On Tue, Mar 16, 2004 at 08:54:30PM -0600, Stephen Sprunk wrote: > Thus spake "Scott Michel" <scottm@xxxxxxxxxxx> > > On Tue, Mar 16, 2004 at 07:09:12PM -0600, Stephen Sprunk wrote: > > > When you add in the (assumed) requirements of backwards compatibility > > > with existing routers and hosts that don't implement a proposed > extension, > > > it gets messy real quick. > > > > The immediate handwave would be "Tunnel it." I'm not denigrating > > backwards compatibility, but a lot of good work has relied on tunneling in > > the past, e.g., Mbone and v6-v4. I'm currently waiting with baited breath > > the day that service providers provide v6-to-v4 as the special case to > > v4-only hosts. > > The Mbone and 6bone are different beasts, as they're about tunneling traffic > from capable hosts across an incapable core. In the case of an identity > layer between IP and TCP, we would need to be backwards-compatible with > non-capable hosts and applications (not just non-capable routers) and so > tunnels don't seem a workable solution. Tunnelling can exist at multiple layers. Overlays are just a different version of tunnelling. Proxies can be viewed as a very limited form of application tunnelling. Dealing with the complexity of different tunnelling methods and requirements makes my handwave less tractable (which was actually more to my point.) > > You never know until you submit a proposal what DARPA **really** wants > > even after you get through the program-speak. > > All too true. We do, however, know many of the IETF's needs in the > identifier/locator arena, e.g. for Mobile IP and IPv4/6 multihoming. That > may be a good starting point to determine what, if any, additional > requirements DARPA has. No argument there.