Capturing packets with the GigaStor
Chapter 6: Packet Captures 217
♦
Previously indexed data has no effect on any other 15 second interval,
except for the need to see the SYN-SYN/ACK-ACK to begin collecting
“new” server data. This means that if in one 15 second period the
maximum number of entries was reached and a new conversation is
started that continues into the next 15 second interval, there is nothing
that prevents the subsequent 15 second interval from beginning to index
the new conversation that was not indexed in the previous 15 second
interval.
♦
When GigaStor Control Panel > Settings > Enable Intelligent TCP protocol
determination is enabled, a SYN-SYN/ACK-ACK is required. After the
GigaStor sees a SYN-SYN/ACK-ACK for a server, it no longer needs to see
the SYN-SYN/ACK-ACK to collect data from that server on the port that
it saw the SYN-SYN/ACK-ACK. If for any reason the GigaStor probe is not
running, it needs to see the SYN-SYN/ACK-ACK to index data. If GigaStor
Control Panel > Settings > Enable Intelligent TCP protocol determination
is unchecked, the GigaStor does not need to see the SYN-SYN/ACK-ACK to
ever index data.
For more details about indexing in the GigaStor continue reading the rest of this
section.
Every 15 seconds the GigaStor writes indexed, statistical data into a
GigaStor.ometa file on the D: drive. It contains only statistical (indexed)
information “collected” by the GigaStor. This file and the statistics it contains
have no relationship to what packets are written to disk. When the capture card
sees any packet, it is immediately timestamped and passed to the GigaStor
buffer. The GigaStor writes all packet data to disk regardless of whether a packet
is indexed.
Also on the D:\ drive are a number of .odat files. These files contain the actual
packets that are written to disk and used for analyzing.
The GigaStor does not index every single packet. There are a number of factors
that result in a packet not being indexed. Anything you see in the GigaStor
Control Panel should be used for reference, not as absolute numbers. For absolute
numbers, you must analyze the packets and view them in the Decode pane.
At the beginning of each 15 second period (the 15 seconds is not based on
the system time clock period, but on timestamps from the captured packets)
the GigaStor takes all of the indexed data that it has and writes it into the
GigaStor.ometa file. The GigaStor then clears out the statistical memory that was
used for indexing during the 15 second collection period and begins analyzing
the next 15 seconds for statistical data. After a packet has been analyzed, it is
written to disk. If for some reason a packet is skipped, it is written to disk before
the next packet is analyzed.
Again, not every packet is indexed. This does not mean that if a packet is not
indexed, that it is not written to disk. The GigaStor writes every packet to disk,
even if it is not indexed. If there are 1,000,000 packets that come in during a 15
second period, and the GigaStor only analyzes 85,000, it will still writes 1,000,000
packets to the hard drive.
If the Screen Resolution in the GigaStor Control Panel is set to less than 15
seconds, the GigaStor does not use the index file (GigaStor.ometa) to see what
was indexed because the time frame is smaller than 15 seconds. Instead it reads
the data that is written to disk in the .odat file to produce the reports and not
the indexed data.
Summary of Contents for Apex Enterprise G3-APEX-ENT-32T
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