PS... Joe Touch wrote: > > Noel Chiappa wrote: >> > From: Keith Moore <moore@xxxxxxxxxx> >> >> > Regarding SRV, it's not acceptable to expect that as a condition of >> > deploying a new application, every user who wishes to run that >> > application be able to write to a DNS zone. Most users do not have DNS >> > zones that they can write to. >> >> Yes. Architecturally speaking, it's somewhat dubious that information which >> really only needs to be localized to the host (application<->port binding) >> has to be sent to the DNS. >> >> It would be easy to run a tiny little USP "binding" server that took in an >> application name (yes, we'd have to register those, but string-space is >> infinite), and returned the port. > > Only if it asked a well-known server ON THAT MACHINE. I.e., pick a port, > reserve it for resolution (e.g., like the RPC portmapper works). > > But we cannot assume a hosts' DNS is available for that purpose. For > most of us, the DNS entry isn't under our control, nor is it likely to > be for the forseeable future. > >> About the only reason I can see that that would not be desirable would be to >> avoid an extra RTT to the do that binding lookup. (DNS/SRV solutions might >> avoid this RTT too, but in that case that benefit doesn't outweigh the >> costs.) The "obvious" way to do it, which is have the ICP use the strings >> directly (as the CHAOS protocols did) is not really feasible now - it would >> require a change to TCP. > > That could be done using a late-binding trick like we used for > string-based source routing (www.isi.edu/datarouter); we could have a > TCP option where the service name occurs (as below), and send it at > first to the 'portmapper' port, which would demux it and return it. That > does require a mod to TCP to allow the dest port to be unbound (e.g., > '0') if the option is present, and enable the return SYN-ACK to update > the TCB on arrival. Since it seems like this might be useful, I'll pull a draft together on how to do this without 1078's extra connection, more like the late-binding we do in datarouter, very shortly... Joe _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf