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RYU Part5:

In this exercise, We are going to include the flow expiry/timeouts (hard timeout and idle timeout) in the simple_switch_13.py(Layer 2 Switch).

Idle Timeout:

If the flow is Idle(no packets hitting this flow) for the specified time(Idle Time), the flow will be expired.

Hard Timeout:

Flow entry must be expired in the specified number of seconds regardless of whether or not packets are hitting the entry

In simple_switch.py, the default timeout values(for idle and hard) are not set(0). it means, the flows are permanent. it will never expiry.

High level Steps:

  1. in the flow addition function, specify the timeouts

Code changes:

Copy the simple_switch_13.py to ex4_flow_timeout.py file

cp simple_switch_13.py ex4_flow_timeout.py

Modify the ex4_flow_timeout.py file as below,

  1. In the add_flow function, include idle, hard parameters with default value as 0.
  2. OFPFlowMod API include the idle_timeout,hard_timeout parameters.
            mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                    idle_timeout=idle, hard_timeout=hard, priority=priority, match=match,
                                    instructions=inst)
  1. Call the add_flow function with idle, hard value

Note : The default command is command=ofproto.OFPFC_ADD

Test

Ryu Application

ryu-manager ex4_flow_timeout.py

Mininet Topology

sudo mn --controller=remote,ip=127.0.0.1 --mac -i 10.1.1.0/24 --switch=ovsk,protocols=OpenFlow13 --topo=single,4

Lets Ping and watch the flows

OVS flows

sudo ovs-ofctl -O OpenFlow13 dump-flows s1

Reference:

  1. https://www.opennetworking.org/software-defined-standards/specifications/

page 155 contains timeout details.

  1. API details http://ryu.readthedocs.io/en/latest/ofproto_v1_3_ref.html?highlight=OFPFlowMod