Path: utzoo!attcan!uunet!convex!killer!tness7!bellcore!faline!thumper!karn
From: karn@thumper.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Proxy ARP (was Re: Dumb vs. smart host routing)
Summary: AMPRNET does use ARP
Message-ID: <1093@thumper.bellcore.com>
Date: 20 May 88 22:44:35 GMT
References: <864@kaos.UUCP> <12398059730.20.BILLW@MATHOM.CISCO.COM> <1725@pt.cs.cmu.edu>
Organization: Bell Communications Research, Inc
Lines: 22

> I suppose I should give Phil Karn a chance to say this first, but
> AMPRnet (Amateur Packet Radio, network 44) generally won't - hidden
> terminal problems and unreliable broadcast performance make it impractical.

My code, written specifically for AMPRNET, does use ARP. We even have
our very own officially registered "hardware type" -- see the Assigned
Numbers RFC.

ARP on amateur packet radio works exactly like it does on Ethernet. Lost
ARP requests aren't a problem, since there'll be a retransmission (from
TCP or whatever) that simply gets turned into another ARP request. There
being no formal broadcast address in the AX.25 link layer protocol,
however, we had to define our own -- "QST". (You hams out there will
understand the significance of these letters :-)).

The only complication comes when "digipeaters" are used. These are
simple store-and-forward repeaters that use a source routing feature in
the link protocol.  Broadcasting through digipeaters doesn't work, so
you have to manually enter the proper source route and destination
address into your ARP table.

Phil