The most recent Solaris releases have not included NIS service. Up to now, NIS service had to be installed from the unbundled NSKit. NIS has now been included in the Solaris Release 2.6 and there is no 2.6 Release NSKit.
Because NIS service is now part of the Solaris 2.6 Release, the SUNWnsktu and SUNWnsktr packages no longer exist. Instead, NIS is now installed via the NIS Server cluster (containing the SUNWypu and SUNWypr packages).
NIS service is no longer started with the /etc/init.d/yp script which no longer exists. With the Solaris 2.6 Release, you first configure your master server NIS maps with the ypinit script, and then start NIS with ypstart. NIS service is stopped with the ypstop command.