Accessing Mainframe and Minicomputers: X marks the spot
Many large organizations have made the move from minicomputers and mainframes with character-based terminals attached to stand-alone PC systems running either Windows 95 or Windows NT. In many cases, though, it’s impossible to totally replace the larger systems because of legacy applications or the need for company-wide single-point data access. In those cases, terminal emulation software on a Windows PC allows access to the larger systems. Unfortunately, the software provided with Microsoft’s Windows versions is a lackluster terminal emulation package, lacking support for many popular terminals and more advanced protocols like NFS. To fill that void, a healthy third-party market of TCP/IP suites, dedicated mainframe access packages, and X client software has evolved.
In this article we look at what you need to consider when purchasing a TCP/IP suite. A number of suites have been tested for overall performance and reliability, as well as their end-user friendliness. We also take a long look at NFS clients and servers, as many organizations have to integrate new Windows NT machines into networks that rely on UNIX or mainframe-based NFS file sharing.
Third-party TCP/IP packages fall into a number of categories, primarily based on whether you need mainframe terminal emulation only, TCP/IP emulation suites, X client software, and NFS access. Some packages are available in flavors that cover one or more of these categories, while others are specifically designed for a single task. A different approach is taken by some vendors who offer hardware-based connectivity options for TCP/IP networks and mainframes, providing fast and efficient emulation of terminals.
Hardware based systems have two major advantages over software systems: speed and flexibility. These allow for very fast connection to a network with support for ESCON and Bus & Tag interfaces, which software cannot hope to properly model. These solutions will not suite many organizations unless they are still very mainframe dependent and need to offer an interface between PC subnetworks and the mainframe.
Polaris Communications is one of the largest vendors of such solutions, offering their boards as OEM products to a number of vendors. The Polaris hardware is PCI-based and supports data transfer at rates up to a blazing 200Mb per second (using ESCON). Plugged into a Windows NT workstation, the hardware and software integrate smoothly with mainframes and can emulate a number of IBM control units. From a system that runs one of these Polaris boards, you can support a network of SNA clients (including Windows NT and Windows 95) with full TN3270 terminal emulation. The problems with hardware-based access solutions is their cost: a typical system will cost about $12,000. There are several alternatives to Polaris boards, including OBM, BusTek, and General Signal.
Sometimes it seems that everywhere you turn there’s a new TCP/IP suite on the market. With the virtual demise of IPX/SPX for larger networks, TCP/IP integration is vitally important for all machines. While Windows NT and Windows 95 offers basic TCP/IP capabilities as delivered by Microsoft, more advanced features are often required. That’s given rise to a lucrative third-party TCP/IP software market, into which many newcomers have rushed over the last couple of years. Although all these packages offer TCP/IP capabilities, not all offer industrial-strength enterprise-wide support. Selecting the right TCP/IP suite for your organization requires you to consider a number of factors, including the protocols you will be running on your networks. For example, if you run NFS or AFS, you need a TCP/IP suite or add-on that supports these protocols. We’ll look at NFS clients specifically later, so for now we’ll concentrate on suites that may or may not have NFS support included (often as two different versions of the same suite).
Windows NT handles TCP/IP through part of the layered operating system design. Device drivers define the hardware-specific characteristics of the network interface card. The device drivers talk to a low-level software layer (Network Drive Interface Specification – NDIS, Open Data-Link Interface – ODI, or one of several packet drivers) which control how the network interface card handles data. This data handling is independent of the network operating system protocol. Above the low-level software layer are subsystems to handle specific network protocols (TCP/IP in this case, although IPX/SPX and NetBIOS are supported in the same way). Windows NT places the Windows Socket API above the TCP/IP layer to perform network-related high-level tasks for applications.
Several of the TCP/IP suites have taken a bottom-up design approach, trying to replace the Microsoft TCP/IP kernel with a faster, more secure and reliable kernel. Others build upon the Microsoft kernel with extra capabilities. Of the two, the replacement kernel approach is a better solution as it does offer a noticeable performance enhancement, as well as better integration with the rest of the suite.
