CSC 718 Answers 4 - Cloud infrastructure & SDN

IS-Q4a Advantages of SDN in cloud data centres

Whole-network view - one controller plans routes and balances load globally.
Programmable/automated - policies are code pushed to all switches; fits cloud automation.
Cheap hardware - simple white-box switches; intelligence in software; less vendor lock-in.
Fast changes - reconfigure by a controller action, matching elastic cloud workloads.
Works with NFV - services (firewall, load balancer) placed dynamically along paths.

Legacy boxes fuse control and data planes, so changes are manual and local. Separating them gives one software-definable source of truth.

IS-Q4b How P4 goes beyond OpenFlow

OpenFlow can only match a fixed set of header fields the switch chip was built for; a new header means waiting for the vendor. P4 is a protocol-independent data-plane language: you write a parser (read packets), match/action tables (what to do), and a deparser (write packets). The compiler turns it into the switch pipeline at line rate, so new protocols and logic run with no new hardware. OpenFlow made the control plane programmable; P4 makes the data plane programmable too.