On Thu, 28 Feb 2002, Bill Cunningham wrote: > In what layer is PPP in the TCP/IP suite? It's _everywhere_. What started out as a roughly HDLC-equivalent framing encap for IP with a checksum, intended for point-to-point links, has become deeply embedded in network stacks for e.g. mobile operators, tied in with AAA... anything PPP over L2TP (over UDP) over IP... As the protocol that can tunnel everything (not just IP) over everything, PPP forms the new waists in the overblown multi-tiered hourglasses. PPP is the ubiquitous encapsulation that mpls or AAL5 always wanted to be. L. is waiting for someone to notice that ubiquitous PPP means that multicast is doomed. Oh, and PPPoE dooms broadcast, too. <L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>