This is an old revision of the document!
Data Center Fabrics
Stage count - is number of devices I need to pass through in order to get from source to the destination.
Clos fabric is a non-planar graph - there is no way to draw all those connections on a flat plane without crossings.
5-stage fabrics type:
- Fat tree
- Benes
- Butterfly
Over-subscription - is the ratio between total bandwidth offered to workloads and to total available fabric bandwidth.
Total Edge port count = spine ports * over-subscription * break-out ration.
Example 1 - three stage Clos using 64×100 spines and leafs with over-subscription 2:1 can provide 4096 edge ports.
Example 2 - 5 stage butterfly using 64×100 fabrics with over-subscription 2:1 can provide 65536 edge ports.
It's possible to add 7th stage, which often used for DCI.
Optics
| Name | Meaning | Distance | Notes |
|---|---|---|---|
| SR | Short Range | Up to 100m | Multimode Fiber |
| DR | Data Range/Rate | Up to 500m | SMF or MMF |
| FR | Far Range | Up to 2km | SM |
| LR | Long Range | Up to 10km | SM |
| ER | Extended Range | Up to 40km | SM |
| ZR | Zero Dispersion/Coherent | Over 80 km | SM |
Number indicates number of fibers: SR8 has 8 fibers, FR4 has 4 fibers etc…