Ethernet Frames

Ethernet Frames

1. Ethernet_II

   • Preamble 7 bytes
     • Alternating 1,0 pattern
       • Provides a 5MHz clock at the start of each packet
   • SFD 1 byte
     • 10101011, where the last pair of 1s allows the receiver come into the pattern in the middle
       • Syncs up receiver to detect the start of the data.
   • Destination MAC 6 bytes
     • Transmits a 48-bit value using the LSB first.
     • Can be an individual address or a broadcast or multicast address
   • Source MAC 6 Bytes
     • Is a 48-bit MAC address
     • Broadcast and Multicast formats are illegal
   • Type 2 Bytes
     • Identifies the Network layer protocol
       • Most likely IPv4 or IPV6
   • Data and Pad 46-1500 Bytes
     • Sent down from the network layer
   • FCS 4 Bytes
     • Stores the CRC answer