SIP Interoperability and Integration 2

Question 1

Which SIP header is used to indicate the protocol version and transport when a request traverses multiple proxies?

Accepted Answer

Via

Answer

The Via header records each hop a SIP request traverses, including the protocol version and transport (UDP, TCP, TLS).

Question 2

When integrating SIP with H.323, which gateway function translates between the two signaling protocols?

Accepted Answer

Interworking function (IWF)

Answer

An Interworking Function (IWF) handles the translation of signaling and media between SIP and H.323 endpoints.

Question 3

Which IETF RFC defines the SIP-T framework for carrying ISUP information within SIP messages?

Accepted Answer

RFC 3372

Answer

RFC 3372 defines SIP-T, which enables ISUP signaling to be encapsulated within SIP for PSTN interworking.

Question 4

A SIP UA sends an INVITE to a PSTN gateway that supports only G.711. The UA's SDP offer includes G.729 and G.711. What determines which codec is used?

Accepted Answer

SDP answer from the gateway selects the mutually supported codec

Answer

The gateway's SDP answer selects one or more codecs from the offer that it supports, finalizing the codec choice.

Question 5

In a SIP-to-WebRTC interworking scenario, which protocol adaptation is typically required for media?

Accepted Answer

RTP to SRTP with DTLS-SRTP keying

Answer

WebRTC mandates DTLS-SRTP for media encryption, so a SIP-WebRTC gateway must convert plain RTP to SRTP with DTLS-SRTP keying.

(SIP) Session Initiation Protocol Practice Test

(SIP) Session Initiation Protocol Practice Test

SIP Interoperability and Integration 2