• Bus: A logically bus-like topology

  • The fault lies at the top, in this case the transport layer, or transport layer

Ethernet provides connectionless and unreliable services

  • No connection: there is no handshake between the sender and receiver.
  • Unreliable: The data frames of the sender are not numbered, and the receiver does not need to confirm to the sender. If an error occurs, the receiver will directly discard the frame. The upper-layer transmission layer is responsible for error correction
  • Reliable transmission means that the sender sends the data frame, the receiver must receive; Reliable transmission requires the resolution of data frame errors, loss, dissequence, and duplication

Development of Ethernet transmission media and physical structure

  • Hub: Mindless data forwarding

Ethernet MAC Frames

  • In order to synchronize data between the sender and receiver, a leading code needs to be added from the MAC layer to the physical layer
  • Destination address: 1, unicast address, a single address. 2, broadcast address, all F, send information to all hosts; 3. Multicast address
  • Type: protocol specified at the network layer
  • Data: 46 (min frame length,) -1500 (MTU fixed)
  • FCS: Frame check sequence of data frames, CRC
  • Question: Why is there a leading code at the beginning but no ending code at the end? Because of the Manchester code, there are two symbols per bit, the change of data can be felt clearly when sending data, but the voltage does not change when not sending data