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From: garryh@seeding.apple.com (Garry Hornbuckle)
Newsgroups: comp.sys.mac.comm
Subject: Open Transport FAQ part 6 - Compatibility
Date: Tue, 31 Oct 1995 08:47:58 -0800
Organization: Apple Computer, Inc.
Lines: 259
Message-ID: <garryh-3110950847580001@seeding.apple.com>
NNTP-Posting-Host: seeding.apple.com
Apple Open Transport
Frequently Asked Questions
Part Six - Compatibility
Extracted from:
Open Transport Background Q & A
Version 1.8 (OT 1.0.8 Release)
October 19, 1995
Applications Compatibility
Q: Is Open Transport compatible with existing applications and network
extensions?
A: Apple and third party developers have to date announced over 130 Open
Transport compatible applications. A compatibility list is available from:
ftp://seeding.apple.com/opentransport/ OT_Compat_List
Open Transport provides "backward compatibility" services in four areas:
* to support existing applications using the documented AppleTalk APIs;
* to support existing applications using the documented MacTCP APIs;
* to support existing Chooser devices; and,
* to existing NuBus based network interface cards to work with Open Transport.
Q: How is backward compatibility for AppleTalk implemented?
A: AppleTalk applications backwards compatibility is accomplished by
intercepting all AppleTalk networking calls at the ".ddp" driver API.
Above this protocol layer, applications written to the classic AppleTalk
APIs continue to rely on the classic (680x0 based) implementation of
AppleTalk. Calls to the ".ddp" driver are translated to the corresponding
Open Transport XTI calls and are then passed to the new native
implementation of DDP for processing. The process is reversed for incoming
packets.
Using this approach, backwards compatibility is very robust - the
classic implementations of ADSP, ASP, ATP, NBP, ZIP, and PAP are actually
present (vs. simply mimicked). This also decreases the total memory
footprint of backwards compatibility as compared to an implementation
based on individual adaptation layers for each of the AppleTalk protocols.
The primary trade-off of this approach is that applications relying on
backwards compatibility do not gain any meaningful performance increases
on Power Macintosh; essentially only native DDP is actually in use in
these cases. (see Figure 1)
Open Transport/AppleTalk also includes broad support for existing
applications software and network devices that rely on the Chooser or the
Network Control Panel software for selection and configuration, known as
"cdevs" and "adevs" respectively.
Q: How is backward compatibility for MacTCP implemented?
A: TCP/IP (MacTCP) applications backwards compatibility is accomplished by
intercepting all MacTCP networking calls at the ".ipp" driver level. Calls
to the ".ipp" driver are translated to corresponding Open Transport XTI
calls and then passed to the native TCP/IP stack for processing. The
process is reversed for incoming packets.
This approach allows most MacTCP applications to benefit from the
native implementation of the TCP/IP protocols on Power Macintosh, at least
to some degree. While the backwards compatibility layer itself must run as
680x0 code, most of the handling of the packet happens in the new native
Open Transport/TCP implementation. The drawback of this implementation is
that "warts and all" backward compatibility is somewhat less robust;
applications depending on idiosyncrasies of MacTCP or referencing internal
MacTCP data structures are likely to need an update. (See Figure 1)
TCP/IP backward compatibility also includes targeted support for select
software products that rely on the MacTCP (or Admin TCP) Control Panel
software for configuration. Support for these software modules, known as
MacTCP Link Access Modules, or simply "mdevs", is more limited than that
provided for AppleTalk "adevs", due to certain technical considerations.
Q: How is backward compatibility for other network products implemented?
A: Certain networking extensions - such as MacIPX from Novell or PathWORKS
(LAT and DECnet) from Digital Equipment Corp. or Thursby Software Systems
- as well as applications such as Insignia Solutions SoftWindows do not
access the AppleTalk or MacTCP APIs; instead they deal directly with the
Macintosh OS ethernet driver software. With the introduction of PCI bus to
the Macintosh this driver architecture and software has changed.
Additional backward compatibility software included with the System
Enabler 1.1 for System 7.5.2 (i.e., System 7.5.2 version 2) allows these
networking extensions and applications to communicate with the new DLPI
based ethernet driver as if it were a "classic" ethernet device.
