21CN, BT's 21st Century Network, creates an IP network (digital) for all telephone services (PSTN) with new controlling systems replacing many old inter-linked analogue phone systems and databases.
As a spin-off from that BT can then have an all-digital broadband network with higher capacity than now and higher speeds. That has two basic flavours, WBC and WBMC. IPSC is an interim stage.
To make that available the equipment at each end of your connection changes. At the exchange end you get connected to a 24Mbps-capable MSAN instead of a DSLAM. However the connection from the exchange to you will still be analogue (ATM) otherwise every telephone and business internal telephone switchboard would need replacing. (Samknows covers WBC and WBMC with saying WBC as he means these MSANs are working).
At the ISP end their BT Centrals and/or Central Pluses will become redundant over time. Instead they will have equipment to receive the new IP-only broadband traffic. This is where the differences between WBC and WBMC come in.
BT route all 21CN broadband traffic to 20 Wholesale Broadband Connect (WBC) nodes around the country. An ISP can connect at these nodes, (using MSILs - corresponding to the Centrals), and get the traffic onto its own backhaul from there. This is what Entanet have done - their own fibre links to every WBC node. So they get control of it at an early stage.
The BT MSANs at exchanges are each linked to a particular node, and not all MSANs at that exchange necessarily go to the same node. There are some very strange linkages.
If an ISP doesn't want to/can't afford to make that huge investment they can instead use Wholesale Broadband Managed Connect (WBMC) where BT can provide MSILs at one (or more?) of the WBC nodes and typically take the connection from there all the way to the ISP premises as now.
In broad terms I think WBMC corresponds to current IPStream and WBC corresponds to Datastream.
IPStream Connect (IPSC) is where BT have not yet WBC-enabled an exchange, (so no 24Mbps service available from BT Wholesale at that exchange), but the traffic from those exchanges gets to 10 IPSC nodes and again can be lifted off at those points. I assume ISPs using WBMC will find it arriving at their premises in the same way as above. How much of the IPSC link from the exchange to IPSC nodes is IP-only and how much legacy mixture including ATM I’m not sure.
So WBC/WBMC brings up to 24Mbps connectivity to your exchange and IP links all the way from there to your ISP where there is also an IP link, using BT Wholesale equipment. It does not bring Local Loop Unbundling.
It does mean that LLU ISPs such as O2/Be will be able to offer "up to 24Mbps" services at exchanges they have not unbundled, but these will be based on BT Wholesale products and subject to such constraints as IP Profiling just like the current IPStream. The profiles in fact are currently in 1Mbps steps above 8Mbps, instead of the 512kbps or less below that on IPStream - which stay the same on WBC. The package prices will normally be higher than LLU, like O2 Access and Sky Connect are now.
IPSC is still only “up to 8Mbps” between the user and the exchange but allows the ISPs to get rid of their old Centrals and handle this traffic over their new WBC/WBMC links.