All things related to multicast

["Richard Mavrogeanes" <>]

It depends.
 
For public networks, I would argue 300 seconds would be adequate.  For 
private networks where the sources are very dynamic (come and go every few 
seconds), 30 seconds is reasonable.
 
The announcements from the VBrick MPEG-1, MPEG-2, MPEG-4, WM, and H264 
devices default to 30 seconds.
 
The announcement frequency has to be more often than the timeout of any SAP 
listener, which we default to 25 seconds in our servers, players, set top 
boxes, etc. and change it to match the use case.  Not sure what the timeout 
is on other devices. 
 
/rich
 
 

________________________________

From: Fulchiero, Frank (Information Services) 
[mailto:]
Sent: Sun 6/29/2008 2:27 PM
To: Marshall Eubanks; 

Subject: RE: miniSAP



Hi, pardon my somewhat ignorant background in these matters, but it seems one 
announce every 30 seconds or so is normally adequate. 5 sec seems more than 
needed.
30 seconds is the default in our Visionary Systems MPEG2/MEPG4-H.264 
encoders, and I believe also in the VBricks, not that defaults are always 
best!

We have been satisfied with 30 seconds for our publication needs.
It's also an effort to be "network friendly" and not put out any more packets 
than really necessary.

If a shorter announce period is needed, maybe 10-15 seconds would be enough?

Frank Fulchiero
Digital Media Specialist
Connecticut College


-----Original Message-----
From: Marshall Eubanks 
[mailto:]
Sent: Sun 6/29/2008 12:16 PM
To: 

Subject: Fwd: miniSAP

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/