I'm learning about Ethernet and the sources I've found seem to be controversial regarding the role of the physical sublayers of Ethernet displayed on the following image. enter image description here

Just to mention an example for that: the en.wikipedia.org/wiki/Physical_Medium_Dependent Wikipedia page says the transmitters/receivers are located in the PMD layer while the Cisco Technology Handbook states they're located in the PMA.

My questions are the following:

  1. What are the roles exactly of the reconciliation, PLS, PCS, MII, PMA and PMD sublayers?
  2. Does the reconciliation sublayer handle errors, also is one of its responsibilities to hide the different MII interfaces from the MAC layer?
  3. Where is line encoding like NRZ/NRZI performed?
  4. Where is scrambling/descrambling done?
  5. Where is signaling like MLT performed?
  6. Where is auto negotiation performed? Some sources say it's done in the PCS, some displayed it separately below the PMD layer.
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Commented Jan 5, 2021 at 1:48

1 Answer 1

  1. read up on the standard: http://standards.ieee.org/about/get/802/802.3.html
  2. 10GE+ PHYs actually do forward error correction (FEC), FCS error frames are dropped in the MAC layer
  3. Basic line encoding (4b/5b, 8b/10b, 64b/66b group codes) is done in PCS, with PMD doing some additional, medium-specific coding (e.g. MLT-3)
  4. Scrambling/descrambling is part of PCS
  5. PMD
  6. Auto-negotiation somewhat bypasses the sublayers since it's using its own encoding.
  • 1
    Actually, Fast Ethernet uses NRZI (MLT-3 is also called NRZI-3).
    – Ron Maupin
    Commented May 28, 2017 at 22:30
  • @Ron: you're right, sorry
    – Zac67
    Commented May 29, 2017 at 8:16

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