It is used for basically everything that port 139 TCP does and allows the
same functionality with netbios over tcp/ip is disabled. Yes it is required
for AD replication traffic and is used for file and print sharing. It is a
core port/protocol for AD replication/Group Policy/authentication on domain
controllers. It may not be needed however on computers that do not need to
offer shares/printers nor be managed remotely via Computer Management/SMB
tools such as a dedicated web server. If you disable/uninstall file and
print sharing you should not see that port used anymore. --- Steve