Which device might be installed at a branch office to enable and manage an IPsec site-to-site VPN?

An example of IPsec site-to-site VPN is your corporation has departments in many countries which need to communicate with each other. A popular solution is site-to-site (LAN-to-LAN) VPN to create private networks through the Internet. But as we know, Internet is not a safe environment for important data to be transferred. That is the reason why we need IPsec, a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session.
Cisco Adaptive Security Appliance (ASA) supports IPsec, thats all I can say! If you wish to learn more about the configuration, please read http://www.cisco.com/ en/US/products/ps5855/products_configuration_example09186a0080a9a7a3.shtml