Perle Systems PERLE P850 - Manual (Page 76)

70
A
PPENDIX
B
O
CTET
L
OCATIONS ON
E
THERNET
F
RAMES
This appendix provides octet locations for the various portions of
three of the common Ethernet frames. When creating pattern filters
these diagrams will assist in the correct definition of the patterns. The
offset numbers are indicated by the numbers above the frame
representations.
Note the differences in the TCP/IP and Novell frames when bridging
and when routing. When routing, the TCP/IP and Novell frames are
examined after the Level 2 Ethernet portion of the frame has been
stripped from the whole data frame. This means that the offset
numbers now start from 0 at the beginning of the routed frame and
not the bridged frame.
Some of the common Ethernet type codes are also shown here. The
Ethernet type codes are located at offset 12 of the bridged Ethernet
frame.