AVB / Milan

AVB / Milan

GigaCore switches support AVB / Milan. In the current firmware versions (as of writing: GigaCore v1.4.1 of gen2 and GigaCore v3.1.0 for gen1), AVB is enabled by default on all ports.

Enabling AVB on GigaCore

To enable AVB on second generation GigaCore switches, follow this guide.
To enable AVB on first generation GigaCore switches, follow this guide.

AVB

AVB or audio video bridging is a technology to provide synchronized, low latency, reliable and deterministic transport of data streams. It consist of a set of technical standards that all work together to reach this goal:
  1. IEEE 802.1AS-2011: Timing and Synchronization for Time-Sensitive Applications (gPTP)
    1. gPTP makes sure that all devices in the AVB network are synchronized to the same time.
  2. IEEE 802.1Q: VLAN Reservation Protocol (MRP, MVRP)
    1. All AVB devices will set up a common VLAN using the MVRP protocol which will be used to transmit the AVB streaming data. This is typically VLAN ID 2.
  3. IEEE 802.1Qat-2010: Stream Reservation Protocol (SRP, MSRP)
    1. The stream reservation protocol is used to set up 'streams' between AVB 'talkers' and one or more 'listeners'. All switches on the path for this stream will reserve bandwidth for the stream to guarantee that the stream data will not get congested or dropped. The amount of this reservation is determined by the AVB talker and matches what is needed. By default, AVB supports up to 150 streams, but each stream can contain multiple audio channels depending on the stream format.
  4. IEEE 802.1Qav-2009: Forwarding and Queuing for Time-Sensitive Streams (FQTSS)
    1. FQTSS makes sure that AVB data streams are not transmitted in burst and don't exceed the reservation made by the stream reservation protocol. This is done using credit-based shapers (CBS). Additionally, FQTSS ensures that there stays bandwidth available for non-streaming data such as gPTP, ATDECC, other management data or non-AVB applications.
  5. IEEE 1722 Layer 2 Transport Protocol for Time-Sensitive Applications (AV Transport Protocol, AVTP)
    1. IEEE 1722 outlines what the AVB streams should look like and which stream formats are available.
  6. IEEE 1722.1 Device Discovery, Enumeration, Connection Management and Control Protocol (AVDECC, ATDECC)
    1. AVB end-points and AVB controllers use ATDECC to set up streams and to discover and control the end devices.
The requirements for AVB switches (in IEEE terminology called AVB bridges), are specified in IEEE 802.1BA-2011: Audio Video Bridging (AVB) Systems. These 'special' AVB switches are needed in order to meet the deterministic and reliable transport of the AVB streams. Note that all AVB switches should work together with Milan end devices since Milan is built onto the AVB network protocol. There is no special 'Milan certification' for switches, only Avnu AVB certification.

Milan

Milan is the application layer built onto the AVB network protocol that adds a framework of interoperability for professional A/V devices: While AVB addresses issues at the network infrastructure level, such as synchronization and quality of service, Milan is application focused, addressing the unique requirements of media networking including reliability, stability, scalability, and audio quality.
Milan is developed by professional audio members in the Avnu Alliance with a common goal of making sure that AVB / Milan products of different vendors work together.

Luminex is an Avnu Alliance promotor and actively participating in the various Avnu working groups, along with other Avnu companies such as L'Acoustics, d&b audiotechnik, Meyer Sound, Adamson and many others.

AVB / Milan Controllers

There are many AVB controllers available which use ATDECC to manage the end devices. Network switches cannot be managed by these controllers.
A few noteworthy controllers:
  1. Milan Manager
  2. Hive
  3. Meyer Sound Nebra

AVID

GigaCore's can be used in an Avid S6L system. More information on this application is available in this article.

Araneo

Araneo has various tools to monitor and manage your AVB network:
  1. Ports which have AVB enabled are indicated with the Avnu icon when the AVB overlay is active. Ports that have a red border are 'not asCapable' / not AVB-capable ('as' from IEEE802.1as, meaning gPTP). This indicates that the device does not support AVB or that something else is wrong.
  2. the gPTP grandmaster clock ID and gPTP port states are visible when enabling the gPTP overlay. Hovering over the gPTP port state will give the delay to the neighbor of this port. Based on this delay, Araneo can estimate the cable length when using RJ45 copper ports.
  3. When selecting a GigaCore, using the AVB tab on the bottom will list all streams active on the GigaCore, either shown per port or per stream. Hovering over a stream will highlight the path of the AVB stream in the network.
  4. The reserved bandwidth for each port is visualized in the same AVB tab:
    1. Green through orange to indicate the bandwidth used for AVB streams
    2. The purple section highlights the reservation of the selected stream
    3. The shaded section indicates the 25% bandwidth that is always available for non-AVB streaming data
    4. The blue part indicates non-AVB traffic


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