PATHWORKS: PC Integration Software Digital Technical] ournal Digital Equipment Corporation Volume 4 Number 1 Winter 1992 Editorial Jane C. Blake, Editor Kathleen M. Stetson, Associate Editor Helen L. Patterson, Associate Editor Circulation Catherine M. Phillips, Administrator Sherry L. Gonzalez Production Mildred R. Rosenzweig, Production Editor Margaret L. Burdine, Typographer Peter R. Woodbury, Illustrator Advisory Board Samuel H. Fuller, Chairman Robert M. Glorioso Richard]. Hollingsworth John W McCredie Alan G. Nemeth Mahendra R. Patel F. Grant Saviers Victor A. Vyssotsky Gayn B. Winters The Digital Technicaljournal is published quarterly by Digital Equipment Corporation, 146 Main Street ML01-3/B68, Maynard, Massachusetts 01754-2571. Subscriptions to thejournal are $40.00 for four issues and must be prepaid in U.S. funds. University and college professors and Ph.D. students in the electrical engineering and computer science fields receive complimentary subscriptions upon request. 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Abstracting with credit of Digital Equipment Corporation's authorship is permitted. All rights reserved. The information in the journal is subject to change without notice and should not be construed as a commitment by Digital Equipment Corporation. Digital Equipment Corporation assumes no responsibility for any errors that may appear in the journal. !SSN 0898-901X Documentation Number EY-J825E-DP The following are trademarks of Digital Equipment Corporation: ALL·lN-1, DEC, DEC EtherWorks, DECnet, DECperformance, DECquery, DECwindows, Digital, the Digital logo, DNA, eXcursion, LAT, PATHWORKS, ULTR!X, VAX, VAX C, VAX Performance Advisor, VAX 4000, VAX 6000, VAXcluster, VAXstation, and VAX. 3Com is a registered trademark of 3Com Corporation. Apple, AppleShare, AppleTalk, LocaiTalk, and Macintosh are registered trademarks and QuickStart is a trademark of Apple Computer, Inc. CodeView, Microsoft, MS, and MS-DOS are registered trademarks and Windows is a trademark of Microsoft Corporation. CRAY is a registered trademark of Cray Research, lnc. i386, i486, and Intel are trademarks of Intel Corporation. IBM, Micro Channel, and OS/2 are registered trademarks of International Business Machines Corporation. Motif is a registered trademark of Open Software Foundation, Inc. Motorola and 68000 are registered trademarks of Motorola, Inc. CoverDesign NetWare and Novell are registered trademarks of Novell, Inc. The red and blue threads woven together in our cover design Network General and Sniffer are registered trademarks of represent the many PC clients and server systems that are inte­ Network General Corporation. grated in a network environment by the outstanding "thread" NFS and Sun are registered trademarks of Sun Microsystems, Inc. of PATHWORKS software. PATHWORKS software for the integration UNIX is a registered trademark of UNIX System Laboratories, Inc. of PCs over fANs and WANs is the featured topic in this issue. X/Open is a trademark of X/Open Company Limited. The cover was designed by Kathryn Cimis of the Corporate Book production was done by Digital's Database Publishing Group Design Group. in Northboro, MA. I Contents 6 Foreword Joseph A. Carchidi PATHWORKS: PC Integration Software 8 An Overview of the PAIHWORKSProduct Family Alan Abrahams and David A. Low 15 PAIHWORKS for VMS File Server Edward W Bresnahan and Siu Yin Cheng 24 The Development of an OptimizedPAIHWORKS Transport Interface Philip). Wells 31 Design of the PAIHWORKS for ULTRIXFile Server Anthony). Rizzolo, Elizabeth A. Brewer, and Martha A. Chandler 40 DECnet Transport Architecture Mitchell P Lichtenberg and jeffrey R. Curless 47 Microsoft WindowsNetwork Virtual DeviceDrivers in PATHWORKS for DOS Andrew W Nourse 56 eXcursion for Windows: Integrating Two Windowing Systems Dennis G. Giokas and Andrew T. Leskowitz 68 Capacity Modeling of PAIHWORKS Client-Server Workloads Christopher E. Methot I Editor:JsIntroduction server system on a LAN. However, as Anthony Rizzolo, Beth Brewer, and Martha Chandler explain in their paper, a multiple process model was cho­ sen rather than the single process used in the VMS file server. The authors give their reasons for this different approach as part of a general discussion of the server design and implementation. The network is key to the exchange of data in the PATHWORKS environment, and as is the case for the server software, multivendor systems must be addressed to ensure smooth integration. Mitch Lichtenberg and Jeff Curless describe how Digital Jane C. Blake has extended Microsoft's LA.i\f Manager across a LAN Editor or a WAN by using the DECnet transport protocol as