TOPIC
This article contains information about the implementation of multihoming and multinode support in Apple products. This is an advanced technical article provided for informational purposes only. Apple will not provide assistance with interpreting or understanding this information.
DISCUSSION
Question: What is meant by the terms multihoming and multinode support? Answer: Multihoming is the term applied to the capability to communicate using more than one network interface (card), at the same time, using the same protocol. In such a situation, the different network cards can each be connected to different zones and have different addresses, but each must be using the same protocol, such as TCP/IP, AppleTalk, and so on. Multinode support (often referred to as Single link multi-homing), however, is the capability to communicate using multiple network protocol addresses through a single network interface (with different datalink addresses) using a single protocol.
Question: Which Apple products include multihoming or multinode support? Answer: Multihoming Support Open Transport 1.1 introduced AppleTalk multihoming support to developers at the API level. This change allowed developers to re-write existing applications to take advantage of this feature. With the release of Open Transport 1.1, AppleShare 4.2.1 incorporated AppleTalk multihoming support. With AppleShare 4.2.1, you can install multiple network interface cards into the server allowing users to connect to volumes and servers with the same name in different zones, allowing multiple network interfaces to be active simultaneously. By supporting multiple network connections, multihoming support provides additional "pipelines" to the server, which increases the amount of network traffic that can reach the server. This enables servers to support more clients, to offer greater total performance, and to increase the reliability of mission critical applications. Please note that multihoming does not bridge or route those network segments into a LAN. The network segments will not see each other by being connected to this one computer, but clients on the unique network segments will all see the AppleShare server. AppleShare IP 5 and 6 also take advantage of multihoming. Note that multihoming support is still limited to AppleTalk. The Apple Internet Router v3.0 modifies the Classic AppleTalk stack to allow multihoming. A re-write of the router is required to use the built-in AppleTalk multihoming capabilities of version 1.1 of the Open Transport/AppleTalk stack.
The ARA Client supports AppleTalk multihoming for a single limited case: two ports only--one LAN and one serial, in both Classic and Open Transport network configurations.
This configuration could also be loosely defined as multihoming because even though the Mac OS and DOS environments use the same network controller protocols, they appear as separate hardware addresses on the network. Essentially, one physical network interface appears as two. To further describe the full capabilities of these advanced Apple systems, the implementation of a protocol stack in the Mac OS or DOS environment may itself include multinode support. For example, the TCP/IP protocol stack installed in the DOS environment may support assigning multiple IP addresses to a physical interface using the primary hardware address. In this type of configuration, a Macintosh computer with the enhanced Ethernet controller, Open Transport 1.1 or later and a PC Compatibility Card can accept connection to three or more IP addresses. Note: By default, Open Transport/TCP can only be configured to use one port at a time. IPNetLink, a utility from Sustainable Softworks, http://www.sustworks.com/~psichel , removes this limitation. Tenon's MachTEN, http://www.tenon.com , and Vicom's SoftRouter and SurfDoubler products, http://www.vicomtech.com , also allow a Macintosh to use two or more ports concurrently with TCP/IP. Question: How does the network connectivity for the DOS and Mac OS environments on the enhanced PCI-based Power Macintosh computers differ from previous Macintosh computers using DOS or PC Compatibility Cards? Answer: In other Macintosh computers that use DOS or PC Compatibility Cards, you do not have multinode or multihoming support. Instead, you only have one effective instance of an TCP/IP protocol stack. You can be connected using either the Mac OS or DOS environment, but you cannot be connected using both environments simultaneously. Question: If I have a PC Compatibility card installed in an enhanced Power Macintosh ** or a Power Macintosh G3, can I install an additional network adapter card for use in the DOS environment? Answer: No. The installed PC Compatibility Cards are hard-coded to use the built-in Ethernet interfaces. However, you can add an additional network card to provide additional network services, such as AppleTalk for the Mac OS. The Mac OS and DOS environments would then use the built-in Ethernet for TCP/IP, and the Mac OS could use the Ethernet card for AppleTalk. Even though you are providing another network interface for the computer to use, you do not get any network performance advantage by doing this. However, this is a viable solution if the DOS and Mac OS environments need to be physically located on different networks. **Note: Following are the Enhanced Power Macintosh computers: |
|||||||||||||||||||||
| Document Information | |
| Product Area: | Communications-Networking |
| Category: | Protocol and File Format Information |
| Sub Category: | General Topics |
Copyright © 2000 Apple Computer, Inc. All rights reserved.