Re: Hitting web site consistently dropped ppp connection?

[Heikki Vatiainen <hessu@cs.tut.fi>]

Nathan O. Siemers wrote:
> I've got a weird one, folks.

Not really, it's just a feature in your modem :)
 
> I've got a debian slink box serving as router for a network connected
> to the internet by a dialup ppp connection.  It does some masquerading
> for the other systems on the local network, which include another
> slinkbox and a redhat 5.2 system.
> 
> 
> Yesterday, following the link:
> 
> http://slashdot.org/comments.pl?sid=99/03/20/1158230&pid=0#35 ,
> 
> reading with netscape 4.07 on the redhat 5.2 system,
>
> killed my ppp connection to the internet from my slink router.
> 
> This happened reproducibly (5 times) when I hit that particular page
> (not a couple other pages at slashdot), at around 64K of download.  I
> sent lots of other test stuff over the ppp connection with no
> problems.
>                                                                                
> Is there a ghost in the machine?  How could that happen? Is this a
> freak coincidence or the tickling/exploit of a pppd bug?  It there an
> escape sequence embedded in the transfer that could reset the modem?

Escape sequence is probably the correct quess. I just
downloaded the page and one of comments had this signature:

-- + ++ATH0
    ^
Space added by me to protect modem owners. My guess is your 
modem saw the three plus signs and hung up.

Thus bug was discussed on linux-kernel last month. If you
go to http://linuxhq.com/lnxlists/linux-kernel/ and check
the linux-kernel mailing list archives for Feb 1999 - Week 1
and Feb 1999 - Week 2, you'll find the whole discussion
under subjects:
    "PPP bug", 
    "Re: plus plus plus [was: PPP bug]" and 
    "Modems and the + + + bug"
 
Here is a quote from a message by matti.aarnio@sonera.fi:

  Like has been mentioned here recently (last week, I recall),
  if you have this problem, turn off the local modem escape by
  issuing  AT S2=255 command before doing dialing; or dial by:
        ATS2=255DTnnnnnnnnnnn
  that is, prefix the dial command (DTnnnn) with escape disable
  command.

  Check your modem manual for the S-register number, and
  disabling value. Document I used said 'escape is turned off
  with any value above 127'.

  If the problem is at your ISP's side, then you need to inform
  them.

> Perhaps I am just a victim of a freak coincidence.
> 
> Thanks for any ideas,
> 
> 	nathan

// Heikki
-- 
Heikki Vatiainen                  * hessu@cs.tut.fi
Tampere University of Technology  * Tampere, Finland