Blink: Fast Connectivity Recovery Entirely in the Data Plane

In this paper, we explore new possibilities, created by programmable switches, for fast rerouting upon signals triggered by Internet traffic disruptions. We present Blink, a data-driven system exploiting TCP-induced signals to detect failures. The key intuition behind Blink is that a TCP flow exhibits a predictable behavior upon disruption: retransmitting the same packet over and over, at epochs exponentially spaced in time. When compounded over multiple flows, this behavior creates a strong and characteristic failure signal. Blink efficiently analyzes TCP flows, at line rate, to: (i) select flows to track; (ii) reliably and quickly detect major traffic disruptions; and (iii) recover data-plane connectivity, via next-hops compatible with the operator’s policies.

We present an end-to-end implementation of Blink in P4 together with an extensive evaluation on real and synthetic traffic traces. Our results indicate that Blink: (i) can achieve sub-second rerouting for realistic Internet traffic; (ii) prevents unnecessary traffic shifts, in the presence of noise; and (iii) scales to protect large fractions of realistic Internet traffic, on existing hardware. We further show the feasibility of Blink by running our system on a real Tofino switch.