Although no TCP/IP products we evaluated are yet ready for the next generation of IP (IP v 6, or IP next generation), most of the vendors are readily IPv6-compatible suites for release as the protocol is rolled out. Having an upgrade path to an IPv6-compatible system should be a major requirement for anyone investing in a large-scale TCP/IP suite rollout or moving to WinSock 2.0 (neither of which Microsoft TCP/IP supports). For smaller groups, the addition of IPv6 and WinSock 2.0 may not be as critical and can be added later.
What should you look for in a TCP/IP suites? A replacement TCP/IP kernel is an excellent place to start, as it tends to offer better security, reliability and performance than Microsoft’s product. A suite that has been around for a while and been thoroughly tested in a variety of networks tends to be a logical choice. Then look at configuration protocols. When a machine joins the network, you either configure each machine manually with an IP address, or let a server configure it automatically. IP address assignment can be achieved through Windows’ DHCP (Dynamic Host Configuration Protocol) or through BOOTP (Boot Protocol). If you need IP assignment, look for one or both of these protocols (DHCP is almost always Windows NT Server based, while BOOTP is almost always UNIX-based).
The next consideration is the ease of configuration and maintenance. This is often hard to judge from product literature or reviews, but look for a package that offers both Windows and command-line interfaces for maximum flexibility. The best suites offer both types of interfaces, as well as consistent interfaces between all the support tools and components in the suite.
A complete set of tools would seem to be logical, but there are some suites that skip one or more of the following components for one reason or another: telnet and rlogin (for remote connection and remote execution of commands); FTP and TFTP (for file transfers), LPD or LPR (network printing), basic utilities like ping and sendroute, and support for protocols like Network File System (NFS), Network Information Service (NIS) and Domain Name Service (DNS). Other components often included in a TCP/IP suite are e-mail packages, X clients, support for PPP and SLIP (for remote access through a modem), and Web browsers.
If you do use a suite’s e-mail component, look for a suite that includes all the standard protocols like Simple Mail Transfer Protocol (SMTP), Post Office Protocol 3 (POP3), and Internet Mail Access Protocol 4 (IMAP4). Verify that the suite’s e-mail system will integrate with your existing organization’s e-mail system, as some won’t work well with proprietary mail systems.
X clients are a source of much of the TCP/IP suite’s sales, allowing Windows systems to access UNIX X and Motif servers with a similar interface. X implementations vary considerable with these suites, and not all behave well. The speed at which X clients operate also varies noticeably depending on the suite, and some suites offer extra features that enhance a user’s session, allowing better integration between X and Windows NT. Since this is not intended to be a comparison of X packages, per se, we didn’t evaluate the suites that do offer X any differently than those that don’t. Of the X implementations that we did experiment with, though, two stood out: Hummingbird’s eXceed and WRQ’s Reflection X. Both have talented, flexible, and highly configurable X clients that worked with all our X servers.
TCP/IP suites can be used to access non-UNIX systems, of course, using terminal emulation. If you are accessing a mainframe or minicomputer, flexible terminal emulation options are a boon. Many suites limit terminal emulation support to a couple of basics: IBM 3270 and DEC VT220. Some packages add TN5250 emulators, used to connect to IBM AS/400 systems. While these do allow reasonable behavior connected to larger systems, more versatile emulations add features such as split screening, better color and font support, and graphics. If the suite you are choosing will be used to access a larger non-X system, make sure that applications users will access work well with the terminal emulators provided. Having to buy an additional terminal emulator on top of your TCP/IP suite is annoying and expensive.
Of the suites we tested, most vary only in the configuration and administration features. All offer the basic TCP/IP protocols and utility support, with fairly consistent performance. The accompanying table shows the basic features and performance results achieved through a repeated script that exercised almost all the protocols and utilities in turn, looping for twenty times. Variation in performance numbers was marginal over the test length, making this a poor indicator of which suite to choose. We’ve also rated all the suites based on their features. This is a composite rating of the ease of installation, configuration and management, combined with the ease of use of each of the components. While several of the suites offer different ways of achieving the same end, we judged the products as a single suite instead of by comparison to other suites. A suite that continues the same interface, actions, user friendliness and help system from component to component scores high. Also scoring high are tools that add extra features to the suite.
