Refer to the exhibit.

Which out-of-dialog SIP OPTIONS ping response put dial-peer tag 1111 into its current operational
state?

A.
501 Not Implemented

B.
504 Server Time-out

C.
408 Request Timeout

D.
486 Busy Here

E.
503 Service Unavailable

Explanation:
SIP 503 Service Unavailable is commonly seen in a VoIP network when a SIP device (such as a SIP
server) is knowingly unable to process a call. Typically when this happens the endpoint that
originated the Invite will try the next available host it receives in the SIP Contact header.