DTJ Number 3 September 1987 - Digital Technical Journals

New Products1. At a node called SOURCE::, the command$ TYPE TARGET::"O=TIME"is entered from a process running underaccount USER.2. The TYPE image issues ari RMS OPEN toTARGET::"O=TIME".3. The OPEN service issues an ASSIGN requeston the string, which results in a QIOIO $_A.CCESS being issued to DECnet-VAX .4. A connect request for network task TIME isrouted to node TARGET, where the DECnet­VAX software creates a process to run a commandprocedure called TIME.COM. DECnet­VAX then creates the logical name SYS $NET,whose translation contains a network taskspecifier identifying the source of the logicallink.5. TIME .COM issues the commands$ DEFINE SYS$0UTPUT SYS$NET$ SHOW TIME6. DCL issues an RMS OPEN using the logicalname SYS $0UTPUT for its output. OPEN inturn issues an ASSIGN. When one logicalname points to another, the names are translatedin an iterative fashion until no fu rthertranslation is required. Since the logicalname SYS $0UTPUT points to the logicalname SYS $NET, the latter translation is usedby ASSIGN. ASSIGN finds the network taskspecifier and issues a QIO 10 $-ACCESSrequest to DECnet-VAX. The formation ofthe logical link is then completed. TheTYPE image at the source node now issuesan RMS GET, which then translates to aQIO IO $_READVBLK request on the networkchannel.7. The time is sent as a string by an RMSPUT operation, which then issues aQIO IO$_WRITEVBLK request on the channelestablished for SYS $0UTPUT. Since thisis a network channel, the QIO is handled byDECnet-VAX and passed across the logicallink to the source node.8. At the source, the data satisfies the QIOIO $_READVBLK, which in turn satisfies theRMS GET, allowing the TYPE image to displaythe time sent from the target node.Throughout this example, only two networkfu nctions were performed at the applicationlevel: the use of a network destination name inthe TYPE fu nction, and the reference to theSYS $NET logical name in the TIME commandprocedure.IDECnet-VAX Features fo r theVMS Environment / .Besides implementing thoe functions definedfor all DECnet implementations, the DECnet­VAX product supplies added-value featuresdesigned for the VMS environment. These extensionsto the architecture enhance the wayDECnet-VAX blends into the VMS system. Severalexamples are illustrated in the following·paragraphs.Proxy Log-inOne traditional problem with password-basedaccess control is making the required passwordavailable to all users needing access to a restrictedresource . If the user membership needsto change (e.g., if someone changes jobs andthus no longer has the right to access theresource) , a new password, which must be communicatedto all current members, is required.To address this problem, tbe concept of "proxyIlog-in" was added to the DECnet-VAX software in1983.21With proxy log-in, each node maintains adatabase of those network users having proxyaccess to specific accountS on the local system.The database is used t() provide a one-toonemapping between the user, identified asNODE::USERNAME, and the target proxyaccount. For example, take the case of the arrivalof a logical link request having no explicit accesscontrol information from user whose name is inthe database. In this case the process created byNETACP to handle the logical link will be runusing the authorization context of the proxyaccount. This mechanism allows members to beadded to or deleted from a particular proxyaccount without their a priori knowledge of theaccount.Cluster Alias AddresfDECnet-VAX nodes can dperate on VAXclustersystems. A cluster is a loo$ely coupled, multipleprocessor network featuring full sharing of diskstorage and common user !environments on eachrDigital Technical JournalNo. 3 September 198695