switch and half-duplex lines ?

Discussion in 'Cisco' started by jh3ang, May 20, 2006.

  1. jh3ang

    jh3ang Guest

    Hello !

    I don't understand that in the following situation how come each host
    can have 10 Mbps ?
    I mean the router that serves internet connection has just only one
    wire to Switch, how can each host can have 10Mbps internet connection ?

    *******
    Switch is connected with Router, and this Switch has 10 hosts connected
    to it with half-duplex.
    Switch serves 10Mbps. Router serves internet connection.
    *******
     
    jh3ang, May 20, 2006
    #1
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  2. In article <>, "jh3ang" <> writes:
    >I don't understand that in the following situation how come each host
    >can have 10 Mbps ?
    >I mean the router that serves internet connection has just only one
    >wire to Switch, how can each host can have 10Mbps internet connection ?
    >
    >*******
    >Switch is connected with Router, and this Switch has 10 hosts connected
    >to it with half-duplex.
    >Switch serves 10Mbps. Router serves internet connection.
    >*******


    A 10Mbps connection means the standard definition on how the two devices
    exchange information. This doesn't necessarily mean that the actual data
    rate is rellay this high. It is similar to electricity: one circuit has a
    fuse with 10A, the other may have 16A. This doesn't mean that the actual
    flow is that high, it is usually a lot smaller.

    Regards,
    Christoph Gartmann

    --
    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Immunbiologie
    Postfach 1169 Internet: gartmann@immunbio dot mpg dot de
    D-79011 Freiburg, Germany
    http://www.immunbio.mpg.de/home/menue.html
     
    Christoph Gartmann, May 20, 2006
    #2
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  3. jh3ang

    BernieM Guest

    "jh3ang" <> wrote in message
    news:...
    > Hello !
    >
    > I don't understand that in the following situation how come each host
    > can have 10 Mbps ?
    > I mean the router that serves internet connection has just only one
    > wire to Switch, how can each host can have 10Mbps internet connection ?
    >
    > *******
    > Switch is connected with Router, and this Switch has 10 hosts connected
    > to it with half-duplex.
    > Switch serves 10Mbps. Router serves internet connection.
    > *******
    >


    They don't. They have a 10 Mbps link to the switch. The router I assume
    also has a 10 Mbps link to the switch that traffic from all 10 hosts gets
    funnelled through. Its Internet connection then become a bigger bottleneck
    limiting traffic flow from all 10 hosts. TCP then reduces throughput to
    some degree based on end-to-end latency etc.

    As a side note ... if using a switch configuring links as half duplex is a
    bit of a waste.

    BernieM
     
    BernieM, May 21, 2006
    #3
  4. jh3ang

    Peter Guest

    Greetings,

    > *******
    > Switch is connected with Router, and this Switch has 10 hosts connected
    > to it with half-duplex.
    > Switch serves 10Mbps. Router serves internet connection.
    > *******


    Each of the 10 hosts has a road capable of passing 10 cars at a Time,
    however all those roads meet at an intersection to travel down a MAIN
    road that can only pass 10 cars at a time. All 100 cars cannot access
    the MAIN road at the same time, so they have to QUEUE up to pass
    though the intersection to access the MAIN road. This is exactly what
    a Switch does, it sequences access for 10 dedicated ports to 1 SHARED
    port by Queuing traffic. If all 10 Hosts wanted access at EXACTLY the
    same time, then they would only be able to get the equivalent of 1Mb
    of bandwidth each.

    The PHYSICAL path is 10Mb, but it is extremely rare that you would
    find 10 x 10Mb ports all wanting 10Mb at EXACTLY the same time. In
    real terms the road is almost NEVER full of traffic, so the 10Mb
    Shared port is shared out by Multiplexing the traffic from the other
    ports. This multiplexing is handled by a "store and forward" approach.

    BTW, if your Switch truly is an Etherswitch and not a Hub, then to get
    the best possible performance you should be using a FULL Duplex
    setting for all hosts that can support that. A Hub can only do
    Half-Duplex.

    Cheers.............pk.

    --
    Peter from Auckland.
     
    Peter, May 21, 2006
    #4
  5. jh3ang

    jh3ang Guest

    Great Answer !
     
    jh3ang, May 21, 2006
    #5
  6. jh3ang

    MC Guest

    jh3ang wrote:
    > Great Answer !
    >

    All hosts most likely are not streaming a full 10mb worth of data out
    either. most are small amoutns of data at anyone time. Most PC's will
    not push near that amount of data out with normal web browsing.

    We have a few 1000 hosts on our netowrks all going out a 20mb
    connection, not using 25 percent of that bandwidth at any peak time.
     
    MC, May 24, 2006
    #6
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