| | 124 | - '''Simplified Load Balancer: ''' [[BR]] |
| | 125 | The above question requires the user to implement a web server on both left node and right node to report the querying results about token bucket buffer statistics. At the same time, the openflow controller that the experimenter implemented should pull the web page, parse the content to get those statistics, which seems to be too complicated. [[BR]] |
| | 126 | An alternative way to accomplish this is, by querying Flow statistics directly from the OpenFlow switch. [[BR]] |
| | 127 | Upon the arrival of a new TCP flow, the OpenFlow controller should send out a `FlowStatsRequest` message to the OpenFlow switch. The OpenFlow switch will reply with statistics information about all flows in its flow table. This flow statistics message will be fetched by the `stats_reply` function in Trema. Based on the statistics, experimenters can apply their own policy on which path to choose in different situations. For more information about !FlowStatsRequest and !FlowStatsReply, please refer to http://rubydoc.info/github/trema/trema/master/Trema/FlowStatsRequest and http://rubydoc.info/github/trema/trema/master/Trema/FlowStatsReply. [[BR]] |
| | 128 | The difference between this Load Balancer and the Load Balancer introduced in the previous section is, this Load Balancer only reports the cumulated statistics of each flow over-time while the previous Load Balancer fetches the real-time network traffic information from both paths. |
| | 129 | |
| | 130 | We have already implemented a sample Load Balancer that decides path based on the accumulated number of bytes sent through left and right path (such that the new flow will go to the one path with less number of bytes sent). [[BR]] |
| | 131 | Experimenter can download the sample Load Balancer [http://www.gpolab.bbn.com/experiment-support/OpenFlowExampleExperiment/load-balancer-simple.rb HERE]. |
| | 132 | |
| | 133 | '''Question: Try modify the downloaded load balancer so that it decides path based on the average per-flow throughput observed on each path''' |
