Multicast is rare in SoHo kit and irrelevant anyway
Very little consumer kit supports IP4 multicast - I believe Zen have a list somewhere on their website, it's not long, and the list of kit which works is shorter than the list of kit which claims to have it. As the number of punters with modems reduces (more folks with routers), the number of punters for whom multicast "just works" therefore also reduces.
Multicast is economically irrelevant anyway. Today, the narrowest/most expensive bit of the network between punter and content provider is the "BT Central" which connects the ISP's network to BTwholesale's national access network. By the time the streams reach this point, they are no longer multicast, because of the way the access networks are currently implemented (using PPPoA not pure IP). Consequently 100 punters on the same ISP all watching the same thing at the same time still means 100 parallel streams through the Centrals. So there is no saving in bandwidth, and therefore no saving in cost for the ISP, and therefore no motivation for ISPs to bother with multicast.
When BT's marvellous 21CN comes along, multicast will likely still be irrelevant, although the details are afaik yet to be confirmed.
Multicast *might* have some value in the LLU ISPs, if they have a pure-IP network all the way from punter to content provider and the skills to use it properly, but unfortunately the LLU ISPs are currently the ones with least technical clue (Orange? TalkTalk? Tiscali? See what I mean?).
If you're the BBC, multicast makes you a nice saving in bandwidth between you and the ISP (bandwidth which is already relatively cheap, certainly a whole lot cheaper than bandwidth between ISP and punter).
On that basis, multicast is (at least in the UK) irrelevant for the foreseeable future; there's no motivation for ISPs to use it.
Register
Multicast is rare in SoHo kit and irrelevant anyway
Very little consumer kit supports IP4 multicast - I believe Zen have a list somewhere on their website, it's not long, and the list of kit which works is shorter than the list of kit which claims to have it. As the number of punters with modems reduces (more folks with routers), the number of punters for whom multicast "just works" therefore also reduces.
Multicast is economically irrelevant anyway. Today, the narrowest/most expensive bit of the network between punter and content provider is the "BT Central" which connects the ISP's network to BTwholesale's national access network. By the time the streams reach this point, they are no longer multicast, because of the way the access networks are currently implemented (using PPPoA not pure IP). Consequently 100 punters on the same ISP all watching the same thing at the same time still means 100 parallel streams through the Centrals. So there is no saving in bandwidth, and therefore no saving in cost for the ISP, and therefore no motivation for ISPs to bother with multicast.
When BT's marvellous 21CN comes along, multicast will likely still be irrelevant, although the details are afaik yet to be confirmed.
Multicast *might* have some value in the LLU ISPs, if they have a pure-IP network all the way from punter to content provider and the skills to use it properly, but unfortunately the LLU ISPs are currently the ones with least technical clue (Orange? TalkTalk? Tiscali? See what I mean?).
If you're the BBC, multicast makes you a nice saving in bandwidth between you and the ISP (bandwidth which is already relatively cheap, certainly a whole lot cheaper than bandwidth between ISP and punter).
On that basis, multicast is (at least in the UK) irrelevant for the foreseeable future; there's no motivation for ISPs to use it.