Three and Vodafone in traffic-throttling probe
Mobile companies Three and Vodafone are under investigation over the way they manage data on their networks.
The investigation, by telecoms regulator Ofcom, will examine whether the two are compliant with net neutrality rules that state all traffic on the network must be treated equally.
In particular, Ofcom will examine whether the operators throttled speeds while customers were abroad.
Vodafone said it was "very disappointed" by the investigation.
The company said it was surprised that Ofcom had singled out one of its services - Vodafone Passes.
"Our Passes allow customers to access their favourite content without fear of running out of data or attracting out-of-bundle charges.
"Vodafone does not 'throttle' speeds on Vodafone Passes, either in the UK or while customers are roaming.
"The Video Pass is optimised so that all of our customers have a high-quality experience when streaming content on the network.
"Optimising means making the bandwidth available that enables videos to be delivered in a faster, more efficient way, while still providing the best smartphone viewing experience, and without compromising the experience of other customers who do not use a Vodafone Pass."
Three said that it would be "working closely with Ofcom to understand their concerns".
European Union rules mean that broadband operators - both internet service providers and mobile operators - cannot impose restrictions on internet traffic.
But providers may use reasonable measures to manage their internet traffic to ensure networks run efficiently.
They must be clear and transparent about their traffic-management policies, which should be based on providing technical quality of service.
The investigation will examine the following:
Three's practices of:
- restricting tethering - the practice of using one device to connect another one to the internet - on certain plans offered by Three
- imposing restrictions on the devices in which a Sim can be used - eg where a Sim purchased for a mobile phone cannot be used in a tablet
- traffic-management practices such as "throttling" or intentionally slowing down particular categories of traffic (eg video traffic, peer-to-peer and virtual private network traffic), including where traffic management is applied when customers are roaming
In relation to Vodafone:
- traffic-management practices relating to Vodafone Passes - eg throttling particular categories of traffic - including where traffic management is applied when customers are roaming
- the transparency of exceptions to zero rating within the Vodafone Passes products, which mean that certain functions within certain zero-rated applications will use customers' general data allowance and not be zero-rated
Ofcom plans to publish its findings in June.