AES67 is a very flexible protocol for transmitting audio data via Ethernet (AoIP). The protocol uses PTP (precision time protocol) for synchronising. AES67 is used in the Ravenna Network but is also an independent protocol on its own. Unlike AES50 and AVB, AES67 is not limited to a specific medium, it can be transmitted through any IP-based medium. The transmission itself is isochronous, which means that a minimum bandwidth is provided. AES67 can also be used in mixed networks, the QoS (Quality of Service) is provided by DiffServ, which, unlike IntServ, classifies the packages, so that clock-, audio- and controlsignals can be prioritized differently. The maximum transmission distance depends on the medium. AES67 doesn’t need any special networks requirements. The maximum samplingrate is 96 kHz. AES67 uses five layers of the OSI model: IP on Layer 3, UDP on Layer 4 and RTP on Layer 5. RTP provides a flexible buffer, timestramps of the individual data packages as well as identification for the different data formats and streams. RTP does not provide a timely transmission in the right order and packages won’t be resent. AES67 features a low latency (less than 5 ms) and thus can be used in live audio situations. The maximum number of channels is dependent from the network architecture.

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