AVB RESOURCE GUIDE Covering the Basics of AVB
Table of Contents AVB Brings AV and IT Together .................................................. 3 AVB for IT Professionals................................................................ 4 What is AVB and What Does It Do? ............................................................. 4 The AVB-Related IEEE Standards ............................................................... 4 Industry-Supported and Future-Proofed Solutions ................................. 4 How Does AVB Work? .......
AVB Brings AV and IT Together The AV industry has experienced exponential growth in the last 10 years and shows no signs of slowing down. The development of Digital Signal Processing (DSP) has required a number of protocol innovations both in telephony and in transporting digital media around a facility. Traditionally this has been handled by the use of licensed or proprietary audio or video protocols.
AVB for IT Professionals What is AVB and What Does It Do? AVB is a collection of IEEE 802.1 standards that have increased the capacity for information exchange, support and AV product standardization. Commonly referred to as a switch, the purpose of an audio video bridge is to provide timesynchronized, low latency streaming capabilities for audio and video data that guarantees bandwidth reservation.
How Does AVB Work? Clocks: Accurate, Synchronized Communications The commonly referenced network clock in every AVB-enabled device on a network ensures that every device will have a very close representation of what the precise time is in any given instance. After the devices communicate with each other, one AVB device is selected as the best master clock and communications proceed from talker endpoint to listener endpoint.
Step 3: Talker endpoint sends stream and listener endpoint receives it. Endpoint Endpoint Endpoint Sending Stream! Ready! Ready! Receiving Stream! Ready! Endpoint Endpoint The AVB bridge/switch guarantees time-sensitive, loss-sensitive, real-time AV data transmission while allowing audio and video data to seamlessly share the same network. The switches will only allow up to 75% of each network port to be used for AVB traffic, preventing other forms of data from being delayed or lost.
• Provides higher channel count capabilities than are possible using CobraNet®. • Works over existing Ethernet infrastructure with proper switches. • Stream reservation protocol (SRP) defends bandwidth against oversubscription and ensures quality of service (QoS) through the use of admission control and traffic shaping. It also prevents information from being lost in cases of oversubscription. • Queuing and forwarding rules ensure AV streams pass through the network with the delay specified.
Why AVB? Streamlined For AV integrators and IT managers, AVB means end-to-end digital networks that are simple to design and easy to manage. AVB follows the IEEE 802.1 standards, which are open, industry-accepted standards for transporting audio over networks.
Simple To use, AVB is as easy as analog, but with next generation functionality and scalability.
AVB Questions and Answers Q: How does AVB fit with other technology like CobraNet® and VoIP? A: See diagram below: Q: Why do I need different switches to use AVB? A: The most important enabler for AVB technology is the AVB bridge/switch. Unlike current Ethernet switches, AVB switches have additional CPU processing to handle the additional traffic shaping, time synchronization and QoS requirements inherent in AVB-aware networks.
Q: Can I use AVB with a mixed network? A: Yes. Q: What is the latency of AVB? A: The latency for AVB is very low. Stream Reservation Protocol (SRP) and the IEEE 802.1Qav Protocol together ensure end-to-end timely delivery of all reserved media streams. Without these protocols, there is no way to know how much intervening non-media traffic, or how many media packets, the switches may queue up.
Q: What are switch manufacturers doing with AVB? A: In order to leverage the use of AVB, the switching network is used to perform the heavy lifting items such as traffic shaping and stream reservation. In order to do this, there is a requirement for updated features in the switch chipsets. Many switches already have the hardware built-in and it’s simply a matter of upgrading the software to enable the AVB feature set. Typically this is enabled with a software license on the switch.
Q: What are the bandwidth requirements of AVB? A: There are two factors used to calculate AVB bandwidth requirements, which means the calculation is not linear. The first is the stream overhead, which is a fixed requirement and is used to assist in the traffic shaping requirements of the AVB data streams. There is also a calculation for the number of channels of audio the stream contains. Example channel streams: Stream Channel Count Gigabit Ethernet link utilization 1 0.63% 2 0.78% 4 1.09% 8 1.
Q: Can CobraNet be in the same network as AVB? A: It’s certainly possible to mix CobraNet and non-CobraNet traffic on the same network with no perceived problems. However, this is highly topology and usage dependent. There’s no guarantee that artifacts wouldn’t occur in different use cases. The CobraNet conductor assumes control and provides scheduling for all traffic on the network.
Q: How do I know if AVB is working properly in my system? A: This can be done via the switch console by monitoring the Multiple Stream Reservation Protocol. Tesira devices also have alarm indicators viewable in software, and the front panel of the device shows alarms due to AVB streams not operating as expected. Q: Is AVB traffic unicast or multicast? A: AVB data traffic is 100% Layer 2 multicast. The standard allows for the use of unicast, but only if locally administered MAC addresses are used.
AVB Glossary AVB Endpoints A device used at the edge of the network that has correct hardware to receive or send signals into or out of an AVB network. These will then be configured as talkers or listeners on the network. A common application will be to have a talker transmitting a microphone audio signal to a listener elsewhere on the AVB network. AVB Timing Domain The boundary between an AVB-capable bridge/switch and non-AVB-capable bridge/switch.
Listener An AVB endpoint capable of receiving one or more streams from the network. Multiple Stream Reservation Protocol (MSRP) Allows various devices to communicate their network resource requirements (from a stream talker to a stream listener) for their audio and video streams. Multiple VLAN Registration Protocol (MVRP) A standards-based Layer 2 network protocol, for automatic configuration of VLAN information on switches.
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