[Serusers] question about multiple SER server register.

[ZHANG, YI2 -HCHBJ]

Can SER server cascaded connected?
That's to say. There a centeralized SER registrar server.
below top layer, there are serval subordinate SER registrar server which must be registered on that centeralized registrar server.
In this case, how to configure those subordinate SER registrar servers to register onto that server?how to send "REGISTER" message onto center server?