Cisco Systems IGX 8400 manual Planning for Cellbus Bandwidth Allocation, OC3

Universal Switching Module Enhanced

The card-baseddefault and maximum cellbus bandwidth for each interface appears in Table 4-5.Note that FastPackets require substantially less cellbus bandwidth than ATM cells. The FastPacket requirements in the figure and table reflect the restriction of FastPackets to one lane and the maximum processing rate of the gateway on the UXM-E.

The values you can view with the cnfbusbw and dspbusbw commands are:

•Minimum Required Bandwidth, the necessary bandwidth that switch software has calculated for the existing connections on the local UXM-E. The display shows the requirements for FastPackets, ATM cells, and the equivalent in total UBUs.

•Average Used Bandwidth is the average bandwidth usage.

•Peak Used Bandwidth is the peak bandwidth usage.

•Maximum Port Bandwidth is the maximum bandwidth that the back card can support. The FastPackets per second field has a dash-mark because only cells pass through the port.

•Allocated Bandwidth is the current cellbus allocation for the card. The field shows the UBUs, the bandwidth when only ATM cells are on the bus, and cells plus Fastpackets. The reason for cells alone and cells plus Fastpackets is that cells can exist on the cellbus with or without FastPackets. The last field under Allocated Bandwidth shows the formula to which the allocated values must adhere. (A description of the formula follows the example screen.)

Table 4-6		Cellbus Bandwidth Allocation for UXM-E Interfaces
			Default			Max.
			Cell	Default		Cell	Maximum
Inter-			Traffic	Cell + Fpkt		Traffic	Cell + Fpkts
face		Default	Only	Traffic	Max.	Only	Traffic
Type	Ports	UBUs	(cps)	(cps and fps)	UBUs	(cps)	(cps and fps)
OC3	4 or 2	44	176,000	132,000, 88,000	235	708,000	473,000, 470,000
T3	6 or 3	24	96,000	72,000, 48,000	235	708,000	473,000, 470,000
E3	6 or 3	20	80,000	60,000, 40,000	235	708,000	473,000, 470,000
T1	8	8	32,000	24,000, 16,000	32	128,000	96,000, 64,000
T1	4	4	16,000	12,000, 8,000	16	64,000	48,000, 32,000
E1	8	10	40,000	30,000, 20,000	40	160,000	120,000, 80,000
E1	4	5	20,000	15,000, 10,000	20	80,000	60,000, 40,000

Planning for Cellbus Bandwidth Allocation

With the Network Modeling Tool™ (NMT), you can use the projected load for all UXM-Es in the network to estimate their cellbus requirements. During normal operation, you can use Cisco WAN Manager to obtain the trunk and port statistics then decide whether to use cnfbusbw to increase the UBU allocation. If you are using only the CLI, you would need to establish a virtual terminal (vt) session to each node then execute dspbusbw or cnfbusbw.

Trunk Cards 4-11