This soft copy for use by IBM employees only.
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| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 |
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| 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
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TB | TBE | LCBAul SB | LCBAuh |
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RH (8 byte)
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| NBA | F1 | F2 |
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GFC | VPI |
| VCI |
| PT CL ATM Header | ||||
(4 byte: without HEC)
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ATM payload (48 byte) | ||
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Future Use
TB: | Target Blade |
TBE: | Target Blade Extension |
LCBAul: | Leaf Control Block Address up(inbound) lower port |
LCBAuh: | Leaf Control Block Address up(inbound) higher port |
NBA: | Next Buffer Address |
F1: | Format Field 1st |
F2: | Format Field 2nd |
GFC: | Generic Flow Control |
VPI: | Virtual Path Identifier |
VCI: | Virtual Channel Identifier |
PT: | Payload Type |
CL: | Cell Loss Priority |
HEC: | Header Error Control |
Figure 11. Internal Cell Format of the IBM 8285 Nways ATM Workgroup Switch
3.2.1.2 Switching without the Switch Chip
When no expansion chassis is connected, the IBM 8285 Base Unit implements a direct connection between CAD_up and CAD_down. This means that inbound cells would undergo the following process:
1.The SFE_up strips the HEC from valid cells and forwards the cell to the CAD_up.
2.The CAD_up prepares the internal cell and forwards it directly to the CAD_down.
3.The CAD_down uses the RH information to determine which ports to forward the cell to, strips the internal header, and forwards the
