At 02:42 AM 3/6/2002, you wrote: >I don't see how classification of PPP as a layer 2, layer 3, or any other >layer >would have had an affect on how we designed L2TP (perhaps it would have >affected >the name of the protocol though). PPP actually consists of two distinct and separate sets of protocols. The LCP and its negotiation should be totally separate from the NCPs and their negotiation. >Layers aside, PPP was already deployed and it >was pretty obvious what we wanted to do - make it run over IP without the >installed base of PPP clients being made aware of it. Do it right would not have changed that. >How would you have done >this that is substantially different than L2TP? (As an aside, of the list of >obscene things we did have to do to make L2TP work, the worst were more due to >badly implemented PPP stacks than anything else.) <sigh> It has been many years since I argued this with Karl Fox back when he chaired the L2TP WG. At that time he agreed but also said that there was too much water under the bridge to fix L2TP at that time so it was going to go forward in its subtlely-broken form. I haven't looked at it since then. I don't even remember the lexicon so I will undoubtedly sound uninformed. The LCP negotiation should take place with the L2TP equivalent of the NAS. That is independent of anything else that happens and nothing associated with that needs to be communicated to the edge device at the target network. The authentication phase then takes place so you can do authorization and configuration. Once that is complete you can do the MLPPP and NCP negotiation(s) because then and only then do you know what the end system is authorized to do. "But MLPPP is negotiated during LCP," you say! Right. That is broken and I helped make it broken and, in retrospect, I am *really* sorry I did. So, as I said, this is water under the bridge and it isn't going to change. Any attempt to do so would be met with a barrage of "but we have lots of systems in the field and this would break them" arguments. >Tunneling, particularly L2 tunneling, is by its very definition a "layer >violation". The perfect world where this is not necessary or desirable >does not >exist beyond textbooks and laboratories. So here we are in the real world, >tunneling not just PPP but a plethora of L2 or L2-like layers. There is nothing wrong with tunneling per-se. In fact, it solves many problems. IMHO tunneling is a good thing. My comments had only to do with the fallacy of rigid layering, how many people don't really understand layering, and as a side issue, how PPP was really a suite of protocols at different layers and how that affects MLPPP and L2TP. YMMV Brian Lloyd brian@lloyd.com +1.530.676.1113 - voice +1.360.838.9669 - fax