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000003_news@newsmaster….columbia.edu _Mon Sep 29 16:11:08 1997.msg
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From: Vladimir Alexiev <vladimir@cs.ualberta.ca>
Newsgroups: comp.protocols.kermit.misc
Subject: Re: Kermit via PPP under DOS?
Date: 29 Sep 1997 13:53:25 -0600
Organization: University of Alberta, Computing Science
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Message-ID: <omafgv99sa.fsf@tees.cs.ualberta.ca>
References: <k1c7kBQEU5Wv@cc.usu.edu>
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In-reply-to: jrd@cc.usu.edu's message of 26 Sep 97 22:11:11 MDT
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Xref: news.columbia.edu comp.protocols.kermit.misc:7764
In article <k1c7kBQEU5Wv@cc.usu.edu> jrd@cc.usu.edu (Joe Doupnik) writes:
> Let's go through the PPP driver situation again when the driver
> presents an Ethernet Packet Driver interface.
> PPP is a point to point link involving only two stations: this
> end and the other end. It is not a broadcast medium, and thus ARP does not
> apply.
pppd with the proxyarp option allows this. Here's what the pppd(8) man page
says:
Add an entry to this system's ARP [Address Resolution
Protocol] table with the IP address of the peer and the
Ethernet address of this system.
Also, some terminal servers provide such proxy arp. At least the Cisco
terminal server that runs at our uiniversity's login server. (Interestingly,
it only does this when the user properly identified themselves to the server,
otherwise it allows PPP, but does not give proxy arp.)
> A PPP driver presenting an Ethernet interface is indistinguishable
> from real Ethernet at the protocol stack level (i.e., by Kermit). That
> driver must then FULLY simulate a broadcast medium of many stations, yet
> they often fail completely to do that job.
I'm not saying that the Kermit class 1 handling is worse than than of other
WATTCP apps. I suspect that Kermit does some more checks or expects more from
the ethernet driver than other WATTCP apps, in other words it uses the
ethernet driver more properly than other WATTCP apps. But the fact remains
that these apps can use emulated class 1 drivers, while Kermit can't.
Sometimes worse is better.
> Half measures are failures too.
Well, these half measures prove to be adequate for other WATTCP apps.
> SLIP is a point to point link. It is not an Ethernet-style
> interface. Kermit knows about SLIP and treats it as a point to point
> comms pathway without MAC addresses. Use SLIP interfaces.
What are the benefits of an ethernet interface to a SLIP interface:
- there are apps that only support ethernet interfaces. Kermit couldn't
coexist with such apps because it demands a SLIP interface.
- Ethernet interfaces support BOOTP. Is BOOTP impossible with a SLIP
interface?
- How about DHCP?
- RARP is obviously impossible with a SLIP interface, but then it doesn't even
apply.
- Is there anything else?
> There is no such thing as a standardized PPP interface, alas, and thus
> Kermit does not have code to deal with the many PPP interfaces out there.
EtherPPP's documentation mentions class 15 (SLFP). Is that an example of a
non-standardized PPP interface?
> Avoid badly designed PPP drivers, please.
Since Kermit doesn't work with EtherPPP -k 1, does that make EtherPPP a badly
designed driver too? How about Windows PPP drivers, do they support an
Ethernet interface?