Specifications

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Cisco MGX 8800/8900 Series Software Configuration Guide
Release 5.1, Part Number OL-6482-01, Rev. A0, January 25, 2005
Chapter 8 Managing PNNI Nodes and PNNI Routing
Managing Connection Grooming
The Priority column lists the available connection priorities. The usedCR Xmt and usedCR Rcv columns
show the bandwidth in use at each priority level in the transmit and receive directions, respectively. The
# of Conns column shows the number of logical connection numbers reserved at each priority level.
Managing Connection Grooming
Connection grooming is the process of checking each connection to determine if a more efficient route
is available. If a prospective new route is significantly better than the incumbent route, the connection
is rerouted.
The Cisco MGX Release 5 software provides many features for implementing and managing connection
grooming. The following sections describe these connection grooming topics:
• How Grooming Reroutes Connections
• Enabling and Disabling Soft Rerouting for Grooming
• Configuring Scheduled Grooming
• Manually Grooming Connections
• Configuring the Grooming Thresholds
• Configuring Orderly Grooming
• Configuring the Trunk Utilization Limit
• Displaying Grooming Configuration Parameters
• Displaying Grooming Configuration Statistics
• Configuring the AIS Delay
• Enabling and Disabling the Soft Reroute IE
How Grooming Reroutes Connections
Cisco MGX switches use two different reroute methods for grooming connections. Prior to Release 5,
Cisco MGX switches use only the hard reroute method. During a hard reroute, a connection that has been
selected for grooming is disconnected, and then a new connection is built over a new route. The
disadvantage to this approach is that the new connection is not validated before the original connection
is released. Another disadvantage is that even when the new connection is operational, hard rerouting
interrupts connection service for a longer period of time than soft rerouting. The hard reroute method is
sometimes called the break-before-make method.
Soft rerouting is introduced in Release 5 Cisco MGX switches for grooming of P2P connections. During
a soft reroute, a new connection is established and validated before the existing or incumbent connection
is released. When the new connection is ready for use, the switch changes to the new connection with a
momentary interruption of service. When the connection is established on the new connection, the
incumbent connection is released. The soft reroute method is sometimes called the make-before-break
method. Figure 8-2 illustrates how a soft reroute operates.