Talk:Gigabit Ethernet

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[edit] does anyone actually make gigabit hubs?

they are certainly allowed by the spec (there is a specific section on repeaters which talks about joinging 2 or more segments) but does anyone actually make them? Plugwash 12:05, 26 March 2007 (UTC)

Are you sure they're allowed by the spec? I don't have a copy to check, but I was under the impression that 1000BaseT was the first 802.3 standard to /require/ full-duplex on all links. At least some of my NICs don't advertise 1000BaseT/half. As far as I've heard, any gear that supports this is extending the specification. I could very well be wrong, of course. Do you have a reference?--ktims (talk) 18:00, 27 April 2008 (UTC)

[edit] Forcing Gigabit

The article says that several implementations allow the user to force gigabit operation to eliminate autonegotiation issues. I belive this is misleading. Autonegotiation is *required* for gigabit transcievers because it sets parameters other than just speed and duplex. These implementations that purport to allow 'forcing' operation really only eliminate non-gigabit modes from the candidates offered by the negotiation mechanism. Autonegotiaion still happens, it just won't allow modes other than gigabit to be negotiated.

[edit] Line Codes

This article says 1000BASE-T expands 8 bits into four 3 bit symbols, while the 8B10B article explains how the same 1000BASE-T expands 8 bits into a single 10 bit symbol. How do they fit together? Also both articles should have links to each other. CannibalSmith 07:25, 1 June 2007 (UTC)

Edit: 8B10B says Gigabit Ethernet, not 1000BASE-T specifically. So is 8B10B for optics only? CannibalSmith 07:29, 1 June 2007 (UTC)
Correct. I added a few words next to the link on the 8b/10b page - feel free to add more here or there if you think it could be made more clear! Mrand T-C 13:10, 1 June 2007 (UTC)

[edit] What is actual data thoughput?

Does the Giga actually move exactly 1000Mb/s, and how much of that data is reserved for error correction and packet addressing (overhead)?

Word is some 20% is for overhead. --Flightsoffancy (talk) 15:50, 28 January 2008 (UTC)

  1. There is no error correction built into GigE itself. Other software or hardware layers would have to perform that function if it is desired.
  2. The packet addressing/overhead (by which I assume you mean things like MAC address, pkt type, CRC checking (which is error detection), is the same for all variants of Ethernet. See Ethernet#Physical_layer for details.
  3. There is 25% overhead for the line coding added to the packet addressing/overhead, as discussed in the article. Are you saying that you don't find that section of the article clear?
—Mrand T-C 17:14, 28 January 2008 (UTC)

[edit] Data transfer limitations under PCI buses?

I just upgraded my network to 1000 Mbps Ethernet and I'm seeing transfer rates at around 30% of maximum. Is this because I am using PCI (not PCI Express) cards? --John Bahrain (talk) 18:40, 5 May 2008 (UTC)

No. Something is wrong there. —Preceding unsigned comment added by 81.216.200.10 (talk) 17:22, 19 May 2008 (UTC)