switch hub and switch

Discussion in 'NZ Computing' started by will, Oct 16, 2003.

  1. will

    will Guest

    will, Oct 16, 2003
    #1
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  2. will

    Nick Guest

    "will" <> wrote in message
    news:...
    > hi,
    >
    > can someone please enlighten me with the difference between a switch hub
    > and a switch?
    >
    > i see some shops are selling 8 Port Switch Hub (XNet for example) at
    > around $45, is it the same as the switch i see at dick smith
    > (http://www.dse.co.nz/cgi-bin/dse.storefront/en/product/XH6767)?
    >
    > thanks
    >
    > will.


    Packets are broadcasted to all ports on a Hub (bad) and in a switching hub
    packets are directed to one port only (destination port) (good).




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    Nick, Oct 16, 2003
    #2
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  3. will

    Shannon Guest

    On Thu, 16 Oct 2003 22:17:12 +1300, "Nick" <>
    wrote:

    >
    >"will" <> wrote in message
    >news:...
    >> hi,
    >>
    >> can someone please enlighten me with the difference between a switch hub
    >> and a switch?
    >>
    >> i see some shops are selling 8 Port Switch Hub (XNet for example) at
    >> around $45, is it the same as the switch i see at dick smith
    >> (http://www.dse.co.nz/cgi-bin/dse.storefront/en/product/XH6767)?
    >>
    >> thanks
    >>
    >> will.

    >
    >Packets are broadcasted to all ports on a Hub (bad) and in a switching hub
    >packets are directed to one port only (destination port) (good).


    That's a Hub compared to a Switch. What's a "switching hub" vs a
    "hub" ? :)

    As far as I can make out, they're one of two things:
    (1) Wrong name for a switch.

    (2) Two-port-switch and two hubs all rolled up into one.

    Basically, there are two hubs internal to the device. One hub takes
    all the 10 mbit traffic, another hub takes 100 mbit traffic. (I
    presume there's some kind of cheap magic select the correct hub based
    on speed chip involved.)

    Of course, you want these two internal hubs to talk to each other
    though, otherewise it would be pretty bad for the user.

    However, you can't connect a 100 mbit hub into a 10 mbit hub directly
    because two 100 mbit machines talking to each other would flood the 10
    mbit segment, or would be kept down to 10mbit speeds or something.

    So, you use a switch. But you're trying to save money, so you have a
    simple two port switch, one end of which is plugged into the 100 mbit
    and the other into 10 mbit hub.

    If I'm right about this, the 100 mbit traffic isn't switched, the 10
    mbit traffic isn't switched but the 100-to-10 and vice versa is.

    (There are many limitiations with this setup - no full duplex (as
    you're working though hubs really) as well as all the other issues.
    Still, for a low traffic typical home user where a 100 mbit hub would
    be basically as good as a switch it's not too bad.)

    ======================10mbit=======================
    | | |
    | | |
    *---- phy *---- phy .... TWO PORT SWITCH
    | | |
    | | |
    ================100mbit===========================

    where phy = physical port and * = the magic select-the-right-hub chip


    I could be wrong, but if anyone knows anything more useful let me
    know.
     
    Shannon, Oct 17, 2003
    #3
  4. will

    AD. Guest

    On Fri, 17 Oct 2003 14:08:25 +1300, Shannon wrote:

    >
    > That's a Hub compared to a Switch. What's a "switching hub" vs a "hub" ?
    > :)
    >
    > As far as I can make out, they're one of two things: (1) Wrong name for a
    > switch.
    >
    > (2) Two-port-switch and two hubs all rolled up into one.
    >
    > Basically, there are two hubs internal to the device. One hub takes all
    > the 10 mbit traffic, another hub takes 100 mbit traffic. (I presume
    > there's some kind of cheap magic select the correct hub based on speed
    > chip involved.)


    <snipped details>

    Perceptive, but I think you are actually describing how all 10/100 dual
    speed hubs work. Due to hubs broadcasting packets to all ports, they can't
    really work natively at multiple speeds. Corrections welcome of course.

    We had one once (a 3Com SuperStack II hub), where it seemed that the
    'switch' broke. All 100Mb users could talk to each other and all 10Mb
    users could talk to each other, but nobody could talk to the others on
    different speeds.

    > I could be wrong, but if anyone knows anything more useful let me know.


    I suspect 'switching hub' is just a sales term for a switch. The word
    'switch' could possibly be confusing/ambiguous to non technical buyers, so
    they invented a term that described a super duper hub.

