SSCA VoIP Architecture 4

Question 1

What is the G.711 codec's bandwidth requirement per call channel in VoIP?

Accepted Answer

64 kbps

Answer

G.711 (PCMU/PCMA) samples audio at 8000 Hz with 8-bit samples, producing a 64 kbps uncompressed audio stream.

Question 2

Which SIP method is used by a UA to deregister from a SIP registrar?

Accepted Answer

REGISTER with Expires: 0

Answer

Sending a REGISTER request with an Expires header value of 0 removes the binding from the registrar, effectively deregistering the UA.

Question 3

What VoIP architecture technique allows a provider to offer multiple tenants on shared infrastructure with isolated configurations?

Accepted Answer

Multi-tenancy

Answer

Multi-tenancy allows a single VoIP platform to serve multiple customers with logically isolated numbering plans, routing, and features.

Question 4

In VoIP, what is 'codec negotiation' and when does it occur?

Accepted Answer

The process of selecting audio encoding during SDP offer/answer exchange in call setup

Answer

Codec negotiation happens during the SDP offer/answer exchange (in INVITE/200 OK) where endpoints agree on a common audio encoding format.

Question 5

What is the primary advantage of using G.729 over G.711 in a bandwidth-constrained VoIP deployment?

Accepted Answer

G.729 uses approximately 8 kbps versus G.711's 64 kbps, saving bandwidth

Answer

G.729 uses CS-ACELP compression to achieve approximately 8 kbps per call versus G.711's 64 kbps, an 8:1 bandwidth reduction.

(SSCA) Sip School Certified Associate Practice Test