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Chapter 3: Overview of Ethernet Audio Video Bridging
P802.1Qat
This specification defines a Stream Reservation Protocol (SRP) which must be used over the AVB network. Every listener that intends to receive audio/video AV traffic from a talker must make a request to reserve that bandwidth. Both the talker and every bridge device that exists between the talker and the listener has the right to decline this request. Only if each device is capable of routing the new AV traffic stream without violating the 75% total bandwidth restriction (when taking into account previously granted bandwidth commitments), will the bandwidth request be successful. However, after granted, this audio / video stream is reliably routed across the network until the reservation is removed.
Note: No hardware components are required for the P802.1Qat specification because this is a pure software task. This software is not provided by the Ethernet AVB Endpoint core.
Typical Implementation
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Audio / | IEEE 1722 | AV |
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Sources / | Packet | traffic |
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Sinks | Manager | Ethernet |
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| AVB | Ethernet |
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| Endpoint | MAC | Ethernet |
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| LogiCORE | LogiCORE |
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| PHY | AVB |
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| legacy |
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| network |
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| Embedded | traffic |
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| Processor |
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| System |
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| with TCP/IP |
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| stack |
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| PLB management |
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| Figure |
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Figure 3-2 illustrates a typical implementation for the Ethernet AVB Endpoint core.
Endpoint refers to a talker or listener device from the example network shown in
Figure 3-1, as opposed to an intermediate bridge function, which is not supported.
In the implementation, the Ethernet AVB Endpoint core is shown connected to a Xilinx Tri- Mode Ethernet MAC core, which in turn is connected to an AVB capable network. All devices attached to this network should be AVB capable to obtain the full Quality of Service advantages for the AV traffic. This AVB network can be a professional or consumer network (as illustrated in Figure 3-1).
32 | www.xilinx.com | Ethernet AVB Endpoint User Guide |
UG492 July 23, 2010