Cabletron Systems 04-0053-01 manual Administrative Weights, Creating Route Metrics

Routing RouteMetrics

Caution Remember that while some special network configurations may require the TimeoutValue to be zero (0), setting TimeoutValue to less than three seconds may cause a UNI route to fail unnecessarily. For this reason, care should be taken when setting the TimeoutValue to less than three seconds.

4.4ROUTE METRICS

Route metrics are assigned to routes using a metric tag (one of the input parameters for add atmroute). The metric tag specifies a particular pair of incoming and outgoing metrics contained within a list of metrics. Metrics are created using the add pnnimetric command (whether PNNI, IISP, or UNI routes). Each metric pair specifies a set of values that describe a route’s Service Category, cell rates, bandwidth, and administrative weight. Locally, metric values determine the behavior of the link. Within PNNI networks, PNNI’s Generic Call Admission Control (GCAC) assesses metrics when establishing calls.

4.4.1Administrative Weights

The administrative weight (AdminWt parameter) of a metric allows you to control the use of a route for call set ups. By default, a metric assigns the lowest value (5040) to the AdminWt parameter. Values less than 5040 (for example 500) are considered to have greater administrative weight. Among parallel routes, the route with the greatest administrative weight is seen as the preferred route; subsequently, most calls are set up through that route. Other parallel routes with lower administrative weights are used as “backup” routes These backup routes will be used only if the route with the greatest administrative weight is either out of bandwidth or down.

4.4.2Creating Route Metrics

The following section describes how to create a route metric and assign it to a route.

Note For a complete description of all pnnimetric parameters, see the SmartSwitch

ATM Switch Reference Manual.

In the following example, a metric pair is created (with metric tag of 9), which specifies CBR as the Service Category, administrative weight of 200, Max Cell Rate of 1000 cells per second, and an Available Cell Rate of 750 cells per second.

Note The default value NotUsed that appears in the add pnnimetric command means “If no value is specified for the parameter, the parameter is not used within the metric.” It does NOT mean that the parameter does not accept values.

SmartSwitch ATM User Guide 4-7