This compatibility software supports only the built-in ethernet adapter
of Power Macintosh systems with PCI bus (7200, 7500, 8500, and 9500). Thus
current versions of such network extensions and applications (those that
write directly to the ethernet driver) cannot access PCI based network
interface cards.
This backward compatibility module was not available in the original
distribution of System 7.5.2 for the Power Macintosh 9500 (with Open
Transport v1.0). It is now included as part of System 7.5.2 version 2, or
more recent, and is recommended for use with Open Transport 1.0.6 or later
(see Availability and Distribution ).
Q: Are there known limitations to applications backward compatibility?
A: Yes. Applications that rely on undocumented APIs or examine private
data structures in current the AppleTalk or MacTCP may not be fully
compatible with Open Transport.
Examples include the MacSNMP AppleTalk and TCP/IP Agents (however,
MacSNMP and the Macintosh System Agent are compatible), the Apple Internet
Router 3.x, the Apple Remote Access Multiport Server 2.x, LaserWriter
Bridge, and some utilities like MacTCP Watcher and MacTCP Spy. Updated
versions of these software products will be required for full
compatibility.
Q: There have been reports of problems with the use of Open Transport and
MacX 1.2. Is there an Open Transport compatible X Window System server
available?
A: Apple MacX 1.5 is compatible with Open Transport, and is a recommended
upgrade for customers who have earlier versions of MacX. There is a known
bug in MacX 1.2 that can cause it to crash when running on a Macintosh
system with System 7.5.2 and Open Transport.
Network Compatibility
Q: Is Open Transport interoperable with installed AppleTalk and TCP/IP networks?
A: Open Transport 1.0.x is compatible with existing AppleTalk and TCP/IP
LocalTalk and ethernet network at the "packets on the wire" level.
Organizations can introduce one, a few, or hundreds of new Macintosh
systems running Open Transport into their environment without worrying
about interoperability with existing networking services.
Q: Is Open Transport compatible with existing Internet Service Provider
offerings?
A: As noted in Network Interface Options Open Transport/TCP currently
supports dial-up connectivity to TCP/IP networks, including the Internet,
through backward compatibility with select third party software modules
known as "mdevs".
With the appropriate mdev installed, end-nodes can use either SLIP or
PPP to connect to Internet Service Providers and other dial-up IP-access
points. However, not all versions of all mdevs are supported by Open
Transport backward compatibility services. It is important that the
recommended versions of software be installed for the greatest level of
compatibility.
It is also important that TCP/IP addressing and other configuration
information be properly configured. As there is a new human interface
provided by the Open Transport/TCP configuration utility, there are some
changes in the process as compared to the older MacTCP software.
Q: Is there documentation available to assist with configuring Open
Transport/TCP?
A: Yes. Although a full user's guide is planned for release with Open
Transport v1.1, configuration tips for Open Transport 1.0.x are already
available from various sites on the internet including:
ftp://seeding.apple.com/opentransport/OT_gen_info/TEXT/OTTCP_Config_Tips
Q: Does Apple offer a solution for SLIP or PPP dial-up to the Internet?
A: Yes. The Apple Internet Connection Kit is a selection of the most
popular Internet applications from third party companies, including the
Netscape Navigator and RealAudio Player from Progressive Networks, as well
as Claris Emailer Lite. The kit includes MacPPP 2.1.4 along with the Apple
Internet Dialer - software designed to make it simpler for Macintosh
customers to register with a qualified Internet Service Provider (ISP) and
get connected to the Internet. To help users work with their Internet
applications, the Apple Internet Connection Kit includes Apple Guide
software for on-line assistance.
Q: What is MacPPP 2.1.4? Is it available on the Internet?
A: MacPPP 2.1.4 is a derivative of the MacPPP 2.1.x SD versions of Merit's
PPP. It includes code contributed by Apple engineering to enhance
compatibility with Open Transport/TCP. These Apple updates have also been
provided to the authors of FreePPP (the successor to the "SD" releases of
MacPPP).
FreePPP 1.0.x also includes these updates, and is available for
download on the Internet.
Q: Does the Apple Internet Connection Kit require Open Transport?
A: The Apple Internet Connection Kit works with either MacTCP or with Open
Transport/TCP.
Q: Which mdevs are currently supported by Open Transport/TCP?
