metrotek Bercut-ET, Operation Manual

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A. Ethernet frame structure
Figure A.1. Ethernet frame structure
•
Destination MAC Address — 6 bytes field that contains MAC ad-
dress of the destination network node.
•
Source MAC Address — 6 bytes field that contains MAC address of
the frame source network node.
• Length/Type — the field contains 16-bits integer and possesses either
of the following values:
– if the contained number is less than or equal to 1500, the value is
set to
Length and defines the length of the data field;
– if contained number is more than or equal to 1536, the value is set
to
Type value and specifies type of the protocol used.
•
Data — data field can contain from 46 or 42 (in the case of a frame
with VLAN-tag) to 1500 bytes.
•
Pad — Padding. If the data field is less than 46 bytes, the containing
frame is complemented to the minimum allowed length (64 bytes) with
the padding field.
• Frame Check Sequence — the 4-bytes field contains the checksum.
Bercut-ET. Operations manual