<resources>
        <default_setup>
            <!-- your default mysql setup here -->
        </default_setup>
        <mssql_setup>
            <connection>
                <host><![CDATA[localhost]]></host>
                <username><![CDATA[dbuser]]></username>
                <password><![CDATA[dbpassword]]></password>
                <dbname><![CDATA[dbname]]></dbname>
            </connection>
        </mssql_setup>
    </resources>

$host = (string)$config->global->resources->mssql_setup->connection->host;
$username = (string)$config->global->resources->mssql_setup->connection->username,
$password = (string)$config->global->resources->mssql_setup->connection->password;
$dbname = (string)$config->global->resources->mssql_setup->connection->dbname;