AppleTalk on the UIUC Campus
3/4/95
Debbie Fligor
CCSO Network Design Office
Abstract — This document is a basic guide to the AppleTalk networking protocol as it is
used on the UIUC campus. The general uses of AppleTalk, security and configuration
issues, and how to get connected to the larger campus AppleTalk network are discussed.
The method of calculating AppleTalk addresses that is used on campus is explained.
Definitions of many AppleTalk terms are provided in Appendix C.
Table of Contents
Abstract
p2
Table of Contents
p2
AppleTalk at UIUC, what it is, and how do I use it
p3
What is AppleTalk, and why do I care?
p3
If AppleTalk is so great, why don’t you just give it to everyone?
p3
Network Numbers
p3
Server and Workstation Security
p4
Printer Security
p4
System 6 Chooser Limitations
p4
What you have to do to get on the campus-wide AppleTalk
p5
What not to do if you are on the campus-wide AppleTalk
p5
Installing Routers
p5
Creating Tunnels
p6
Changing the EtherTalk configuration
p6
Appendix A — Network Numbers—How to compute them,
and how to use them
p7
Appendix B — Example of network addressing and routing
p9
Appendix C — Glossary
p 11
Appendix D — IP subnetting as it relates to calculating network
numbers
p 15
2
AppleTalk at UIUC — what it is, and how to use it
What is AppleTalk, and why do I care?
AppleTalk is basically how Macintosh computers talk to each other, their file servers and
their printers. Until fairly recently, the use of AppleTalk at UIUC was limited to inbuilding networks. This meant that people who wanted to share Macintosh files, and were
on different networks, had two choices. They could use “Sneaker-Net” (carrying floppy
disks by hand from person to person), or one person could move the files to a mainframe
so that another person could move them back to her Macintosh. It was also impossible to
share a server or a printer between networks. Now that AppleTalk is routed on the
campus backbone, all of this has changed.
It is possible to connect two or more AppleTalk networks with a device called a router. On
campus, building networks are hooked together by routers that can route AppleTalk. The
term “campus-wide AppleTalk” is used to refer to all of the building networks that
currently have AppleTalk routed between them. The campus-wide AppleTalk network
allows different networks to see each other’s Macintosh networking setup. Fileservers,
printers, and other network devices are visible from remote networks. The following
examples illustrate how this can be used in our university setting:
• A student sitting in Lincoln Hall can easily see a server in DCL, and read class files
off of the server.
• A professor in the Vivarium can print a copy of a memo to the printer in his
secretary’s office in Morrill Hall.
• A masters student in Everitt Lab can leave a draft of her thesis on her advisor’s hard
drive in Beckman.
Many departments find that having AppleTalk routed over the backbone offers
convenience to their staff and students. It makes it easier to share documents and also to
work while out of the office.
If AppleTalk is so great, why don’t you just give it to everyone?
AppleTalk is great, but there are some caveats when it is used in a large network like the
campus-wide AppleTalk. There are network numbers that have to be coordinated, file
server and workstation security problems to be addressed, printer access to control, a
Macintosh Operating System (OS) limitation, and there are certain costs involved.
Network Numbers
Each AppleTalk network has a network number, or range of numbers that has been
assigned to it (for more detail see Appendix A). What this number is doesn’t matter if you
only have one network. However, the campus is made up of many small networks all
hooked together, and each of these must have its own unique number. If two networks
that are on the campus-wide AppleTalk are using the same network number(s), it could
3
cause problems for both networks and anyone trying to reach them. Because of this CCSO
uses filters on the routers to ensure that you can’t interfere with other networks. The
filters keep any network information that CCSO hasn’t checked for compatibility from
being seen on the network.
