Date: Sun, 22 Dec 96 1:55:13 +0000 From: Andrew.Gordon@net-tel.co.uk To: list:; Cc: freebsd-questions@freebsd.org, freebsd-current@freebsd.org, freebsd-stable@freebsd.org Subject: Re(2): User ppp not hanging up modem. Message-ID: <"84a-961222015526-FEB1*/G=Andrew/S=Gordon/O=NET-TEL Computer Systems Ltd/PRMD=NET-TEL/ADMD=Gold 400/C=GB/"@MHS> In-Reply-To: <Pine.OSF.3.95.961221184603.23960A-100000@packet.eng.umd.edu>
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> On Sat, 21 Dec 1996 dicen@hooked.net wrote: > > Nate Williams wrote: > > > That's *NOT* the correct thing. What happens when for some reason > > > PPP happens to send the sequence '+++' to the modem? All of a sudden > > > it'll drop into command mode and you're screwed. User-PPP (as well as > > > all other PPP/SLIP implementations I've worked with) assumes that > you've > > > disabled the escape sequence at least temporarily. > > > > > Interesting. But, what exactly is the prabobalitity of that? I will have > > think about this one. > > Note that the standard command "&D3" tells the modem to reset itself when > DTR drops. Nate's right, this _is_ standard. What he missed was that > Hayes modems (Hayes originated the protocol that's now a defacto standard) > used to get around the +++ transparency issue by requiring a 2 second dead > time (either before or after the +++ code, I forget which). Before _and_ after - hence you are safe even if a packet begins or ends with "+++". > Hayes > patented that delay, I think, which is why modems don't use it anymore. Good modems still do (USR Courier for example) - presumably having licenced with Hayes. Some junk modems don't.....
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