Skip site navigation (1)Skip section navigation (2)
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>

Next in thread | Previous in thread | Raw E-Mail | Index | Archive | Help
> 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.....



Want to link to this message? Use this URL: <http://docs.FreeBSD.org/cgi/mid.cgi?"84a-961222015526-FEB1*/G=Andrew/S=Gordon/O=NET-TEL Computer Systems Ltd/PRMD=NET-TEL/ADMD=Gold 400/C=GB/">