Layer 7 Switch??
# The Register understands delays were caused when BT
# asked Phorm to develop a network-level opt-out, based
# on its own layer 7 switch, dubbed PL7.
Assuming this is a reference to the OSI Model, WTF is a Layer 7 (application layer) switch, and WTF is one doing in an ISP? Again, assuming OSI, this implies that BT are doing their own DPI.