Server and Workstation Security
Fileservers usually have logins and passwords to keep people from accessing files that they
shouldn’t. Most file servers also come with some kind of guest access for people that don’t
have their own login. Guest accounts aren’t bad if the Fileserver’s administrator has
restricted the access that the guest can have. Unfortunately, the default privileges for the
guest user (called “Guest”) under System 7’s Personal File Sharing is full read and write
access to the entire hard drive. Under System versions 7.0 and 7.0.1, just turning on File
Sharing turned Guest on. Under System 7.1 turning File Sharing on doesn’t turn Guest on,
but turning Guest on gives Guest full access to everything. With full access, a guest can
read any files, copy licensed software, and even erase files on the hard drive. Because of
these defaults, network administrators are cautioned to educate all of their Macintosh
users about File Sharing and guest access before asking for AppleTalk to be enabled for
their network.
Printer Security
Printer access is a smaller issue, usually only of interest to groups that have expensive
color printers. Because all devices are visible over the campus-wide AppleTalk, it is
possible to print to almost any printer on AppleTalk from any Macintosh on campus. It is
possible to use hardware devices between the printer and the rest of the network to isolate
them, but it isn’t always practical. Printer access has not been a problem for most groups on
campus.
System 6 Chooser Limitations
Macintosh System 6.0.x and earlier versions of the OS have a software limitation in the
Chooser. The Chooser is the part of the Macintosh OS that allows the user to select what
file server or printer to use. The amount of memory allocated to hold the list of zones and
the list of devices in the Chooser was quite small in early versions of the Macintosh OS,
and a very limited subsection of the zones can be viewed at any one time. There is no way
to control which zones show up in the list, and although often the computer’s own zone
does show up, there is no guarantee that it will. This keeps System 6.0.x users from being
able to access the services they want with any regularity. There are software packages that
can be purchased that address this problem.
Cost
Last and least is money. Each of the routers that hook the individual networks together
must have special software loaded in order to route AppleTalk. There is a per-router
charge for this software, as well as a monthly maintenance fee. AppleTalk is provided free
to any network that requests it, but since there is a cost to CCSO, it must be requested.
4
What you have to do to get on the campus-wide AppleTalk
It is fairly simple to get on the AppleTalk backbone. There are three steps you must go
through. First, your network needs to be set up according to the campus standard. You
must be using your unique network numbers, and have as few zones on your network as
possible (usually one zone is enough). For information on calculating network numbers,
see Appendix A. When naming your zone, keep in mind that the name needs to be
descriptive. It will be one zone in a list of over one hundred zones on the campus-wide
AppleTalk. People will have to search through this list to find your zone if they need to
access your devices, so it needs to be descriptive or well known.
Second, the network administrator needs to contact CCSO to coordinate the network
information. To do this send E-mail to appletalk@uiuc.edu. The network administrator
should provide the network information in the E-mail — the router’s IP number, the
EtherTalk1 network range, the zone name(s) on the EtherTalk, the network numbers and
zone names of any LocalTalk or other networks that should be seen on the campus-wide
AppleTalk, and the name, E-mail address and phone number of the network
administrator. Any network numbers or zone names that are not provided to CCSO, will
not be seen on the campus-wide AppleTalk. If there is a network or a zone that you do not
wish to be seen on the campus-wide AppleTalk, please provide this information as well,
and it will not be seen. Please note that all network numbers and zone names on the
Ethernet will be seen by campus. It is only possible to “hide” networks or zones that are on
other networks (for example a LocalTalk segment, or an Ethernet behind another router in
the building).
Third, wait patiently. After everything checks out it can take as long as a week for
AppleTalk to be enabled in the router. When it is enabled your network will be part of the
campus-wide AppleTalk.
What not to do if you are on the campus-wide AppleTalk
There are a few things that you shouldn’t do on your network if you are on the campuswide AppleTalk. Installing a routing device with incorrect configurations, setting up an
AppleTalk tunnel to another network, and changing the configuration of the existing
AppleTalk networks without notifying CCSO can all cause problems for your entire
network. Doing any of these could cause your AppleTalk network(s) to not be seen on the
campus-wide network.
