[mythtv-users] IP TV support on the agenda?
Brian J. Murrell
brian at interlinx.bc.ca
Wed Jul 20 11:54:26 EDT 2005
On Wed, 2005-07-20 at 08:40 -0700, Joe Votour wrote:
> (At this point, we're kind of off-topic.)
Yeah. But but so is >50% of the traffic on this list. :-)
> My guess then is that you haven't tried to stream tons
> of multicast data through switches then (either
> high-end or low-end).
> Where I work, we have. And we have found many of
> those switches to be broken, only supporting a few
> IGMP groups (no higher than 16 as I recall), or just
> not able to keep up with a full 38Mbps MPEG-2 stream.
Then network carriers are either going to have to demand a working
product from their vendors, or switch vendors. That some equipment does
not work with a technology does make the technology bad. It makes good
> There's apparently a few DSLAMs (for DSL) that can't
> keep up with anything close to that kind of traffic
If anything, multicast should be easier on a DSLAM than unicast x n
streams will be. Given that a DSLAM is essentially a
multiplexor/aggregator or whatever else you want to call it:
| D |----- DSL customer 1 -----
| S |----- DSL customer 2 -----
---- network pipe ----| L |----- DSL customer 3 -----
| A |----- DSL customer 4 -----
| M |----- DSL customer n -----
Having a single stream of data on that "network pipe" which is
"replicated" in the DSLAM itself has got to be easier to handle than
having that same stream sent n number of times down the "network pipe".
This is essentially the beauty of multicast of course. If there is
*any* device out there that should handle multicast correctly it should
be a DSLAM. That, after-all is the last mile, where the pipe is
dedicated and no longer shared amongst users -- until we start to see
true routers at customer premises, but that's probably going to be a
niche market. In probably most cases there is "one customer" at the end
of a DSL pipe.
> I agree that multicast is the way to go for broadcast
> TV. But if the underlying equipment can't deliver the
> traffic, then there will be problems.
Indeed. And demand will take care of that.
> Then again, we've also had our share of problems with
> GigaBit switches not being able to deliver a GigaBit
> of data. But that's another story.
Customer: Can your switch actually handle a gigabit of traffic?
Vendor: A gigabit of traffic? Sure. Wait. Do you mean like you mean
all in one second? Let me get back to you on that.
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