PWOSPF Step-by-Step Specification
- Maintain a view of the topology;
- Broadcast HELLO packets to maintain a list of neighbours;
- On change, flood the view of the network;
- Run Djikstra to compute the shortest path.
1) Define a topology
- 2 switches
- 2 hosts
- 2 controllers (same as hosts)
2) Send basic traffic
- Send traffic by hand, without PWOSPF;
- Need to install forwarding rule in dataplane (through mininet);
- ping H1 to H2.
- Controller program to install rules;
- Controllers are threads in mininet;
- 1 controller per switch;
- To statically install a forwarding rule, use switch.addRule.
4) Compute rules instead of hard code them
- Data structure for topology (matrix, …)
- Compute nearest neighbours;
- Stub out parsing, sending, receiving of PWOSPF;
- Run Djikstra on topology;
- Install rules.
5) Send packets (HELLO) ==> Who are our neighbours?
- Define packet format with Scapy;
- To send, use sendp();
- To receive, sniff on interface (provided by mininet);
- Data plane code to handle broadcast or Controller sends 1 packet per interface;
- Step 1: control plane sends to everyone;
- Step 2: broadcast in the data plane.
- Parse packet and populate topology.
- Generate HELLOs at Timeouts;
- Handle Timeouts ==> link down.
7) LSU packets
- Build the graph, running Djikstra;
- Flood to everyone;
- Drop if it is your own;
- Parse responses;
- Build topology.