Installing Routers
If you install a new GatorBox, FastPath, ARA server, Shiva NetModem, copy of Liaison,
copy of LocalPath, or any other device or software package that routes AppleTalk traffic, the
default configuration will not usually be set to match the campus standard. If you need to
add a device or software package like these, configure it before you plug it in to the
network. If you don’t know how to configure it, you need to find someone that does. If you
1 When not otherwise qualified, EtherTalk refers to EtherTalk Phase 2, as EtherTalk Phase 1 is no longer
supported by Apple, nor is it routed on campus.
5
aren’t the network administrator, and you are installing one of these devices, you need to
coordinate it with the building network administrator. If you are the network
administrator, then there is someone at CCSO that can help you set it up. Send E-mail to
net-trouble@uiuc.edu, and someone there will be able to help you. The resources of the
support group are very limited, so they will not help people who are not network
administrators, they will just direct a non-network administrator to contact the building
network administrator for their network. Incorrectly configured network devices, could
keep part or all of your network from showing up on the campus-wide AppleTalk
network.
Creating Tunnels
Before AppleTalk was routed on the campus network, some groups shared AppleTalk
networks using AppleTalk tunneled inside IP packets. This typically required a GatorBox at
each end of the tunnel, and resulted in a larger AppleTalk network. Now that AppleTalk is
being routed, tunneling is not an acceptable means for a network to join the campus-wide
AppleTalk. If you do set up a tunnel with someone after you are on the campus-wide
AppleTalk, their network will not be able to see the campus-wide network, although they
will be able to see your network. If a network wants on the campus-wide AppleTalk
network, they need to go through CCSO.
Changing the AppleTalk configuration
The router for your network needs to know about any AppleTalk information you want to
be seen on the campus-wide AppleTalk. If the router doesn’t have the correct numbers and
zones for the EtherTalk that is attached to your network, no traffic will be passed off the
network. If you have LocalTalk or other AppleTalk networks, the router needs to know
the network numbers and zone names on these network, or they won’t be seen by the rest
of campus. If you make a change to your AppleTalk configuration, you need to let CCSO
know so that the router can be updated. To do this send E-mail to appletalk@uiuc.edu, and
coordinate the change with CCSO people.
6
Appendix A
Network Numbers — How to compute them, and how to use them
How we create unique AppleTalk network numbers on the UIUC campus
In the past, to guarantee the uniqueness of a network’s AppleTalk numbers, the AppleTalk
addresses were based on part of the network’s IP addresses, as IP addresses must also be
unique to work. When UIUC used only one subnet, this insured that there were no
duplicate AppleTalk addresses. Now that there are two subnets being used on campus,
things are slightly more complicated. The exact method of calculating AppleTalk network
numbers from your network’s IP address is as follows:
The AppleTalk network numbers are based on the lower 16-bits of the IP addresses. If your
network is part in the 128.174.0.0 address space, then if the first IP address of a subnet is
A.B.C.D (ex: 128.174.18.128 or 128.174.18.0), then the first AppleTalk address in the network
is C*256+D (ex: 18 * 256 + 128 = 4736 or 18 * 256 + 0 = 4608)2. The second number (if needed)
would be C * 256 + D +1 (ex: 18*256+0+1 = 4609).
If your network is in the 130.126.0.0 address space, then the first AppleTalk address in the
network is based on the last number in the subnet (ex: if the mask for the 130.126.18.128 net
is 255.255.255.128, then the last IP address (the broadcast address) would be 130.126.18.255, so
the first number in the AppleTalk range for that net would be 18 * 256 + 255 = 4863). The
second number would be based on 130.126.18.254 (18 * 256 +255 -1 = 4862). For a detailed
list of starting network numbers based on IP address, see Table A.1 below.
