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I read Network Maintenance and Troubleshooting Guide book and in paragraph where Ethernet frame preamble is explained, it says that except for 100BASE-T4, faster versions of Ethernet are synchronous. Is it possible to keep both data and synchronization signal on the same signal path?

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The preamble is simply a series of 1s and 0s that signal the start of a packet. At the end of the preamble is a sfd (start frame delimiter) that signals the actual start of the Ethernet frame. The very next byte is the beginning of the destination MAC address. So yes the synchronization bits (preamble) are on the same signal path.

  • As far as I know, Fast Ethernet and Gigabit Ethernet do not use preamble. – Martin Aug 12 '15 at 18:33
  • I realize that Wikipedia isn't the definitive answer on all matters but the Ethernet_Frame page states that the GigE preamble is"0x55 0x55 0x55 0x55 0x55 0x55 0x55 0xD5". – stephen muth Aug 13 '15 at 15:54
  • For 10Mbps versions of Ethernet, which are asynchronous, each receiving station uses the eight octets of timing information to synchronize its receive circuit to the incoming data, but discards it. 100Mbps and higher speed implementations of Ethernet are synchronous, so the timing information is not actually required at all. It is there for compatibility reasons. – Martin Aug 13 '15 at 20:05

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