All things related to multicast

[Zenon Mousmoulas <>]

OK so let me see if I understand correctly:

The cause of the problem was not that a video stream (corresponding to  
the SAP announcement) was somehow "relayed" to the SAP group itself,  
as we first thought (at least I did). On the contrary, the problem was  
caused by miniSAPserver sending otherwise "normal" SAP announcements  
at the amazing frequency of 33KHz, instead of the intended 0.03 Hz.  
Right?

If that is so, and that is what happened in each and every recent case  
of a "SAP storm", then how do we explain the different bit/packet  
rate, assuming everyone tried to set the suggested sap_delay=30?

However Frank also notes this behavior was not consistent. So, do you  
have any ideas what else could have triggered it, apart from this  
setting? A specific video stream type perhaps?

Would someone from Univ. Paris 13 want to share their experience? Jean- 
Francois Florence perhaps?

Thanks for the info.

Z.

On 20 Ιουν 2008, at 3:13 ΜΜ, Frank Fulchiero wrote:

> On Jun 20, 2008, at 7:04 AM, Niels den Otter wrote:
>
> > > I'm not sure if this is 'the bug', but I got an answer from the  
> > > person
> > that initiated the SAP stream yesterdam.
> >
> > He was setting up a miniSAP server (VLC) to announce a session via  
> > SDR.
> > This appeared to work too good. Problem was in the announcement
> > interval. The documentation said that the announcement interval  
> > should
> > be provided in seconds, while the sourcecode would have a
> > usleep(interval) so in microseconds.
>
> If that's true, that's probably how we caused the SAP storm in  
> February.
> But it's not always a consistent bug, as we ran it with a delay of  
> 30 for a whole day without problems:
>
> # sap.cfg - Configuration file of the mini SAP server
>
> # Global miniSAPserver options
> [global]
>
> # Number of seconds between announces. 5 is default. Internet  
> announces better use 30.
> sap_delay=30
>
> # The network interface on which to stream.
> interface=en0
>
> # Then you should have one "[program]" section per program announced
>
> # Note that only announces for MPEG2 TS streams are supported.
> # Though announces of other types of streams may work for some  
> clients,
> # they will not be compliant to the announce spec. and are not at all
> # guaranteed to work.
>
> # IPv4 example
> [program]
> # Name of the program (as it will show up in the VLC playlist)
> name=ConnProgram1
>
> # Name of the streaming entity (organisation)
> user=conncoll
>
> # DNS or IP of the machine on which you run the stream
> machine=136.244.96.102
>
> # Website of the streaming entity (organisation)
> site=http://www.conncoll.edu
>
> # Multicast IP address of the program
> address=233.88.214.137
>
> # UDP Port
> port=1234
>
> # The name of the playlistgroup your announce will be part of in the  
> VLC playlist
> playlist_group=ConncollPlaylist