mask
subnet
start
255.255.255.240
255.255.255.224
255.255.255.192
255.255.255.128
255.255.255.0
255.255.254.0
C.D
C.D
C.D
C.D
C.D
C.D
128.174.C.D
EtherTalk range
(C*
(C*
(C*
(C*
(C*
(C*
256)
256)
256)
256)
256)
256)
+
+
+
+
+
+
D
D
D
D
D
D
subnet end
(broadcast)
130.126.C.D
EtherTalk range
number of
hosts
C.(D +15)
C.(D + 31)
C.(D + 63)
C.(D + 127)
C.(D + 255)
(C + 1).(D + 255)
(C * 256) + D + 15
(C* 256) + D + 31
(C* 256) + D + 63
(C* 256) + D + 127
(C* 256) + D + 255
((C+1)* 256) + D + 255
13
29
61
125
253
506
Table A.1 – EtherTalk ranges calculated for IP subnet A.B.C.D, with mask indicated.
Table A.1 is easier to use than it looks. Here’s how it works:
example 1: subnet 130.126.10.32 has mask 255.255.255.224
Start with the row beginning with mask 255.255.255.224, and then look at the column
labeled “130.126.C.D EtherTalk range” which says (C * 256) + D + 31. For subnet
130.126.10.32, C = 10, and D = 32. The formula becomes (10 * 256) + 32 + 31 == 2560 + 63 ==
2623. So the AppleTalk network number for your Ethernet is 2623, and the “next” number
if you need it for LocalTalk or a NetWare server would be 2621, then 2620, etc. (skip one
number for expansion).
2 If you do not understand why the IP address of your network is not the same as the IP address of your router,
please see Appendix D.
7
example 2: subnet 128.174.10.32 has mask 255.255.255.240
Start with the row beginning with mask 255.255.255.240, and then look at the column
labeled “128.174.C.D EtherTalk range” which says (C * 256) + D. For subnet 128.174.10.32 C =
10, and D = 32. The formula becomes (10 *256) + 32 = 2560 + 32 = 2592. So the AppleTalk
network number for the Ethernet is 2592, and the “next” number if you need it for
LocalTalk or a NetWare server would be 2594, then 2595, etc. (skip one number for
expansion).
There is a chance that the network numbers might overlap between networks on
128.174.0.0 and 130.126.0.0, so CCSO must check all AppleTalk numbers before you use
them. To do this, send E-mail to appletalk@uiuc.edu. Please include your network’s IP
address (in most cases this is one less than the IP address of your router), your network’s IP
mask, your E-mail address, and the number(s) that you have calculated as your AppleTalk
network numbers. If there is a conflict or it looks like there might be a conflict in the
future, CCSO will assign you other numbers that will not be in conflict.
Things to keep in mind when assigning network numbers
When deciding how large an EtherTalk range should be, it is a good idea to keep in mind
how many devices you might want to support on the network in the long term. A range of
size 1 (the same number for start and finish — ex: 4736-4736) supports 253 network devices.
A range of size 2 (ex: 4736-4737) would support 506 devices. Table A.2 shows the first 7
ranges.
range of numbers
1
2
3
4
5
6
7
total # of nodes supported
253
506
759
1012
1265
1518
1771
example
4736-4736
4736-4737
4736-4738
4736-4739
4736-4740
4736-4741
4736-4742
Table A.2 – Range vs. nodes supported
The standard on campus is for the Ethernet connected to the building router to use the first
number in the range, so the typical EtherTalk range in this example would be 4736-4736.
After numbering the EtherTalk range, the next numbers are available for the LocalTalk
segments. It is a good idea to skip a number after the EtherTalk range in case the network
needs to be expanded. So if on a 128.174 subnet the EtherTalk is 4736-4736, one would
probably use 4738 for the first LocalTalk, 4739 for the second, etc. For a 130.126 subnet, you
are starting at the highest number and working down. If your subnet is 128.174.18.0 and
your mask is 255.255.255.0, then your EtherTalk would be 4863, and you would skip 4862
before using 4861 as your first other number.
