To protect a VoIP infrastructure against a denial-of-service (DoS) attack, it is MOST important to
access control servers.
session border controllers.
intrusion detection system (IDS).
Session border controllers enhance the security in the access network and in the core. In the
access network, they hide a user’s real address and provide a managed public address. This public
address can be monitored, minimizing the opportunities forscanning and denial-of-service (DoS)
attacks. Session border controllers permit access to clients behind firewalls while maintaining the
firewall’s effectiveness. In the core, session border controllers protect the users and the network.
They hide network topology and users’ real addresses. They can also monitor bandwidth and
quality of service. Securing the access control server, backbone gateways and intrusion detection
systems (IDSs) does not effectively protect against DoS attacks.