SSCA VoIP Technologies & Network Integration 2

Question 1

Which codec is most commonly used in G.711 VoIP calls and what is its bitrate?

Accepted Answer

G.711 uses PCM at 64 kbps

Answer

G.711 uses Pulse Code Modulation (PCM) and operates at 64 kbps, providing toll-quality audio.

Question 2

What is the primary function of a Session Border Controller (SBC) in a VoIP network?

Accepted Answer

To control signaling and media at the border between networks

Answer

An SBC sits at the network edge to protect, control, and monitor SIP signaling and RTP media flows between networks.

Question 3

In VoIP, what does jitter refer to?

Accepted Answer

Variation in packet arrival times

Answer

Jitter is the variation in the delay of received packets, which can cause choppy audio if not compensated by a jitter buffer.

Question 4

Which transport protocol does RTP typically run over in VoIP implementations?

Accepted Answer

UDP

Answer

RTP runs over UDP because the low overhead and real-time delivery of UDP are more suitable for voice than TCP's reliability mechanisms.

Question 5

What is the role of RTCP in a VoIP call?

Accepted Answer

To provide quality statistics and synchronization for RTP sessions

Answer

RTCP sends periodic control packets alongside RTP to report statistics like packet loss, jitter, and round-trip time.

(SSCA) Sip School Certified Associate Practice Test