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.