Packet Loss Problem - TCP-IP

This is a discussion on Packet Loss Problem - TCP-IP ; Dear all, I've been fighting with a never ending issue for quite some time now and require your help... I have the following network equipment : 1 PowerEdge 1800 Server 1 Switch Dell 2616 (3 years old) 1 Switch Dell ...

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Thread: Packet Loss Problem

  1. Packet Loss Problem

    Dear all,

    I've been fighting with a never ending issue for quite some time now
    and require your help...

    I have the following network equipment :

    1 PowerEdge 1800 Server

    1 Switch Dell 2616 (3 years old)

    1 Switch Dell 2716 (brand new)

    And about 10 Dell stations, 3 network printers, etc... connected to
    these switches.



    My problem started with one computer which faced intermittent network
    connexion loss, which is a big deal since our sales software is
    freezing in that scenario (we use Sage).

    1- So I replaced the computer of that personn. The problem was still
    there

    2- I decided to update with latest BIOS/network drivers... problem is
    still there

    3- I decided to change the network cable from switch to this computer.
    Problem is still there.



    Finally I started to monitor network health using ping method to a
    couple of computer FROM our poweredge server. What I noticed is that
    for ALL, from time to time, packets are loss. And what seems to
    happen is that, from time to time, not only one packet is loss but
    connection is going down for 10-20s. But this specific scenario
    happened only to one person till now.



    So first of all, is that normal that over a LAN packets can be lost
    (last test today, 6 packets lost over 2709)?

    What else could I do to troubleshoot that problem? I'm about to
    change the server network cable to see if it will make a difference.

    Could it be our old switch and if so how could I test it ?



    Thanks a lot !

  2. Re: Packet Loss Problem

    On Oct 3, 4:48*am, The Bass Man wrote:
    > So first of all, is that normal that over a LAN packets can be lost
    > (last test today, 6 packets lost over 2709)?


    No. Something is wrong.

    > What else could I do to troubleshoot that problem? *I'm about to
    > change the server network cable to see if it will make a difference.


    Yes try that and...

    > Could it be our old switch and if so how could I test it ?


    Get crossover adapter and do direct connect from the big Dell to each
    computer in turn and try pings.

    1. If new cable works with switch, without crossovers, it's the cable.
    2. If ping works without switch, with crossover, and old cable, it's
    the switch.
    3. If ping does not work with crossover, without switch, new cable, I
    would check to make sure no one has been fat-fingering the plugs when
    inserting them (surprising number of people ruin jacks this way).

    If all of this fails, it might be your environment. Very strong EMI
    and/or dirty signals can cause loss, and if you're in a part of the
    world where buildings are "mature"...

    You could check that length limitations are not violated, etc. The new
    switch will be a great tool. I would make it the primary, and not use
    the secondary at all during testing.

    I'd also get Wireshark to see more of what data is actually being sent
    to eliminate any possibility for software issues:

    http://www.wireshark.org/

    -Le Chaud Lapin-

  3. Re: Packet Loss Problem

    On Fri, 3 Oct 2008 02:48:14 -0700 (PDT), The Bass Man wrote:
    > Dear all,
    >
    > I've been fighting with a never ending issue for quite some time now
    > and require your help...
    >
    > I have the following network equipment :


    [a switched Ethernet, with ~10 hosts acting as clients against one]

    > My problem started with one computer which faced intermittent network
    > connexion loss, which is a big deal since our sales software is
    > freezing in that scenario (we use Sage).
    >
    > 1- So I replaced the computer of that personn. The problem was still
    > there
    >
    > 2- I decided to update with latest BIOS/network drivers... problem is
    > still there
    >
    > 3- I decided to change the network cable from switch to this computer.
    > Problem is still there.
    >
    >
    >
    > Finally I started to monitor network health using ping method to a
    > couple of computer FROM our poweredge server. What I noticed is that
    > for ALL, from time to time, packets are loss. And what seems to
    > happen is that, from time to time, not only one packet is loss but
    > connection is going down for 10-20s.


    What do you mean by that -- is the host reporting that the (Ethernet)
    link is down? The thing that also makes the LED at the connector go
    out?

    > But this specific scenario
    > happened only to one person till now.


    > So first of all, is that normal that over a LAN packets can be lost
    > (last test today, 6 packets lost over 2709)?
    >
    > What else could I do to troubleshoot that problem? I'm about to
    > change the server network cable to see if it will make a difference.


    If you have the time, it's better IMHO to find out what's wrong
    *before* starting to make changes.

    > Could it be our old switch and if so how could I test it ?


    If it is one of those switches which you can login to, do that and
    check its statistics.

    One thing to double-check in either case is that all Ethernet adapters
    have negotiated 100 MBit/s (or whatever the switch and hosts can
    handle) and that it is full-duplex. If it degrades to 10 MBit/s
    half-duplex or something, you often get packet loss and poor
    performance in general.

    /Jorgen

    --
    // Jorgen Grahn \X/ snipabacken.se> R'lyeh wgah'nagl fhtagn!

  4. Re: Packet Loss Problem

    On Oct 3, 2:48*am, The Bass Man wrote:

    > Finally I started to monitor network health using ping method to a
    > couple of computer FROM our poweredge server. What I noticed is that
    > for ALL, from time to time, packets are loss. *And what seems to
    > happen is that, from time to time, not only one packet is loss but
    > connection is going down for 10-20s. But this specific scenario
    > happened only to one person till now.


    I had a similiar problem. Try locking the computer at 100Mb/s and see
    if the problem goes away. If it does, the problem is either the cable
    or the network adapter just not getting along with the switch. On one
    computer, I simply added a $25 *modern* Gigabit adapter and the
    problem went away.

    > So first of all, is that normal that over a LAN packets can be lost
    > (last test today, 6 packets lost over 2709)?


    Yes, assuming there's any chance something in the network is
    overloaded. Older switches don't throttle very well.

    > What else could I do to troubleshoot that problem? *I'm about to
    > change the server network cable to see if it will make a difference.
    >
    > Could it be our old switch and if so how could I test it ?


    It could be that the switch doesn't handle overloading or negotiating
    very well, but I doubt it. Most likely, it's the cable. Is it Cat 5E
    or cat 6? How long is it? Try another network card.

    DS

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