NFS and NT
Network File System, developed by Sun Microsystems, is the standard network-wide file-sharing method on most UNIX systems. Since any network that has a mix of NT and UNIX platforms (whether workstations, minicomputers, or larger systems) will have to share files between the two operating systems, NFS is the most logical method to accomplish this task. Support for NFS on NT platforms is excellent, with at least a baker’s dozen different software packages claiming NFS support, and several NT-based NFS servers also available.
Since the number of NFS servers for NT is small, it’s worth while starting with that aspect. Why bother using a Windows NT system as an NFS server if you have UNIX platforms available? Most likely because the applications that most need sharing are NT-based. By placing an NFS server on an NT platform, all the NFS-compatible clients (NT, Windows 95, and UNIX) can gain access to the application files. Since a network can have any number of NFS servers, it makes a lot of sense to spread the NFS server load across several systems when large networks or several applications on different operating systems are involved.
Integrating NFS and Windows NT offers software developers an interesting problem. They must balance the need for providing translation between NFS-specific file requests and Windows NT filesystem requests (Both FAT and NTFS) as fast as possible, while adding support for Windows NT user authentication, group identifications, and Access Control List (ACL permissions). Throw into the mix NFS’ security and UNIX naming conventions, and development has the chance to become sticky. A quick warning for those of you running NT with FAT or FAT32 filesystems: NFS’ file-based security mechanisms do not translate to these filesystems because NT does not have ACLs for each file. To enforce proper NT and NFS security you must be running either HPFS (pre-NT 4) or NTFS.
To test NFS server software, we installed three products on different NT Server 4.0 systems and used several of the client packages described later to access data on them. To test UNIX access, we used four IBM, HP and Sun workstations to access data files on each NT server through a Fast Ethernet network. The Servers were all identically configured ALR Revolution 2XL systems with dual 266MHZ Pentiums, 128MB RAM, and 9.1GB Fast-SCSI hard drives. To compare performance of the NT-based NFS servers, we tested against a Sun Solaris 2.5 NFS server running on a 120MHz SPARCstation, as well as an HP-UX 10.2 server running on a 715 workstation. The test procedure is described later.
We tested Attachmate’s PathWay Server NFS for Windows NT (version 1.0), FTP Software’s InterDrive Server (version 2.0) and Hummingbird’s NFS Maestro Server (version 5.1). All three are stand-alone NFS packages, which offers the maximum flexibility for administrators. Some TCP/IP client suites also include NFS server software but they tend to have less flexibility and features than the stand-alone products. Therefore we ruled them out of the server test. A fourth server package, Intergraph’s DiskShare, could not be obtained for review. The versions we tested don’t support NFS 3, the latest standard. New versions with NFS 3 support are expected to be out by the time you read this.
Comparing the three NT servers with UNIX server yielded an interesting result; the fastest packages weren’t UNIX-based. Both the Hummingbird NFS Maestro Server and FTP InterDrive Server were faster than the Solaris NFS server, with the Attachmate PathWay Server NFS running neck and neck with the HP-UX server, slightly slower than Solaris (although it was difficult to obtain proper results for PathWay Server due to software crashes discussed shortly). UNIX-based NFS administration and configuration has never been user friendly, and while all three NT packages do a very good job of using the Windows interface to make the setup and management process better, Hummingbird’s NFS Maestro Server took top honors with a superbly designed interface. Considering the price point of NFS Maestro Server, this is the NFS Server product of choice despite the fact that it was a little slower than the fastest, FTP InterDrive Server. InterDrive Server does have a slight edge on NFS Maestro Server in administrator statistics and NFS usage monitoring, and a better ability to fine-tune the server’s priorities.
