Very Computer

Not true at all. See RFC 1661 & 1662.

Quote:> But when we use PPP on modem, is the modem working in
> asynchronous mode ? (Sun's version is called "Async PPP" ! )

If you're talking about regular modems, yes, it's asynchronous. And the
bundled asppp in Solaris will only do asynchronous PPP.

Quote:> If so, does
> it mean that each octet in the PPP frame is further encapsulated in
> those start/stop bits ?

That depends on the settings of the serial port / modem. PPP does not
care about start/stop/parity bits.

Quote:> Can you use the synchronous mode of the modem
> such as HDLC when using PPP ?

Yes (but not with asppp). Solstice PPP (and the free pppd) supports
synchronous mode of operation on Sparc-based serial ports.

Quote:> Can you use PPP on ethernet (is that
> considered a tunnelling ) ?

Yes. See RFC 2516. It's a form of tunneling (although some folks
out there disagree with this statement).

for free pppd, look at ftp://cs.anu.edu.au/pub/software/ppp

Adi

it used to be that sun had a special version of PPP for SunISDN, to do
synchronous. BUt i thought they eventually merged it into the standard PPP. So
in theory, later sun ppp should do synchronous as well. But I have no idea
how to take advantage of that.

--
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The word of the day is mispergitude

Sun has SunLink ISDN which works only with the DBRI S-bus ISDN card (ISDN is
synchronous). The Solstice PPP works with the built-in (or extended) serial
ports both asynchronous and synchronously (the later works if the serial
port supports it). The bundled PPP works only in asynchronous mode.

So I'm afraid your assumption is quite incorrect about the synchronous support
on 'sun ppp' - which I assume to be asppp.

Adi

Not "standard" PPP.  Solstice PPP (aka v3.0.1).

  -Greg
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I don't know anything about the Gnu PPP.

Solstice PPP can talk through a synchronous serial port to
another synchronous device.  Whether that other device is
a modem or some other piece of hardware doesn't really matter.
I believe (but don't know for sure) that the Solatice PPP can
use the V.something synchronous command set to make the modem
dial.

But your question actually depends on the capabilities and
configuration of your modem, and the devices on the other
end of the phone line.

First, a large number of "conventional" modems don't support
synchronous operation through their serial ports.  Obviously,
the Solstice PPP (or any other PPP) would not be able to work
in sync mode with such a modem.

Second, you wouldn't be able to enjoy the benefits of data
compression in the modems, unless your modem supports the
V.somethingelse packetizing and compression standard, which
might not even exist.  (I remember hearing about a proposed
modem standard for doing this in sync mode several years ago,
but I don't know if it ever became reality)

Third, if you're calling into an async service, the data path
through the modems will go from a bit-synchronous framing scheme
on the Solaris end, to a byte-oriented asynchronous framing scheme
on the other end.  I don't know if there's a standard for converting
between those two types of framing methods.  If there is, then one
or both modems would have to support it, or the data would just seem
garbled when it comes out the other modem.

So unless you know exactly what you're doing and exactly what kind
of equipment is being used on both ends of the phone line, you want
to stick with just synchronous or just asynchronous.

The Solstice PPP can talk with the modem in synchronous or
asynchronous mode.  It just needs the appropriate serial port
hardware, cable, and modem.  For most "conventional" modems,
only asynchronous mode is available.

  -Greg
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Yes for both, but only if the serial port(s) support synchronous mode - such as
those in Sparc-based machines. For Intel, you're on your own.

By the way, the free pppd is *not* GNU PPP (if the later ever exists). From the
perspective of Copyrights, it was not written under GNU license. Read the
README.sol2 file for more info on how to setup the synchronous mode.

Adi