AppleTalk Protocols
This section lists the AppleTalk protocols implemented in NetWare for Macintosh and provides a brief description of their basic functionality. It also provides some information about how AppleTalk zones work on an internet that will be useful to AppleTalk internet administrators.
This section provides a basic introduction to the AppleTalk terms and concepts used in this guide. For a complete introduction as well as the complete technical specification for AppleTalk, please see Inside AppleTalk, Second Edition.
Figure 75 shows the AppleTalk protocols implemented in NetWare for Macintosh. The diagram below represents the standard AppleTalk protocols as described on page I-20 of Inside AppleTalk:
Figure 75
AppleTalk Protocols
Table 30 explains the role of each of the AppleTalk protocols.
Table 30. AppleTalk Protocols
| Protocol | Description |
|---|---|
AFP |
(AppleTalk Filing Protocol). AFP allows Macintosh users to share files by interacting directly with the NetWare file system, at the same level as NCP interaction. |
PAP |
(Printer Access Protocol). PAP allows Macintosh users to access printers or print queues on the AppleTalk network. |
ADSP |
(AppleTalk Data Stream Protocol). ADSP allows two programs to communicate via a full-duplex data stream connection in which either program can read or write data bytes with reliable delivery. |
ZIP |
(Zone Information Protocol). ZIP maps zone names to network numbers and uses queries to maintain this mapping when new zones are added to an internet. AppleTalk uses zones to logically subdivide the internet so that the names of services are easier for users to find. All service name- searching is done within one zone at a time. The ZIP protocol is used by routers to request and provide zone information when a router comes up with a new network configuration. Please see How Zone Information Is Maintained on an Internet. |
ASP |
(AppleTalk Session Protocol). ASP works with and extends ATP functionality (described below) by allowing two processes to exchange a sequence of transactions reliably. |
RTMP |
(Routing Table Maintenance Protocol). RTMP is used by routers to exchange routing information needed to build and maintain each router's routing table. When a router receives a packet, it consults the destination network number in the packet and compares it with the network numbers in its routing table; it can thereby find a way to route that packet to the destination network or to another router closer to the destination network. All AppleTalk routers on the internet continuously maintain their routing tables by exchanging RTMP packets. Please see for more information. |
AEP |
(AppleTalk Echo Protocol). AEP is a support protocol that provides a way for a node to "bounce" a packet off another node. In NetWare for Macintosh , both the router and the stack support the Echo protocol. The ATCON utility provides an Echo test function. |
ATP |
(AppleTalk Transaction Protocol). ATP is a basic transport protocol that provides loss-free transaction services. ATP detects errors and timeouts, providing reliable packet exchange. |
NBP |
(Name Binding Protocol). NBP maps names (user-designated character strings) to network addresses and to services. When users request an AppleTalk service such as a printer in the Chooser, NBP is responsible for broadcasting the request in the selected zone and displaying the names of responding services in the Chooser. One or more routers might forward the request to the appropriate zone. See AppleTalk Zones. |
DDP |
(Datagram Delivery Protocol). DDP opens sockets on AppleTalk nodes and permits datagram (packet) delivery between sockets. It provides a mechanism to address any node on an AppleTalk internet uniquely. |
LLAP |
(LocalTalk Link Access Protocol). LLAP is AppleTalk's data-link level protocol for LocalTalk. At this level, AppleTalk adds hardware-specific header information and sends packets out onto the specific hardware link. See Frames for Nonextended Networks. |
ELAP |
(EtherTalk Link Access Protocol). ELAP is AppleTalk's data-link level protocol for Ethernet. At this level, AppleTalk adds hardware-specific header information and sends packets out onto the specific hardware link. See SNAP Frames for Extended Networks. |
TLAP |
(Token Ring Link Access Protocol). TLAP is AppleTalk's data-link level protocol for Token Ring. At this level, AppleTalk adds hardware-specific address and other "packet-frame" information and sends packets out onto the Token Ring hardware. Please see SNAP Frames for Extended Networks. |
AARP |
(AppleTalk Address Resolution Protocol). This protocol maps AppleTalk addresses (network and node numbers) into Ethernet or Token Ring hardware addresses and is used to manage the process of each AppleTalk node acquiring its unique node address on these media. |
An AppleTalk zone is a logical grouping of devices that enables users to locate and access network services in the Chooser. A zone name is a logical name associated with some or all of the services on a network or a set of networks.
