ACA Quality of Service & Media Handling 2

Question 1

What does the G.729 codec offer compared to G.711 in VoIP deployments?

Accepted Answer

Lower bandwidth usage (8 kbps vs 64 kbps) at the cost of slightly reduced audio quality

Answer

G.729 uses 8 kbps versus G.711's 64 kbps by applying compression algorithms, reducing WAN bandwidth requirements with a minor, usually acceptable, quality trade-off.

Question 2

In AudioCodes Mediant, 'Voice Activity Detection (VAD)' when enabled will:

Accepted Answer

Suppress RTP transmission during silence to conserve bandwidth using comfort noise generation

Answer

VAD detects silence periods and suspends RTP transmission, replacing it with Comfort Noise Generation (CNG) signals, reducing bandwidth usage during pauses in speech.

Question 3

What is echo cancellation in AudioCodes gateway media processing designed to eliminate?

Accepted Answer

Acoustic or hybrid echo caused by signal reflection on PSTN lines coupling into the receive path

Answer

Echo cancellation removes the echo artifact caused by electrical or acoustic coupling of the far-end signal back into the return audio path, which is common on PSTN connections.

Question 4

Which RTP header field is used by AudioCodes and VoIP devices to detect out-of-order or duplicate packets?

Accepted Answer

Sequence Number

Answer

The RTP Sequence Number increments by one for each packet sent, allowing receivers to detect missing, out-of-order, or duplicate packets.

Question 5

AudioCodes RTCP (Real-Time Control Protocol) is used alongside RTP to provide:

Accepted Answer

QoS statistics including packet loss, jitter, and round-trip delay for active media streams

Answer

RTCP carries sender/receiver reports with statistics on packet loss, interarrival jitter, and round-trip time, enabling real-time monitoring of RTP stream quality.

ACA - Audiocodes Certified Associate Practice Test

ACA - Audiocodes Certified Associate Practice Test

ACA Quality of Service & Media Handling 2