8
Appendix B — Example of network addressing and routing
As an example of how network ranges and node number acquisition works, let's say there
is an Ethernet with a range 200-203 (supporting 1012 total nodes on the Ethernet) and a
LocalTalk with the net number 205 (supporting 254 total nodes on the LocalTalk). There is
a GatorBox acting as a router between the Ethernet and LocalTalk networks. The network
structure would look something like this:
200.230 GatorBox
UIUCnet
205.220
LocalTalk
Ethernet
repeater
On an extended network, such as an EtherTalk network, when a node is powered on, it
gets a temporary network and node addresses. The first time the node is powered on, the
network address is chosen randomly from the reserved startup range of 65280-65534. The
node address is chosen randomly from 1-253. If the node has been started on a network
before, it will first try to use the last network and node numbers that it had. If all the node
numbers are taken on the network, then it will use a network number from the startup
range, and an unused node number on that network. Then either way it asks for a router
to tell it what the current network number is, and adjusts its numbers accordingly. For
example:
Mac1 is on the Ethernet, and when it was turned on it asked for net information, and
“remembered” that it’s last address was 201.5. No one else was using that address, and the
router confirmed that the network number was okay so Mac1 kept 201.5.
Mac2 is on the Ethernet and it “remembered” that its last address was 200.40. No one else
was using that address, and the router confirmed that the network number was okay so
Mac2 kept 200.40.
Mac3 is on the Ethernet and tried 201.5, but Mac1 said "hey, that's me" so Mac3 had to try
again, so Mac3 ended up with 201.6, after the router confirmed that 201 was a valid
network number.
On a nonextended network, such as a LocalTalk network, the node address is remembered,
and the network address requested from a router. If no router answers, it will use a
network number of 0. For example:
Mac4 is on the LocalTalk and remembered node number 30, and the GatorBox told Mac4
that the network number was 205, so Mac4’s address was 205.30.
9
Here’s an idea of what this network might look like:
200.230 GatorBox
UIUCnet
Ethernet
205.220
LocalTalk
repeater
Mac1
201.5
Mac2
Mac3
201.5
200.40
Mac4
205.30
201.6
205.120
Now, if Mac4 wants to mount the hard drive of Mac1, then it sends out a request to 201.5.
Mac4 got the net number and node number of Mac1 when the user opens the chooser and
selected the volume. Nothing on the LocalTalk knows anything about net 201 except the
GatorBox, which says "hey! that's on my other side" and passes on the request. The return
packets from Mac1 to Mac4 are addressed to 205.30, and again the GatorBox has to pass the
information, this time back to the LocalTalk side.
If Mac4 wanted to mount the hard drive of Mac2, it would send its request to 200.40,
everything else would be the same as it was for Mac1.
If instead of the above addressing scheme, the EtherTalk range was 200-200, the only thing
that would be different is that Mac1 and Mac3 would have addresses starting with 200, and
not 201. They would be restricted to that one network address, instead of having a range to
choose from, thus limiting the total number of nodes on that network to 253.
10
Appendix C — Glossary
AppleTalk — The name of the protocol suite that Apple Macintosh computers speak to
each other natively. AppleTalk addresses are in the form of ‘network.node.socket’. The
suite includes specific hardware protocols such as LocalTalk and EtherTalk, and higherlevel protocols such as the Printer Access Protocol and the Apple Filing Protocol.
Sometimes AppleTalk is incorrectly used to describe a LocalTalk network.
Ethernet — A physical layer specification that defines the hardware and media to be used
for the 10 Mbits/second carrier sense standard (IEEE 802.3). Ethernet has different cabling
types such as 10base2 (also called thinwire, thinnet, or cheapernet), 10base5 (also called coax
and thicknet), and 10baseT (also called twisted pair Ethernet).
EtherTalk — The protocol for sending AppleTalk over Ethernet. EtherTalk supports full
Ethernet speed and all of the different Ethernet cable types. In most cases EtherTalk refers
to EtherTalk Phase 2, as Phase 1 is no longer supported.
