This directory contains an SDN router implementation that routes packets based on ethernet addresses it learns.

Modules

• init.py maintains the permanent flows on each switch.
• broadcast.py builds and maintains a broadcast tree. To broadcast a packet it should be send to the broadcast group table entry.
• router.py monitors packets and tries to learn on what switch/port a mac address is connected. If it learns a mac address it adds flows to all switches to efficiently route packets there.

Note that routing still works without the router.py module, in that case is all traffic be broadcasted over the spanning tree. In that case are all packets also send to the controller since no ethernet addresses are learned. Editing the table miss entry in the entry flow table to not forward to the second flow table can fix that.

Flow tables

Entry flow table, this flow table decides what port a packet should be send out of. If the switch doesn't know an output port broadcast is using group table 0.

Priority	Amount	Module	Name	Match	Instructions
20	1 per learned local mac	router.py	Locally learned mac forwarding rules	eth.dst == learned mac	goto-table(1) AND write-action(output port)
10	1 per learned foreign mac	router.py	Foreign learned mac forwarding rules	eth.dst == learned mac	goto-table(1) AND write-action(output port)
0	1	init.py	Table miss entry	everything	goto-table(1) AND write-action(group 0)

Second flow table, this flow table looks up if the source ethernet address is known so the packet isn't forwarded to the controller without containing new information. This ensures the controller only receives packets of which it doesn't know the ethernet address. A switch also shouldn't forward packets to the controller it received from other switches since the source port that the controller learns would be wrong.

Priority	Amount	Module	Name	Match	Instructions
20	1 per learned mac	router.py	Learned mac rules	eth.src == learned mac	No actions
10	1 per connected switch	broadcast.py	Broadcasted forwarding rule	in port == other switch	No action
0	1	init.py	Table miss entry	everything	apply-action(output controller)

Group table, this table only has 1 entry with the ports to forward on for broadcasting packets.

Identifier	Module	Name	Type	Buckets
0	broadcast.py	Broadcast group	all	{Output port1, Output port2, ...}