Network configurations
This section covers possible network redundancy schemes and describes behavior specific to Meyer Sound Milan endpoint and CAL loudspeakers.
Network redundancy options
GALAXY processors support two kinds of network redundancy: Milan and cable. Milan redundancy, an optional functionality defined in the Milan standard, is a fully redundant network, as shown in the first figure below. cable redundancy, shown in the second figure below, is an additional capability of Meyer Sound GALAXY processors. This configuration is not required or defined by the Milan specification but provides added flexibility to users.
Fully redundant network—Milan redundancy
Cable redundant network — Meyer Sound additional option
Meyer Sound recommends using a Milan redundant topology wherever possible. AVB networks can be configured in a variety of ways; more robust configurations come at the expense of additional hardware; specifically network switches. Recognizing that specific applications may have restrictions in terms of cost or special requirements, alternative topologies are shown in the following pages. It is the responsibility of the system designer to balance the specific requirements against the available resources for any particular application.
Note
When connecting third-party devices that might flood the network with multicast streams or non-AAF/ CRF packets to a GALAXY, the connection should be made to port 2, or a switch connected to the secondary network. Connecting these devices to the primary network or GALAXY port 1 could cause unstable network behavior in extreme cases involving many devices (100+) or large amounts of multicast traffic. This practice should be followed when connecting RMServers to the same network to which GALAXY processors are connected.
Analog signals can also be used as a backup; with this approach, there will be no automatic failover in the event of a network failure.
Caution
In network setups where multiple paths can exist, a failure that triggers a Rapid Spanning Tree Protocol (RSTP) failover can result in a different path length, which would result in the system recalculating latency. Thus, Meyer Sound recommends using a fully redundant (Milan redundancy) network. For the other options shown below, RSTP should be disabled on network devices to ensure the network topologies perform as described. If RSTP is not disabled on network switches in networks that are not fully redundant, redundancy and overall network operation may not behave as expected. See the “Galileo GALAXY AVB Extreme Switch Configuration User Guide” (PN 05.230.105.01) available at meyersound.com/documents for instructions on configuring Extreme switches with RSTP disabled.
For cable redundancy to work, you must make both connections from each Meyer Sound talker and each Meyer Sound listener.
Milan redundancy
The most robust network configuration is a fully redundant network, referred to as Milan redundancy (this optional functionality is defined in the Milan standard). This topology uses two independent networks; each network consists of discrete cabling, network switches, and time domains. Both networks distribute audio signals simultaneously. In the event of a network failure, there is no pause or drop in audio, as audio is already being transmitted across the secondary network.
A control computer running Compass control software can be connected to either network. If control redundancy is desired, a second computer can be connected to the other network, or a second network interface card in the same computer can be connected to the secondary network.
All primary network connections should be made to AVB port 1 on GALAXY processors. All secondary connections should be made to AVB port 2. The figure below shows one possible configuration that demonstrates Milan redundancy.
Milan redundancy configuration
Note
Loudspeakers with Milan endpoint input modules are not shown for clarity. When used, they are connected to the network switches. Loudspeaker endpoints capable of redundancy can connect to both networks. Non-redundant endpoint loudspeakers are connected to the primary network.
Primary network only — cable redundancy
The primary network only — cable redundancy configuration, is a Meyer Sound feature that is not part of the Milan standard.
This topology uses a single network with redundancy in the cabling paths between the network switches and the Galileo GALAXY AVB Talker and AVB Listener. A control computer running Compass control software is connected to the network. Each AVB port of a GALAXY is connected to the same network switch. Both GALAXY port 1 and port 2 receive the same source data. In the event of an input data failure on port 1, the GALAXY processor automatically switches to port 2 to maintain the signal flow from the source to the endpoints.
All primary network connections should be made to AVB port 1 on GALAXY processors. Redundant connections should be made to AVB port 2. The figure below shows a configuration that demonstrates cable redundancy.
While not as robust as operating dual independent networks, this configuration offers an additional layer of protection beyond simply running one cable from each AVB device.
Primary network only — cable redundancy configuration
Caution
Cable redundancy is only supported by Meyer Sound devices at this time. For cable redundancy to work, you must make both connections from each Meyer Sound talker and each Meyer Sound listener.
Primary network-only — no redundancy
The primary network only — no redundancy configuration is the simplest and least robust configuration available. Each GALAXY connects to a network switch via AVB port 1. The AVB port 2 is not used. A loss of any single cable, network switch, or AVB entity will result in at least a partial loss of audio or control.
Primary network only configuration
Meyer Sound Milan endpoint loudspeaker network behavior
Meyer Sound endpoint loudspeakers with Type 3M input modules have only one Ethernet connection. This single connection brings with it the following restrictions:
Position of Meyer Sound Milan endpoint loudspeaker in the network
CAL network behavior
CAL network behavior is similar to GALAXY but with two significant differences:
CAL bridges gPTP between the two Ethernet connectors
CAL can receive Milan AVB audio and CRF, but will only forward CRF.
Caution
Do not loop (daisy-chain) the Milan signal from one Ethernet connector to another — this applies to both the CAL loudspeaker and the GALAXY processor.
Because CAL bridges gPTP across its two Ethernet connectors, it is not fully compliant with Milan redundancy, which is why it is not Milan-certified. When a CAL is connected to both the primary and secondary networks, gPTP information will no longer be redundant.
Synchronization of an AVB network is dependent on a stable master clock. If the master clock device changes, it can temporarily degrade the quality of the audio on the network.
The primary and secondary networks use independent time domains. When a CAL is connected to both networks, it bridges them and creates a network with a single gPTP time domain. Instead of having a master clock for each network, one device will serve as the gPTP master clock for both. The master clock device is chosen based on the Best Master Clock (BMC) algorithm. This algorithm first considers which device has the lowest “Priority 1” value, a parameter that is fixed and inherent for a Milan AVB device. If there is a tie, the device with the lowest MAC address will be selected as the master.
CAL network redundancy behaves similarly to GALAXY—a failure of a component of the primary network will result in a seamless transition to the secondary network without any pause or break in audio. However, unlike GALAXY, the clock will become unlocked for a short period (generally several seconds) before automatically locking again. During this period audio will continue to pass, but there may be phase drift until the clock re-locks.
CAL and GALAXY
CAL redundancy
The figure below shows an example system consisting of a console source, a single GALAXY, and a single CAL. The connections shown here between CAL, GALAXY, and network switches can be expanded to accommodate additional devices. CAL bridges the gPTP information between the two networks.
CAL redundancy configuration
CAL cable redundancy
In the configuration shown in the figure below, the network behaves identically to the GALAXY-only example described in Primary network only — cable redundancy. It is not as robust as using separate switches but offers additional reliability compared to using a single network cable between AVB devices and switches. This configuration is a Meyer Sound extension to redundancy and not part of the Milan redundancy specification.
Caution
Cable redundancy is only supported by Meyer Sound devices at this time. For cable redundancy to work, you must have both connections made from each Meyer Sound talker and each Meyer Sound listener.
CAL cable redundancy configuration
CAL primary only — no redundancy
The CAL primary-only configuration, as shown in the figure below, is the simplest and least robust, with only a primary network and a single network cable that connects each AVB device to a switch.
CAL primary-only configuration