Spirent SmartBits System, Reference Manual

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Glossary of Terms
Features and Terminology
SmartBits System Reference 263
Possible uses of VFDs 1&2:
•
Specific MAC addresses (unicast, multi-cast or broadcast).
•
Multiple MAC addresses.
•
Sequencing IP headers with correct header checksums.
•
Set VFD1 offset to sequence location, use incrementing VFD.
•
Set VFD2 offset to checksum location, use decrementing VFD.
VFD3 (Protocol VFD)
Unlike VFDs 1 and 2, that support up to 6 bytes of static, increment, decrement or random
data, VFD3 supports a buffer of up to 2048 bytes that is segmented into pieces. Each of the
pieces is then placed into outgoing frames, one piece per frame. This expanded capability
makes it useful for defining the upper layer protocol fields for a frame.
The following picture is the main setup for VFD3.
In this case, a Custom Hex state for the VFD has been selected at an offset of 96 bits into
the frame. Similar to VFD2, VFD3 supports an option to place the VFD adjacent to
VFD2.
In this example, the number of packets (or more easily understood as the number of
patterns ) has been chosen as 10 and the length of the pattern as 4 bytes. This produces 10
patterns of 4 bytes in length each. The product of these two numbers cannot exceed the
2048 byte VFD3 buffer length.
Once the number of packets and the VFD length are chosen, the data contents of the VFD
can be modified by pressing the Edit button. A dialog showing the edit buffer is then
presented: