Before revision:  We show that in a differential pricing regime 1) a CP offering low QoS can make more revenues than a CP offering better QoS through sponsorships. 2)  QoS (mean delay) for end users can degrade compared to the case where no differential pricing is allowed .
After revision:  We show that in a differential pricing regime 1) a CP offering low QoS can make more revenues than a CP offering better QoS through sponsorships. 2) QoS (mean delay) for end users can degrade under differential pricing schemes. In the oligopolistic market with multiple ISPs, users tend to select the ISP with lowest ISP resulting in same type of conclusions as in the monopolistic market. We then study how differential pricing effects the revenue of ISPs .