Research And Implementation Of Forwarding Path Consistency Update Technology In SDN

Software-Defined Networking(SDN)has the characteristics of forwarding and control separation.When the network needs to update the forwarding paths in data plane due to link congestion,link failure,or firewall rule adjustment,the controller will report to the relevant switches issue update instructions and new flow rules.However,due to the distributed nature of the data plane,the time for the update instructions to arrive at each switch and the time for each switch to complete the update operation are different,resulting in an unpredictable sequence for switches to complete update.Therefore,intermediate paths including forwarding loops may appear in the network,or special network infrastructure such as firewalls are bypassed during the update period.Aiming at the problem of introducing forwarding loops and temporary paths bypassing special network infrastructure in the process of SDN forwarding path update,in this paper,we studied the existing methods to ensure the consistency of path updates.And we proposed an SDN forwarding path consistent update technology based on multi-round update.It can ensure that no forwarding loops and no special network infrastructure are bypassed during the update period,while reducing update rounds and avoiding update deadlocks in some cases.The research content and contributions of this paper mainly include:(1)We proposed a multi-round update nodes selection algorithm,which distinguishes the update process according to odd and even rounds.In odd rounds,we update a set of switches with the same forwarding direction in the old and new paths to shorten the distance(hop)between the source and destination switches of the forwarding path as much as possible.In even rounds,we update all switches that have deviated from the current forwarding path between the source and destination switches at one time.Repeat the above process until all switches are updated.The experimental results show that our algorithm can effectively reduce update rounds on the basis of ensuring that the forwarding path is acyclic during the update.(2)We proposed an update algorithm that guarantees no special network infrastructure are bypassed.The update topology is divided into different update areas along the current forwarding path according to special network infrastructure such as firewalls.And then allowing same-area updates and preventing cross-area updates.When update deadlock occur,we reverse the relationship of the new and the old path and calculate other update schemes.The experimental results show that our algorithm can effectively avoid update deadlocks in some cases on the basis of ensuring that no special network infrastructure are bypassed during the update.(3)We researched and designed a set of SDN forwarding path consistent update system.The system is based on the multi-round forwarding path consistent update technology proposed in this paper to achieve consistent SDN forwarding path update operations.The system includes an update event monitoring module,an update topology generation module,an update scheme calculation module,an update deadlock processing module,and an update issuance module.