>So terminating the application session at layer 7 and then originating a fresh one at the point where the numbering scheme changes appears to me to be a simple and principled approach. > There are two ways I can read this, and I suspect I've got them both wrong. The first is the "flag day" meaning for "where the numbering scheme changes"--that is, re-deploy all applications on some day at which we decide the numbering scheme changes. The second is that you mean that any device which serves as an intersection point between v4 and v6 must also serve as a back-to-back user agent for all applications that run across it. That is, for the scenario v6-endpoint---[boundary]--v4 segment---[boundary]--v6-endpoint there would be a full-on termination of the application at each boundary, and a new application flow, which is itself not guaranteed to reach the original destination of the flow. Is either of those what you meant? If not, can you clarify? thanks, Ted Hardie _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf