SIP Interoperability and Integration 5

Question 1

A SIP endpoint receives a 421 Extension Required response. What does this indicate?

Accepted Answer

The server requires a specific SIP extension listed in the Require header of the response

Answer

The call was rejected due to missing authentication

Answer

The codec negotiation failed

Answer

The registration was rejected due to an expired certificate

Question 2

Which SIP feature allows a UA to detect that a remote peer has gone silent (e.g., due to a network failure) without waiting for a BYE?

Accepted Answer

SIP OPTIONS keep-alive

Answer

RTCP sender reports

Answer

SIP PING method

Answer

DNS TTL expiry

Question 3

When integrating SIP with a legacy PBX using a SIP trunk, which parameter mismatch most commonly causes one-way audio?

Accepted Answer

NAT traversal failure causing incorrect RTP IP/port in SDP

Answer

Mismatched Max-Forwards values

Answer

Different SIP timer values (T1/T2)

Answer

Mismatched From header display names

Question 4

In SIP, the P-Asserted-Identity (PAI) header is typically used to:

Accepted Answer

Carry the verified caller identity within a trusted network domain

Answer

Authenticate the SIP REGISTER request

Answer

Encrypt the SDP body

Answer

Specify the preferred codec order

Question 5

Which SIP header is used to convey the original DNIS (Dialed Number Identification Service) information when a call is forwarded or transferred?

Accepted Answer

History-Info

Answer

Diversion

Answer

P-Called-Party-ID

Answer

Request-URI

Question 6

A SIP B2BUA differs from a SIP proxy primarily because:

Accepted Answer

A B2BUA terminates and re-originates each SIP dialog, maintaining full control of both legs

Answer

A B2BUA only modifies the Via header

Answer

A B2BUA operates only on UDP transport

Answer

A B2BUA cannot handle INVITE transactions

Question 7

When SIP is used over TLS (SIP/TLS), which port is conventionally used for secure SIP signaling?

Accepted Answer

5061

Answer

5060

Answer

443

Answer

8443