I have received several responses and most people say it's in the data layer, and a couple of people think it's in the network layer. I don't really pay much attention to the OSI model, I think it complicates the complicated. I try to focus more on TCP/IP. Does PPP establish a link, then terminate, or continue throughout session in UDP and TCP? I posted this question on the PPP mailing list with less familiaritive response than ietf general list. ----- Original Message ----- From: "Brian Lloyd" <brian@lloyd.com> To: "Bill Cunningham" <billcu@CITYNET.NET> Cc: <ietf@ietf.org> Sent: Thursday, February 28, 2002 11:52 AM Subject: Re: PPP > 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@lloyd.com > +1.530.676.1113 - voice > +1.360.838.9669 - fax >