EtherType

EtherType is a field in the Ethernet networking standard (Ethernet II framing, specifically). It is used to indicate which protocol is being transported in an Ethernet frame.

It is claimed that some older (Xerox?) Ethernet specification had a 16-bit length field, although the maximum length of a packet was 1500 bytes. Versions 1.0 and 2.0 of the Digital/Intel/Xerox (DIX) Ethernet specification, however, have a 16-bit sub-protocol label field called the EtherType, with the convention that values between 0 and 1500 indicated the use of the original Ethernet format with a length field, while values of 1536 decimal (0600 hexadecimal) and greater indicated the use of the new frame format with an EtherType sub-protocol identifier.

With the advent of the IEEE 802 suite of standards, the SNAP header, with the IEEE 802.2 LLC header, is used to transmit the EtherType of the packet for IEEE 802 networks other than Ethernet, as well as for non-IEEE networks that use the IEEE 802.2 LLC header, such as FDDI. However, for Ethernet, the Ethernet Version 2 header is still used.

EtherType for some common protocols

External links

* [http://standards.ieee.org/regauth/ethertype IEEE EtherType Registration Authority]
* [http://standards.ieee.org/regauth/ethertype/eth.txt IEEE list of Ethertype values]
* [http://www.wildpackets.com/support/compendium/reference/ethertypes WildPackets list of Ethertype values]
* [http://www.cavebear.com/CaveBear/Ethernet/type.html Michael Patton's list of Ethertype values]