All things related to multicast

["Marshall Eubanks" <>]

Dear Alan;

   I think that you have run into the common periodic loss
patterns on the Internet - see some of the plots in

http://www.multicasttech.com/rr/

such as
http://www.multicasttech.com/rr/u_oregon.12_apr.gif

(these are old, but the same thing is still going on...)

There seems to be at least two causes for such problems,
typical symptoms are 100% loss for 1 second out of every 60
to 65, and, at least in the few cases where I can check this,
***it occurs for the unicast too***.

This was happening to U Oregon over the weekend, but it seems to
have stopped (to there) for now.

Explanations I have heard include frame relay timing errors and
injection of DVMRP floods into PIM domains.

I would be glad to work with someone out there to try and get
a better handle on this, but I suspect that it would take a serious amount of
time to characterise and debug.

Marshall

P.S. Join one of our groups with an RTCP compliant player
and we'll get packet loss statistics to Columbia too.


Alan Crosswell wrote:
> 
> So I am trying to view some sources and have been seeing the following
> very consistently:
> 
> - "U0 Broadcasts NASA Videos (01)" jumps around between 30 fps and 0 fps 
> every

>   couple of seconds.  50% short term drop rate.  S= blaster.uoregon.edu
> 
> - "UW-Milwaukee" pretty consistent at 27-30 fps.  4% short term drop rate.

>    S=IPTV-manager.imt.uwm.edu.  Content is like watching paint dry:-)
> 
> - "GigaPort demo" conistently 24-25 fps.  0% short term drop rate.
>    S=surfnet-tv3.hvu.nl
> 
> - "CPAC on CA_net 3..." similar jumpiness to the UO session, perhaps
>    even worse.  S=iptv.canet3.net
> 
> - "Window on NDSU" about 5 fps with no loss.  S=ruby.cs.ndsu.NoDak.edu and

>    and rover.cc.ndsu.NoDak.edu.  Note these are lower frame rate 
> sessions....

> 
> Could others possibly view these same sessions and compare?
> Is there a better way than these subjective measurements to compare these?

> 
> It would be nice if IPTV Content Manager would stop announcing sessions
> for which the "managed server" is down.  90% of the clutter in IPTV viewer

> is these kinds of sessions.
> 
> /a
> PS: imj.ucsb.edu is refusing connections right now so I can't get to some

>     of the tools and papers referenced off the wg web page.

-- 


                                   Regards
                                   Marshall Eubanks


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