E T H E R N E T N E T W O R K S & S W I T C H E S
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WheatNet-IP
/ Apr 2009
adversely affect the real time performance of medium to large IP audio
networks.
• Rack Mounting - Rack mounting is a useful option for most broadcast
systems.
• Chassis Based - Large enterprise systems may benefit from installing or
expanding existing chassis based managed switch solutions.
Unmanaged vs. Managed Switches
An unmanaged Ethernet switch is a low cost WYSIWYG device and has no
configuration software interface. Most unmanaged switches do not support
IGMP snooping and will therefore act as repeaters to IP audio multicast packets,
effectively flooding all ports with audio packet traffic. Unmanaged switches are
relatively inexpensive, though, so in very small systems this may be a perfectly
acceptable cost vs. performance compromise.
Managed switches, on the other hand, allow users to configure the switch
hardware with a software interface of some kind, such as Telnet, Web, Terminal,
etc. Primary configuration features applicable to your Ethernet audio network are
the ability to configure VLAN’s, IGMP management, built in diagnostics, and
routing. We highly recommend the deployment of managed switches throughout
the network.
Managed switches fall in to several market niches. Low end managed
switches, or “Smart Switches,” offer some configuration, but may not provide the
level of configurability required in a medium to large Ethernet audio network. For
example, these switches may forward IGMP host messages and multicast traffic
but can not act as the IGMP router. In medium to large applications at least one
switch capable of being the IGMP Querier is required. Mid-priced managed
switches are better suited to the task and will provide more configuration
flexibility.
In larger systems it makes sense to employ a “core and edge” model. This type
of system balances the switching horsepower (cost) according to the throughput
requirements at different physical segments of the network. Lighter bandwidth
“edge” segments can use lower cost switches, while central rack room “core”
segments utilize higher performance devices.
Rules of Thumb
The WheatNet-IP system will work with a minimum number of devices on an
unmanaged switch. If the system is to include more than six BLADEs, two
Control Surfaces, and two PC drivers it is recommended that an IGMP compliant,
managed switch be used.
In large systems, careful attention must be paid to the placement of core and
edge switches.
• Each I/O (88a, 88d, 88ad) BLADE requires 36.9Mb/s for eight Stereo
connections.
• Each I/O (88a, 88d, 88ad) BLADE Requires 73.7Mb/s for 16 Mono
connections.