SSCA VoIP Architecture 3

Question 1

Which VoIP component converts between PSTN TDM circuits and IP packet networks?

Accepted Answer

Media Gateway

Answer

A Media Gateway (MG) performs protocol and media conversion between the circuit-switched PSTN and packet-switched IP networks.

Question 2

What is the function of RTCP in a VoIP call?

Accepted Answer

To provide quality-of-service monitoring and statistics for RTP streams

Answer

RTCP (RTP Control Protocol) runs alongside RTP to provide feedback on call quality metrics like jitter, packet loss, and delay.

Question 3

In VoIP jitter buffer design, what is the trade-off when increasing jitter buffer size?

Accepted Answer

Reduced packet loss but increased end-to-end latency

Answer

A larger jitter buffer absorbs more delay variation and reduces perceptible jitter effects, but adds to the overall end-to-end delay.

Question 4

What VoIP architecture pattern uses a central controller to manage distributed media gateways using MGCP or Megaco/H.248?

Accepted Answer

Decomposed gateway architecture

Answer

The decomposed gateway architecture separates call control (Media Gateway Controller) from media processing (Media Gateway), linked by MGCP or H.248.

Question 5

Which QoS mechanism marks VoIP packets at Layer 3 to give them priority in the network?

Accepted Answer

DSCP

Answer

DSCP (Differentiated Services Code Point) marks IP packet headers at Layer 3 to indicate traffic class for priority queuing.

(SSCA) Sip School Certified Associate Practice Test