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What is the physical difference between 10Mpbs, 100Mbps and 1000Mbps (BASE-T) INITIALIZATION.

10Mbps and 100Mbps does not use all of the 8C8P(RJ45) pins. Does 1000Mbps utilize the full 8 pins for setting up the link, or does it use the same as 10/100Mbps?

EDIT

After some good input from reviewers I would like to clarify; When I plug in the cable to the RJ45-connector. What will happen at the very beginning and are those actions standardized? Signals on specific pins etc.

Why I am asking if because I see strange behavior when I connect different end-devices to a switch. There is a HW-issue 100%. But it makes me wonder if my end devices uses different technique to setup the link.

E.g. One end device uses PIN 1 & 2 for first pulse. The other devices uses pin 3 and 4.

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  • I think you are confusing some thing. layer 1 & 2 considerations like wiring, link speed, and duplex mode occur at a much lower level on the network stack than TCP does (Layer 4) so the "physical characteristics" of a TCP handshake are indistinguishable from any other activity when observed at layers 1 & 2.
    – Frank Thomas
    Commented Jan 11 at 14:08
  • Yes, good point! But if I use a CAT-cable with only 2 pairs it will make the handshake on those and establish a connection. Why I am asking is because I would like to know if there is a standard that says: "Always use the pin X & Y before using all other pins." Like a INITIALZE-state on the PHY.
    – Aard
    Commented Jan 11 at 14:33

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According to Wikipedia Ethernet over twisted pair, the answer is positive:

1000BASE-T uses all four pairs bi-directionally using hybrid circuits and cancellers. Data is encoded using 4D-PAM5; four dimensions using pulse-amplitude modulation (PAM) with five voltages, −2 V, −1 V, 0 V, +1 V, and +2 V. While +2 V to −2 V may appear at the pins of the line driver, the voltage on the cable is nominally +1 V, +0.5 V, 0 V, −0.5 V and −1 V.[18]

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  • So if I attach an oscilloscope I will see parallell communication on all pairs when the PHY has left RESET-state? Setting up MDI-MDI or MDI-MDIX; are those specified on specific pins?
    – Aard
    Commented Jan 11 at 14:35
  • There is no concept of MDIX on 1000BASE-T; however there is a master/slave negotiation. This takes place on all pins simultaneously, so the answer is still the same.
    – Paul
    Commented Jan 11 at 15:29
  • @Aard: See IEEE 802.3 section 3, p228 and p269. Although if I understand it correctly, MDI/MDI-X only matters during the auto-negotiation stage (which is the only part that's still done "the old way"), as afterwards the link switches to all four pairs bidirectional.
    – grawity_u1686
    Commented Jan 11 at 17:06
  • @u1686_grawity this is exactly what I was looking for.
    – Aard
    Commented Jan 12 at 21:18

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