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000420_news@newsmaster….columbia.edu _Sat Sep 27 00:48:48 1997.msg
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From: jrd@cc.usu.edu (Joe Doupnik)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: Kermit via PPP under DOS?
Message-ID: <k1c7kBQEU5Wv@cc.usu.edu>
Date: 26 Sep 97 22:11:11 MDT
Organization: Utah State University
Lines: 22
Xref: news.columbia.edu comp.protocols.kermit.misc:7744
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. Frames do not use MAC addressing.
Ethernet is a broadcast medium. ARP is REQUIRED to identify one
of many possible stations on the wire. Also many stations can be in the
same IP subnet and thus reachable by first soliciting their hardware
(Ethernet MAC) address via ARP and then addressing frames to that address.
All frames require MAC addressing. ARPing for one's own IP address must
produce NO RESPONSE.
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. Half measures are failures too.
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. 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. Use SLIP interfaces.
Avoid badly designed PPP drivers, please.
Joe D.