Connecting Legacy and Open SystemsBy Michael Callahan, Stelias Computing Inc.
Summary by Gordon Galligher
Michael talked about how Linux (an open system) will fit into various Legacy LANs composed of computers connected via Novell's IPX, Microsoft Networking (SMB), and Apple's Appletalk. He spent most of his time talking about the various protocols used to communicate with the legacy systems and the implementations of these protocols available on the Linux platform. He also discussed plans for future changes and enhancements of the Linux implementations. He covered both the freely available versions as well as any commercially available versions. In some cases, the protocols used for communication are not publicly documented; therefore, having a free implementation may take a long time (while porters work on reverse-engineering the protocol with the help of network analyzers). There are cases where the lack of documentation makes implementation next to impossible.
Novell Networking Support. Novell has had two popular versions of its protocol: NCP and NDS (Network Directory Services), otherwise known as version 3 and version 4. Unfortunately, neither of these protocols is publicly documented, but there are available both free and commercial products that support this protocol. The Linux kernel supports the IPX protocol and has programs to supply routing for both PPP and IPX protocols (as well as IPX over PPP), which makes some of the implementations mentioned later easier and more stable.
For client services, there is a freely available program written by Volker Lendecke called NCPFS. This kernel module is included in all 2.x implementations. It allows the mounting of fileservers, printer queues, manipulation of the bindery objects, and can change the protection information on a server. This package supports only the NCP version of the protocol, so it can be used only with Novell 3 servers or Novell 4 servers using Novell 3 emulation. There is also commercially available a package from Caldera Software that is based on code licensed directly from Novell. As such, it can be used to browse the hierarchy supported by NDS as well as providing authentication in all hierarchies.
For server-based services, there are two freely available programs. One, written by Ales Diryak, is called LWARED, but it is no longer in active development. It was, however, the first hint of a server implementation of NCP. The other freely available version, written by Martin Stove, and called MARS_NWE, is a collection of programs. It functions as a Novell 3 server for file and print queue sharing only. Caldera Software has plans to offer a commercially available server called the Open Linux Server. As with the client implementation, it is based on code licensed from Novell, so it has full NDS support as well as NCP. They have announced that a five-user license will be "under $1,500" for the file and print services.
Microsoft Networking Support. Microsoft utilizes a Server Message Block (SMB) protocol and typically layers that on top of the NetBEUI, IPX/SPX, and NetBIOS over TCP/IP protocols. The SMB protocol supports dynamic dialects, which makes it easy to support new features that come after the protocol was originally designed-the features are simply negotiated at connect time. The SMB protocol is well documented, but the latest additions that Microsoft has made, such as adding the concept of a Domain (a collection of principles and objects), are not publicly available. This, like NDS for Novell, means that freely available ports of the new features may take a considerable amount of time before they are available, if they ever are.
For client services using TCP/IP only, there is a program written
by Poal-Kr. Engstad and Volker Lendecke called SMBFS. This is
implemented via a kernel module as well as an smbmount program. The
program allows the mounting of SMB shared files, but no domain
support. To attach to shared printers, the
For server-based services on TCP/IP only, there is a program written by Andrew Tridgell called SAMBA. This program allows the Linux host to share directories as well as printer queues. It can join and/or manage any browser lists. It can be a WINS server. Because the new Domain structure is not documented, it does not support any of those functions. Along with this program is a freely available package from the Internet Software Consortium called DHCPD, which allows Windows95 clients to successfully obtain IP addresses via the network. A number of members of the audience had had excellent success with the combination of SAMBA, SMBFS, and DHCPD for integrating Linux into Microsoft environments.
It is unfortunate for the free software community that Microsoft has kept its Domain additions to the protocol private. A reference port of the new features would surely be added quickly should the specifications of the protocol enhancements be made available.
Apple Networking Support. Apple has implemented a number of protocols for its Appletalk networking, including DDP (generic network datagram protocol), RTMP (routing protocol), NBP/ZIP (name resolution in "zones"), AFP (file sharing), and PAP (printer sharing). Unlike those previously mentioned, all of these protocols are very well documented, and freely available versions of the server-side modules are readily available. There has yet to be a client-side implementation because most sites prefer to use the speed and stability of Linux for the server side and just use their existing Apple machines as the clients.
For the client there, are two packages: netatalk and CAP (Columbia Appletalk Protocol). Michael did not mention the originator of the netatalk program, but the CAP program originated from Columbia University. The netatalk program is a kernel-based implementation that provides file and printer sharing. The CAP program was originally completely a user-level port, but now there are patches to the kernel to support this version.
The future of Apple networking is not yet clear, especially since the integration of NeXT Software under Apple's corporate umbrella. There are a number of Macintosh operating system updates planned before the NeXTSTEP port to the PowerPC is planned, so it is even more confusing to predict what will be supported where.
Evolution of PC Networks. Michael spent a little time covering information about where the land of PC networking might take us. The LDAP protocol for directory services has been endorsed by both Microsoft and Novell, and if they truly make their own directory hierarchy services LDAP compliant, then a freely available version of the clients and servers will be relatively easy to implement. The problem is that there is a lot of difference between endorsing a particular protocol and actually implementing it in a timely fashion.
Microsoft has also mentioned that it is planning on delivering Kerberos support as the authentication model in NT Version 5. Kerberos is not a simple authentication method, but it is fairly well understood in the Linux community. Microsoft has not, however, made it clear if it will be using Kerberos v5 or a "kerberoslike" authentication model. If it is Kerberos v5, then that support could quickly be added to the SAMBA and SMBFS programs to make Linux boxes first-class citizens in a Microsoft-dominated network.
Originally published in ;login: Vol. 22, No.2, April 1997.
Last changed: May 28, 1997 pc