OpenFlow Protocol: Programming Flow Tables on Open vSwitch

I programmed OpenFlow 1.3 flow tables directly on Open vSwitch using match-action rules with priorities, idle timeouts, and output actions. Installing proactive flows revealed exactly how the southbound protocol turns controller intent into packet forwarding.

Objective & Context

OpenFlow is the canonical SDN southbound protocol: a switch matches packet fields against prioritized table entries and applies actions. This lab manipulates flows by hand with ovs-ofctl to make the abstraction concrete before automating it from a controller.

Environment & Prerequisites

• Open vSwitch with OpenFlow 1.3 enabled; a Mininet topology.
• ovs-ofctl and ovs-vsctl tooling.
• Understanding of match fields (in_port, dl_dst, nw_dst).

Step-by-Step Execution

1. Install a proactive forwarding flow

2. Add a higher-priority drop rule

3. Inspect counters per flow

priority=300,ip,nw_dst=10.0.0.9 actions=drop  n_packets=14
priority=200,in_port=1 actions=output:2       n_packets=88

Validation & Testing

Send traffic and confirm the higher-priority drop wins over the forward rule, with packet counters incrementing on the matched entry. Pass criteria: priority ordering observed and counters confirm which flow handled each packet.

Key Results

• Installed proactive flows with explicit priority and action semantics.
• Verified priority resolution between a forward and a drop rule.
• Read per-flow packet counters to confirm handling, not assumptions.
• Built the manual baseline later automated via an SDN controller app.