| This value is a byte offset from the beginning
of the packet. If this offset is such that any
portion of the filter extends past the end of the
packet (for wildcard filtering purposes, the FCS
is part of the packet), then the filter is
considered not to match, and the packet is not
filtered.
For a particular filter, the wildcardUserOffset
must be greater than or equal to the
wildcardOffset.
wildcardUserOffset must be between 0 and 1514,
inclusive.
The wildcardUserOffset, wildcardOffset pair must
conform to one of the following four relationships
and also be subject to the range restrictions
listed above. For n = 0,..,378
Offset 4n 4n 4n 4n+2
UserOffset 4n 4n+1 4n+2 4n+3
As an example, consider four examples in the
following table for locating the filter at or near
the beginning of a packet:
- 6 filter/mask bytes - - desired -
0 1 2 3 4 5 6 - position -
A|f/m0 f/m1 f/m2 f/m3 00 00 00 |0,4,8,12,...
B| 00 f/m0 f/m1 f/m2 f/m3 00 00 |1,5,9,13,...
C| 00 00 f/m0 f/m1 f/m2 f/m3 00 |2,6,10,14,...
D| 00 00 00 f/m0 f/m1 f/m2 f/m3|3,7,11,15,...
Example A corresponds to a UserOffset/Offset pair
such as 0/0 (4n/4n). Example B represents a pair
such as 0/1 (4n/4n+1). Example C is 0/2
(4n/4n+2). Finally, example D is 2/3 (4n+2/4n+3).
If any of the above constraints is not honored,
the SET Response will indicate genErr. |
