Chapter 11: Packet Trimming; How To Trim Packets - Network Instruments Matrix User Manual

Chapter 11: Packet Trimming

How to trim packets

Any time egress packet sizes must be controlled—not the volume or type—packet trimming is the solution. Use
packet trimming to set the maximum number of bytes per packet to forward to analysis tools.
Prerequisite(s):
These steps require that at least one rule exists in your rules library. You can create a new rule if necessary.
Some benefits of packet trimming with the Matrix include:
Lowering link utilization between tool ports and tools
Removing sensitive payload from further analysis
Extending the effective storage space of a protocol analyzer
To enable packet trimming in a rule:
1. Starting in the dashboard, click Rules.
The rules and filters designer appears, where rules and filters can be created and edited.
2. Ensure the Rules tab is selected.
3. Click a rule from the list.
The rule opens and is ready to edit.
4. Select Packet Trim.
If selected, packets larger than the Trim Length value are truncated to a specified size. Packets smaller than
the Trim Length value are unchanged.
Note:
Packet trimming is especially useful for increasing monitoring tool performance and removing sensitive
information from analysis.
5. In the Trim Length list, click a trim length.
Only the first N-bytes of each ingress packet are forwarded to tool ports. A new 4-byte CRC value is affixed to
each trimmed packet. Valid values are: 64, 128, 192, 256, 384, and 512.
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