Threshold And Timeout Resend Mechanisms Combined - Basler ace acA640-90gm User Manual

Basler Network Drivers and Parameters
A.2.4 Threshold and Timeout Resend Mechanisms
Combined
Figure 94 illustrates the combined action of the threshold and the timeout resend mechanisms
where the following assumptions are made:
All parameters set to default.
The frame includes 3000 packets.
Packet 1002 is missing within the stream of packets and has not been recovered.
Packets 2999 and 3000 are missing at the end of the stream of packets (end of the frame).
The default values for the performance driver parameters will cause the threshold resend
mechanism to become operative before the timeout resend mechanism. This ensures maximum
efficiency and that resend requests will be sent for all missing packets.
With the default parameter values, the resend request threshold is located very close to the front
end of the receive window. Accordingly, there will be only a minimum delay between detecting a
missing packet and sending a resend request for it. In this case, a delay according to the Resend
Timeout parameter will not occur (see Figure 94). In addition, resend request batching will not
occur.
(1) (2)
995 996 997 998 999 1000 1001 1003
Fig. 94: Combination of Threshold Resend Mechanism and Timeout Resend Mechanism
(1) Stream of packets, Gray indicates that the status was checked as the packet entered the
receive window. White indicates that the status has not yet been checked.
(2) Receive window of the performance driver.
(3) Threshold for sending resend requests (resend request threshold). The first resend request
for packet 1002 is sent to the camera. The camera does not respond with a resend.
(4) Interval defined by the Resend Response Timeout parameter.
(5) The Resend Timeout interval expires and the second resend request for packet 1002 is sent
to the camera. The camera does not respond with a resend.
(6) Interval defined by the Resend Response Timeout parameter
(7) The Resend Timeout interval expires and the third resend request for packet 1002 is sent to
the camera. The camera does not respond with a resend.
266
(3) (5) (7)
1004 1005 1006 1007 1008 1009
(4) (6)
DIAGRAM IS NOT DRAWN TO SCALE
(9)
1010 1011 1012 1013 1014 1015 2996 2997 2998
(8)
(10) (11)
(12)
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