SSCA VoIP Technologies & Network Integration 3

Question 1

What is the purpose of a jitter buffer in VoIP?

Accepted Answer

To store incoming packets temporarily and smooth out arrival time variations

Answer

A jitter buffer holds arriving packets for a brief period to reorder and smooth out delivery before passing audio to the decoder.

Question 2

Which SIP method is used by a UA to de-register from a SIP registrar?

Accepted Answer

REGISTER with Expires: 0

Answer

A UA sends a REGISTER request with an Expires header value of 0 to remove its binding from the registrar.

Question 3

In SIP, what does the Contact header field indicate?

Accepted Answer

The URI where the UA can be reached directly for subsequent requests

Answer

The Contact header provides a direct URI (typically including IP and port) that can be used to send future requests directly to the UA.

Question 4

Which technology allows a PBX to connect to the PSTN over an IP network instead of traditional T1/E1 circuits?

Accepted Answer

SIP trunking

Answer

SIP trunking replaces traditional PSTN circuits by carrying voice calls over an IP connection to an ITSP.

Question 5

What is the maximum acceptable one-way mouth-to-ear latency recommended by ITU-T G.114 for voice quality?

Accepted Answer

150 ms

Answer

ITU-T G.114 recommends that one-way latency should not exceed 150 ms for acceptable conversational voice quality.

(SSCA) Sip School Certified Associate Practice Test