DTJ Number 3 September 1987 - Digital Technical Journals

New ProductsThe DECnetjSNA VMS DISOSS documentexchange facility (DDXF) is an example of thegateway access model. DDXF allows documentsto be transferred between V AXJVMS systems andIBM DISOSS. On the other hand, the DECnetjSNAVMS remote job entry (RJE) is an example of theserver model. RJE is a traditional remote batchworkstation emulator that allows VAXjVMS usersto submit jobs to an IBM host for processing andto have the job output returned to the V AXJVMSsystem.Building a product to the gateway modelallows the greatest use of common code modules.The product designer need concern himselfonly with the functional layer and, if no standardinterface module is available, with the SNA interfacelayer. Also, no product-specific software hasto be included in the gateway node.Building a product to conform to the servermodel can re move some of the processingfrom the host node. The cost, however, will beCONNECTincreased use of gateway resources and the introductionof product-specific; support in the gateway.Whether those trade ,offs are acceptable1depends on the product.DDXF as an Exa mple of the GatewayAccess Model ·The IBM DISOSS system use three important IBMarchitectures:• The Document Content Architecture (DCA) ,which prescribes the format and content ofdocuments• The Document Intercnange Architecture(DIA) , which defines the ! format and protocolsused to transfer documents between office systems• The logical unit type 6.2 (LU6.2), whichdescribes the SNA session protocols used toimplement the communications functionf' JCONTROL--'---=---i INITIATE-SELFPOINTLcoNTROL-,Nmm jBIND IBIND-DATASEQUENCEOFEVENTSI BIND-ACCEPT-DATAj_I DATADATADATAUNBIND IUSERPROGRAMJABORTGAP OVER ADNA LOGICALLINKL JGA'EWAYSNA SESSIONPROTOCOLSlPR,MARYLOGICALUNITFigure 9Gateway Access Message FlowDigital TecbnicalJournal 45No. 3 September 1986