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COM, DCOM and Software Components

COM, DCOM and Software Components. Nat Brown COM Program Management Microsoft Corporation natbro@microsoft.com. Agenda. What are COM and DCOM? What’s right with COM What’s wrong with CORBA / IIOP Interesting COM Research Topics Additional Reference Material. In the same process

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COM, DCOM and Software Components

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  1. COM, DCOMandSoftware Components Nat Brown COM Program Management Microsoft Corporation natbro@microsoft.com

  2. Agenda • What are COM and DCOM? • What’s right with COM • What’s wrong with CORBA / IIOP • Interesting COM Research Topics • Additional Reference Material

  3. In the same process • Fast, direct function calls Component Client Client Process Server Process • On the same machine • Fast, secure IPC Component COM Client • Across machines • Secure, reliable and flexibleDCE-RPC based DCOM protocol Server Machine Client Machine Component DCE RPC COM COM Client The COM Programming ModelA scalable programming model

  4. TCP, UDP IPX, SPX HTTP Msg-Q DCOM ArchitectureFlexible and extensible Pluggable Transports Client Machine Server Machine D C O M D C O M COM Object Clients

  5. TCP, UDP NT4 Security SSL/ Certificates IPX, SPX NT Kerberos HTTP DCE Security Falcon DCOM ArchitectureFlexible and extensible Pluggable Security Client Machine Server Machine D C O M D C O M COM Object Clients

  6. DCOM ArchitectureEfficient and scalable • Multiplexing - Single Port per-protocol, per server process, regardless of # of objects • Scalable - Connection-Less Protocols like UDP Preferred • Established Connection-Oriented (TCP) Sessions Reused by same client Client Server Client

  7. DCOM ArchitectureEfficient and scalable • Low Bandwidth • Header is 28 bytes over DCE-RPC • Keep-Alive Messages bundled for all connections between Machines Client Machine Server Machine Keep-Alive Traffic for all connections Client #1 Server Logical “Connections” or “Sessions” Client #2

  8. What’s Right with COM • Focus is on binary object standard and scalable/fine-grained component re-use • Concreteness and depth of definition, for example security, lifetime management, activation, installation & deployment • Architected extensibility

  9. What’s Wrong with CORBA/IIOP • Focus is on cross-node or network reuse/integration • in practice useful for vertical solutions, not horizontal reuse/integration • Incomplete specification • marshaling format of certain types of data-structures • implications of lack of services (e.g. Naming, Events, Lifetime management) • No architected extensibility

  10. COM Research Areas • High-Level Language Integration • Application Management • Ease-of-use Deep/Robust Extensibility

  11. Language Integration • Re-Use Mechanisms • Inheritance, Containment, Delegation, Aggregation • “Interception” • Constructs of modern OO languages • classes, fields, exceptions • Constructs of modern 4GL/RAD tools • data-binding • auto-persistence, -everything • Meta Data

  12. Application Management • Distribution of Code + Data + Configuration Information • Security and Security Delegation • Security “roles” and re-use of components • Performance Monitoring • Runtime Environment

  13. Ease-of-Use • What’s the next programming model layer to vastly improve ease-of-use? • Transactions? • Auto-caches & state management? • Auto-distribution & -execution?

  14. Receiver Class Factory Queue Class Factory DLL Register Connections DLL Register RefCounting Context Security RefCounting Management Configuration Query Interface Thread Pool Query Interface IDispatch Service Logic IDispatch Connection Points Connection Points Synchronization Meta Data Type Info Shared Data Methods Server Methods Component Component Ease-of-Use: First Steps Clients Network Receiver Queue Connections Context Security Management Configuration Thread Pool Service Logic Synchronization Shared Data Server MTS = easier servers Easier components?

  15. Reference Material • [Box1 97]D. Box, Q&A ActiveX/COM, Microsoft Systems Journal, March 1997, pp. 93-105. • [Box2 97]D. Box, Q&A ActiveX/COM, Microsoft Systems Journal, July 1997, pp. 93-108. • [Brockschmidt 93]K. Brockschmidt, Inside OLE 2, Redmond, Washington: Microsoft Press, 1993. • [Brown 96]N. Brown, C. Kindel, Distributed Component Object Model Protocol -- DCOM/1.0http://ds1.internic.net/internet-drafts/draft-brown-dcom-v1-spec-01.txt • [Chappell 96]D. Chappell, Understanding ActiveX and OLE, Redmond, Washington: Microsoft Press, 1996. • [COM 95] The Component Object Model Specification, http://www.microsoft.com/oledev/olecom/title.htm • [DCE 95]AES/Distributed Computing - Remote Procedure Call, Revision B, Open Software Foundation, http://www.osf.org/mall/dce/free_dce.htm • [Rogerson 96]D. Rogerson, Inside COM, Redmond, Washington: Microsoft Press, 1996. • [Wang 97]Y. M. Wang, COM/DCOM Resources, http://www.research.att.com/~ymwang/resources/resources.htm

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