Phase 1 — the ‘old way’ of sending AppleTalk over Ethernet. No longer supported
by Apple, it only allows 254 nodes to be used on the Ethernet by supporting only a
single network number on the entire Ethernet. CCSO discourages the use of
EtherTalk Phase 1, since there are many devices that no longer support it. Phase 1 is
not routed across the campus backbone.
Phase 2 — the ‘new way’ of sending AppleTalk over Ethernet. A configurable range
of network numbers allows for extremely large numbers of nodes to be used on a
single network. Each network number in the range supports 253 nodes.
Theoretically you could have 16,515,587 nodes on the network, but a simple Ethernet
couldn’t support them.
Extended Network — An extended network uses a range of network numbers for
addresses, each network number in the range can support 253 nodes. A network range in
an extended network can support multiple zones, theoretically up to 255.
FDDI — An acronym for Fiber Distributed Data Interface, FDDI is a 100 Mbit/second token
passing ring that uses single or multi-mode fiber as its transmission medium.
FDDITalk — The protocol for sending AppleTalk over an FDDI Ring. It is very similar to
EtherTalk.
Internet — 1. Short for Research Internet, the Internet is a large group of networks that
have been connected world-wide. Originally used primarily for educational and scientific
work, it is available to anyone who can afford to purchase a connection. 2. A group of
smaller networks that have been hooked together so that traffic can pass between them.
IP — An acronym for Internet Protocol, IP is a network-layer protocol responsible for
directing information packets from one computer to another over an internet. IP accepts
11
data in segments, encapsulates the data in packets, and determines the correct path for
routing the packet to its destination.3
IP address — A 32-bit number assigned to each device on a TCP/IP network. IP addresses
are commonly written as 4 8-bit numbers separated by decimal points (dotted decimal
notation). This 32-bit number is used to identify the network, subnetwork and host address
of each machine. It also can be used to identify a network or subnet.
IPTalk — A way to have AppleTalk encapsulated in IP packets. This is often used with
Unix fileservers running the CAP software. If you aren’t running this software, you don’t
usually need to use IPTalk.
LocalTalk — 1. The name of the hardware connectors and wires made by Apple to do
AppleTalk over these wires. The characteristics of the Apple system include shielded
twisted pair wire, and self-terminating connectors. 2. The generic name of a network that
uses some brand of connectors to connect Macintosh devices to each other using the builtin AppleTalk port on the device. A LocalTalk supports up to 254 nodes on the network, at
a speed of 230 KBits/second.
Network numbers — Each physical AppleTalk network needs a unique network number.
AppleTalk network numbers are 16-bit numbers. The network number ensures that traffic
from one network can be distinguished from traffic on another network when the two are
connected with a router. In particular if a network wishes to be on the campus-wide
AppleTalk, the numbers must be unique across campus. How numbering works is
different depending on the type of network you are using:
Nonextended Network — A nonextended network uses a single network number
that is the address of a LocalTalk or of an EtherTalk Phase 1 network. Each
nonextended network can only have a single zone. Two examples of nonextended
networks, and how their numbering works are:
LocalTalk — All LocalTalk networks have a single network number, which
can theoretically support up to 254 nodes. In reality, 254 is way too many
nodes for a LocalTalk network.
EtherTalk Phase 1 — Phase 1 works just like the LocalTalk does, with one
network number that supports up to 254 nodes. When Ethernet networks
started getting larger than 254 nodes, Phase 1 broke. Phase 1 is no longer
supported by Apple.
Extended Network — An extended network uses a range of network numbers that
are the addresses of an EtherTalk Phase 2 network. A network range in an extended
network can support multiple zones, theoretically up to 255. Two examples of
extended networks, and how their numbering works are:
EtherTalk Phase 2 — Phase 2 is how Apple changed the network numbering
3 From the Cayman GatorBox manual, Appendix A: Glossary (available from ftp.cayman.com as glossary.txt
and glossary.ps).
