Router R1 sits at an Enterprise branch office, using the Internet for its only connectivity back to the rest of the EnterprisE. Which of the following is not a ben efit of using an IPsec tunnel for packets sent through the Internet, between R1 and the rest of the Enterprise?（）

• A、Privacy
• B、Authentication
• C、Allows using an IGP between R1 and the Enterprise
• D、Secure communications