[Serusers] SER server as a client

Hello List, I am working on an assignment to develop a load balancing asterisk cluster. I started with google and found out that SER+ASTERISK is the best way to do it. Here is what I am trying to do. I have a sip account / DID (18xx xxx xxxx ) from an abc company. Now the company is gateway for between my asterisk server and PSTN network. My Asterisk server registers with abc company's gateway to receive and make calls. How can I do load balancing in this case. I understand that my SER server should register with the gateway, the gateway should forward call to SER server and then the server should forward call to one of the asterisk servers. Is it possible have the SER server register with another SER or Asterisk server and act like a client to receive and make calls? Can some one please point me to some documentation or case study? Thank you, -JK