the transport layer. In addition, they present the The integration of personal computers in a net­ reasoning behind the design of the transport com­ work environment is the subject of this issue of the ponent for DOS and OS/2 products, and review Digital Te chnical jo urnal. The software products steps taken to reduce memory usage and improve that bring about this integration are known collec­ performance. tively as PATHWORKS and are derived from Digital's Further details on the integration of DECnet and Personal Computing Systems Architecture. The LAN environments are provided in the paper on two engineering challenge for developers was to inte­ network virtual device drivers for the Microsoft grate a variety of client (PC) and server systems­ Windows environment. As Andy Nourse explains, DOS, Windows, OS/2, Macintosh, VMS, and ULTIUX­ these drivers manage DECnet and NetBIOS opera­ and to ensure that the intricacies of the meshing tions and enable the Windows operating system of these systems remained transparent to PC users. to support peripheral devices, memory resources, In the opening paper, Alan Abrahams and David and software applications. Andy first gives readers Low provide background for the papers that follow background on the Windows operating modes, and by describing the technical aspects of the various then describes the development of the two virtual hardware and software platforms, physical net­ device drivers. works, and protocols that had to be addressed by A significant new application in the PATHW ORKS PATHWORKS developers. They also present an over­ family, called excursion, brings together the capabil­ view of the PATHWORKS components which allow ities of X Windows, DECnet, and the Microsoft envi­ PC users to access network resources. ronment, resulting in the display of both Windows Among the capabilities PATH\VORKS enables, PC and X Windows on the same screen. Dennis Giokas access to files on server systems is one of the most and Andy Leskowitz present the integration philos­ important for users. Two file servers, one for VMS ophy behind the display server and the implemen­ and another for ULTRIX, were developed for this tation of the server architecture. They also relate purpose. A paper on the development of the first of how designers approached the mapping of the win­ these, written by Eel Bresnahan and Siu Yin Cheng, dows in the X and Windows environments. contains an architectural overview of the VMS file The issue concludes with a paper by Chris server. The authors also detail the mapping done to Methot on capacity modeling of PATHWORKS bridge the differences between DOS, OS/2, and VMS client-server workloads. Chris describes a queuing operating systems. In a related paper, Phil Wells analytical model used to understand resource con­ describes performance improvements made in ver­ sumption on the server and the special modeling sion 4.0 of the file server which were achieved by process required in the client-server environment. optimizing the transport interface and the data The paper works through a specific example of the buffering algorithm. He discusses the analysis of model's identification of bottlenecks in the system. server performance for various interface models, The editors thank Star Dargin and Carne! Hoover the implementation of the algorithm in the VlVlS for their help in preparing this issue. server, and test results. Like the VMS file server, the PATHWORKS software for ULTRJX systems integrates PC clients with a 2 Biographies I Alan Abrahams Alan Abrahams is a consultant engineer in the Personal Com­ puting Systems Group Technical Office. He develops management and security strategies for integrating PCs into enterprise-wide networks. Alan joined Digital in 1982 and designed and implemented the PRO/Communications package. Since 1985, he has been the architect responsible for integrating Microsoft's LAN Manager into Digital's PCSA and helped design Digital's NetBIOS emulation and remote boot of MS-DOS systems. Alan received B.S degrees in computational and statistical science and in mathematics from the University of Liverpool. Edward W. Bresnahan Senior software engineer Edward Bresnahan has been developing the PATHWORKS for VMS software since joining Digital's PCSG Server Engineering Group in 1988. He is currently responsible for the design and devel­ opment of a high-performance data cache to be used in future PATHWORKS server products. Prior to this, he was a co-op student at General Electric Company and at Charles Stark Draper Laboratory. Ed holds a B.S.C.S. (1988, hon­ ors) from Northeastern University and is pursuing an M.S.C.S. part-time. ElizabethA.