1. HOT TO MAKE ZERO-RATING BETTER FOR USERS
Yiannis Yiakoumis, Sachin Katti, Nick McKeown
Stanford University

2. Zero-rating
So there has been a lot of excitement around zero-rating services and this is obvious just by looking the new programs that became available over the last two years.
Wikipedia Zero, Facebook’s Free Basics, Music Freedom and Binge On from T-Mobile, a partnership between Netflix and Australian ISPs, and the list goes on and on...

3. Zero-rating
But along with excitement, there are many concerns on whether these services are good for users. For example, after many people complained Netflix had to publicly apologize and stop its partnership with Australian ISPs, Indian regulators banned Free Basics in India after a big backlash from users, and FCC said it is monitoring existing zero-rating services by T-Mobile.

4. What if we let users decide?
Neutral Network
ISP-defined
Fast Lanes
This debate is not new: One side says that the network should be neutral and treat all traffic the same, and the other says that ISPs should be able to partner with content providers in order to provide some sort of differentiated services, either for QoS of pricing.
But there is a paradox here: everyone is talking on behalf of the users, but as users we don’t have any say on the debate. So, why don’t we let users decide how their own traffic is treated?
User-Driven

5. Do users want zero-rating?
1000 smartphone owners, US, year old, SurveyMonkey Audience, 08/15
To get a better sense of how zero-rating programs would look like if we were to enable users to express their preferences, we run a survey with 1000 smartphone owners in the US and asked them directly.
63% of them said they would be interested to use some sort of zero-rating functionality.

6. What music do users want to zero rate?
Long-tail of user preferences
Then, we became a bit more specific. We asked them, which music applications they would like to see included in a program like Music Freedom.  This user preference graph summarizes their responses. On the x-axis you see the different music applications, while on the y-axis you see the number of users asking for this application. Now, the most interesting thing on this graph, is the long tail of user preferences. And it is sort of expected, there all these applications, and each of us has his own unique and diverse preferences.

7. What music do users want to zero rate?
66% of user preferences not in Music Freedom (November 2015)
So, we should be seeking to preserve this long-tail, and unfortunately we are not doing that well in that front. For example, last November when I did the survey, 66% of the uniquely listed applications were not present in T-Mobile’s music freedom program.

8. What do users really want to zero-rate?
Which application would you choose for ZeroCharge?
We then gave even more choice to users: We asked them if they could choose a single application to be zero-rated for their own purposes, which one would that be? And now the tail became much heavier and we had several other profiles popping-up besides music fans. Some people wanted to watch video, other wanted to follow the news, or social networks, or , or maps etc. And each category had numerous applications of varying popularity, from the ones with hunderds of millions of downloads, to others that had a few thousands downloads.

9. Boost (deployed at 160 homes)
This long-tail is not present only on zero-rating programs, but also in other services, like fast lanes. I collaborated with Google when they were building their OnHub home router, and we gave people in 160 homes the capability to express which websites get priority in their home network, just by clicking a button in their browser. 

10. What do users want to Boost?
Very Popular (Alexa ranking)
Less Popular
Long-tail of user preferences
And what we saw again, was this long-tail of user preferences.
So, the first point I want to make is that users have their own unique preferences, and they are willing to express them if there is a practical way to do so. And if we try to guess what users want, we will be ignoring this long-tail.

11. How can users express their preferences?
Respect user preferences!
Clear and transparent process to get zero-rated
Enable users to decide
How can users express their preferences?
There are two basic steps to come-up with services that are more inclusive and better serve users. First is to have clear and transparent processes on how certain traffic can get special treatment. For example, T-Mobile could maintain a public database of everyone that requests access to Music Freedom, and then guarantee that any legal streaming provider will be included within a week. The second and ideal outcome, would be to let users directly decide what they want.
And this brings me to the second point: if we were to let users express their preferences, how would we do it? What technical mechanism we can use in order to communicate these preferences to the network?

12. High-level Requirements
Simple & expressive
Deployable
Respect Trust (accountability, authentication, privacy, revocation)
I believe there are three high-level requirements to do something like this:
First, we need something that is simple, for people to understand and use, and expressive, so that it can capture the long-tail of user preferences, covering complex structures like websites or mobile applications.
Second, we need something which can be practically deployed. So it should have low overhead, work in the presence of encryption, CDNs, and middleboxes like NATs, and it should be incrementally deployable without requiring big changes in existing infrastructure.
And finally, we need something that respects the trust relationships between different stakeholders, and provide necessary primitives for accounting, authentication, revocability, confidentiality, and user privacy.
What we realized is that existing mechanisms like Deep Packet Inspection, DiffServ, or an SDN-like Out-of-band approach cannot meet these requirements. And so, we came up with a very simple mechanism to express user preferences tot he network called network cookies.
I will not dive into technical details, but I just want to give you a high level idea of how network cookies work. 
Deep Packet Inspection, DiffServ, Out of band
do not meet these requirements… 

13. Step 1: Think of network services as “lanes”
Best-Effort Lane
Zero-rated Lane
The first step is to think of network services like zero-rating and prioritization, as “special lanes”. So, all we have to do is enable users to say what traffic goes into what lane, and then it is up to the network to decide how to take this user preference and configure their network appropriately. 
Fast Lane

14. Network Cookies: a mapping abstraction
Network Cookie : A small piece of data users append to their traffic
Get cookie for each service
User appends cookies to the desired traffic
Network matches against them and enforces service
Best-effort Lane
Free Lane
A network cookie is a small piece of data that users append to their traffic to consume a specific service. Each user gets a cookie for each service available to them. Whenever they want to use one, they append the relevant cookie to their traffic, and then the network detects it, and enforces the desired service.
It’s very similar to HTTP cookies but instead of sending them to webservers to customize the user interface of a webpage, we send network cookies to the network to customize the way traffic is delivered to us. 
So nothing complicated here, cookies provide a very simple mapping abstraction. There are some extra bits to make sure that cookies are secure, cannot be replayed, they are revocable etc, but in the interest of time I won’t discuss them here. 
Fast Lane

15. Respect user preferences!
Clear and transparent process to get zero-rated
Enable users to decide
Network Cookies
a mechanism to express user preferences to the network
Simple and expressive, can be practically deployed, respect trust
More inclusive, better auditable, user-driven network services
The high-level point is that cookies provide a straight-forward, low-overhead and transparent mechanism to express which traffic gets special from the network.
And because of this they can enable network services that better serve users, by being  more inclusive, better auditable, and ideally, directly driven by users.

16. thanks! yiannisy@stanford.edu
If you have any questions about cookies, or if you are interested to do a trial with a user-driven approach or network cookies, please let me know.
Thank you very much!