A: Open Transport 1.0.8 supports the following MacTCP Link Access Modules
(mdevs).
* FreePPP - version 1.0 or more recent; compatible with Open Transport.
* InterPPP(tm) - use version 1.2.9 or more recent.
* InterPPP II - use the most current version.
* MacSLIP - use version 3.0 or more recent; compatible with Open Transport.
* MacPPP - use version 2.1.3 SD, or more recent (version 2.2.0 is not
recommended).
Apple is continuing to work with developers to better support existing
mdevs; contact the third party developer of interest for the most recent
information on compatibility.
Q: Are there known limitations to backward compatibility mdev support?
A: Yes. Due to differences in the underlying architectures (between MacTCP
and Open Transport/TCP), and some current (1.0.8) shortcomings in the
backward compatibility services, there are some additional limitations to
mdev support:
* Some mdevs, when used with Open Transport, may not be able to
auto-dial, i.e., automatically connect to the service provider when
launching a TCP/IP application. This is being addressed by updated
versions of the mdevs.
* Once a TCP/IP application launches and uses a SLIP or PPP mdev, use of
a different mdev may require restarting the Macintosh. Disconnecting from
and redialing a service provider may also require restarting the
Macintosh. This is planned to be addressed in Open Transport v1.1 (See
Future Directions).
* Some Internet Service Providers do not strictly follow standards
practices, which call for assigning end-node IP addresses on the same
subnet as the router (gateway). Open Transport strictly enforces this
requirement in versions prior to 1.0.7.
Beginning with Open Transport 1.0.7, the TCP/IP configuration utility
software will automatically generate a compatible router address to
facilitate connectivity to the ISP if the user leaves the router address
field empty.
Q: If a user needs an updated copy of one of these mdevs, how can they get
the software?
A: Sources for mdev software will vary, as some of the noted products are
commercial and some are shareware or public domain.
* FreePPP is shareware and can be found on a variety of internet sites;
typically at "info-mac" mirror sites in the comm/tcp directory. A list of
info-mac mirror sites can currently be found at:
http://www.mcp.com.hayden/iskm/info-mac-mirrors.html
Some sites where FreePPP can be found currently include:
ftp://mirrors.aol.com/pub/info-mac/comm/tcp/
ftp://mirror.apple.com/mirrors/Info-Mac.Archive/comm/tcp/
* InterPPP(tm) and InterPPP II are commercial software products. For
availability and ordering information contact InterCon Systems, US +1(703)
709-5500
* MacSLIP is commercial software available developed by Hyde Park
Software. For availability and ordering information contact TriSoft, US
+1(800) 531-5170.
* MacPPP (v2.1.4) is available as a component of the Apple Internet
Connection Kit, Apple Computer Inc., US +1(800) 462-4396 for fax
information or +1(800) 538-9696 to locate an Apple authorized reseller
near you.
Q: There have been reports of problems with Open Transport, PPP, and the
use of Virtual Memory. Is Open Trasnport compatible with Virtual Memory?
A: Open Transport fully supports the use of virtual memory. However there
are problems identified with MacPPP 2.1.2 SD and FreePPP 1.0 when used
with Open Transport and Virtual Memory (including RAM Doubler). These
problems are under investigation, with Apple engineering working together
with the authors of FreePPP. Current plans call for an update to FreePPP
to be available once a fix is determined. In the interim, users who
experience problems with PPP and Virtual Memory are advised to turn VM
off.
Q: Will Apple provide a "native" SLIP or PPP solution for Open Transport?
A: Apple is developing an implementation of PPP for Open Transport as a
part of the next generation of Apple Remote Access products. This is
planned to support dial-up access to both AppleTalk and TCP/IP networks.
(see Future Directions).
Q: Is Open Transport compatible with PowerTalk built-in support for SMTP mail?
A: Apple recently announced that it has licensed, and will distribute and
maintain, the PowerTalk Internet PMSAM formerly available from StarNine
Technologies. This software provides the MacOS with built-in support for
Internet SMTP mail. The Apple Internet PMSAM is fully compatible with Open
Transport 1.0.x when used on a LAN. When the PMSAM is to be used over a
dial-up SLIP or PPP link, the same recommendations and limitations noted
above for SLIP and PPP currently apply.
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