"Various tools relating to the Simple Network Management Protocol"
If this library isn't already installed and also not available as a package for your platform, you can get it at: http://sourceforge.net/projects/net-snmp/.
Ethereal uses the source Net-SNMP distribution at http://sourceforge.net/projects/net-snmp/. Then libsnmp is compiled with the "libsnmp - Win32 Release" project using MSVC++ 6.0. A file called "README.ethereal" has been placed in the net-snmp zip archive at http://anonsvn.ethereal.com/ethereal-win32-libs/trunk/packages/ describing the changes in more detail.