    Cheers
    Anton
     
    AD., Oct 17, 2003
    #4
  5. will

    Gavin Tunney Guest

    On Fri, 17 Oct 2003 15:57:10 +1300, "AD." <> wrote:

    >Perceptive, but I think you are actually describing how all 10/100 dual
    >speed hubs work. Due to hubs broadcasting packets to all ports, they can't
    >really work natively at multiple speeds. Corrections welcome of course.
    >
    >We had one once (a 3Com SuperStack II hub), where it seemed that the
    >'switch' broke. All 100Mb users could talk to each other and all 10Mb
    >users could talk to each other, but nobody could talk to the others on
    >different speeds.
    >


    Curiously I've just had a 3com hub with exactly the same problem,
    first time I've seen it.

    >> I could be wrong, but if anyone knows anything more useful let me know.

    >


    I figured pretty much the same Anton. A hub is just a repeater so it
    must ultimately work at the speed of the slowest connection. There's
    probably a few tricks they can use, like buffering the 10mb packets,
    but it would only be noticeable on a low traffic network.

    I always used to install dual speed hubs when 100mbit came out,
    switches were too expensive for most people, but did have that nagging
    feeling I was the victim of a marketing con.

    >I suspect 'switching hub' is just a sales term for a switch. The word
    >'switch' could possibly be confusing/ambiguous to non technical buyers, so
    >they invented a term that described a super duper hub.
    >


    I've found the opposite.... people with a hub trying get a better
    price by making it sound like a switch.

    Gavin
     
    Gavin Tunney, Oct 17, 2003
    #5
  6. will wrote:

    > hi,
    >
    > can someone please enlighten me with the difference between a switch hub
    > and a switch?


    A hub is a generic name given to multiport ethernet devices to connect several
    computers together.

    A repeater hub is the bad old sort that is half duplex, has collisions. A
    switching hub is the better sort with what is effectivly a muliple port bridge
    in it to put the traffic to the correct destination ports only, it can handle
    full duples and multiple clients sending into it at the same time.

    Because the repeater hubs were all there was for some time, they got called
    hubs, the better ones are still hubs, but they are switching hubs.

    There is a bastard child called a dual speed hub, this connects clients to
    either the 10 or 100 megabit side of a bridge depending on what the port runs
    as, each side is repeated, but communication between the 2 are bridged.


    > i see some shops are selling 8 Port Switch Hub (XNet for example) at
    > around $45, is it the same as the switch i see at dick smith
    > (http://www.dse.co.nz/cgi-bin/dse.storefront/en/product/XH6767)?


    Maybe, the cheap small ones often have limited backplane bandwidth.

    The dse one has auto crossover so you dont need to worry about having the wrong
    cable for the thing you are connecting. It has 802.1p as well, but I suspect
    thats of no use in a domestic environment.
     
    Richard Malcolm-Smith, Oct 17, 2003
    #6
  7. will

    Shannon Guest

    On Fri, 17 Oct 2003 15:57:10 +1300, "AD." <> wrote:

    >Perceptive, but I think you are actually describing how all 10/100 dual
    >speed hubs work. Due to hubs broadcasting packets to all ports, they can't
    >really work natively at multiple speeds. Corrections welcome of course.


    I agree - there has to be *something* that lets the 10 and 100 speeds
    talk together. However, I wouldn't be terribly surprised if somebody
    could show that all 10/100 hubs are markeable as "swtiching hubs."
    I'm probably just overcynical of marketing though. :)

    A co-worker has another theory - the switching hubs don't have all the
    features you'd expect from a decent switch. (For example, they'll
    only support store-and-forward instead of cut-through. They almost
    certainly won't implement the Minimum Spanning Tree algorithm or Layer
    III switching capability. :)

    >We had one once (a 3Com SuperStack II hub), where it seemed that the
    >'switch' broke. All 100Mb users could talk to each other and all 10Mb
    >users could talk to each other, but nobody could talk to the others on
    >different speeds.


    Sounds plausable, that's for sure. :)

    (BlackBox had a stackable series of 10/100's where they were honest
    about all this in their catalog. There was a "master module" which
    contained the bridge (which an older term for a two port switch) as
    well as so many phyiscal ports, and slaves, which were cheaper as they
    didn't have the bridging module in them but provided additional ports.
    They explicitly said that you didn't need to buy the master - just
    slaves - if all your users would be on one speed or the other.)
     
    Shannon, Oct 19, 2003
    #7
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