Ethernet is widely used for all kinds of applications. However, for demanding multimedia streaming applications in a fully-loaded network, Ethernet is not the right choice due to its limited Quality-of-Service (QoS) support. IEEE 802.1 Audio/Video Bridging (AVB) standard, an extension to legacy Ethernet, provides the QoS features needed for multimedia streaming such as time synchronized low latency streaming services and bandwidth reservation.
AVB replaces both the physical complexity of cables and the network complexity of earlier proprietary solutions with an open, standards based approach that greatly simplifies network management and support.
System level modeling of AVB based system provides a greater visibility into the network architecture, node to node delay, and available bandwidth on channels and even helps in digging out potential challenges and bottlenecks in proposed system architecture. This also enables user to conduct variety of analysis by changing traffic rate, traffic pattern, and routing between talker and listeners to compute the throughput and network latency. Availability of these highly crucial system characteristics will enable the designer to define optimal network architecture that meets user requirements.
Our trade-off and analysis focuses on performance, power and reliability. To facilitate this, we have constructed an event-driven timing simulation model using VisualSim Architect from Mirabilis Design Inc. This model will be simulated by the designer to experiment with topologies, workload and AVB configurations. We have shown a simple example to illustrate our usage. The simulation model represents video recording and storage system. The video recorder is connected to an AVB node that is transmitted via an AVB Switch to an AVB node hosting the Solid State Recorder. In AVB terminology, the Video Recorder is the talker and Recorder is the listener. The real system would involve 100’s of these talkers and listeners.
VisualSim model of the proposed simple design is shown in figure 1.0.
Figure 1: Simple AVB System
Here the Camera module is a traffic generator. We used the VisualSim AVB library to assemble the network topology. The configurations were edited in a CSV files and provided to the simulation model. Examples of configurations include the Routing Table, Bandwidth to Type of Service, Class A and B to Type, and the traffic streams for each Talker. The user will start with a VisualSim distribution-driven workload generation. If the designer has any trace files captured from the real hardware then those files can be used as source files. Simulation results that you may look for would be throughput, end-to-end latency, utilization, network latency.
Bringing the real hardware device in loop with VisualSim modeling flow provides greater level of leverage towards system verification and test case generation. Here is one scenario, interfacing VisualSim with a physical switch and a recorder device as shown in figure 2.
Figure 2: Hardware-in-loop with VisualSim
In this case, the AVB model in VisualSim will generate multiple streams from a single IP address. The latency at the Receiver is saved in a file during the system model run. When the model is running with the hardware-in-the-loop, the latency is compared with the expected latency from the system model.
Model based system development for AVB based system eliminates the risk of product re-spin and increases the confidence of system designers on the selected architecture. At the early stages of product development designers can even inject faults to the simulation model to detect possible challenges that your system may come across. Identifying all bottlenecks, resource limitations early in the design flow enables the designers to develop their system error free and also eliminate the risk of product re-spins and also met the time to market requirements.