To install Oracle Solaris on SPARC clients over the network, you must set firmware keys on those clients. You set the keys by issuing commands on the OBP command prompt.
set-security-key wanboot-aes key sets the encryption key.
set-security-key wanboot-hmac-sha1 key sets the SHA1 firmware key.
set-security-key wanboot-hmac-sha256 key sets the SHA256 firmware key.
Caution - Using these same commands without specifying values for key deletes corresponding keys in the client. This deletion would prevent a SPARC client from using install services that have been configured to require server and client authentication.