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December 6, 1999

Network-Management Transformation
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Beyond a few basic must-have components, policy-based network-management solutions vary. For switch makers such as Cabletron or Extreme Networks, policy management encompasses virtual LAN membership and Layer 2 network security. Lucent and Nortel, among others, lump in IP address and domain name system management as part of policy management.

Most players see a directory-enabled policy-management solution in their futures, but how the vendors will use the directory differs greatly. Extreme Networks sees the directory as a way for policy servers to share information, allowing scalability and third-party interoperability. For Allot, using a directory enables its customers to insert new policies without having to develop a special API. Lucent sees the directory as a giant storehouse of information, where each user has a private subtree. For Lucent, the directory is the single sign-on for complete network resource management, both voice and data services. The vendor plans to accomplish this via a directory-independent LDAP schema.

There are other roles for policy-based network management as well. HP, for instance, sees it as an end-to-end tool for Cops-enabled desktops as well as network hardware.

Policy-based network-management rules can be grouped into three categories: conditions, actions, and roles. Conditions are events that cause a certain policy to take effect. Actions define what is done when a condition is met, while roles define how a device or interface implements an action.

Policy conditions can be defined at almost any layer of the OSI model, a communications standard that defines a framework for implementing protocols in seven layers. The amount of functionality is limited only by the software implementation and the capability of the hardware.

Most vendors concentrate their software on the IP layer and above. Notable exceptions are Extreme, HP, Nortel, and Spectrum. Spectrum has the widest range of condition support, including some very specific Internetwork Package Exchange network quality-of-service features unique to its product.

Support for Layer 3 Differentiated Services is relegated primarily to traditional software-based routers. HP and Cabletron are the only vendors with Layer 3-aware switches capable of operating based on information in the IP Type-of-Service field during our tests. DiffServ is a critical part of policy management, as it enables end-to-end IP quality of service. If your edge devices don't offer Layer 3/Layer 4 intelligence, your policies will be relegated to the WAN and the core of your infrastructure.

Once a traffic flow has been defined in the policy server and identified by the switching or routing hardware, a number of actions can be applied to that flow. The role of a particular router interface describes how that router interface will enforce an action. For some vendors, such as Extreme and Lucent, the role applies to the entire device. For others, such as HP, roles cannot be configured in their current software release. Roles affect traffic only when the network is congested. These parameters are the most important for defining your network application behavior, but their effects are the most difficult to measure.

Roles were best supported by Cisco, IPHighway, and Orchestream. Every vendor whose products we tested plans to roll out support for these features in a future release.

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