  The ongoing net neutrality debate has generated a lot of heated discussions
on whether or not monetary interactions should be regulated between content and
access providers. Among the several topics discussed, `differential pricing'
has recently received attention due to `zero-rating' platforms proposed by some
service providers. In the differential pricing scheme, Internet Service
Providers (ISPs) can exempt data access charges for on content from certain CPs
(zero-rated) while no exemption is on content from other CPs. This allows the
possibility for Content Providers (CPs) to make `sponsorship' agreements to
zero-rate their content and attract more user traffic. In this paper, we study
the effect of differential pricing on various players in the Internet. We first
consider a model with a monopolistic ISP and multiple CPs where users select
CPs based on the quality of service (QoS) and data access charges. We show that
in a differential pricing regime 1) a CP offering low QoS can make have higher
surplus than a CP offering better QoS through sponsorships. 2) Overall 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.