12
scheme. Instead of a single network number, it uses a range of network
numbers each of which can support up to 253 nodes. One can make a range of
1 that supports 253 nodes, or a range of 40 that supports 10120 nodes. This
allows for significant growth in a network. EtherTalk Phase 2 is commonly
just called EtherTalk.
FDDITalk — uses the exact same numbering system as EtherTalk Phase 2.
Node — A number between 1 and 253 on extended networks, and between 1 and 254 on
nonextended networks. It is unique for a device on a physical network. This number is
determined by the device at its boot time, and it keeps that number (at least) until it is
powered off or restarted. Node numbers 1-127 are “client” numbers (ie: regular
Macintoshes), and numbers 128 - 253 (254 for nonextended networks) are “server”
numbers (ie: printers and file servers).
Nonextended Network — A nonextended network uses a single network number that is
the address the network, and supports 254 nodes on the network. Each nonextended
network can have only a single zone.
PhoneNet Connector — The name of the hardware made by Farallon to do LocalTalk over
a regular phone cable, in order to utilize existing phone wire like the campus B-Jacks. The
connector is not self terminating, so if only 1 cable is connected, a terminating resistor
must be used in the empty port on the connector. Both ends of a PhoneNet network must
be terminated. If one end of the network goes into a B-Jack, then it is terminated at another
location.
Protocol — A set of rules that allows different devices to intercommunicate on a network.
Router — A router is a device that moves some kind of network traffic between two or
more networks. It does this by looking at a destination address in the traffic off of the first
network, and copying the traffic to whichever network gets the traffic closer to the network
that the address in the traffic indicates is the destination. Depending on the type of router,
the address could be one of many different protocols, such as AppleTalk, IP, or DECnet.
Socket — A socket is a logical entity in a node connected to an AppleTalk network. A
socket is owned by software that can send and receive data through the socket. There can be
254 different sockets on a node, and various sockets are reserved for different things.
TCP — An acronym for Transportation Control Protocol, TCP is responsible for keeping
track of packets of data, and retransmitting them if they are lost.
TCP/IP — The common name of the Department of Defense (DOD) protocol suite which is
the standard of communication for the Internet. TCP and IP are not the only protocols in
the suite, just the two most commonly used ones.
Token Talk — The protocol for sending AppleTalk over an IBM TokenRing. It supports
both 4 Mbit and 16 Mbit rings.
13
Tunnel — An AppleTalk tunnel is a connection between two networks who have at least
one other network between them that is not routing AppleTalk. A typical AppleTalk
tunnel would be to have a GatorBox on the first network that encapsulated the AppleTalk
packets inside some other kind of packet such as IP, and then sent the packet to a GatorBox
on the second network. Then the GatorBox on the second network would take the
AppleTalk data out of the IP packet, and put the information out on its network as an
AppleTalk packet.
TurboNet Connector — The name of the hardware made by Focus Enhancements Corp.
which is basically the same device as Farallon’s Phone Net Connector. It costs less and has
LEDs that indicate traffic flow. It also has self terminating ports that don’t need resistors.
Zone — Also Zones, or Zone Name. A zone is basically a text name that represents some
parts or all of a network. Zones make it easy to find groups of devices in the Chooser. A
zone can consist of only one network, or it can group together several network numbers
into a single “logical” network. This allows devices on EtherTalk and LocalTalk networks
to be seen together in the Chooser under one name. Thus allowing all departmental
servers and printers to be found in one place, even if they have more than one network. It
is also possible to have a list of zone names that are all used by a single extended network.
