Network Bandwidth - Gigabit Vs. 100M - Networking

This is a discussion on Network Bandwidth - Gigabit Vs. 100M - Networking ; Hello Everyone, I have a really strange problem at hand and am hoping to find someone that could shed some light on it. I run a few lan centers with approximately 40 PCs in each location. I am not a ...

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Thread: Network Bandwidth - Gigabit Vs. 100M

  1. Network Bandwidth - Gigabit Vs. 100M

    Hello Everyone,
    I have a really strange problem at hand and am hoping to find
    someone that could shed some light on it. I run a few lan centers with
    approximately 40 PCs in each location. I am not a networking guru and
    am hoping to find someone that is.

    Problem:
    A few month ago, we opened a new location that used Gigabit ethernet
    PCs vs. the old 100Mbit PCs. From day one, we started to experience
    serious lag on the network of which we assumed was the problem of our
    T1 provider. To make a long story short we never resolved it (lots of
    finger pointing). The only thing that we figured out was that one PC
    can actually max out the entire T1 line and if a second PC came on
    line, it did not a share of the line which should be half the
    bandwidth. The first PC just continues to max out the line until its
    finished!

    We just recently upgraded one of our old stores with new PCs. Before
    the upgrade, we had over 30 PCs on line at the same time with
    absolutely no lag and lots of bandwidth un-used. But just as soon as
    the PCs were switched to Gigabit ethernet PCs, the same lag as I
    described above showed up. The only difference in the two stores now
    is that the new store has gigabit switches and the upgraded store has
    100Mbit switches.

    Question:
    Can anyone figure out what is wrong? The PCs are sent to autosense and
    do. The upgraded store PCs do switch down to 100Ms but something
    causes just one PC to utilize the entire bandwidth. Essentially
    something that used to cause the old PCs to share the line, goes away.
    What??? What is different in between 100Mbit and 1Gbit protocal?

    It's driving me crazy and my customers out of the store...


  2. Re: Network Bandwidth - Gigabit Vs. 100M

    togemailtest@gmail.com wrote:
    > Hello Everyone,
    > I have a really strange problem at hand and am hoping to find
    > someone that could shed some light on it. I run a few lan centers with
    > approximately 40 PCs in each location. I am not a networking guru and
    > am hoping to find someone that is.
    >
    > Problem:
    > A few month ago, we opened a new location that used Gigabit ethernet
    > PCs vs. the old 100Mbit PCs. From day one, we started to experience
    > serious lag on the network of which we assumed was the problem of our
    > T1 provider. To make a long story short we never resolved it (lots of
    > finger pointing). The only thing that we figured out was that one PC
    > can actually max out the entire T1 line and if a second PC came on
    > line, it did not a share of the line which should be half the
    > bandwidth. The first PC just continues to max out the line until its
    > finished!


    How are your PCs connected to the T1 line?

    >
    > We just recently upgraded one of our old stores with new PCs. Before
    > the upgrade, we had over 30 PCs on line at the same time with
    > absolutely no lag and lots of bandwidth un-used. But just as soon as
    > the PCs were switched to Gigabit ethernet PCs, the same lag as I
    > described above showed up. The only difference in the two stores now
    > is that the new store has gigabit switches and the upgraded store has
    > 100Mbit switches.
    >
    > Question:
    > Can anyone figure out what is wrong? The PCs are sent to autosense and
    > do. The upgraded store PCs do switch down to 100Ms but something
    > causes just one PC to utilize the entire bandwidth. Essentially
    > something that used to cause the old PCs to share the line, goes away.
    > What??? What is different in between 100Mbit and 1Gbit protocal?


    Probably that gigabit ethernet uses all 4 pairs of wires in the cable.

    Robert

    >
    > It's driving me crazy and my customers out of the store...
    >


  3. Re: Network Bandwidth - Gigabit Vs. 100M

    On 26 Apr 2007, in the Usenet newsgroup comp.os.linux.networking, in article
    <1177627893.809287.292750@r30g2000prh.googlegroups. com>,
    togemailtest@gmail.com wrote:

    >A few month ago, we opened a new location that used Gigabit ethernet
    >PCs vs. the old 100Mbit PCs. From day one, we started to experience
    >serious lag on the network of which we assumed was the problem of our
    >T1 provider.


    What have you got for a router between your LAN and the "T1" provider,
    and how big are the pipes? A "T1" is 1.544 Megabit/Second, and even
    the _predecessor_ to Thick Ethernet (10Base5) from the 1970s can fill
    a T1 in a heartbeat.

    >To make a long story short we never resolved it (lots of finger
    >pointing). The only thing that we figured out was that one PC can
    >actually max out the entire T1 line and if a second PC came on line,
    >it did not a share of the line which should be half the bandwidth. The
    >first PC just continues to max out the line until its finished!


    TCP Window? Jumbo Frames? The first box is cramming a whole bunch of
    data over the local wire, and the router is buffering this. That may
    leave no room for the extra packets from the "other" systems unless
    the router is doing traffic shaping.

    >We just recently upgraded one of our old stores with new PCs. Before
    >the upgrade, we had over 30 PCs on line at the same time with
    >absolutely no lag and lots of bandwidth un-used. But just as soon as
    >the PCs were switched to Gigabit ethernet PCs, the same lag as I
    >described above showed up. The only difference in the two stores now
    >is that the new store has gigabit switches and the upgraded store has
    >100Mbit switches.


    And you may have selected the high performance options to allow the
    maximum bandwidth on your Gigabit end, while your downstream is still a
    soda straw maximum. ifndef Blivit...

    >Can anyone figure out what is wrong?


    I'd use a packet sniffer, and look specifically at the window sizes. I'm
    guessing you'd see one box absolutely stuffing the pipe full, and if you
    were able to look at the ACK numbers, you'd see that the limiter is your
    upstream. Think what it's like to have ten-twenty boxes talking very
    well on 10 Megabit, but that isn't going to help when your connection
    to the world is a 56k modem. Now, scale those numbers. 1.544M/56k 27:1
    10Base? 27:1 = what?

    >It's driving me crazy and my customers out of the store...


    If you are trying to demo gigabit speed, do it locally, or pay a bunch
    of bux for a wide pipe outside.

    Old guy

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