The VoIP administrator starts receiving reports that users are having problems placing phone calls. The VoIP
administrator cannot determine the issue, and asks the security administrator for help. The security
administrator reviews the switch interfaces and does not see an excessive amount of network traffic on the
voice network. Using a protocol analyzer, the security administrator does see an excessive number of SIP
INVITE packets destined for the SIP proxy. Based on the information given, which of the following types of
attacks is underway and how can it be remediated?

A.
Man in the middle attack; install an IPS in front of SIP proxy.

B.
Man in the middle attack; use 802.1x to secure voice VLAN.

C.
Denial of Service; switch to more secure H.323 protocol.

D.
Denial of Service; use rate limiting to limit traffic.