ADDER A.I.M. User Manual page 48

spanning Tree Protocol (sTP)
In order to build a robust network, it is necessary
to include certain levels of redundancy within the
interconnections between switches. This will help to
ensure that a failure of one link does not lead to a
complete failure of the whole network.
The danger of multiple links is that data packets, especially
multicast packets, become involved in continual loops as
neighbouring switches use the duplicated links to send and
resend them to each other.
To prevent such bridging loops from occurring, the
Spanning Tree Protocol (STP), operating at
used within each switch. STP encourages all switches
to communicate and learn about each other. It prevents
bridging loops by blocking newly discovered links until it
can discover the nature of the link: is it a new host or a
new switch?
The problem with this is that the discovery process can
take up to 50 seconds before the block is lifted, causing
problematic timeouts.
The answer to this issue is to enable the portfast variable
for all host links on a switch. This will cause any new
connection to go immediately into forwarding mode.
However, take particular care not to enable portfast on
any switch to switch connections as this will result in
bridging loops.
AlIF transmitter video settings
Each ALIF transmitter includes controls to help you
customize how video data is transmitted. When configured
correctly for the application, these can help to increase
data efficiency.
background Refresh
The transmitter sends portions of the video image
only when they change. In order to give the best user
experience, the transmitter also sends the whole video
image, at a lower frame rate, in the background. The
Background Refresh parameter controls the rate at
which this background image is sent. The default value is
layer 2, is
'every 32 frames', meaning that a full frame is sent in the
background every 32 frames. Reducing this to 'every 64
frames' or more will reduce the amount of bandwidth
that the transmitter consumes. On a high-traffic network
this parameter should be reduced in this way to improve
overall system performance.
colour Depth
This parameter determines the number of bits required to
define the color of every pixel. The maximum (and default)
value is '24 bit'. By reducing the value you can significantly
reduce bandwidth consumption, at the cost of video color
reproduction.
Peak bandwidth limiter
The transmitter will employ a 'best effort' strategy
in sending video and other data over the IP network.
This means it will use as much of the available network
bandwidth as necessary to achieve optimal data quality,
although typically the transmitter will use considerably less
than the maximum available.
In order to prevent the transmitter from 'hogging' too
much of the network capacity, you can reduce this setting
to place a tighter limit on the maximum bandwidth
permissible to the transmitter.
Frame skipping
Frame Skipping involves 'missing out' video frames
between those captured by the transmitter. For video
sources that update only infrequently or for those that
update very frequently but where high fidelity is not
required, frame skipping is a good strategy for reducing the
overall bandwidth consumed by the system.
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