[NoInterfaceObject, Exposed=(Window,Worker)]
interface NavigatorNetworkInformation {
   readonly attribute NetworkInformation connection;
};

Navigator implements NavigatorNetworkInformation;
WorkerNavigator implements NavigatorNetworkInformation;

[Exposed=(Window,Worker)]
interface NetworkInformation : EventTarget{
  readonly attribute ConnectionType type;
  readonly attribute EffectiveConnectionType effectiveType;
  readonly attribute Megabit downlinkMax;
  readonly attribute Megabit downlink;
  readonly attribute Millisecond rtt;
  attribute EventHandler onchange;
};

typedef unrestricted double Megabit;
typedef unsigned long long Millisecond;

  enum ConnectionType {
    "bluetooth",
    "cellular",
    "ethernet",
    "mixed",
    "none",
    "other",
    "unknown",
    "wifi",
    "wimax"
  };
  

  enum EffectiveConnectionType {
    "slow-2g",
    "2g",
    "3g",
    "4g"
  };
  

• Fingerprint a user based on characteristics of a particular network (e.g. type and downlink estimates) at a point in time, and by observing change in such characteristics over a period of time.
• Fingerprint a user based on transitions between one or more networks (e.g. based on order of transitions by type, downlink estimates, and time).
• Infer user location (e.g. are they home, at work, or in transit) based on above criteria.

• The attacker can use JavaScript to observe the duration (e.g. time from start of fetch to `onload` event) of any network fetch on the client, and may get more detailed timing data about the same fetch via the Resource Timing API.
• The attacker can use WebRTC to identify client's public and private IP addresses via STUN, or similar mechanisms.
• The attacker can observe the client IP, fetch duration, RTT, transfer speed, and other low-level socket metrics of a fetch on the server.

• If the attacker can initiate or observe a network fetch of any kind from the client, then they can observe its performance characteristics and how they change over time.
• If the attacker can convince the client to fetch a resource from their server, then they can similarly observe the performance characteristics of the fetch and how they change over time.