Real-time web application roadblock: Performance penalty of HTML sockets

HTML socket streams, such as XHR-polling and HTML5 websockets, are being rapidly embraced because they operate over HTTP(S) protocols and ports, allowing them to easily traverse security firewalls and HTTP proxies, unlike raw TCP streams. This paper presents an active measurement study of these protocols and compares their performance to raw TCP. Our results indicate that HTML socket streams impose significant performance penalties with respect to protocol overhead (up to 5×), data payload delivery delay (up to 3× more), and throughput (up to 3× less). The performance divide between HTML socket streams and TCP is particularly severe for the more important case of small data payload sizes (100s of bytes). Moreover, our results demonstrate the HTML socket streams introduce higher jitter as compared to TCP streams. Our experiments indicate that the real-time capabilities of HTML socket streams are significantly poorer than TCP streams, particularly over 3G cellular data Internet connections.