Any zones in that list could also be used on other networks. Here are some examples of the
use of zone names on networks:
Network Type
Network Number(s)
Zone(s)
EtherTalk
4608-4608
CCSO-Staff
CCSO-NDO
LocalTalk
4611
CCSO-NDO
EtherTalk
8448-8449
CCSO-Staff
LocalTalk
8450
CCSO-Staff
EtherTalk
51456-51456
CCSO-Resource Center
CCSO-Staff
LocalTalk
51458
CCSO-Resource Center
Any machine on the network 4608-4608 could choose between zones CCSO-Staff and
CCSO-NDO, while a machine on 4611 would have to be in CCSO-NDO. A machine on
8448-8449 or 8450 would have to be in CCSO-Staff, while a machine on 51456-51456 could
choose from CCSO-Staff or CCSO-Resouce Center. Any machine on 51458 would have to
be in CCSO-Resource Center. So while only three zones would show up in the chooser,
there would actually be 6 networks that were connected and accessible.
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Appendix D — IP subnetting
IP routing is a very important part of all UIUC networks. Even though it might not be
obvious, IP routing is a very important part of AppleTalk routing on the UIUC networks
as well. The most important thing to realize about an IP address, is that even though it is
most commonly written as four decimal-seperated numbers, it is really one 32-bit
number.4 Each IP address conveys what network, sub-network, and host the IP address
represents. This quick look at IP subnetting does not cover all of the detail of IP subnetting,
it only looks at the parts that have something to do with calculating your AppleTalk
network numbers.
128.174.0.0 (80AE0000 in hexadecimal, or 2158886912 in decimal) is the address of the main
network on the UIUC campus, this is why almost all of the IP addresses on campus start
with 128.174. There is no machine with an address of 128.174.0.0, this number represents a
network assigned to UIUC. The information provided by this number is used by networks
outside of the 128.174.0.0 network, so that they can route traffic correctly. Since they know
that any IP address that starts with 128.174 is located at UIUC, they can send traffic for that
IP address to UIUC routers. The local routers then use the rest of the number in the IP
address to send the traffic to the correct host.
128.174.18.0 is the address of the subnet assigned to a network on campus. No machine has
this address, but the routers on campus know that any IP address that starts with 128.174.18
should be forwarded to this network. 128.174.81.240 is the address of another subnet on
campus, even though to many people it looks like it should be a machine on the subnet
128.174.81, it isn’t. UIUC uses variable length subnets, and the only way to tell what is the
subnet and what is the host is to use the mask.
To understand what masks tell you, you have to think of the IP address and mask in
binary. The mask represents the network part of the IP address with ones, and the host part
of the address with zeros. For the IP address 128.174.18.2, the mask is 255.255.255.0 in dotted
decimal. To see which part of the IP address is the network and which part is the host, first
write the two numbers in binary and line them up:
128.174.18.2
01000000
255.255.255.0
11111111
network part
01000000
host part
first EtherTalk network #
first EtherTalk network #
10011110
11111111
10011110
128.174.81.245
01000000
255.255.255.224
11111111
network part
01000000
host part
first EtherTalk network #
first EtherTalk network #
10011110
11111111
10011110
00010010
11111111
00010010
00010010
00010010
01010001
11111111
01010001
01010001
01010001
00000010
00000000
00000010
00000000
11111111
(128.174 network)
(130.126 network)
11110101
11100000
111
10101
111 00000
111 11111
(128.174 network)
(130.126 network)
4 A 32-bit number is a number that if written in binary would have no more than 32 ones or zeros. An 8-bit number
has no more than 8 ones or zeros, etc.
15
If the host part of an IP address is all zeros, then that IP address is indicating the network,
not a specific host. If the host part of an IP address is all ones, then that IP address is
indicating all machine on the network (the broadcast address), not a specific host.
However, if the host part isn’t the entire last 8-bit number then it isn’t always obvious that
this is what is going on.
The IP network number is what is used to calculate the first EtherTalk network number on
a 128.174.0.0 subnet, the IP broadcast address is used to calculate the first EtherTalk network
number on a 130.126.0.0 subnet. The second EtherTalk number in a range greater than one,
or any other LocalTalk or other network numbers uses the next few IP addresses on the
net, starting with the first usable address of the subnet for the 128.174.0.0 subnets, and the
last usable addresses for the 130.126.0.0 subnets.
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