Chris Perl

Systems and infrastructure engineer at Jane Street, where he has worked since 2012. Perl specialises in digging into the detailed mechanics of complex systems — a tendency Ron Minsky describes as an unusual willingness to confront the horrible specifics until they become comprehensible. His most substantial project at the firm was a full redesign of Jane Street’s clock synchronisation infrastructure, driven by European financial regulation (MiFID II) requiring clocks to be demonstrably within 100 microseconds of UTC.

That project required Perl to go back to first principles on both NTP (Network Time Protocol) and PTP (Precision Time Protocol): reading the original David Mills papers, working through the four-timestamp offset calculation by hand, and evaluating the robustness trade-offs between the two protocols in a production financial-markets environment. He settled on a hybrid architecture — PTP from GPS appliances to a tier of Linux servers, hardware-timestamped NTP from there to all clients — that achieves 20–40 microseconds of worst-case error while preserving NTP’s falseticker-detection redundancy.

Core positions

Perl holds that inspectability is the primary currency of systems work: the measure of an infrastructure decision is how easily you can observe and reason about failures, not how elegant the design looks on paper. He was initially drawn to PTP’s theoretical precision but backed away when he found that its single-grandmaster architecture offered no protocol-level defence against a misbehaving GPS appliance, and that open-source NTP — with hardware timestamping tuned on — could meet the regulatory requirement with more robust failure modes. He is sceptical of black-box components and network switches as shared responsibilities in a timekeeping stack.

In the wiki

• Chris Perl on Clock Synchronization — Signals and Threads, 14 October 2020: how computer clocks drift, the NTP four-timestamp protocol, PTP’s advantages and redundancy weaknesses, and Jane Street’s hybrid GPS/PTP/NTP architecture for microsecond-accurate timekeeping