I changed from "sets of headers" to attempt to achieve some kind of consistency in the wording. Some places used "header block", other places used "sets of headers", other places talked about sequences of HEADERS frames, etc. We need to come up with clear language that states that a "Header block" is a logical set that can span either a sequence of PUSH_PROMISE frames or a sequence of HEADERS frames... wait... maybe that's the exact language we need ;-)