IE10 WebSocket: single‑threaded implementation causes latency under concurrent connections

Goal

Evaluate the impact of IE10’s documented WebSocket limits on real‑time applications that open many sockets to the same host.

Constraints and Uncertainty

IE10 enforces a hard limit of six WebSocket connections per domain and processes all socket traffic on the main UI thread. When more than six sockets are opened, latency spikes are observed, especially under heavy JavaScript execution. The Microsoft documentation does not indicate whether future updates will raise the connection limit or adopt a multi‑threaded approach.

Unresolved Decision

It remains unclear whether the 6‑connection cap or the single‑threaded design will be altered in subsequent IE10 patches or Windows updates, and how that would affect latency behavior.

Questions

• Will future IE10 updates increase the WebSocket connection limit or switch to a multi‑threaded implementation?
• What mitigation strategies can developers employ to reduce latency when exceeding the six‑connection threshold?
• How can we reliably measure the impact of the UI thread’s CPU usage on WebSocket latency in IE10?