Choosing Interoperability Solutions

A complex migration environment requires many tactical decisions on interoperability solutions. This section looks at the interoperability solutions strategy and outlines factors that affect tactical decisions. (For specific advice on solutions, see the discussion of development and live environments in Chapter 7, Creating the Development Environment, and Chapter 13, Creating the Live Environment. )

For example, an administrator might decide that developers require only telnet access to the UNIX servers from their Windows-based computers. However, there one specific X Windows application might need to be referenced during the migration. In this case, a limited tactical implementation of X Windows servers for specific developers might be appropriate, even though it is not in the strategic plan.

Here are some major strategic factors to consider:

• Ease of use

  The solution should be appropriately easy to use. The appropriate level depends on target users and the target environment.

• Ease of administration

  The solution should be easy to administer. Ease of administration means different things to UNIX and Windows administrators.

• Transparency in the target environment (Windows)

  This is closely linked to ease of use. However, because the target environment is Windows, the interoperability solution should have the look and feel of Windows.

• Lifetime of the UNIX environment

  The UNIX environment does not disappear overnight. In some migrations, a cross-platform, heterogeneous environment may continue for years . In others, the UNIX environment phases out after the migration is complete. The level of integration required for short-term and long- term interoperability is quite different.

• Cost

  A cost-benefit analysis is always needed. Even freeware solutions such as Samba have costs for administration and configuration.

• Functionality

  The technical features of an interoperability solution must meet the requirements of the users.

Interoperability Solutions for Windows Environments

When Windows is the chosen target environment, there usually exists a plan to move the development and live environments to a Windows-based platform as well. Therefore, interoperability solutions should also be Windows-based. Wherever possible, the UNIX environment should be hidden from Windows users. In addition, interoperability solutions should not constrain or further complicate the administration of the Windows environment.

Here are specifics of the three major categories of interoperability issues to consider when choosing interoperability solutions for Win32 environments:

• Connectivity

  The live environment should not require any connectivity to the UNIX environment. Developers will need connectivity during the migration. Connectivity solutions should be Windows-based, but their cost must take into consideration the lifetime of the UNIX environment: for example, there is no point in procuring an expensive connectivity solution if the UNIX environment is to be decommissioned within a matter of months.

• Authentication and authorization

  Security should be Windows-based and transparent to Windows users. It is not necessary to integrate accounts using Services for NIS (or a similar product) because the UNIX environment has a short lifetime.

  Security differences should be managed by using either separate or duplicate accounts for developers and others who need UNIX access, and by User Name Mapping.

• Resource sharing

  During a migration to the Win32 environment, resource sharing might be needed for access to UNIX-based files in the development environment or for access to migration data in the live environment. The resource-sharing solution should be transparent in the Windows environment.

  It is possible to use Samba servers or Windows Services for UNIX NFS clients and gateways. If the priority is to move administrators to the Windows environment, using SFU NFS moves administration to the Windows platform. However, by using a UNIX solution, the Windows environment is not complicated by non-native protocols and systems such as NFS. Which solution to choose depends on the relative advantages to a particular migration project.

Interoperability Solutions for Interix Environments

When the target environment is Interix, the application and its environment can retain many UNIX characteristics. Because of this, users, developers, and support staff sometimes want to emphasize UNIX-style solutions.

However, Interix creates Windows-based solutions by using UNIX-style source code and development tools. Because Interix can do this, a Windows environment is still desirable. For that reason, the discussion that follows assumes that the UNIX environment will be phased out.

Here are specifics of the three major categories of interoperability issues to consider when choosing interoperability solutions for Interix environments:

• Connectivity

  Both live and development environments probably still require UNIX-style connectivity. If the Interix application continues to use an X Windows or character-based user interface, then Windows-based terminal emulators or X Windows servers will be required.

• Authentication and authorization

  Security should still be Windows-based and transparent to Windows users. Interix provides account interoperability.

  However, if the UNIX environment lifetime is short, integration of accounts by using Services for NIS or another product might be unnecessary.

  Separate or duplicate accounts for those who need UNIX access and user name mapping can be used to manage security differences.

• Resource sharing

  During a migration to the Interix environment, users might need to share resources for access to UNIX-based files in the development environment or for access to migration data in the live environment. The resource-sharing solution should be transparent in both the Windows and the Interix environments.

  As explained earlier in this chapter, Windows shares can be mapped to Interix paths by using Interix and Microsoft Windows Services for UNIX (similar to how UNIX mounts NFS shares). To retain native Windows file sharing, any NFS share required by the application either should be shared as an SMB share by using Samba or should be accessed by using the Windows Services for UNIX NFS client.

  An Interix solution will probably use NFS and SMB shared resources. However, it is still desirable to move to a native Windows environment.

Cross-Platform Support

The most important factor to consider when choosing solutions is the need for ongoing cross-platform support. A detailed analysis of this subject is beyond the scope of this guide, but this section introduces the main points.

Cross-platform support often requires an integrated environment across Windows and UNIX with common source code and development tools. In such an environment, it is important to make interoperability as transparent as possible to both UNIX users and Windows users. In a cross-platform scenario, the most difficult interoperability issue is security.

Here are specifics of the three major categories of interoperability issues to consider when planning cross-platform support:

• Connectivity

  In a cross-platform environment, Windows to UNIX connectivity is particularly important. All connectivity options probably need to be implemented on the Windows clients. Developers who want remote access to Windows-based servers can use either the Windows Telnet server or a remote desktop running Terminal Services or Citrix MetaFrame.

• Authentication and authorization

  Even in a cross-platform environment, security should be transparent in the Windows environment. In this case, it should also be transparent in the UNIX environment. Due to the potential for human error, as well as the additional administration burden , user name mappings and password synchronization should not be done manually in a cross-platform environment. Depending on the level of interoperation of the two environments, the Windows Services for UNIX Services for NIS could be appropriate for handling user name mapping and password synchronization.

• Resource sharing

  Resource sharing is particularly important in a cross-platform environment, and probably requires a mixture of NFS and SMB solutions. Such a mixture means that both Samba and Windows Services for UNIX services must be implemented.