Story: BBC throws down broadband gauntlet

Posted by: Jim Evans (Thursday 11 November 2004, 11:57 AM)

This involves some interesting technical issues which have so far been ignored by (most / all?) UK ISPs and the Broadband Equipment manufacturers.

1) The BBC is going to want to send streams at 300k to 1Mbps+ for reasonable quality.
2) for real time true 'broadcast' streams IP Multicasting was designed to eliminate the need for a stream per listener -Using Mulitcasting you need one stream per programme out of the BBC and a stream per ISP out of the Internet Exchange.
3) The BBC has been experiementing with MC for years.

The problems are
a) Few ISPs have any experience of Mulitcasting or even mention it on their web sites.
b) Although it is a "mandatory" part of IP it is not AFAIK implemented (fully) in most domestic ADSL equipment - it should be available in Cisco based equipment.
c) The current BT ADSL infrastructure based on ATM cannot easily handle Multiicasting - it creates a Virtual circuit for every user back to the ISP's router, so BT in the present design AFAIK cannot benefit from the bandwidth savings without overlaying a whole virtual mulitcast support out to the local exchanges where the DSLAMs are. located.
d) Broadband Cable Modem infrastructures with their LAN like architectures can potentially benefit from Mulitcasting more easily
e) and then there is NAT and firewalling which I have not even thought through as to what its implications are.