without sharing application state. An  
aim is
   to integrate with the IETF session architecture, unlike the old T. 
120
   protocol. Henning outlined the requirements and summarised an  
initial
   protocol design outline using RTP to convey bitmap display output  
and
   keystroke/mouse input.

   After a number of questions for clarification, there was  
considerable
   discussion of the "big picture" open issues. Carsten Bormann  
wondered
   if this is now the right time to solve the problem, and if AVT is  
the
   right home for the work? Carsten was unconvinced by the arguments  
for
   using RTP: there are definitely some requirements for real-time  
data,
   but general remote access is not always perceived as a real-time
   application (indeed, the protocol uses RTP over TCP). The landscape
   of requirments varies: some applications have latency and timing
   constraints, particularly for input; others do not. It is not clear
   that the appropriate trade-off has been made, or that we have a good
   handle on the problem space. Carsten also noted that different types
   of operating system have become more similar over time, so the  
problem
   might be easier than when previous solutions were last developed,  
and
   that now might be a good time to attempt a new solution.

   Keith Lantz expressed similar concerns: this is clearly an important
   problem to solve, but he is not sure this is the right  
architecture and
   AVT may not be the right home. Perhaps we need to better  
understand the
   architecture to know if this is the appropriate solution?

   Some interest was also expressed in scaling one small screen  
devices,
   although it is unclear how that use case fits into this model.

That previous work wasn't adopted in AVT, due to those concerns, and  
I don't see anything in the current draft that addresses them either.

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



_______________________________________________
Audio/Video Transport Working Group
avt at ietf.org
https://www.ietf.org/mailman/listinfo/avt