[Asterisk-Dev] Images in IAX2

[Derek Smithies]

Hi,
 It seems to me that the format for sending images in IAX2 has some 
issues, and I wonder if we can discuss it here.

As you know, I have helped develop a C++/MPL implementation of the IAX2 
protocol, that is part of the opal library.
http://lists.digium.com/pipermail/asterisk-dev/2005-August/014416.html

One of the current issues that I am facing is the sending of images.

it seems that an image (of any size) is sent in one UDP frame.

I do not understand why images are sent this way, and wonder what will 
happen with large images (eg 1 mb)
 - the network stack may just delete the image and never attempt to send 
    it.
 - the network stack may partition the image up into fragments.
   if one fragment is lost in the network, the remote IAX2 endpoint will 
   never see the image at all.
   Then, of course, the sending end will resend the frame (as the IAX2 
   protocol for full frames demands)
   At which point, we have an excesssively busy network..


My view is that if there is no partitioning of the image at a level above 
chan_iax2, then we need to partition images in chan_iax2.

Perhaps we can add an IE to the head of the FullFrameImage specifying that 
it is  section x of N, and give an identifying image number.
We need the identifying image number cause we might be sending two images 
at the same time....
Then, the binary data could be added in a second IE


Thanks in advance,

Derek.


-- 
Derek Smithies Ph.D.                 Any fool can write code that 
IndraNet Technologies Ltd.                a computer can understand.        
Email: derek at indranet.co.nz         Good programmers write code 
ph +64 3 365 6485                          that humans can understand.
Web: http://www.indranet-technologies.com/            Martin Fowler