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date: “2016-12-01” draft: false title: “Ethernet”

Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination MAC addresses, and error-checking data so that damaged frames can be detected and discarded; most often, higher-layer protocols trigger retransmission of lost frames. As per the OSI model, Ethernet provides services up to and including the data link layer.1

Ethernet Headers

                          1   	 
byte  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4              
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-.   D   ....-+-+-+-+-+
	 |Destination|  Source   | E | ..   A   ... |  CRC  |
     |MAC Address|MAC Address| T | ...   T   .. | cksum |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-....   A   .-+-+-+-+-+

Ethernet Header Descriptions

Bytes Name Description
ether[0:4], ether[4:2] Dst MAC Address
ether[6:4], ether[8:2] Src MAC Address
ether[12:2] EtherType indicates which protocol is encapsulated in the payload of the frame

Additional resources

References