Hummingbird NFS Maestro Server supports UNIX-style export files which allow your NT system to look just like an NFS export file on a UNIX box. If you administer both operating systems, then this little item makes moving between platforms a breeze. FTP’s InterDrive Server doesn’t support standard exports, but it does have a proprietary scheme that allows partitions to be exported in such as way as to appear like a standard export. As a side benefit of a proprietary scheme, though, InterDrive does allow some features like automatic switching of case of FAT and FAT32 filenames.
What about Attachmate’s PathWay Server NFS for Windows NT? It crashed. And crashed. And continued to crash at regular intervals. When it was running, PathWay Server chewed up our server’s RAM at alarming rates. Norton Utilities for Windows NT reported continued alarms as memory got short. After a two hour testing cycle, our 128MB RAM was completely used up, mostly by PathWay Server (by contrast, the other two products never exceeded 20MB total). To top that off, PathWay Server took up our entire NT file cache of 75MB in the same time span. We can only assume that these problems are endemic to version 1 of this software, and that a much more seasoned and robust product will follow with version 2.
NFS client packages are a different kettle of fish altogether, and there’s a lot to choose from. To test the client software we used a Windows NT Workstation 4.0 Pentium Pro system with 64MB RAM and 9.1GB Fast-SCSI hard drives. Over a Fast Ethernet network, we had each client package run three sessions of a test script. We used Mercury Interactive’s WinRunner to control the scripts. Each script read and wrote files of sizes from 1kB to 3.5MB to each of the three NT NFS servers and two UNIX NFS servers, with the emphasis weighted to reading files (as would be the case in most networks). Each script was run for two hours, and used to gauge performance of the client and each server. Only one client ran at a time when the client evaluations were being performed, but eight clients (that’s all the machines we had) ran simultaneously when testing the servers under load. We used NFS 2 for all our tests. As a reference, we also used IBM AIX, SunSoft Solaris, and HP HP-UX workstations to repeat the NFS client tests.
As with the server packages, Hummingbird and FTP both provided excellent NFS client packages. This time the NFS Software package wins top honors because if its excellent configuration flexibility, performance, and price. WRQ’s Reflection NFS was the fastest of the products we tested.
Although most of the NFS client packages offer clean configuration and administration interfaces, FTP Software’s InterDrive Client stood out for its ability to interface with the Network Neighborhood integration. When you right-click on an NFS exported object InterDrive allows you to create aliases that applications that are limited in their network and drive abilities can understand. For many older Windows and DOS applications, this ability may be the only way to provide access to NFS objects. InterDrive lets you set up user and password access rights for each object, as well as use the Properties window to show details about the NFS export. Not many other NFS clients are this capable and Windows-friendly. Even better, during all the testing we conducted InterDrive didn’t once lose a mount or attributes associated with a mount, which cannot be said for most of the other clients. There are a couple of weak spots with InterDrive: it doesn’t have a convenient and simple way to establish an NFS export and there’s no support for industry-standard NFS utilities. There’s also no NIS capability provided for verifying access to NFS exports, but these factors didn’t change our mind about the best of the bunch.
Century Software’s TERM Professional crashed on us in our testing, although it did behave just under average for the few cycles we recorded. We did confirm that our copy (version 3.3) was recent, and didn’t manage to solve the problem. TERM Professional has no integration with NT to speak of; all changes are through the Network applet.
Esker’s Tun NET also didn’t complete the testing suite properly due to crashes we couldn’t solve. Based on the brief testing we did complete, performance was poorer than average. A positive aspect of Tun NET is its ability to connect to exports in three ways: through the Network Neighborhood, Explorer, or from the command line. It was nice having the choice, although we’re not sure how many people would require this option.
Frontier Technologies SuperNFS is part of the company’s growing TCP/IP suite. However, while some other components in the Super suite are feature-rich, this one isn’t. There’s only a poor configuration routine and some utilities are either very badly implemented or missing altogether. SuperNFS doesn’t support server-specific logins. Performance was average. SuperNFS can be configured as a peer-to-peer NFS server.
