Appendix
A
GigE Network Configuration
A-30
Getting Started with Visionscape GigE Cameras
cameras give 128MB per second which is more than the 1000Base/T
link can handle).
The Correct Procedure
The first thing to do is to make sure that the NIC is configured correctly.
Hopefully this is an Intel Pro/1000 NIC card. If so, go to the network
adapter properties and click on the
Configure
button next to the network
card description:
Next, click on the Advanced tab and you should see a list of parameters
that can be tuned by the user.
Look for
Jumbo Frames
(sometimes called
Jumbo Packets
) and
Receive Descriptors
(sometimes called
Receive Buffers
). On some
drivers these may be buried inside
Performance Options
.
Jumbo Frames: Make sure this is set to the maximum available – typically
8192 bytes but only 5k on some NICs.
Receive Descriptors: Set this to the maximum – typically 2048.
Save the changes.
You have just enabled the NIC to handle larger packets. This means that,
instead of sending image data from the camera in chunks of 1500 bytes
they can now come in chunks of 8192. That means about six times fewer
packets for each image.
Increasing the number of receive descriptors enables the NIC to handle
more packets at any one time. If the processor is busy when an image
arrives, the NIC may not be able to send on the data immediately, but
data is still coming in from the camera. These receive descriptor buffer
the system against this. (It is almost essential when using a CMG50
camera).