TLS Session Resumption: Full-speed and Secure

At CloudFlare, making web sites faster and safer at scale is always a driving force for innovation. We introduced “Universal SSL” to dramatically increase the size of the encrypted web. In order for that to happen we knew we needed to efficiently handle large volumes of HTTPS traffic, and give end users the fastest possible performance.

CC BY 2.0 image by ecos systems

In this article, I’ll explain how we added speed to Universal SSL with session resumptions across multiple hosts, and explain the design decisions we made in this process. Currently, we use two standardized session resumption mechanisms that require two different data sharing designs: Session IDs RFC 5246, and Session Tickets RFC 5077.

Session ID Resumption

Resuming an encrypted session through a session ID means that the server keeps track of recent negotiated sessions using unique session IDs. This is done so that when a client reconnects to a server with a session ID, the server can quickly look up the session keys and resume the encrypted communication.
At each of CloudFlare’s PoPs (Point of Presence) there are multiple hosts handling HTTPS traffic. When the client attempts to resume a TLS connection with a Continue reading