SDN: Week 6: Module 7.3: Google backbone B4

[gdt]

Google has two backbones: user and inter-data centre.

Google has many WAN-intensive applications. The cost per bit doesn't decrease as network size increases.
- complexity of pairwise interactions
- manual management
- non-standard vendor APIs

Solution: "WAN fabrics"
- manage it as a fabric, not as individual boxes
But
- many boxes and protocols are box-centric
- distributed routing protocols aren't aware of congestion caused by each other
- want centralised traffic engineering: better network utilisation, faster convergence, more control, can specify intent, mirror prodution event streams for testing, modern server equipment for controller (about 50x faster than a router's CPU)

SDN also helps testing
- decentralised networks require full scale testbed replica of network to test new TE features
- centralised control can use the real production network as input, use a replica controller with production binaries, but virtualised switches. This is exactly what is done with mininet.

Summary
- choose hardware based on features
- choose software based on protocols
- logical centralised TE: easier mgnt, easier testing
- separates monitoring, mgnt and ops from individual boxes.