QUIC at Snapchat - Snap Engineering

To reduce network latency and error, we make requests and responses smaller, reduce unnecessary sync, utilize global content distribution partners to bring media close to the people who use it, and use an efficient, next generation network protocol called Quick UDP Internet Connections, or QUIC for short. As the above diagram depicts, QUIC does not alter the low-level operating system network protocols nor does it alter high-level HTTP.Compared to the TCP+TLS+HTTP2 stack, QUIC offers the following advancements:Faster connection establishment: QUIC handshakes support zero roundtrips before sending payload, compared to 1-3 round trips for TCP+TLS.Improved congestion control: QUIC has pluggable congestion control, and provides richer information to the congestion control algorithm than TCP. However, QUIC connections are recognized by a QUIC protocol layer randomly generated 64 bit identifier, so a client using QUIC can continue in-flight requests, uninterrupted across a change in IP address, allowing for an undisturbed user experience.Detection of lost connection: QUIC detects connection loss quickly and avoids long hanging requests.QUIC advancements fit well with Snapchat use cases:Faster connection establishment: At Snapchat, before QUIC, p90 connection setup took up to 300ms. Faster connection on QUIC directly reduces user waiting latency and improves the user experience.Improved congestion control: At Snap, the size of upload media can be as large as 10MB.