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will multicast traffic count as normal for VMBU?

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will multicast traffic count as normal for VMBU?

With the BBC trials going on it made me wonder whether such multicast traffic would count towards my usage limits in the normal way.

It would seem reasonable that, if implemented properly, multicast traffic should only use up a (relatively) tiny amount of traffic in all directions. Or does BT's ATM network interfere and stop the traffic being truly multicast?
10 REPLIES
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will multicast traffic count as normal for VMBU?

In short YES
JonathanW
Grafter
Posts: 2,648
Registered: 02-10-2007

will multicast traffic count as normal for VMBU?

At the moment, the multicast stream goes to our gateways, which is where you pick it up from, and then goes over the BT Central to your machine. Which means that it still counts the same towards bandwidth usage on your account.

What the trial does do is decrease the load on the BBC server, as they only need to send out one stream per ISP, and it also reduces the transit costs to get the data from the BBC servers to our gateways.
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will multicast traffic count as normal for VMBU?

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At the moment, the multicast stream goes to our gateways, which is where you pick it up from, and then goes over the BT Central to your machine. Which means that it still counts the same towards bandwidth usage on your account.

Are there any plans to bring BT in on the action? Setting up something to allow transporting one stream per channel to each exchange would be relatively low-cost, surely?

Of course The Right Way to do it would be for the providers to give a single stream direct to every BT exchange, but with all the different ISPs the data has to go through all the top-layer routers, becoming one stream per channel per ISP. Another point where competition destroys the advantage of the technology, I suppose.

Sometimes I wish we lived under communism Smiley

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What the trial does do is decrease the load on the BBC server, as they only need to send out one stream per ISP, and it also reduces the transit costs to get the data from the BBC servers to our gateways.

So the major transport costs for plusnet are the BT IPStreams, not the upstream links?
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will multicast traffic count as normal for VMBU?

As far as multicast is concerned, it doesn't know anything about ATM (and does not need to) as it's just another layer in the stack..
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will multicast traffic count as normal for VMBU?

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As far as multicast is concerned, it doesn't know anything about ATM (and does not need to) as it's just another layer in the stack..


Sorry, I didn't describe what I meant properly: if you have two Plusnet subscribers on the same exchange watching the same channel, it would be sensible for a multicast-aware router to pass the data to the exchange only once. My point about BT's ATM network wasn't specifically that it was ATM, more that it introduces an extra network hop which might not necessarily be multicast-aware.
Community Veteran
Posts: 26,450
Thanks: 695
Fixes: 8
Registered: 10-04-2007

will multicast traffic count as normal for VMBU?

I'd go further than that.

If you have a Plusnet, a Zen and a Claranet user all watching the same channel on the same exchange you have three copies of the data going different routes to get to the exchange.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Ianwild
Grafter
Posts: 3,835
Registered: 05-04-2007

will multicast traffic count as normal for VMBU?

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So the major transport costs for plusnet are the BT IPStreams, not the upstream links?


Indeed - Our peering with the BBC is almost free, as we peer with them directly through links at Telehouse.

Our costs are described in detail in this article:

http://www.plus.net/support/broadband/network/capacity_guide.shtml

Regards,

Ian
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will multicast traffic count as normal for VMBU?

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Our costs are described in detail in this article:

http://www.plus.net/support/broadband/network/capacity_guide.shtml


Is your IPStream cost really that high? £120,000 per month for a 600Mb... hmmm... gosh, yes it is! (1652760.00/12=138k)

As that's the case I don't see multicast TV being properly significant until either a) the exchange equipment can be more involved, preferably with a multicast route directly between BT and the BBC or b) BT Central prices get cut to about a quarter of their current levels. I'm certainly not going to watch a significant amount of TV at 400kbps or whatever it is, I'd hit my usage limit after 5 hours of TV a day (which is generally what we watch, on average).
prichardson
Grafter
Posts: 1,503
Registered: 05-04-2007

will multicast traffic count as normal for VMBU?

Hi,

Multicast isn't strictly designed to make it cheaper for the internet providers to supply the stream to the customer. It mainly designed for content providers.

Taking the BBC as the best example, a standard stream will see many thousands of users connected at the same time. Each of these users taking their own unique data feed.

Although not through the same internet provider, this presents a cost problem to the BBC in terms of moving the next step in content quality.

I can't find it off hand and it may have even been Ian Wild who provided the information, that BBC had 5gbps of Real Media streams running at any one time (about 8 months back iirc).

Multicast allows the content providers to dish out maybe only 100 streams of very high quality media. They don't particualy care what the service providers then do with that, as frankly, they can't control that process.

Unfortunatly, BT's network can't be Multicast aware at this time with it running on ATM bassed network. Your connection from your exchange is tunneled between there and the providers home gateway router.

At the time, the only real way to make Multicast function in this way is through an IP bassed network, which may be possible in the future if things change through the invent of 21CN.

Kind Regards,
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will multicast traffic count as normal for VMBU?

You used to be able to access the Beeb's MRTG stats, they've changed the permissions for those pages now though, but yes, it used huge amounts of bandwidth. They used to provide Quicktime streams too, but that was subsidised by Apple. The beeb are heavily investing in alternative forms of IP based content distribution, Multicast is one, another is the iMP project. They're even developing their own codecs Smiley