AVB / Milan

showstack / protocols / avb-milan

Also called AVB, Audio Video Bridging, Milan, TSN for pro audio.

IEEE 802.1 Audio Video Bridging with the Avnu Milan profile on top: Layer 2 ethernet media streams with bandwidth reserved hop by hop and clocked by gPTP. It is used where the network has to behave like a fixed wiring loom, mostly in touring PA rigs built around Avid, Meyer, d&b and L-Acoustics gear.

Audio transportOpen, free sign-upAvnu AllianceReported

Stewarded by Avnu Alliance (Milan profile) on top of IEEE 802.1 and IEEE 1722.

Media Large, continuous, on time and in order

Continuous streams that are large enough to be sized properly, and that must arrive in order and on time.

What kills it. Anything that starves the link — usually a management transfer nobody scheduled — and jitter that outruns the receive buffer.

The four flows, and why the model is worth having →

Multicast

Streams are addressed with Layer 2 multicast MAC addresses allocated by MAAP, not with IP multicast groups. There is no IGMP involved and nothing for an IP-only network tool to show you.

What it carries

Sample rates: 48 kHz
Audio bit depth: 24-bit
Audio encoding: AVTP Audio Format, linear PCM

Audio: Milan fixes 48 kHz and 24-bit as the interoperability baseline, which is the point of Milan — AVB itself is more permissive and correspondingly less predictable between vendors.

What goes wrong

Every switch in the path has to be AVB capable. One ordinary switch, one media converter or one unmanaged patch in the middle and the bandwidth reservation never completes, so the stream simply never establishes.

AVB is Layer 2. It does not route. You cannot carry it across a subnet boundary, a VPN or a WAN link, which rules it out for anything spread across a campus without dedicated fibre.

gPTP (IEEE 802.1AS) is its own PTP profile running over Layer 2. It will not share a grandmaster with the IP-based IEEE 1588 clocks used by AES67, Dante and ST 2110 without a device that deliberately bridges the two.

"AVB capable" and "Milan certified" are different claims. Milan is a profile over IEEE 1722 and 1722.1 that pins down stream formats, media clocking and redundancy, and generic AVB gear may not meet it.

The Milan document is free after registration, but the IEEE standards it normatively references (802.1AS, 802.1Q, 802.1BA, 1722, 1722.1) are paid. A full implementation is not a zero-cost read.

Connection state lives in the endpoints, managed over AVDECC. Power-cycling a switch is usually survivable, but a device swapped for a spare comes back with no streams until it is reconnected in the controller.

What speaks AVB / Milan (7)

Product	Direction	Notes
L-Acoustics LA12X L-Acoustics	in	AVB network audio input; L-Acoustics is a founding Milan proponent.
L-Acoustics LA7.16i L-Acoustics	bidirectional	Networked audio.
L-Acoustics P1 L-Acoustics	bidirectional	Networked audio.
Luminex GigaCore 10 Luminex Network Intelligence	bidirectional	AVB support depending on model and firmware.
Luminex GigaCore 16Xt Luminex Network Intelligence	bidirectional	The manual states full AVB and AVB Milan support.
Meyer Sound Galileo GALAXY 816 Meyer Sound	bidirectional	AVB network audio streams alongside analog and AES3 I/O; Milan-certified firmware exists for GALAXY.
NETGEAR M4250 (AV Line) NETGEAR	bidirectional	AVB licence available on M4250, making it one of the few mainstream switches that can carry Milan.

Open source implementations

OpenAvnu — C
L-Acoustics AVDECC (IEEE 1722.1) — C++, LGPL-3.0-or-later

Typical use

Console to amplifier and loudspeaker networks in touring PA
Redundant audio paths where a single cable failure must not be audible
Deterministic low-latency links between stage and front of house
Discovery, connection management and control via AVDECC (IEEE 1722.1)

Sources

Milan Specification — Avnu Alliance primary
Avnu Alliance Specifications — Avnu Alliance primary
OpenAvnu — gPTP, MAAP, mrpd and AVTP pipeline components — Avnu Alliance primary
Industry Leaders Join to Launch Milan Network Protocol Based on AVB for Pro AV Interoperability — Avnu Alliance via PR Newswire

Understand the mechanism

Show networks Numbers that stand for signals

Something wrong, or missing?

Known gaps on this entry: default_ports. If you can source one of them, that is a ten minute pull request.

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Work at Avnu Alliance (Milan profile) on top of IEEE 802.1 and IEEE 1722? Confirm or correct this entry — it is free, it stays free, and nothing about it is for sale.