2 — Interoperability and Compatibility

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2.1 Overview of Compatibility with Other DCE Systems

Gradient DCE for Tru64 UNIXis based on OSF DCE Release 1.2.2. This product provides source-level runtime compatibility with DCE systems from other vendors for applications that conform to the OSF DCE Application Environment Specification (AES).

2.2 Overview of Interoperability with Other DCE Systems

Gradient DCE for Tru64 UNIX provides interoperability with DCE systems from other vendors as long as the implementations of DCE on those systems conform to the OSF DCE Application Environment Specification (AES).

2.3 DCE DFS Interoperability and Compatibility

Gradient DFS for Tru64 UNIX is a 64-bit implementation of OSF DCE Release 1.2.2. DFS, capable of supporting fileset sizes larger than 2 GB. It is compatible with the Cray 64-bit implementation of DFS.

Because most 32-bit systems cannot handle fileset sizes larger than 2 GB, operations involving these large filesets can produce unpredictable results. Take measures to prevent fileset interactions between 32-bit and 64-bit file servers in your environments. One approach is to avoid mixing 32-bit and 64-bit file servers in your environments.

2.4 CDS and DECnet/OSI DECdns Compatibility

The Compaq Distributed Name Service (DECdns) and the DCE Cell Directory Service (CDS) can coexist in a DECnet/OSI network, but they cannot interoperate. You can run both CDS and DECdns servers on the same machine, and you can build applications that make calls to both APIs. The CDS and DECdns libraries are maintained separately, as are the namespaces.

2.5 Interoperability with DECnet Phase IV and DECnet/OSI

To use Gradient DCE for Tru64 UNIX over DECnet/OSI, you must use DECnet in Phase IV compatibility mode. DECnet Phase IV compatibility mode consists of assigning a Phase IV node address to your system. A Phase IV-compatible address is a DECnet/OSI address that falls within Phase IV limits: the area number is less than 63, and the node ID number is less than 1023. For a complete explanation of Phase IV compatibility mode, refer to the DECnet-ULTRIX Installation and Transition Guide.

Before you start or stop DECnet/OSI, you should first stop the DCE services. Then, after you start or stop DECnet, restart the DCE services. Use the dcesetup command clean, as described in the system configuration chapter, to stop the DCE services.

Enter the following command sequence to stop and start DECnet and DCE Services.

You also have to stop and restart any DCE server applications that are running.

2.6 Interaction Between DCE DTS and DECnet/OSI DECdts

When you install Gradient DCE for Tru65 Unix, DTS is automatically installed. Normally, DTS synchronizes system clocks with other systems that use the RPC transport. The RPC transport runs on Tru64 UNIX and on other DCE systems. In addition, you can choose to synchronize system clocks with hosts running DECnet/OSI DECdts. In this section, we refer to the DTS that runs on Tru64 UNIX as DCE DTS.

The benefit of allowing DCE DTS to synchronize with DECnet/OSI DECdts is that the DECnet/OSI DECdts servers can be connected to time sources to which the DCE DTS servers do not have access. In this way, resources can be shared across a network.

One drawback to this scheme stems from DECnet/OSI DECdts servers using DECnet protocols to communicate with other DTS entities, such as servers and clerks. These protocols provide a less secure environment than the RPC protocol because the servers are unauthenticated. For example, any node can become a DECnet/OSI DECdts server at any time and could maliciously broadcast invalid times to other DECnet/OSI DECdts servers. Servers using the DECnet protocols accept and propagate this time around the network. Servers using RPC do not accept time from a server unless the server's authenticity is verified.

If your network must use authenticated connections, do not allow DCE DTS entities to accept time from DECnet/OSI DECdts servers. If your network can tolerate a small security risk, then consider allowing this interoperation.

When you answer y to the following configuration question, you are accepting time from DECnet/OSI DECdts servers: 

Should this node accept time from DECnet/OSI DECdts servers? (y/n) [n]:

To verify whether your node is accepting time from DECnet/OSI DECdts servers, enter the following command: 

% dtscp show all characteristics

Look for the command output line that says: 

DECnet Time Source                       = FALSE

If you want to allow a DCE DTS entity to accept time from DECnet/OSI DECdts servers after you have configured the cell, you must reconfigure or use the dtscp set decnet time source command, as follows: 

% dtscp set decnet time source true

To prevent a DCE DTS entity from synchronizing with DECnet/OSI DECdts servers, you must reconfigure or use the dtscp set decnet time source command, as follows: 

% dtscp set decnet time source false

NOTE: False is the default value for the decnet time source attribute.

The nodes on your network can have different DECnet time source settings. For example, you may want to allow some DCE DTS clerks to accept time from DECnet/OSI DECdts servers, while ensuring that other DTS clerks receive time from DCE DTS servers only. This scheme works because DTS clerks receive time, but they do not propagate time to other DTS entities.

However, if even one DCE DTS server can accept DECnet/OSI DECdts time, the DECnet time eventually propagates to other DTS entities throughout the cell. The result is the same as allowing all DCE DTS entities in a cell to accept DECnet/OSI DECdts time.

DCE DTS servers also give time to DECnet/OSI DECdts clients. If you have three or more Compaq DCE DTS servers and a DECnet/OS DECdts client on your LAN, ensure that either the DCE DTS servers have access to a time provider or that at least one DCE DTS server has the decnet time source attribute set to true wherever the DECnet environment has access to a time provider. Otherwise, the three DCE DTS servers do not have an accurate time base and can give incorrect time information to a DECnet client.

You can use the DTS dtscp show command to display the names and values of the following specified attribute groups:

If you have DECnet/OSI installed on your system, you can also use the DECnet/OSI NCL commands to manage the DCE DTS.

2.6.1 Changing the Default for DCE DTS to RPC

DCE DTS is installed by the dcesetup configuration program at system startup. Gradient DCE for Tru64 UNIX uses RPC to transport timing synchronization. Former versions used DLI, a feature of DECnet. To return to accepting time synchronization on DLI, you can change the default value in the dcesetup configuration program or you can issue a dstd command with the new -m option to override the default: 

dtsd -m Accept time synchronization messages on DLI only.

DLI (Data Link Interface) is a more specific reference than DECdts. DECdts can communicate through DECnet and DLI. DLI is narrower in meaning and not synonymous with DECdts.

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