🚀 go-pugleaf

The encapsulation he was talking about is appletalk in UDP.  No TCP,
and only one Ethernet.  Many (most?) large university installations do
their campus-wide AppleTalk that way.  It is partly historical.  When
the practice started there was no EtherTalk.  So this was the simplest
way to connect LocalTalk networks that were on opposite ends of
campus.  Use a Kinetics box to take LocalTalk packets in one side,
stick a UDP header on them, and then put them on a campus Ethernet
where they would be routed to a Kinetics box on the destination
Ethernet.  Now that there is an EtherTalk, one could consider having
the packets travel through the campus network as EtherTalk.  This
would still require the same hardware, since you'd still have to get
the packets from the LocalTalk to the Ethernet.  But you would be
saving yourself is the extra UDP and IP headers.  While we're always
happy to save a few bytes in packets, there are two problems with
this:

  - many people consider EtherTalk inappropriate for a large network.
	The excessive broadcasting is only one problem.  There are
	also questions about the quality of the routing algorithms.

  - some university networks consist of a complex combination of
	Ethernets, serial lines, broadband, fiber, etc.  It's hard
	enough to route IP reliably through this.  We don't want
	to have to manage a separate routing structure for every
	vendor's protocol.  So we'd rather stick an IP header on
	the packets for transit through the network than have to
	maintain Appletalk routing over the whole network.  (And
	this assumes that our routers even support Appletalk.  Many
	do not.)

OSI is still not widely enough available to be a real alternative for
most campuses.  But I assume if networks move from IP to OSI, similar
encapsulation will be done using the OSI equivalent of UDP. (Of course
one could hope that by then Appletalk would have direct support of
OSI.)  IP may or may not be the be-all and end-all of network
development.  (Many of us suspect that, like Algol 60, it is a great
improvement over all its successors.)  But at the moment there are
good reasons why it is the basis for most campus networks.  Any
company interested in selling to us needs to realize that our campus
network is based on IP, and there's probably not much they can do to
change that.