Appletalk The Tutorial

Appletalk The Tutorial f

05.02.01

I, like many network engineers, have little experience with the Appletalk protocol. It is not that I have avoided it (although I hear that I should!), I have just not encountered it in any of the networks that I have worked on. I have found what appears to be an excellent tutorial on Appletalk that you may want to hold on to in event that you do need to use this protocol. Read on and enjoy!

Best Wishes,
Jay

WHY IS THIS HERE?
I just recently had the misfortune of having to troubleshoot an Appletalk networking problem that took over a month to resolve. I learned a lot more about Appletalk than I had ever wanted to, but the most important thing that I learned is that there aren't very many people who know anything about it, which is why I am writing this tutorial. Apple is selling a ton of computers right now with the release of the IMAC which increases the chances that you will wind up in a situation like I did. Fortunately, Apple will be abandoning Appletalk in the near future (they know it sucks too).

INTRO
Appletalk is a suite of protocols developed by Apple designed to have the following features:

- Plug and play - Link independence - Simplicity - Peer-to-peer networking

In this suite of protocols are sub protocols that perform many of the same functions as protocols that you may already be familiar with, like TCP/IP. For example, Appletalk has a Name Binding Protocol(NBP) which is very similar to DNS. There is Apple Address Resolution Protocol(AARP) which is similar to ARP. We will not go into much depth on each of these as it is outside the focus of this paper. We will mainly concentrate on addressing and routing.

ADDRESSING
Before getting into addressing there are a few terms that you should be familiar with.

Network number A 16-bit number that identifies the network to which a node is connected.

Node ID Each appletalk device receives a unique 8 bit node number.

Zone name Zones are logical groupings of devices similar to workgroups or domains in a Windows environment.

Socket number An 8-bit number that identifies a socket.

Appletalk addresses appear in the form of xxx.yyy, where x is the network number and y is the node number.

NON-EXTENDED NETWORKS
There are 2 types of Appletalk networks - Phase 1 and Phase 2. Phase 1 networks are also referred to as "non-extended". An AppleTalk nonextended network is one in which:

The network has one network number assigned to it. The network supports only one zone.

All nodes on the network share the same network number and zone name. Each node on the network has a unique node ID.

Since appletalk uses an 8 bit node ID, it can support up to 255 devices, however, 255 is reserved for broadcasts and 0 + 154 are reserved leaving 253 possible nodes.

EXTENDED NETWORKS
An AppleTalk extended network is one in which: The network has a range of network numbers assigned to it The network supports multiple zones. Each node on the network has a unique network number node ID combination to identify it.

Phase 2 allows multiple zones to be associated with a network number range and is the more common of the 2 types, in fact, you will rarely run into a phase 1 network anymore. Appletalk uses network numbers to identify cable segments. Valid numbers are between 1 and 65,279. Network numbers 65,280 and up are reserved for non-extended networks. Each of these networks can support up to 253 nodes for a total of over 16 million possible nodes. Of course, Appletalk is so chatty that this network would never be able to function.

ROUTING
So where do Appletalk devices get their network and node numbers? Well, it depends on the type of network. In a non-routed or peer-to-peer network, it works on a first come first serve basis. The network number will start at 65,280 and node number will start at 1. In a routed network, things behave a little differently. There are 2 types of routers as far as Appletalk is concerned. They are "seed routers" and "learning routers". Seed routers are responsible for "seeding" the network, which means that they define network numbers and zones to be assigned to each Appletalk device. In many ways, this process behaves much like DHCP. Each Appletalk device dynamically receives a network number and node number from the seed router and if the device is rebooted it will attempt to attain the same network number and node ID. This information is stored in the device's PRAM.

On the other hand, a learning router gets it's Appletalk information from a seed router and does not propagate network information.

In order to route packets successfully, all routers on a network segment must know the network number range and zone list to use for that segment. The network range is a contiguous range of valid network numbers. The size of the network range determines the maximum number of nodes allowed on that network. The zone list for each segment can contain up to 255 zone names, one of which is designated as the default zone. All routers on the network must agree on the network range and the contents of the zone list. They must also agree which zone from the zone list is the default zone for that network.

When an AppleTalk router is added to the network or brought back on-line after a shutdown, it propagates a list of its zones and network numbers. It also receives information from all adjacent routers on the network. This information is stored by each router in a routing table. This routing table is maintained by the Routing Table Mapping Protocol(RTMP). The routing table includes information about all of the networks it can see, including their network number ranges, associated hop-counts (the number of routers it takes to get to the network),

the identifier of the next router needed to get to that network, and an entry state that tells whether the route is more likely to be reliable or outdated. This information can change as networks and routers are brought on-line and off-line.

