Scalable Node.js 1x1 chat platform

I am to build a chat platform over Node.js, that in core, must be able to to provide chat screens 1-1, much like Olark provides

The chat update rate is not priority, but scalability and browser compatibility are.

My question is: Which back-end strategy and which way to transmit, would be best?

EDIT: Thanks, @Brandon_R. It is just that I am not sure if we开发者_运维技巧bsocket is the way to go here, I am between it and AJAX.

I want my server to be able to host multiple calls, and websocket do keep a open connection for each client; isn't it limiting?

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Socket.io falls back on ajax polling/other transports if websockets are not available and is probably the way to go. You can also disable websockets/other transports if you prefer not to use them.

socket.io 0.8 also has support for "rooms" which will namespace and multiplex your sockets.