Apex domains cannot have CNAME records.
Question and response
Question
dig icss.net. NS
Answer
icss.net. 5 NS dogbert.icss.net.
icss.net. 5 NS ns.htc.net.
Authority
The response has no authority records.
Additional
dogbert.icss.net. 5 A 216.114.114.132
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0