NT SERVER AS AN APPLETALK ROUTER
An NT server can be used as a seed router or a learning router on an Appletalk network. Below, we will discuss how to do this.

First, you must install Services For Macintosh. Once this is completed and the server has rebooted, you will be able to configure your Appletalk settings. To do this, follow these steps:

Right click on "network neighborhood" and select properties. Select the "services" tab.

Highlight "Services for Macintosh" and click the "properties" button. Here you will see 2 tabs - General and Routing. Click on the routing tab. By default, the NT server is configured as a regular Appletalk device. If you click on the routing tab, you will see an option to make the server perform routing. Click this box makes the server act as a learning router. You will also see a "Use the router to seed the network" checkbox. If you select this one, the server will become a seed router. Once this box is checked, you will need to specify the network range that you wish to use. For performance and growth reasons, it is best to select the smallest range that will accommodate the number of Appletalk devices that you have on your network. For example, if you have 100 MACS on the network, then you should only use 1 network number as follows: For the range select something like 1-1. This means that only the network number 1 will be used. From the previous discussion, you will remember that each network number will support up to 253 nodes. Let's say that you had 600 appletalk devices. You would then want to specify a network range of 1-3 or some similar spread. This configuration would support up to 3x253 nodes which equals 759 possible nodes. Remember that the network numbers that you specify must be unique to that network segment.

Next, you will need to configure the zones. Click the "Get Zones" button to view the list of zones available. If no zones currently exist on the network, then you will need to create one by clicking the "Add" button at the bottom. Once these values are configured, you will be required to restart Appletalk for them to take effect. This one stumped me - I kept having to reboot the server because I could not find a place to restart Appletalk. Here is the secret: Go to the control panel and select "devices". Here you will have the ability to stop and restart the Appletalk protocol.

Finally, the most important thing regarding Appletalk routing... If any major changes are made on an Appletalk network such as removing a zone and the zone still shows up in the clients' chooser or other weird situation, you have to turn off ALL Appletalk devices, bring up your seed router and then bring up the rest of the routers and Appletalk devices.

TROUBLESHOOTING CONNECTIVITY
Following are some of the things that you can check out if having networking problems in a MAC environment. Keep in mind that these are just some of the basic steps to perform.

NOTHING SHOWS IN THE CHOOSER:
1) Make sure that you are in the right zone(if applicable). It is possible to have a zone with nothing in it.

2) Go to the Appletalk control panel and make sure that it is set to the correct connection type(i.e. ethernet). If you are aware of the network number that the MAC should be picking up from a seed router(if applicable), from the edit menu select "user mode" and change it to "advanced". You will then be able to see the network and node numbers that the MAC is picking up.

3) Go to the chooser and make Appletalk inactive. Wait about 10 seconds and reactivate it.

4) Check your cabling and when you are done with that double-check your cabling.

5) As with any computer, try rebooting it just for fun.

ONE OR MORE DEVICES NOT SHOWING UP IN THE CHOOSER:

1) Make sure that you are in the right zone (if applicable). Make sure that the other device lives in the correct zone.

2) Make sure that the device that you are looking for is actually turned on. You wouldn't believe how many times this one gets overlooked.

3) Can you see the device from any other Macs? If not, make sure that your sharing is set up correctly.

4) Check the Appletalk settings of the device and make sure that it is picking up the correct network number.

5) Still not working? Contact the manufacturer of the device in question.

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TROUBLESHOOTING PRINTING
This section will be a little vague, but should still be helpful. If it is not a problem that was already covered in the previous troubleshooting section, then odds are good that it is 1 of 3 things as follows:

1) The most common issues involve incorrectly configured drivers. Check with your printer manufacturer on this one. The legacy of printers and drivers on the MAC is a complicated one that involves many incompatibilities that depend on OS version, driver type, driver version, printer model, PPD, etc...

2) If you are experiencing strange behavior when printing, especially when involving multiple printers, you may have a problem with your desktop printing extensions. Over the years, desktop printing has been flaky at best. It is advisable to just disable it if possible. If this is not an option, try the following steps:

Disable all desktop printing extensions. Trash your printing preferences Re-enable desktop printing extensions During reboot, rebuild the desktop Allocate more memory to desktop printing

3) Try turning background printing off.

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