• Virtualbox Internal network problem?

    From mark@mark@someemail.com to alt.os.linux.ubuntu on Sat Apr 10 06:26:48 2021
    From Newsgroup: alt.os.linux.ubuntu

    I set up internal network.

    Connect Mint and Ubuntu and Windows.

    Now, when I send one big file from OS to another OS it works.

    But, when I send alot small files, transfer start and after minute hang
    and latter stop.

    Why is that?
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  • From Paul@nospam@needed.invalid to alt.os.linux.ubuntu on Sat Apr 10 01:32:48 2021
    From Newsgroup: alt.os.linux.ubuntu

    mark wrote:
    I set up internal network.

    Connect Mint and Ubuntu and Windows.

    Now, when I send one big file from OS to another OS it works.

    But, when I send alot small files, transfer start and after minute hang
    and latter stop.

    Why is that?

    Makes no particular sense.

    *******

    Fire up Wireshark and capture a trace.

    See if it's doing Path MTU, or it is looking for
    and not finding a "gateway". Basically, the last
    packets in your trace, should hint at where the
    protocol stopped and dropped dead. Maybe it's
    requesting to "discover something" and that something
    never responds, because it does not exist.

    There's no DNS in there nor DHCP. When I tested
    that "internal network", it was more aggravation than
    I was able to put up with.

    *******

    There is TCP and UDP. TCP uses a reliable three-packet
    protocol and is "unstoppable". An error message should
    always result. That's what is unstoppable about it.

    UDP is a single packet thing, where the developer designs
    any necessary reliability features on top of the basic transport.
    UDP is excellent on a LAN, because the odds of packet
    loss are relatively low, and the overhead is lower. If
    for some reason, you designed a file transfer program to
    use UDP, there were no retries or timers, the protocol
    might easily drop dead. All it would take is one lost
    UDP packet, for it to drop dead.

    For file transfer, TCP is an excellent choice - if the
    protocol is failing, there should be an error message of
    some sort. "Destination unreachable". That sort of thing.

    However, TCP does have one failure case. Black hole routing.
    Differences in MTU size, the need to discover the minimum
    MTU to make a path work. On a home LAN, the MTU is normally
    about 1500 bytes. If a user, uses a VPN, the MTU is typically
    smaller, and then it may be necessary to use path discovery.
    Path discovery requires some portion of ICMP to be working.
    I have seen this with my ISP and their email server - I would
    send a message slightly bigger than 1500 bytes, the transfer
    would stop, no error message would appear. The two machines
    (my client, the email server) will happily sit there all day
    long, with the unused ends of the connection still lashed up.
    The email server had a lower MTU than normal, plus the twits
    had entirely disabled ICMP, not just the ping part of it.

    https://blog.cloudflare.com/path-mtu-discovery-in-practice/

    There are workarounds for that.

    In any case, get your Wireshark working and check out
    what protocol thing is going on, before the LAN drops
    to "silence".

    Paul
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  • From Adrian Caspersz@email@here.invalid to alt.os.linux.ubuntu on Sat Apr 10 07:33:35 2021
    From Newsgroup: alt.os.linux.ubuntu

    On 10/04/2021 05:26, mark wrote:
    I set up internal network.

    Connect Mint and Ubuntu and Windows.

    Now, when I send one big file from OS to another OS it works.

    But, when I send alot small files, transfer start and after minute hang
    and latter stop.

    Why is that?

    If windows is involved, maybe it's frightened of the virtual network interfaces potentially larger bandwidth than physical.

    Check: Network Throttling Index in the following. https://www.speedguide.net/articles/lan-tweaks-for-windows-7-8-10-5819

    Whatever OS, there will be logs. Or that from virtual box itself.

    --
    Adrian C
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