CONNECTIVITY (Special Edition) by Nark Krieger SunExpert May 1994 vol. 5 No. 5 PP 46 - 51
Unix has had TCP/IP networking software built in from its early days, but PC networking solutions have typically been diverse and aftermarket. The PC based networking models, with both a PC client and PC server, have now been extended to offer Unix servers. This article reviews these two alternatives of PC UNIX connectivity : the UNIX-centric, based on the UNIX TCP/IP model; and the PC-centric, based on one of several widely used PC models.
Among the suite of standard UNIX networking programs are applications to exploit network resources: telnet and rlogin let users log in to other machines ftp allows files to be copied back and forth among machines; smtp can deliver mail to and from machines; rsh makes it possible to execute a command remotely. Network File system (NFS) is now a standard part of almost all TCP/IP based networks. The UNIX TCP/IP networking standard is the basis for one of the most exciting current developments in computer use in the '90s. The flexibility and standardized networking software of UNIX allows the Internet to be the backbone of this information superhighway supporting millions of users.
PC to PC networking has had a very different history than the UNIX to UNIX networking. First, neither the hardware nor software has been a standard part of the MS-DOS PC. The software choices are "aftermarket", and networks from Novell Inc. (NetWare) Microsoft Corp.(LAN Manager), Banyan System Inc.(Vines) and others vie for the PC network market, with diversity of network protocols among these aftermarket solutions. Novell's NetWare uses the IPX protocol communicate between PCs. Microsoft LAN has had two standards, initially NetBIOS-network basic I/O system and more recently NetBEUI, and extended NetBIOS protocols. NetBIOS uses TCP/IP, so communication with UNIX is reasonably straightforward.
The most widely used today is what we'll refer to as the UNIX centric approach : The standard UNIX networking programs, such as ftp, telnet. Ping, rcp, etc., are placed on the PC. Two products that enable PC resource-sharing with UNIX networks are FTP's PC/TCP and SunSelect's PC-NFS. Both function under either MS-DOS or Microsoft Windows allowing PCs to sharing files with UNIX system, transfer files among machines, print files on network printers, remotely log into UNIX machines, and give a full complement of network commands equivalent to those found under UNIX. Both PC/TCP and PC-NFS give PC users the capability to access remote file systems as if they were physically connected to the PC; The NFS not only can widely used PC application be kept on one central UNIX volume, but both the application and any other file owned by a group of PC users can be backed up by standard high-capacity UNIX backup methods.
Another product, NetManager Inc.'s Chameleon, allows the NFS to go both direction. The UNIX system can "mount" a PC disk drive as an NFS volume for use by UNIX users. This product has one other very nice feature: It is written as a windows Dynamically Linked Library. And thus uses only a tiny bit of memory.
This UNIX centric method has a number of obvious advantages for PC users: They can access files on large drives and know they'll be backup; they can print to the fast, high-quality printer down the hall; and they can use their fast SPARCstation 10 through a telnet or rlogin session for added computer power. Also their PC can double as an X terminal.
There,however, are disadvantage. First, the installation of these products can be confusing. Making changes to autoexec.bat, config.sys and protocol.ini and worrying about Ethernet board addresses or NDIS drivers can be a frustrating experience for the Sun-trained network manager or systems administrator.
Instead of creating a PC copy of a UNIX program, the PC-centric approach puts software on both the PC-the client-and on the UNIX, PC, OS/2 or NT server. The PC-centric philosophy is to hide the PC client function as if it were an integral part of MS-DOS or MS-Windows. The server portion operates in the background, so end users never need to learn new commands. Many PC-PC networks use LAN Manager, NetWare or other PC-centric solutions. With the increased use of Sun and other UNIX workstations in large commercial and educational institutions, the PC community could profitably access resources on these workstations, particularly disk and printer resource. The Microsoft LAN manager server is used at many larger PC sites for whom the UNIX server/PC-centric approach is best suited.
The Sun will act as a file and print server for PC users, and coexist in a network that typically already has a LAN Manager server on some other machine. First, the Sun system administrator installs LAN Manager on the Sun. The installation process automatically adds NetBIOS and/or NetBEUI drivers to the Sun kernel. In either case, the NetBIOS module will work in conjunction with the standard Sun TCP/IP and NetBIOS packets from PC client, and other LAN Manager servers will be read and written. The NetBEUI module will work directly with the Sun Ethernet board, using LLC protocol alongside of the standard Sun TCP/IP stack. The Sun server can run both protocols simultaneously, supporting a PC network of mixed NetBIOS and NetBEUI users.
Once LAN Manager is installed, the PC client user accesses Sun disk drives through standard DOS or MS-Windows/NT systems, very little extra learning is needed on the PC side, and Sun drives and printers look like any other disk or printer on the PC desktop.
In addition to disk and print services, the LAN Manager administrator has a number of advanced services that can be provided to the LAN Manager users. All services can be controlled from the Sun via the net command or a menu-type interface; additionally, the administrator can control the services from a standard MS-Windows application called NetAdmin.
So what are the advantages and disadvantages of using a PC-developed networking model like LAN Manager versus the UNIX TCP/IP model? The people don't care which model they are using but simply want access to their files and printers quickly, easily and with great reliability. Whatever solution is chosen must therefore be easy to install and use, transparent to the end users, and reliable on a day to day basis. Both the PC- centric and UNIX-centric approaches met all of these criteria.
Obviously , an institution that has already made a large commitment to LAN Manager or NetWare will want to add the UNIX machine as a server; this offers low cost, low effort and low training compared with UNIX-style networking model like PC/TCP or PC-NFS. In addition, all network administration can continue to be done by a PC administrator working from a well-known, easy to use Windows tool .
In an installation where UNIX is the accepted networking solution and PC users will be added, the PC/TCP or PC-NFS solution has great merit. The PC user can access UNIX disks and printers reasonably easily
Installation with no prior experience, such as an organization that is downsizing from mainframes, the choice may simply boil down to the question of the systems management and administration and the networking strategy. All of these solutions have merit. The choice is one of cost, perspective and experience.