Phone Service Business VoIP Technology & Protocols 2

Question 1

What is latency in a VoIP call, and what is considered an acceptable one-way delay?

Accepted Answer

The delay between speaking and hearing; under 150ms is ideal per ITU-T

Answer

Latency is the one-way delay in a VoIP call; the ITU-T recommends keeping it under 150ms for acceptable call quality.

Question 2

What does QoS (Quality of Service) do in a network supporting VoIP?

Accepted Answer

Prioritizes voice traffic over other data to reduce latency and jitter

Answer

QoS settings on a network router prioritize voice packets to ensure consistent, high-quality VoIP calls even during high data usage.

Question 3

What is packet loss in VoIP and what percentage is generally considered problematic?

Accepted Answer

Lost audio data packets; above 1-3% noticeably degrades call quality

Answer

Packet loss above 1-3% in VoIP causes audible gaps or clipping because lost audio packets cannot be retransmitted in real time.

Question 4

Which port does SIP most commonly use for signaling traffic?

Accepted Answer

Port 5060

Answer

SIP signaling traffic typically uses UDP or TCP port 5060, and port 5061 for TLS-encrypted SIP.

Question 5

What is SRTP used for in a VoIP deployment?

Accepted Answer

Encrypting voice media streams to prevent eavesdropping

Answer

SRTP (Secure Real-time Transport Protocol) encrypts VoIP audio streams to protect them from interception.

Phone Service Business Practice Test