IBM SG24-4817-00 manual ATM Bandwidth Capacity, Integrated LES/BUS Capacity

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6.2.1.2 ATM Bandwidth Capacity

The ATM bandwidth should be considered in a large network, especially for reserved bandwidth connections, such as the connections between switches. This section describes the ATM bandwidth capacity of the 8285 switch and its components:

•Total Bandwidth

The total bandwidth available for each IBM 8285 Base Unit and ATM module in the expansion unit is 212 Mbps/FDX. This is because, although the switch-on-a-chip supports up to 256 Mbps for each module, the switch uses 64-byte cells internally to transport 53-byte ATM cells. Therefore, the maximum external throughput per module is 256 Mbps x 53/64 or 212 bytes.

•Total Reserved Bandwidth

The total reserved bandwidth available for each IBM 8285 base unit and for each ATM module in the expansion unit is 85 percent of the total bandwidth available and is 180 Mbps when the total bandwidth is 212 Mbps. In addition, the maximum reserved bandwidth for an ATM port is 85 percent of the physical port speed. For example, it becomes 85 Mbps for a 100 Mbps port and 131 Mbps for a 155 Mbps port.

Table 23 shows the summary of the IBM 8285 ATM bandwidth capacity.

Table 23. Bandwidth Capacity of the IBM 8285 Nways ATM Workgroup Switch

Description	Value
Total bandwidth for all ports in the base unit	212 Mbps (256
	Mbps x 53/64)
Total bandwidth per an ATM module in the expansion unit	212 Mbps
Total reserved bandwidth for All ports in the base unit	180 Mbps (212
	Mbps x 85%)
Total reserved bandwidth per an ATM module in the expansion	180 Mbps
unit
Maximum reserved bandwidth per an ATM port	85% of physical
	port speed

6.2.1.3 Integrated LES/BUS Capacity

The IBM 8285 can integrate the LES/BUS server functions in the control point. This section describes the capacity information when the function is configured:

•Maximum Number of LES/BUS Instances

When the LAN Emulation protocol is used, each LES/BUS instance will define an Emulated LAN (ELAN). The IBM 8285 can configure two LES/BUSs instances, and therefore two ELANs. To interconnect these ELANs together requires an ATM router, such as the IBM Multiprotocol Switched Services Server.

•Maximum Number of LECs

The number of LECs can impact LES performance, for example, during the initial registration process and during the MAC-to-ATM address mapping process.

Table 24 on page 100 shows the summary of the IBM 8285 integrated LES/BUS capacity.

Chapter 6. IBM 8285 Planning and Installing 99