Research On Service Quality Guaranteed Virtual Link Technology In Software-Defined Networking

Improving network service quality is one of the key research areas of traditional network technology.It is also much importantly researched in SDN.However,the typical methods used in traditional networks to improve QoS are more or less implemented with complicated network protocols,and cannot effectively guarantee QoS or can only with a few QoS factors.Furthermore,the QoS implementations in traditional networks are not applicable to SDN due to the differences in network architecture.In this paper,we design and implement a virtual link system guaranteeing multiple QoS factors based on SDN.That is,QoS requirement with delay,bandwidth and packet loss rate can be met effectively during the datagram transmission.We take SDN network resources as a sharing pool.After receiving a datagram transmission request with specific QoS parameters,the network controller establishes a virtual link by allocating available network resources for it,and maintains the virtual link for guaranteeing network service quality.The changes of delay,bandwidth and packet loss rate of links are obtained by network measurement.Based on it,system periodically checks the virtual link service quality and adjusts the multipath mapping of the virtual link in time to dynamically maintain the effectiveness of transmission with QoS requirement.System measuring components track the changes of link QoS factors in real time.Controller sends probing messages to switches and after getting replies the corresponding link delay is calculated based on these messages.Compared with the measuring values of the ping tool,the average relative error of link delay measured according to our method is about 6.41%.The link bandwidth and packet loss rate are calculated through the switch port statistics messages.Compared with the measuring values of the iperf tool,the average relative error of bandwidth measured according to our method is about 4.3%,and for packet loss rate,about 13.3%.Through the multi-path searching algorithm under the multi-factor restriction proposed in this paper,the multi-path mapping paths of the virtual link are obtained and then the virtual link is established.We implement the virtual link system in a modular manner for all needed functions.Within it,a QoS maintenance mechanism periodically filtrates bad paths in the multipath mapping of the virtual link,whose QoS parameters are not met with requirements.And,it dynamically rebuilds paths when network resources become available.Simulation shows that the virtual link system can establish an end-to-end transmission channel which meets specific QoS requirements if network resources are sufficient.When a part of links used in the network is getting bad from service quality while the other part is available for supplement or replacement,the virtual link system can timely find it and adjust the multipath mapping to maintain the availability of the virtual link.Compared with the default forwarding way in Floodlight,when the network condition is getting bad,the virtual link system has better performance on bandwidth and packet loss rate,it also effectively improves the utilization of network resources.