Hummingbird Communication’s NFS Maestro Client offers support for most authentication schemes likely to be used in mounts, including NIS. It is also the only NFS client to offer a vendor-developed replacement for PCNFSD, which supports both 16-bit group IDs and full 32-bit file locking (both features lacking in PCNFSD). While perhaps not as friendly as some of the other clients, NFS Maestro is perfectly suited for those who are veteran users and want to get on with the job as quickly as possible.
Intergraph Software Solutions DiskAccess was one of the poorer performers in the client group, and also lost a coupe of mounts over time. On the plus side, DiskAccess does have a very good configuration routines. DiskAccess creates its own Applet in the Control Panel, which few other packages do.
Network Computing Devices’ Marathon for Windows NT had poor behavior in our tests, losing mounts and offering lower-than-average performance. Topping that off, over a two hour test Marathon crashed completely six times. Rather than developing their own tool, NCD seems to have licensed an early version of FTP Software’s InterDrive Client and dropped most of the newer features. There are no NFS utilities bundled with Marathon, and configuration and setup is annoyingly difficult for a relatively simple task.
NetManage Chameleon UNIXLink 97 is the follow-on to a veteran product, ChameleonNFS, which several years ago was one of the few NFS client packages available for Windows. Unfortunately, NetManage hasn’t kept up with the competition in terms of features and utilities, offering no add-ons or support for NT file attributes.. On the positive side, UNIXLink behaved solidly throughout the tests and while performance was only average, one feature stood out. UNIXLink allows you to create groups with pairs of logins and passwords for different servers to access exports transparently, negating the need to login in separately. The process is fast and convenient. A definite weak point in our testing was the Control Panel applet’s ability to retain only one configuration set for the entire system, so reconfiguring for different servers meant losing old configuration data. The ability to save several data sets would help enormously. UNIXLink can be configured as an NFS server, but only for peer-to-peer situations.
SunSoft’s Solstice Network Client (replacing the venerable PCNFS Pro) surprised us with only slightly-above average performance, as we had expected better. The configuration and management utilities are very good, but not noteworthy.
WRQ’s Reflection NFS Connection for NT was slightly faster the InterDrive in our tests and has an excellent NFS Administrator application. NFS Administrator offers an Explorer-like interface to files and drives.
We’ve seen through the testing results that most of the TCP/IP suites behave much the same when it comes to standard functionality. However, they do differ noticeably when configuration and manageability are factored into the formula. Choosing the right package for your needs will be a balance between these factors and the roll-out price. Every company offers multiple unit discounts and site licenses, usually with considerable savings over the per-seat prices shown in the tables.
We’ve also looked at NFS in some detail, based primarily on the need to support NFS on Windows NT workstations and servers. NFS performance is much more variable than straight TCP/IP suite performance, as you have seen. Most of the NFS clients (and some of the servers) can be purchased at a lower price in a combined suite with TCP/IP tools, reducing purchase prices even further. Nevertheless, the combined suites offering TCP/IP and NFS tend to be $400 to $500 per seat, which is an appreciable amount to thrown away on a poor decision. Consider your choices carefully in order to best leverage your existing equipment and legacy applications. Mainframes and minicomputers will be around for years yet, and your Windows NT systems must talk to them. You might as well make the experience as pleasant as possible!
Frontier Technologies Corp.
FTP Software Inc.
North Andover, Mass.
Hummingbird Communications Ltd.
WRQ (Walker, Richer & Quinn Inc. )
NFS Server Packages
FTP Software Inc.
North Andover, Mass.
Hummingbird Communications Ltd.
NFS Client Packages
Salt Lake City, Utah
Frontier Technologies Corp.
FTP Software Inc.
North Andover, Mass.
Hummingbird Communications Ltd.
Intergraph Software Solutions
Network Computing Devices
Mountain View, CA
Mountain View, Calif.
WRQ (Walker, Richer & Quinn Inc. )