At 03:55 AM 2/28/2002, you wrote:
In what layer is PPP in the TCP/IP suite?
I have read some of the other responses and it reinforces my belief that
most people don't understand PPP's relationship to IP and either the
5-layer (internet) or 7-layer (ISO) models.
PPP is really both the link and lower network layers. (The ISORMites
discovered that layer three was really several layers in itself but found
it difficult to say that the 7-layer model was really a 9-layer model so
they created sublayers, i.e. layers 3A, 3B, and 3C. Something about
Padlipsky comes to mind here.) The best way to think of PPP is a degenerate
network of two nodes, not a link between two devices. If you think of it
in this way, things like multilink and L2TP begin to make some sense. The
problem occurs when people forget this.
The way that I think of it is that the LCP negotiation represents
configuration of the link layer while the NCP negotiation configuration at
the network layer.
And I continue to kick myself for allowing negotiation of multilink as part
of LCP instead of doing it after authentication. I fear that this helped
screw up L2TP too. I admit I caved to people who were worried about how
long it took PPP to complete negotiation, something that just isn't very
important.
Brian Lloyd
brian(_at_)lloyd(_dot_)com
+1.530.676.1113 - voice
+1.360.838.9669 - fax