CTS AV Networking and AV over IP

Question 1

Which network quality-of-service (QoS) mechanism is most commonly used to prioritize AV over IP traffic on a managed Ethernet switch?

Accepted Answer

Differentiated Services Code Point (DSCP) marking

Answer

DSCP marking tags IP packets with a priority value, allowing switches and routers to queue and forward time-sensitive AV traffic (audio, video, control) before less-critical data. DSCP is the standard QoS tool for Dante, AES67, and other AV over IP protocols. STP manages loop prevention, NAT handles address translation, and LACP bonds multiple links.

Question 2

What is the primary advantage of using VLANs when deploying an AV over IP system alongside a corporate IT network?

Accepted Answer

VLANs segment AV multicast traffic so it does not flood the corporate network

Answer

AV over IP protocols like Dante use multicast, which by default floods all ports on a switch. Placing AV devices on a dedicated VLAN containing the multicast traffic prevents it from saturating corporate workstations and servers. VLANs do not increase bandwidth or replace DHCP.

Question 3

Dante, the popular AV over IP protocol, uses which transport method to carry audio across a network?

Accepted Answer

UDP/IP multicast and unicast packets

Answer

Dante transmits audio as UDP/IP packets using both multicast (for one-to-many flows) and unicast (for point-to-point flows). UDP is chosen over TCP because its low-latency, connectionless delivery is better suited to real-time audio than TCP's retransmission overhead.

Question 4

An AV technician needs to ensure that network switches support AV over IP multicast without flooding all ports. Which switch feature should be enabled?

Accepted Answer

IGMP snooping

Answer

IGMP snooping allows a switch to listen to IGMP membership messages and only forward multicast traffic to ports that have devices subscribed to that multicast group. Without it, multicast frames are sent to every port, wasting bandwidth. Port mirroring duplicates traffic for monitoring; MAC filtering controls access; jumbo frames increase packet size.

Question 5

What does the term 'latency' mean in the context of AV over IP audio systems, and why is it critical?

Accepted Answer

The delay from audio input to output; excessive latency causes lip sync issues and performer disorientation

Answer

Latency is the time delay between when audio enters the network and when it exits at the destination. In AV systems, excessive latency causes visible lip sync errors (audio lagging behind video) and can disorient performers monitoring themselves through in-ear monitors. Dante systems are configurable for latencies as low as 0.25 ms on a Gigabit LAN.

(CTS) Certified Technology Specialist Practice Test

(CTS) Certified Technology Specialist Practice Test

CTS AV Networking and AV over IP