I have recently read these statement on this list:

...

[snip] There is no security at level 2.

Yes there is rudimentary security at L2. It's called MAC-based filtering,

Full IP filtering (to port level) is in use today at OC3 and OC12 at the edges of some relatively large ATM clouds. [Yea, I know its IP over ATM, but please do not waste energy on that flame-track.] It works with lots of ACL lists and multiple interfaces simultaneously. In one application it is working in conjunction with wire speed per-VC encryption to boot! I will provide a vendor contact via EMAIL to any who request. ..mike.. Mike Trest, ATMNET Voice: 619 643-1805 5440 Morehouse Drive Fax: 619 643-1801 San Diego, CA USA 92121 Pager: 619 960-9070