n-tier architecture solution. How better?

I need to create n-tier application with the following parts:

1. Data server
2. Business logic server
3. Lightweight client with custom features for each customer

Data server(1) and l/w client(3) will be placed on customer server. Application will be as service and all business logic(2) will work on my servers. That is simple, yes. But! Data server owned by customer and data is secret for each customer. I can't hold data on my servers, but i want to publish lightweight clients on customer's side. All clients from all customers will use the same business logic from my server.

Question is:

How can i connect clients(3) with business logic(2) and protect the data to be transferred from customers?

My first solution is VPN or SSH tunnel, but may be there is another w开发者_如何学Cay? Or may be another approach.

Also data transfer between data server and business logic server may be so slow, that because i'm trying to find another approach for this architecture.

Thanks!

I think you are mixing two things here:

-The architecture: I think you'd better google "Multi-Tenant application" designs as this matches the description of your system.

-Security concerns: If this is a web application (which I think it is as you mentioned lightweight) you're better off with a SSL certificate which encrypts all traffic to/from your server by using HTTPS. If that is not applicable, you can chose SSH or VPN as they have almost the same requirements and affect the application the same.