WCF Session, number of clients?

I'm developing as system with a WCF service back end, and thinking about implementing sessions. But I'm worried about the number of client that can be connected at the same time. I will have up to 500 clients connected, and each client will constantly make calls every 5-10 seconds. How expensive w开发者_开发百科ill it be for the service to have one instance per client?

Thanks

Jon

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The Enterprise Library caching and authentication blocks may be used in this scenario. Your infrastructure servers will need high specification SQL and Application machines.