libirs161 1:9.11.5.P4+dfsg-5.1ubuntu2 (amd64 binary) in ubuntu focal

 The Berkeley Internet Name Domain (BIND) implements an Internet domain
 name server. BIND is the most widely-used name server software on the
 Internet, and is supported by the Internet Software Consortium, www.isc.org.
 .
 This package delivers the libirs shared library used by BIND's daemons and
 clients.