100Mb networking... a few queries

Discussion in 'NZ Computing' started by T.N.O., Sep 11, 2003.

  1. T.N.O.

    T.N.O. Guest

    Why do they only have either 100 or 10 as speeds? why not have a 50Mb with
    maybe a bit more range than 100.. just wondered.
     
    T.N.O., Sep 11, 2003
    #1
    1. Advertising

  2. T.N.O. wrote:
    > Why do they only have either 100 or 10 as speeds? why not have a 50Mb with
    > maybe a bit more range than 100.. just wondered.


    100 goes plenty far enough. I cant think of many cases where you would be
    applying copper in the correct place and exceed the distance limitations.
    Inevitably 100+metre runs should be fibre for one reason or another.
     
    Richard Malcolm-Smith, Sep 11, 2003
    #2
    1. Advertising

  3. In article <bjossp$lcjd7$-berlin.de>,
    "T.N.O." <> wrote:

    > Why do they only have either 100 or 10 as speeds? why not have a 50Mb with
    > maybe a bit more range than 100.. just wondered.
    >
    >


    Leaving aside such curiosities as 1Mb Ethernet, there are 10Mb, 100Mb,
    1,000Mb and 10,000Mb Ethernet. However, despite the impression that
    using a 10/100 switch might give you, they are not very similar at the
    bit (ISO layer 1) level. They are of couse essentially identical at
    layer 2.

    10M Ethernet uses a very inefficient mechanism called Manchester
    Encoding, which transmits at 20MHz to send data at 10Mbps. I.e., 2 Hz
    per bit.

    100M Ethernet uses a more sophisticated encoding called 4B/5B, which
    operates at about 30MHz. (31.25MHz to be precise)

    The distance limits of 100Base-T are conservative and MOSTLY based on
    signal loss in the cable (entirely based on signal loss/noise for
    full-duplex operation).

    For example, using fibre, you can get long range driver for 1000Base-F
    (that's gigabit, not 100Mb), which will go about 150km!

    So, the short answer to you question "why not have a 50Mb with maybe a
    bit more range than 100?" is: there isn't any point. The cost far
    outweighs the benefit.

    See http://www.rhyshaden.com/ethernet.htm
    --
    Michael Newbery
    return address is spamtrapped.
    surname at "actrix", 2ld "co", tld "nz"
     
    Michael Newbery, Sep 11, 2003
    #3
  4. On Fri, 12 Sep 2003 22:50:24 +1200, simon.A wrote:

    >
    > The main point is, the more power that you have thrown at the line will
    > dictate what distance you can get. In the instance of Southern Cross, I
    > belive
    > its about 10,000 volts.


    uh.. the 10kV feed is because all the repaters are connected in series. Each
    one only drops a few volts (it's hard to run individual power feeds
    underwater...)
     
    Uncle StoatWarbler, Sep 12, 2003
    #4
  5. T.N.O.

    T.N.O. Guest

    "Uncle StoatWarbler" wrote
    > uh.. the 10kV feed is because all the repaters are connected in series.

    Each
    > one only drops a few volts (it's hard to run individual power feeds
    > underwater...)


    why not solar power... with big leads to a floating solar panel on the
    surface...

    sorry, I'm in a clean green mood today :)
     
    T.N.O., Sep 12, 2003
    #5
  6. In article <3f61a4d5$>,
    "simon.A" <> wrote:

    > "Michael Newbery" <> wrote in message
    > news:...
    > >
    > > For example, using fibre, you can get long range driver for 1000Base-F
    > > (that's gigabit, not 100Mb), which will go about 150km!

    > ------------------------
    > Fibre is extremely variable in what distances it can go without repeaters,
    > example, the main backbone cable from Christchurch to Dunedin has repeaters
    > based in most towns (obvious reasons - pop), which leaves the maximum
    > distance without a repeater about 60km. However, look at the Southern Cross,
    > its about 150k or so between each repeater.
    >
    > The main point is, the more power that you have thrown at the line will
    > dictate what distance you can get. In the instance of Southern Cross, I
    > belive
    > its about 10,000 volts.


    At high speed, dispersion smears the waveform, which limits the distance
    you can go without regeneration. You can aid by using dispersion shifted
    fibre, but even that only works up to a point.

    The drivers I'm refering to are special GBICs, which plug into a
    standard GBIC port on a switch, and drive 100-150km on standard
    dispersion fibre. They are fed up to 5.5VDC.

    See
    http://www.extremenetworks.com/services/documentation/ConsolidatedHWRev3-
    Chapter10.asp (LX100)
    and http://www.foundrynet.com/services/faqs/media.html (LHB)
    --
    Michael Newbery (email my .Mac account---my surname)
     
    Michael Newbery, Sep 13, 2003
    #6
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Ryan Goolevitch
    Replies:
    1
    Views:
    503
    shope
    Oct 17, 2003
  2. Replies:
    0
    Views:
    590
  3. Johnny

    100MB zip drive.

    Johnny, Oct 15, 2003, in forum: Computer Support
    Replies:
    3
    Views:
    443
  4. W3HUB

    100MB Web Hosting Free Domain $34.80/year

    W3HUB, Jan 17, 2004, in forum: Computer Support
    Replies:
    2
    Views:
    461
    Richard
    Jan 17, 2004
  5. Tony
    Replies:
    8
    Views:
    816
Loading...

Share This Page