Am I incorrect in saying a BNG is acting as an LNS ? What is the difference with a BNG terminating lets say PPP connections compared to an LNS ?
AFAIK, BNG is basically a generic term for what used to be called a BRAS or LNS (which are both essentially the same thing) I think the thing is, traditionally everything would be done over L2TP tunnels, which is why it was called an LNS, (L2TP network server), (think old Cisco 7200s connecting to BT with ATM).
However today, MPLS Pseudowires or things like PWHT (Psuedowire headend termination) might be used instead of L2TP, so the end device (BNG) is still terminating PPPoE sessions, just not using traditional L2TP, so the term has generally changed to call it a BNG, to better reflect the different types of access technology available, rather than everything relying solely on L2TP.
Cisco's take on it, if you're interested; https://www.cisco.com/c/en/us/td/do...-cg52xasr9k/b-bng-cg52xasr9k_chapter_010.html