When you configure AppleTalk zone names in the router, the zone names act as a top-level organizer in the Chooser. A user selects the zone name that indicates where a service is located; for example, a zone named "Building 1" or "Engineering" could indicate where a printer or file server resides. After selecting a zone name, the user clicks a service icon (such as the file server or printer icon) and these events occur:
Figure 76
How Services Are Accessed in a Zone
In NetWare for Macintosh, the default zone is always the first zone name entered in a zones list. Macintosh workstations always belong to the default zone until the Macintosh user explicitly chooses another zone in the Macintosh Control Panel. The zone in which a Macintosh workstation is registered is the zone in which its services (if any) will be advertised. It does not restrict the Macintosh user's ability to view and access network services in other AppleTalk zones by using the Macintosh Chooser. On an extended network, a Macintosh workstation is automatically registered in the default zone. To register in another zone, the Macintosh user should perform these steps: When you bring up an AppleTalk router on the network, it is initialized with its own zones and network numbers. It then begins to receive and send RTMP packets with every other router on the internet. When other routers receive RTMP packets informing them of a new network on the internet, those routers send a query to the router that represents the new network, asking for the zone name or zones list associated with the network. The new router responds to this query with its zone information. Eventually, all routers on the internet have an updated global list of all zones on the entire internet. This global list allows all Macintosh users on the internet to see services in all AppleTalk zones. Once one router has acquired zone information from another router, it does not query for zone information related to that particular network again. As long as the network has a good entry in the routers' RTMP tables, there is no way to force routers to query for its zone information again. One of the side-effects of this situation is that routers are not automatically informed about changes to zone configurations. For example, if you delete a zone name from a router configuration for one AppleTalk network, routers connected to other networks still have the deleted zone name in their lists, so it continues to be visible in the Chooser. In addition, those routers are now inconsistent with the reconfigured router, because they are still maintaining the old zone information. This inconsistency can cause a zone name to show up in the Macintosh Chooser for some time after you have deleted it, and can even cause users to see zone names appearing and disappearing in the Chooser. The only way to update zone information in all routers is to wait long enough for the RTMP tables in all routers to recognize that the relevant network is down. This usually takes between ten and twenty minutes, but it can take longer on a large internet. (Alternatively, you can down all routers on the internet and bring them up again --- this action forces an update of the RTMP tables.) If you must reconfigure zones on a network, remember that all routers directly connected to that network must be reconfigured. To assure that the old zone names disappear uniformly on the internet, follow these steps: Down all AppleTalk routers directly connected to the network. To change the zone configuration in a server that already supports working AppleTalk ports, you must first bring down the AppleTalk router by unloading the AppleTalk module. To unload the AppleTalk module, type this command at the console prompt: UNLOAD APPLETLK <Enter>
If there are third-party AppleTalk routers in use on the internet, bring them down following the usual procedure for that router. Note that when you unload the AppleTalk module, AppleTalk is automatically unbound from its interfaces. Create the new zones list (or name) in a global ATZONES.CFG file, and copy the global file to SYS:SYSTEM on each file server. If you are not using ATZONES.CFG, you can manually edit the zone names in each server's AUTOEXEC.NCF file. NOTE: Make sure ten to twenty minutes have elapsed (or more, if your internet is very large) to allow other routers on the internet to recognize that the "old" zones are no longer there. If you are not sure that you have allowed enough time, check the RTMP table in one or more routers by using the ATCON utility, as described in Viewing the RTMP Routing Table.What Is the Phase 2 Default Zone?
How Zone Information Is Maintained on an Internet