Telecommunications Voice over IP (VoIP) 2 — Questions and Answers
Question 1: What is a PBX in the context of business telephony?
- Public Broadband Exchange
- Private Branch Exchange (Correct answer)
- Primary Backbone Extension
- Protocol Buffer Extender
Correct answer: Private Branch Exchange
A PBX (Private Branch Exchange) is a private telephone network used within an organization to manage internal and external calls.
Question 2: What is E.164 number formatting used for?
- Encoding voice codec parameters
- Standardizing international telephone numbers (Correct answer)
- Defining SIP URI structure
- Configuring QoS policies
Correct answer: Standardizing international telephone numbers
E.164 is the ITU-T standard that defines the format for international telephone numbers (e.g., +1-800-555-0100).
Question 3: Which transport protocol does SIP most commonly use?
- TCP only
- UDP only
- UDP or TCP (Correct answer)
- SCTP only
Correct answer: UDP or TCP
SIP can use UDP for low-overhead signaling or TCP for reliable delivery, with the choice depending on deployment needs.
Question 4: What does PSTN stand for?
- Private Switched Telephone Network
- Public Switched Telephone Network (Correct answer)
- Protocol Standard Telecom Node
- Primary Session Transfer Network
Correct answer: Public Switched Telephone Network
PSTN (Public Switched Telephone Network) is the worldwide circuit-switched telephone network, also known as POTS.
Question 5: What is G.729 commonly used for in VoIP?
- High-definition wideband audio
- Low-bandwidth compressed voice at 8 kbps (Correct answer)
- Video conferencing signaling
- Fax over IP transmission
Correct answer: Low-bandwidth compressed voice at 8 kbps
G.729 compresses voice to 8 kbps using CS-ACELP, making it ideal for bandwidth-constrained VoIP deployments.
Question 6: What is the function of a VoIP gateway?
- Manage SIP user registrations
- Convert between VoIP and PSTN/analog signals (Correct answer)
- Assign extensions to IP phones
- Monitor call quality metrics
Correct answer: Convert between VoIP and PSTN/analog signals
A VoIP gateway converts voice signals between IP-based VoIP networks and traditional analog or digital PSTN circuits.
Telecommunications Voice over IP (VoIP) 2
What is a PBX in the context of business telephony?