[h323plus] Dynamic Bandwidth Management!!

Paul E. Jones paulej at packetizer.com
Wed Jan 23 02:46:10 EST 2008


I do not know what the H323 Plus software has, but there are procedures defined for H.323 and facilitated with RTCP information to help control bandwidth.  For example, if packet loss is observed by looking at RTCP reports, then an H.323 device could use the "flow control" command, "request mode", or even close and open a channel that uses a lower bit-rate codec.

The problem, though, is that while a mode shift can be made to a lower bit-rate codec, there are dangers in doing the reverse.  I mentioned in my previous e-mail that what can happen is that devices get into a constant state of increasing and decreasing bandwidth usage based RTCP feedback.

One possible way to help mitigate that is to utilize a Gatekeeper to allocate and revoke bandwidth to a terminal.  This works acceptable well, unless you have a network connection that is utilized by other applications.  And, in fact, most network connections are used by a multiplicity of applications.  As a consequence, using the Gatekeeper for bandwidth management is often non-workable.

There are two tools to help address this issue, and those are RSVP and DiffServ.  We are presenting defining Recommendations for the use of both RSVP and DiffServ within H.323 systems, with the initial recommendations expected to be approved in May 2008.  Using these tools will generally work well if you can control the end-to-end network and/or your service provider will provide some kind of service agreement and honor your DiffServ packet markings accept RSVP requests and use DiffServ or other means to increase the likelihood that your packets will arrive at the remote end as desired.

In short, this is not a simple issue of H.323 or any particular stack like H323 Plus or the IP link, but rather a whole system problem that requires coordination and cooperation to work.


  ----- Original Message ----- 
  From: Abhishek Rohilla 
  To: h323plus at lists.packetizer.com 
  Sent: Wednesday, January 23, 2008 1:09 AM
  Subject: [h323plus] Dynamic Bandwidth Management!!


  By dynamic bandwidth management I mean that when a video call is in progress , the bandwidth keeps on increasing or decreasing, So does h323+ takes care of that and keeps the bitrate of encoder in control by some means.Suppose encoder is producing more no of bits for a frame than can be send on currnet available bandwidth. how does H323 deal with that?

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