rpc.rquotad is a rpc(3) server which returns quotas for a user of a local filesystem which is NFS-mounted onto a remote machine. quota(1) uses the results to display user quotas for remote filesystems. rpc.rquotad is normally invoked by inetd(8).
rpc.rquotad uses an RPC protocol defined in /usr/include/rpcsvc/rquota.x.