MTU question - PPP

This is a discussion on MTU question - PPP ; I have a problem sending emails with 600kb attachment to one sight. Emails with smaller attachments get there. The error message I get is: conversation with mail.mullen.com[208.12.118.16] timed out while sending message body) I am able to send and recieve ...

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Thread: MTU question

  1. MTU question

    I have a problem sending emails with 600kb attachment to one sight.
    Emails with smaller
    attachments get there.
    The error message I get is:

    conversation with mail.mullen.com[208.12.118.16] timed out while
    sending message body)

    I am able to send and recieve emails with 600KB to yahoo.com. Why
    would it be a problem sending to mullen.com?

    I read postings and they mentioned that by lowering the MTU that might
    help, but I am to send emails to yahoo. Is Yahoo system configuration
    able to handle my emails, but not mullen.com?
    Thank you


  2. Re: MTU question

    rogv24@yahoo.com writes:
    > I have a problem sending emails with 600kb attachment to one sight.


    Where is PPP in this mix, and why are you posting to
    comp.protocols.ppp about an email or networking problem?

    Some hints about what sort of computer you're using, what operating
    system, what protocols, and how they're configured would be
    appreciated. Better still if you could indicate something about what
    you've tried to do to investigate the problem.

    > Emails with smaller
    > attachments get there.


    Some sites have intentional size limits on email messages. This
    _could_ be what you're running into. Generally speaking, sending huge
    attachments is impolite, and you should send a link instead so that
    the recipient can download the file if he feels like it (rather than
    be forced to accept the giant quota-chewing blob in the middle of his
    mailbox).

    > The error message I get is:
    >
    > conversation with mail.mullen.com[208.12.118.16] timed out while
    > sending message body)
    >
    > I am able to send and recieve emails with 600KB to yahoo.com. Why
    > would it be a problem sending to mullen.com?


    Have you contacted the postmaster there?

    > I read postings and they mentioned that by lowering the MTU that might
    > help, but I am to send emails to yahoo. Is Yahoo system configuration
    > able to handle my emails, but not mullen.com?


    Possibly. There's little way for us to know.

    At a 600KB limit, it seems extremely unlikely to me that this is
    related to MTU. MTU problems tend to affect things pretty early in
    the connection (around the third or fourth packet sent).
    Possibilities include:

    - There's a broken NAT or stateful firewall somewhere in the middle.
    It takes you so long to transfer that large file that this device
    discards the flow state and loses the ability to transfer your
    packets.

    This is fairly likely, diagnosing it will be very hard, and fixing
    it nearly impossible. The main symptom is that the TCP acks
    coming back will just cruise along for quite a while in steady
    state and then just ... stop.

    - The administrator of that site just doesn't want you to send giant
    email messages and has put some sort of restriction in place.
    Have you asked?

    - Bugs in the TCP implementation on one side or the other. This is
    also hard to diagnose, and involves studying the transfers
    carefully. It's sometimes hard to discern this problem from a
    broken NAT.

    - If your entire network link gets stuck when this happens -- no
    more packets in and out, not even a ping -- then it's possibly
    some sort of low-level problem. Having a PPP link with
    misconfigured serial flow control parameters can have this sort of
    effect.

    None of this seems to be directly related to PPP.

    --
    James Carlson, KISS Network
    Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

  3. Re: MTU question

    Sending the same attachment sending it from yahoo.com it arrives with
    no problem.


  4. Re: MTU question

    rogv24@yahoo.com writes:

    >I have a problem sending emails with 600kb attachment to one sight.
    >Emails with smaller
    >attachments get there.
    >The error message I get is:


    >conversation with mail.mullen.com[208.12.118.16] timed out while
    >sending message body)


    >I am able to send and recieve emails with 600KB to yahoo.com. Why
    >would it be a problem sending to mullen.com?


    >I read postings and they mentioned that by lowering the MTU that might
    >help, but I am to send emails to yahoo. Is Yahoo system configuration
    >able to handle my emails, but not mullen.com?
    >Thank you


    Because mullen.com has set up their site differently.

    Some sites do not like huge emails being sent.




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