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L
OCAL
-L
INK
(F
AILSAFE
)
If Spark’s default IP Address setting (Dynamic) should ever fail to provide a usable IP address within a minute
or two – as when an active DHCP server is not found on the network – you can locate your Spark Pro on the
network using its failsafe Local-Link (APIPA) feature.
In this scenario, temporarily set the network adapter of your computer to a static IP address in the APIPA
address block (such as 169.254.0.254, with a netmask of 255.255.0.0) and connect the Spark Pro.
Then run Studio Monitor on the computer, as described earlier to locate the unit. This will allow you to use
Spark Pro‘s web page to set a suitable static IP of your choosing, after which you can restore the computer’s
normal network configuration settings.
M
ULTICAST
Click Multicast to transmit video using multicast, rather than the default unicast method. Please take time
to consider the following information before enabling multicast.
M
ULTICAST OR
U
NICAST
?
Multicast can seem like a bandwidth-saving miracle. Unlike NDI’s default mode (unicast), multicast does not
require a unique stream from the source to each receiver. When using unicast, each connection to the sender
reduces the bandwidth available by a similar amount.
By contrast, multicast connections do not add significantly to the bandwidth required as connections
multiply. You might wonder why anyone would ever turn this option off – yet, it is off by default. Why?
This is because multicast requires more careful network
configuration. While you might not notice any issues in a
simple network setting; a poorly configured multicast
environment can have serious impact on more complex
networks.
Specifically, it is essential that IGMP snooping be
enabled for each switch on the network. This lets the
device listen to traffic between other hosts, switches
and routers, and identify receiving ports using
various IP multicast streams.
We strongly recommend that all network switches
be of the ‘managed’ type (see the sidebar above), and
that you obtain assistance from IT professionals if
you have multiple switches online.
2.6
TALLY
Your Spark Pro unit provides ‘tally’ notification from NDI
devices supporting it. Specifically, two large LEDs, on red
and the other green, will light up to tell you when video
Managed vs. Unmanaged
An un-managed (a.k.a., ‘dumb’) network
switch will broadcast a multicast stream
to all devices on the network, with
potentially very serious ramifications.
For example, even though a device
broadcasts a multicast stream, the un-
managed switch will pass unicast
packets to downstream switches and
clients. This can flood the network with
unnecessary traffic, and slow it down as
upstream devices are forced to wait for
responses from the over-saturated
devices.
The result of a poor setup can fairly
be likened to a self-inflicted Denial of
Service attack, and will definitely not
endear you to your colleagues.