Hello!
The GSS itself only supports A records, meaning it only responds to that type of query from a client. You can configure an NS forwarder to push non-A records to another server that can handle it. As well, you can run CNR in conjunction with the GSS which will respond to MX, SRV, and NS records. Some versions of GSS code allowed you to run CNR on the GSS itself. (CNR = Cisco Network Registrar).
More specifically to your question - CNR supports RFC 2052 (SRV records) and is fully interoperable with Dynamic DNS SRV records (RFC 2782).
Regards,
Chris Higgins