sip.uzsci.net has no CNAME records.
Question and response
Question
dig sip.uzsci.net. NS
Answer
The response has no answer records.
Authority
uzsci.net. 10156 SOA ns01.uzsci.net. root.ns01.uzsci.net. 2026021201 3600 600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0