Research in Distributed Computing

APNIC Guest Post: The role of cellular networks in the Internet

Apr 4, 2018: The growing key role of cellular networks for providing Internet connectivity in many places around the world makes the case for considering such networks as part of the critical infrastructure of these economies. An invited post for the APNIC blog.

Read the full paper here

The tremendous growth of the mobile Internet, with over 11 billion devices connected by 2020, and its economic implications, have motivated several reports. And yet, we still lack an understanding of the impact of cellular networks around the world.

There are a number of reasons for this. For starters, it is currently challenging to tell whether a particular IP address comes from a cellular or fixed-line user.

In much of the world, cellular users reside in networks that combine both cellular and fixed-line customers, which complicates any straightforward attempt at identification. Knowing a device type (smartphone or tablet) has limited value as most mobile devices have multiple interfaces and users tend to offload cellular traffic to WiFi when available.

And while instrumented devices or data collected from a network operator’s core could provide detailed information on cell network usage, scaling these sorts of studies have proven to be difficult.

A comprehensive understanding of cellular access has a wide range of applications for different stakeholders in the Internet. For content providers and delivery networks, identifying access technology would help to diagnose and address performance issues in the wild. Researchers and operators could better understand how networks are being used around the world and identify potential trends, while policy-makers could have a firmer statistical footing for investment decisions.

... continue reading the blog post ...

Tracking your Application Time

Apr 10, 2015: Mobile devices have become an integral part of our lives, however, most of us have little idea how often and how long we are spending with these devices. Track your mobile phone habit by installing Application Time (AppT) today!

Mobile devices have become an integral part of many of our lives, so much so that recent studies have found severe separation anxiety between people and their mobile phones, with participants citing the apprehension of missed communication with friends or loved ones without access to chat or social media applications. Motivated by this as well as anecdotal evidence of the large effect of mobile devices on our lives, we at the Northwestern Aqualab are embarking on a study to collect and analyze the usage patterns and habits of the population. Today, we are releasing our mobile application to help users track, analyze and understand their relationship with their mobile device. Named Application Time – or AppT for short – the app allows users to track and visualize their usage of mobile applications and the frequency and duration of their mobile device interactions. The application is now released to the Android Store for download – a more detailed description of the measurements and mechanic, refer to the project page on our website (appt.aqualab.cs.northwestern.edu).

The screen shots below show how the app allows users to visualize aggregated and individual usage of applications on their device through an easy, intuitive interface. The app also allows users to export their usage data so they can perform their own analytics if they desire.

We have been using AppT for over a year now internally in out lab. To illustrate some of the awareness and insights that this can bring, I present an analysis of my own mobile device usage. The first interesting thing we found was the long tail of application usage, and that the top 10 apps account for over 90% of the device time, and that the other 30 or so apps only account for the remaining 10%. These top apps (shown in Table 1) include common communication related tasks such as calls, SMS and email. It was surprising to see Google Hangouts – a SMS and chat client – was used over 11,000 times over the course of a year; that amounts to just over 23 times a day on average.

Looking at temporal usage patterns, a couple of interesting items can be seen. In the figure below, each dot represents an instance when a mobile application was launched. Besides the overall amount consistent quantity of usage, we see that in general the phone is the first item checked every morning, and is consistently accessed throughout each day and into the early morning.

One point of concern was the peak in usage each day during the middle of the work day in the late afternoon. It was noticed that the device was primarily being used for chat and email messaging even though the user was sitting in front of a computer. This meant that work is being consistently interrupted to check each and every notification on the device, regardless of the notification’s urgency. Such a constant distraction can be very detrimental to long period of focused effort. Once aware of this activity, the user now disables all notifications throughout periods of concentrated work (using several of the apps available), and has seen great improvements in productivity.

Our lab has released the app Application Time to the public on the Google Play Store so others can collect and analyze their mobile device usage. Hopefully, by using AppT you will be able to figure out ways your own ways to break dependence, improve productivity, or be aware of your device habits.

Getting in and out of Cuba

Sep 9, 2015: Change is coming to Cuba - Our early work on characterizing Cuba's Internet connectivity to appear at the next ACM Internet Measurement Conference (IMC) 2015!

Read the full paper here

It may have taken 54 years, but change is coming to Cuba. Last December, the US government announced plans to restore relations with Cuba and ease restrictions on travel and trade. It took little time for American businesses to start scouting opportunities - from Netflix to Airbnb.

Despite the promising news, the state of Cuban infrastruc- ture, particularly in the computing and network segment, pose no small challenges to these plans. Today, less than 5% of the population have their own fixed-line Internet connection and only an estimated 25% of the population are able to get online. Those that are actually connected experience very poor performance. Ookla’s NetIndex, for instance, ranks Cuba among the worst ten countries in terms of average bandwidth – 197th out of 202 – with a measured broadband download speed of 1.67 Mbps.

We have started to characterize the state of Cuba’s access to the wider Internet. Our first paper on the topic - appearing at the ACM Internet Measurement Conference 2015 - reports on some of our early findings, including high RTTs to websites hosted off the island, even after the addition of ALBA- 1, a high degree of path asymmetry in traffic to/from the island that partially traverse high-latency satellite links, and several web services that return invalid responses to requests originating from the island. We plan to make a periodic status report on the state of the Internet in Cuba and the associated data available to the research community.