From the operator's point of view it is necessary to manage each access line and separate critical data with guaranteed SLA from ordinary data without the need for a quick response (SLA). There are plenty of applications for downloading files, playing games, on-line video viewing, listening to audio and access to social networks. Behind a few network ports hundreds of different applications are hidden and the operator must recognize and apply the appropriate SLA for each connection. In terms of data centres its a similar situation as SLA is defined by its accessibility and performance of applications and this is controlled by load balancers- ADC (Application Delivery Controller). Well balanced traffic control of data networks and access to applications within data centers greatly increases user QoE.