[Serusers] request for comments

I have made a diagram using Dia, of a ser footprint that I would like to put together. http://www.ecad.org/~jev/ser/SerFootprint.png The idea is that all user accounts, and locations (Down to ser/rtpproxy fronted) will be stored in the main Billing/User accounts back end. I want to have a farm of front end ser machines which will just proxy invites/registers/byes to the back end for authentication, authorization, and billing, and also proxy RTP by means of either Maxims rtpproxy or AG's mediaproxy. The front end SERs will be able to come and go, and our cisco router will manage the balancing (using things like 'sticky IP'). Depending on load we can just add more front end ser machines, and also possibly add more back end machines (using the t_replicate() mechanism) if need be. Currently I'm playing around in my test network getting this footprint to a functional state, I wanted to share the idea with community and see what you guys think of this setup? Weaknesses, [over|under] complicated? It is possible that some front end machines would be specific for a certain group of phones, based on latency (Different physical location). My main requirement is that I have a single billing/accounting mechanisism... Calls from one end point to the other will allways be mediated through a RTP proxy on one of the front end machines. What do you guys think?