Binary XML Format?

Hi,

I am developing an application on a windows ce device that uses udp
broadcasts as it's transport mechanism. The broadcast is required because it
needs to send the same message to up to 200 windows ce devices on the same
subnet as well as a server which will be collecting that information. The
server will be written in .NET 2.0 and we are planning to use WCF to
communicate with external smart clients (not the windows ce devcies).

Our original plan was to write some proprietory binary protocol for the
windows ce to server communication but then thought that it might make sense
to write WCF on the server side and write a compatible protocol on the
windows ce side.

Is the binary format (which I believe a variation of binary xml) documenated
somewhere?

Cheers,
Clint