All things related to multicast

[Stig Venaas <>]

Fulchiero, Frank (Information Services) wrote:
> -----Original Message----From: Frank Fulchiero 
> [mailto:]
>
> > Don't some set-top boxes have these?
>
> Referring to SAP listeners. Sorry, I don't know that for a fact, if anyone 
> has the answer, I'd like to hear it.
>
>
> > How long after you turn on your TV do you want to see the channel  listings?
>
> I am using the "Home TV model" for my comparison to discovering and viewing 
> multicast videos.
> But is it really the best one to apply? If not, I'd like to hear other models.
>
> Also, working things backwards, how much kilobit/sec SAP traffic would be 
> acceptable to network administrators?

For network administrators it shouldn't be a problem. As long as routers
don't try to listen and use SAP themselves (some have configured their
routers to do so, and I think we all agree it's not a good idea now),
there is no difference for the network between say a 5Mbit/s media
stream and the same with SAP. Well, the main difference is that there
may be more people listening...

> That would help guide good practices, and predict when the SAP announce 
> system would be topped off or saturated.
> It is obviously not going to scale infinitely. How many channels can it be 
> reasonably be expted to scale to?

The problem IMO is from a user's perspective. Let's say that I am using
wireless or something with limited bandwidth and I am looking for some
low bandwidth audio stream. Then it is bad if I have to listen to SAP
and require high bandwidth just to look at the announcements.

I don't have any good answers, but I feel it would be problematic to use
SAP if I had to receive 1 Mbit/s of data. Right now the rate seems to be
about 27Kbit/s which is not a problem at all.

So maybe we shouldn't worry too much about frequent announcements. The
main problem is that the service is very vulnerable. Anyone can by
accident or purpose send really high rates making the service unusable.

Stig

> Thanks,
> Frank