Cisco Systems IGX 8400 Calculating Cellbus Bandwidth Changes, ATM Across a Public ATM Network

Universal Switching Module Enhanced

Calculating Cellbus Bandwidth Changes

To determine how many UBUs are necessary, use the values for average bandwidth used in the following formula:

fps

------- + cps 2

UBUs = -----------------------

4000

In most circumstances, the fps and cps values from average bandwidth used are sufficient. The peak bandwidth used values are primarily informational.

The information in Table 4-5provides the ranges for the interface type. Note that, if you do the math according to the formula, you see that the value in the cells-alone column of Table 4-5equals the result of adding half the FastPacket value to the cell value in the cells plus FastPackets column.

When you use dspbusbw, a yes/no prompt asks if you want firmware to retrieve the usage values. If you enter a “y,” the UXM-E reads—then clears—its registers and thus restarts statistics gathering.

If you enter an “n,” switch software displays the current values that reside in control card memory (on the NPM). The values in memory come from the last update from the UXM-E.

ATM Across a Public ATM Network

The UXM-E can support trunking across a public ATM network so both virtual channel connections (VCCs) and virtual path connections (VPCs) traverse a single virtual path trunk. This feature lets you map multiple trunks to a single port of an NNI. The NNI connects to either a public or private ATM network. The virtual trunk package is a lower-cost alternative to leased circuits but still has the full set of Cisco ATM traffic management capabilities. This application requires two UXM-Es and a clock from an external source. The rates can be OC-3/STM-1, T3/E3, or T1/E1.

Figure 4-4 UXM-Es Configured for a Public ATM Network

	1	Cable 1
UXM-E	2	2	UXM-E	4	Public
trunk	3	3	port		network
slot 8			slot 9

10106

Note the following characteristics of this form of trunking across a public network:

•

•

•

The trunk cannot provide the a clock for transport across the public network.

This feature does not support VPC connections across the public network.

The node number at each endpoint must be 17 or higher.

Refer to Figure 4-3as you read the steps for the following example set-up:

Step 1 Connect a cable between each of the following:

•8.1 and 9.1

•8.2 and 9.2

4-12Cisco IGX 8400 Series Reference