Traditional Ethernet frame header

The four Ethernet frames you mentioned are as follows:

Ethernet II is an Ethernet standard frame format formulated by Xerox, DEC and Intel in DIX 2.0: 1982.

Ethernet 802.3RAW: The standard frame format of private Ethernet published by Novell in 1983.

Ethernet 802.3 SAP: Ethernet frame format of Ethernet 802.3sap version published by IEEE in 1985.

Ethernet 802.3 SNAP: the Ethernet frame format of the Ethernet 802.3snap version published by IEEE in 1985.

The first generation of Ethernet II, because it is the earliest and simplest, the upper layer directly carries three layers of packets. Its MTU is 1500B, which is also the most commonly used frame format in data transmission.

The second Ethernet 802.3 raw has 2 bytes of control bits (actually it is useless as FFFFH), which is used in Novell network, and its MTU is1498b; .

In the third Ethernet 802.3 SAP frame, 0xFFFF of 2 bytes in the original Ethernet 802.3 original frame is changed to DSAP and SSAP of each 1 byte, and the "control" field of 1 byte is added to form the header of 802.2 logical link control (LLC). Therefore, it can carry LLC frames for local area networks that need LLC control, and its MTU is1497b; ;

The last one adds a 3-byte Organization Unique Identifier (OUI ID) field and a 2-byte Type field on the basis of the third one, which is mainly used when passing spanning tree and VLAN information between switches. The MTU is 1492B.

I hope it works for you.