ppp from Windows-XP to GPRS `modem': DNS server negotiation - PPP

This is a discussion on ppp from Windows-XP to GPRS `modem': DNS server negotiation - PPP ; I have a problem when connecting a Windows-XP machine using a GPRS `modem', regarding IPCP negotiation of the DNS server addresses. What happens, from the ppp.log file that you can turn on with `set tracing ppp enable', is that windows-xp ...

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Thread: ppp from Windows-XP to GPRS `modem': DNS server negotiation

  1. ppp from Windows-XP to GPRS `modem': DNS server negotiation


    I have a problem when connecting a Windows-XP machine using a GPRS
    `modem', regarding IPCP negotiation of the DNS server addresses.

    What happens, from the ppp.log file that you can turn on with `set
    tracing ppp enable', is that windows-xp sends an ipcp conf-req with an
    ip address, and null dns server addresses, four times, and then gives
    up on the server addresses, and changes to just including the
    ip-address. When the gprs `modem' finally responds about 20 s later
    (presumably the network is slow, or radio conditions bad) the
    windows-xp machine has stopped asking for the dns server addresses,
    and so does not accept them, even though the `modem' can now supply
    them (it does, in an unsolicited conf-nak). The result is that the xp
    machine can use the ip-over-ppp link, but can't resolve names to ip
    addresses.

    I know the whole business about dns addresses is inelegant, but it's
    the way ms machines want to work.

    So my questions are:

    - Is the behaviour of windows-xp ppp described anywhere in detail, in
    a way that might help? (rfc 1877 says nothing about trying just 4
    times.)

    - Is there any way of configuring windows-xp ipcp so that it waits
    rather longer for the slow `modem'? (I tried a search through the
    registry, but either there isn't anything, or I was using the wrong
    strings).

    Sorry if this has already been addressed; I did search with google,
    both groups and www, as well as reading the microsoft help pages (not
    much help), and James Carlson's book (good stuff, but didn't seem to
    mention this), and the faq for this group.

    Many thanks for any tips,

    --
    David Stone


  2. Re: ppp from Windows-XP to GPRS `modem': DNS server negotiation


    "David Stone" wrote in message
    news:87hdyvwpdb.fsf@diamond.lithoi.demon.co.uk...
    >
    > I have a problem when connecting a Windows-XP machine using a GPRS
    > `modem', regarding IPCP negotiation of the DNS server addresses.
    >
    > What happens, from the ppp.log file that you can turn on with `set
    > tracing ppp enable', is that windows-xp sends an ipcp conf-req with an
    > ip address, and null dns server addresses, four times, and then gives
    > up on the server addresses, and changes to just including the
    > ip-address. When the gprs `modem' finally responds about 20 s later
    > (presumably the network is slow, or radio conditions bad) the
    > windows-xp machine has stopped asking for the dns server addresses,
    > and so does not accept them, even though the `modem' can now supply
    > them (it does, in an unsolicited conf-nak). The result is that the xp
    > machine can use the ip-over-ppp link, but can't resolve names to ip
    > addresses.


    Yes, and from the end user point of view it seems that the GPRS link is
    somehow broken.
    The error messages Windows gives you in this situation are not very helpful.

    > I know the whole business about dns addresses is inelegant, but it's
    > the way ms machines want to work.
    >
    > So my questions are:
    >
    > - Is the behaviour of windows-xp ppp described anywhere in detail, in
    > a way that might help? (rfc 1877 says nothing about trying just 4
    > times.)


    No, it's Micsosoft's own invention. I guess the idea behind this behaviour
    is that if the peer
    doesn't like the DNS options in IPCP-Config-Req and doesn't reply at all
    because of that,
    Windows will then try without the DNS options. Of course, if this happens
    then the peer is not
    working according to PPP specs (it should send IPCP-Config-Reject if it
    doesn't support 1877 options).
    But this is the only reason that I can think of for this behaviour.

    > - Is there any way of configuring windows-xp ipcp so that it waits
    > rather longer for the slow `modem'? (I tried a search through the
    > registry, but either there isn't anything, or I was using the wrong
    > strings).


    No as far as I know..

    > Sorry if this has already been addressed; I did search with google,
    > both groups and www, as well as reading the microsoft help pages (not
    > much help), and James Carlson's book (good stuff, but didn't seem to
    > mention this), and the faq for this group.
    >
    > Many thanks for any tips,
    >
    > --
    > David Stone
    >




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