symfony/symfony-docs — pull request #3880 by greg0ire (2014-05-27 09:09:28+00:00)
Title: document the mysterious abc part of the header

One can't help but wonder what it is about. Disclaimer: I'm far from being a specialist, I barely know varnish. This is what I understand after a cursory reading of [this document](http://www.w3.org/TR/edge-arch). Please check this carefully.