Ethernet frame format
While tracing LAN communications, you might need to look at the transmitted frames. To understand the data that is contained in the frame, you must know how it is formatted.
The following figures show the frame format of two Ethernet standards: IEEE 802.3 and Ethernet version 2.
The Frame Check Sequence (FCS) is a part of the frame put in place to verify that the information each frame contains is not damaged during transmission. If a frame is corrupted during transmission, the FCS on the frame will not match with the recipient's calculated FCS. Any frames that do not match the calculated FCS will be discarded.
IEEE 802.3 frame format
| Starting Delimiter (1 byte) | Destination Address (6 bytes) | Source Address (6 bytes) | Length (2 bytes) | LLC header and Information field (46 - 1500 bytes) | Frame Check Sequence (4 bytes) |
Ethernet version 2 frame format
| Starting Delimiter (1 byte) | Destination Address (6 bytes) | Source Address (6 bytes) | Type (2 bytes) | Information field (46 - 1500 bytes) | Frame Check Sequence (4 bytes) |
Note: The IBM i operating system does not
have integrated support for SNA over Gigabit Ethernet or 10 Gbps Ethernet. Enterprise Extender is
required to run SNA over 1 Gpbs or 10 Gbps Ethernet.