WiFiMon Architectural Components

Mobile User Device and Monitoring Probes

A mobile user device is any user's device connected to the WiFi network (laptop, phone, tablet,...). Crowdsourced measurements are gathered from the user devices when the user visits some chosen webpage which contains WiFiMon JavaScript code that invokes measurements. This is a WiFiMon Software Probe (WSP). In addition WiFiMon offers hardware probes (WHP) which are installed on a small for factor hardware (e.g. RaspberryPi) and placed in fixed positions.

WiFiMon Admin

WiFiMon admin is the network administrator managing the WiFi network and the WiFiMon system. Using the WiFiMon UI, he/she can perform queries to the Elastic ELK Cluster and get the performance of the wireless network.

WiFiMon Agent / UI

• WiFiMon Agent
  

  Processes collected raw and exported measurement data to provide the insight on the wireless network performance per client or AP. The results of correlations are stored in the ELK Cluster.

• WiFiMon UI
  

  Provides temporal graphs of all the performance metrics, allows queries to retrieve the information about the measurements initiated from the WSP or WHP associated to a specific access point and within a specific time period. Other queries could be to retrieve the information about the specific IP ranges, test tools, user browsers  etc.

Data Security

The main WiFiMon service delivery model assumes that the WiFiMon user installs all the WiFiMon components in his/her premises. Therefore all the data remains in the users possession all the time and the WiFiMon team does not have any access to it. All the traffic in transit between the WiFiMon components is TLS encrypted. Furthermore, sensitive and potentially personally identifiable information data such as mobile users IP or MAC address are hashed before being stored in the WAS. The correlation procedure mentioned in the WiFiMon Agent section is performed over the hashed data.

WiFiMon Building Blocks and Measurement Workflow

WiFiMon Test Server (WTS)

WiFiMon uses active probing in order to get the WiFi network performance metrics. Active probe packets are exchanged between the WSP and WHP on one side and WiFiMon Test Server on the other. WTS uses NetTest, Boomerang and SpeedTest measurement software which can provide the information about the packet round trip times and network performance data like bandwidth and latency (represented in Figure 2 as lines marked as 2.1, 2.2, and 2.5).

One of the methodologies that WiFiMon tests use is to measure the upload and download time for a file that WiFiMon administrator chooses. By choosing a larger file, more accurate measurements can be obtained because of the TCP congestion control/windowing mechanisms and slow start. However there is a trade-of because larger transfer sizes mean introducing a larger traffic overhead and this way the negative impact to the WiFi network itself. Therefore it is recommended that the file size is comparable to the size of a typical web page (up to 5MB). This way one measurement would push to the network and user's device probe traffic comparable to one web site visit and the obtained measurements would show the throughput and the time to load the page as user sees it.

The obtained throughput metrics should not be considered as the maximum achievable throughput of the WiFi network at the moment of measurement, but the WiFi network administrator should rather look at the relative differences between the measurements in order to get the insight into the quality of user's experience with the WiFi network he/she uses. The location of the WTS and its topological distance from the monitored WiFi network has a major impact on the crowdsourced measurement accuracy and reliability. You can read more about this here.

WiFiMon Software Probe (WSP)

The WiFiMon Software Probe (WSP) is the JavaScript code integrated in some chosen often visited web page (e.g. captive portal, university web page or similar). Whenever user visits the page, the monitoring tests are being invoked. It is possible that some user repetitively visits that web page or frequently refreshes the browser on the page. Such behaviour may result in excessive probe traffic being injected into the network, overloading WiFiMon components and creating an additional unwanted traffic over the WiFi network. To alleviate this problem, WSPs include a cookie with a customizable blocking time parameter (e.g. 5 mintes). New measurements by the same WiFi network user (same browser) will be possible only after the blocking time in the cookie expires.

WiFiMon Hardware Probe (WHP)

The WiFiMon Hardware Probes (WHPs) are set up on small form factor devices - such as the Raspberry Pi. The WHP probe may be viewed as an end user logged in to the eduroam wireless network, but monitoring continuously from a fixed point. It measures bandwidth, latency, the average values of bit rate, the signal level, the link quality and the transmission power. The WiFiMon team recommends to set up a WHP on Raspberry Pi’s v3 Model B+ or v4.

WiFiMon Analysis Server (WAS)

The WiFiMon Analysis Server (WAS) processes the performance results of crowdsourced and deterministic measurements received from WSPs and WHPs respectively. The WAS consists of the WiFiMon agent, Elasticsearch, Logstash and the WiFiMon UI/Kibana for customizing reports and their visualization.

Websites monitored by WiFiMon are not only visited by end users residing in the monitored subnets, but also from end users external to them. Therefore it is important to prevent WAS from processing excessive traffic and measurements which are not related to the WiFi network that is being monitored. To that end, WiFiMon maintains a list of registered subnets. Upon accepting a connection from an end user, the WiFiMon Test Server inspects if this end user is within a monitored subnet by obtaining the list of registered subnets from the WAS (2.3, 2.4). For WSPs/WHPs residing within the registered subnets, network performance metrics are calculated and streamed from the end devices to the WiFiMon Analysis Server (2.6) to be processed. Afterwards, the WAS correlates performance data with client IPs and AP-IDs (2.7/2.8). Results are stored in the ELK stack.