Re: NFSv4 and the RPC svcgssd-service
"rpcsvrgssd" is the name of the service.
You need it if you are using a gssapi type of authentication (typically Kerberos_ for NFS. Otherwise you don't.
Stop it in and disable it in the system-config-services tool.
406 Not Acceptable - The requested resource is only capable of generating content not acceptable.
499 Client Closed Request - The connection has been closed by client.