Endace Measurement Systems.
http://www.endace.com
EDM01.05-10r1 DAG 4.3S Card User Manual
24
Revision 6. 22 September 2005.
5.1 Starting Capture Session
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Procedure
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Process Description
Setting capture session
parameters.
Parameters are set with
dagfour
.
The card can operate in two modes, variable
length capture
(varlen),
and fixed length
capture
(novarlen)
.
In variable length capture mode, a maximum
capture size is set with
slen=N
bytes. This
figure should be in the range 32 to 2048 and is
rounded down to the nearest multiple of 4.
Packets longer than slen are truncated. Packets
shorter than slen will produce shorter records,
saving bandwidth and storage space. Full packet
capture for example:
dagfour –d dag0 varlen slen=1536
Setting fixed length
mode.
In fixed length mode, packets longer than the
selected slen are truncated to slen.
Packets shorter than slen produce records
padded out to slen length.
Large slen values in fixed length mode should
be used because short packets arriving produce
large padded records, wasting bandwidth and
storage space.
An example, for fixed length 64-byte records,
choose
slen=48
(64 – ERF header size of 16):
is:
dagfour –d dag0 novarlen slen=48
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