Monitoring App Behavior – Are you responsible?
1 Application Note Monitoring Smartphone App Impact on Networks and User Experience with Anritsu MD8475A Definitions, Types and Specifications by TABLE OF CONTENTS 1. Monitoring App Behavior - Page 1 2. Method - Page 2 3. Configuration - Page 3 4. Procedure – Page 4 5. Conclusion– Page 6 Monitoring App Behavior – Are you responsible? It is clear that smartphone and tablets are taking on new tasks that were traditionally associated with laptops or desktop PCs. We can easily download and use numerous and possibly free “applications” written for major mobile platforms for our entertainment, such as social networking, video streaming, browsing, online gaming etc., or utilize them to take the edge off certain serious tasks, like banking. The rising level of popularity of applications usage is proving that most of us who use mobile devices that are classified as “smart” (sometimes referring to the device) find the utility that these applications provide beneficial. If we look deeper, the lifeblood of each app is the data connection through the smartphone that the app is running on, and the wireless network to which the smartphone is attached. For example, when you tap “OK” to finish a transaction on your favorite banking app, you would expect to see some sort of data traffic to let the bank’s servers know you are officially done with your transaction. From a consumer perspective in this example the most important aspects may be privacy and security of the data exchange, followed by ensuring that the consumer understands the data usage of the application. Another point of view belongs to the operators, where proper understanding and testing of the manner in which this connection would be utilized before an app becomes available for users to download is becoming more and more critical. Operators share the same concerns as consumers, as well as more technical concerns, such as whether or not an app is unnecessarily utilizing resources of the network (such as unnecessary and repeated DNS queries). Figure 1 - Smartphone data connection through various network elements 2 Method Introduction In this document we will describe a method of monitoring app-driven smartphone behavior in a controlled environment. We will use an emulated wireless network to get a smartphone to access the internet. We will show an Anritsu MD8475A Signaling Tester which emulates an end-to-end 4G wireless network. It is desirable to use a network emulator since the goal is to monitor and understand the overall behavior of a smartphone and the impact that it would place on a live network before the device or application is permitted to operate on the live network. Don’t let the word “emulate” mislead you, the MD8475A produces an LTE RF Signal equivalent to those generated by live wireless networks complete with the signaling produced by the core network. It is equipped with emulation software and messaging capability that allows a smartphone to register, attach and initiate the data session the same as on the live network. The core network componets that would connect to the internet in a real network are emulated on an integrated Windows 7® PC inside the MD8475A. Figure 2 - MD8475A - 1 Figure 3 - MD8475A – 2 The MD8475A can be configured with the Wireless Radio Access Technologies GSM, WCDMA, CDMA2000 or LTE along with a realistic implementation of the core network in one bench top instrument. It comes with Smart Studio software that simplifies configuring the MD8475A and monitoring UE performance. 3 Figure 4 - Smart Studio Smart Studio allows us to monitor smartphone activity by focusing on the messages sent over the wireless network, either graphically or using a message exchange format. We will get into more detail later in this paper. MD8475A also comes with Wireshark, a free program that allows users to view IP traffic (note the important protocol messages mentioned previously). We will use this program to monitor the IP traffic that the smartphone generates. Again, more will be discussed later in this paper. Configuration The test setup for the Anritsu MD8475A is as shown in the following Figure. Essentially, we are using the emulated wireless network to connect a smartphone to the internet. The connection to the internet is established by enabling a very common Windows 7 feature called connection sharing. Port 0 and Port 1 in the following Figure are shared, in essence creating a direct connection of the DUT with the real internet. Alternatively, one can “host” servers on the integrated Windows 7 PC, essentially creating a closed circuit end-to-end communication scenario. Figure 5 - Setup of data connection over emulated wireless network 4 Procedure 1. After connecting the cables, configure the desired wireless Radio Access Technology and associated Cell Parameters on Smart Studio (Band Class, Channel, RF Power Level, MCC, MNC, Sector ID, etc.). See the following for a screen shot of the MD8475A Cell Parameter Setup: 2. Start the Network Emulation, power the smartphone on, and observe the smartphone's successful attachment to the network. See below. 5 3. Monitor the data traffic using Smart Studio Data Throughput Viewer. See below. 4. Monitor the IP Layer activity using Wireshark. See below. 6 Conclusion In this example, we can see various messages, time stamped data activity and the amount of data traffic immediately after a smartphone is first powered on. One can observe that there is real IP layer communication taking place even when the user does nothing. It is up to the operators and smartphone vendors to agree on whether or not these behaviors are expected and appropriate. Given the number of different companies involved in the design of a smartphone (operating system, smartphone hardware, applications) overall understanding of the complete picture can easily be lost. Interesting scenarios can also be created by using this setup. For example, we can disconnect the internet connection, essentially simulating a case where internet servers are not responding to IP Layer connection attempts. How the smartphone behaves in a scenario such as that should be monitored carefully, and in a controlled environment such as the one described above. Finally, the "smartness" of a smartphone can be measured objectively by how responsibly it uses the data connection when consumers happen to be using any one of the many applications available to them at any given time. 7 ©Anritsu App Note Number: AnritsuMonitoringSmartphone_an1113_v1 Printed November 2013