Extron Electronics Dante Controller - Manual (Page 45)

Dante Controller User Guide
Copyright © 2013 Audinate Pty Ltd. All rights reserved. -45-
The window shows a list of the Tx channels for the device and allows the user to add them to the new
multicast flow that is being created, by checking the tick box next to each channel name. Once the user
has selected all the channels required, the multicast flow can be created by clicking on the Create button at
the bottom of the dialog box. To abandon creating a new multicast flow, click on the Cancel button.
A single multicast flow can contain up to the maximum supported channels per flow for this device. This is
displayed at the top of this window and is 8 channels for this device. If the user selects more than the
maximum allowed channels per flow, multiple flows will be created. Once a flow has been created, it will
appear in the list of flows in the transmit pane, along with the channels contained within that flow.
Channels cannot be added to or removed from existing flows. Each time the dialog is used to select
additional channels, a new multicast flow will be created.
By default, Dante devices "prefer" multicast over unicast. When a user clicks on a transmit channel to
make a subscription, the receiver will automatically connect to the channel via a multicast flow if one
exists. Likewise, when a channel that did not form part of an existing multicast flow is added to a new
multicast flow then any existing unicast subscription to that channel will automatically switch over to use
the new multicast flow.
Care should be taken when deleting a multicast flow, as the existing subscriptions will convert back to
unicast. This has the potential to result in exceeding the link capacity or maximum number of flows at the
transmit device as multiple unicast flows will be established between the transmitter and its receivers. It
may be advisable to remove some or all of the audio routes prior to deleting the multicast flow.
A good rule of thumb is to use multicast when there are more than two receivers for a specific audio
channel. You should also assume that the flow will flood throughout the entire network and therefore
consume bandwidth on all network links.
Note: Certain Ethernet switches support IGMP (Internet Group Management Protocol), a protocol
that provides the ability to “prune” multicast traffic so that it travels only to those end destinations that
require that traffic. If this is the case and IGMP is correctly configured on all the Ethernet switches
then multicast audio will not flood throughout the network but instead be sent only over the links
needs to deliver it to subscribed devices.