All things related to multicast

[Zenon Mousmoulas <>]

The code in miniSAP for the announcement interval is really dead  
simple. No matter what the platform, compiler optimizations or  
configuration, I believe it's highly unlikely to be causing such  
storms "on its' own".

The different bit/packet rates observed in the recent storms support  
(imho) the originally suggested idea that there is an A/V stream  
hidden in this traffic. If we could capture some of it, we should be  
able to prove this (or not).

Even if this were true, however, I still wouldn't be able to say how  
this traffic ended up in the sap group. We'd need detailed information  
about the particular setup to draw any conclusions.

If I may propose something bold, I suggest that some of the people who  
experienced this issue repeat their setup in an isolated environment  
and, as a first step, capture sap traffic. If this behavior is  
reproduced, we can examine the whole setup in greater detail.

My 2 cents,
Z.

On 29 ΙοÏ
ν 2008, at 7:16 ΜΜ, Marshall Eubanks wrote:

> OK, can we find out
>
> - what version people were using
> - at least one repeatable case that causes trouble ?
>
> Regards
> Marshall
>
> Begin forwarded message:
>
> > From: Rémi Denis-Courmont 
> > <>
> > Date: June 29, 2008 5:02:10 AM EDT
> > To: Marshall Eubanks 
> > <>
> > Cc: 
> >
> > Subject: Re: miniSAP
> >
> > Le samedi 28 juin 2008 20:34:33 Marshall Eubanks, vous avez écrit :
> > > We have been having a lot of problems recently with this program
> > > blasting out SAP messages (up to 300 Mbps !), which cause multicast
> > > problems.
> >
> > Yeah, so basically... minisap does not implement any bandiwdth  
> > measurement at
> > the moment. Congestion control is as brain-dead as sending a packet  
> > every
> > total delay divided by total number of _local_ announces.
> >
> > > Is there any possibility that this program could be changed to rate
> > > limit it to < 1 Mbps or some other reasonable level ?
> >
> > minisap should measure the incoming SAP traffic, much like the VLC  
> > built-in
> > SAP sender does. However the official SAP RFC limit (4kbps) sounds  
> > very low.
> >
> > That being noted, the default delay is 5 seconds, so that users  
> > wait no more
> > than 5 seconds to get the full channels lists. If there are so many  
> > announces
> > that you currently receive 300 Mbps of them on a single multicast  
> > group, it
> > would mean there are the order of a million different announces.  
> > This seems
> > unlikely high. I would suppose there is some buggy sender somewhere  
> > that
> > sends way too fast, such as an out-of-date version (< 0.3.4) of  
> > miniSAP.
> >
> > --
> > Rémi Denis-Courmont
> > http://www.remlab.net/