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This soft copy for use by IBM employees only.
The system switching capacity maximums are listed in Table 21 on page 98
below.
Notes
1 Maximum Bidirectional Connections
Defined here as the sum of point-to-point (PTP) and point-to-multipoint
(PTM) connections
2 The module (CAP/CAD) is capable of supporting up to 4,064
bidirectional connections but the number is restricted to 2016 due to
the 8285 ATM Control Point′s capacity (2048 PVC - 32 PVC reserved).
3 Due to the IBM 8285 control point capacity. (The number is 6,000 on
the IBM 8260 A-CPSW.)
4 Sum of PtP and PtM, and also sum of PVP and PVC connections.
In the case of the 8285 switch, the transmit latency is dependent on whether the
switching is done in the base unit, via CAP/CAD, or when it is installed in the
IBM 8285 Expansion Chassis with its switch-on-a-chip. Table 22 shows the
maximum latency for both switching modes under both normal and high
utilization.
Table 21. Connection Capacity of IBM 8285 Nways ATM Workgroup Switch
Maximum
Bidirectional
Connections1
IBM 8285 Base Unit
-With ATM firmware upgrade kit
-Without ATM firmware upgrade kit
2,016 2
992
ATM Module
-With ATM firmware upgrade kit
-Without ATM firmware upgrade kit
2,016 2
992
IBM 8285 (with Expansion Unit)
-With ATM firmware upgrade kit
-Without ATM firmware upgrade kit
2,016 3
2,016
PVCs per IBM 8285 100 4
Maximum Multipoint Parties per IBM 8285 1,024
Table 22. Transmit Delay (Latency per Port)
Switching Mode Utilization ATM Port Latency (in
microseconds)
CAP/CAD normal 25 Mbps 57 µs
155 Mbps 41 µs
high 25 Mbps 61 µs
155 Mbps 44 µs
switch-on-a-chip normal 33 µs
high 40 µs
98 ATM Workgroup Solutions: Implementing the 8285 ATM Switch