SIP Interoperability and Integration 3

Question 1

Which SIP extension allows a UA to learn the capabilities of a remote UA without establishing a call?

Accepted Answer

OPTIONS method

Answer

The OPTIONS method allows a SIP UA to query another UA's capabilities, including supported methods, codecs, and SIP extensions.

Question 2

In SIP federation between two service providers, ENUM (RFC 3761) is primarily used to:

Accepted Answer

Map telephone numbers to SIP URIs via DNS

Answer

ENUM uses DNS NAPTR records to resolve E.164 telephone numbers to SIP URIs, enabling cross-domain routing without a central clearinghouse.

Question 3

A SIP proxy receives a request with a Max-Forwards value of 0. What must the proxy do?

Accepted Answer

Return a 483 Too Many Hops response

Answer

Per RFC 3261, a proxy that receives a request with Max-Forwards: 0 must respond with 483 Too Many Hops.

Question 4

Which header enables a SIP UA behind NAT to advertise an externally reachable contact address learned from a STUN server?

Accepted Answer

Contact

Answer

The UA places its STUN-discovered public IP and port in the Contact header so that remote parties can reach it through the NAT.

Question 5

When integrating SIP with Microsoft Teams Direct Routing, the Session Border Controller must support which audio codec mandatorily?

Accepted Answer

G.711 (PCMU/PCMA)

Answer

Microsoft Teams Direct Routing requires the SBC to support G.711 (PCMU and PCMA) as a mandatory baseline codec for interoperability.

(SIP) Session Initiation Protocol Practice Test