Technical Summary
This specification defines a data format for shared brotli
compression, which adds support for shared dictionaries, large window
and a container format to brotli [RFC7932]. Shared dictionaries and
large window support allow significant compression gains compared to
regular brotli.
Working Group Summary
The document is a stand-alone addition to add dictionary support to
brotli (RFC 7932) which was also published as AD sponsored.
The use of the format documented in the draft was discussed in the HTTPBIS
working group as part of the work on draft-ietf-httpbis-compression-dictionary
but the shared brotli document itself was not a discussion point. The document
describes a stream format that has been in use by brotli for several years and
it was adopted by compression dictionaries as-is (with a prefix header defined
in the compression dictionaries draft got the `dcb` encoding).
Document Quality
The stream/file format has been implemented in the open-source brotli library:
https://github.com/google/brotli
The document has undergone 4 weeks IETF Last Call following the process for
AD sponsored documents. As a result of that LC, two reviews were provided by
people with expertise on compression (Yann Collet, creator of LZ4 and zstd, and
Felix Handte, on the compression team at Meta), in addition to the usual
directorate and shepherd reviews. Given the specificity of the document, this
was considered sufficient by the responsible AD.
Personnel
The Document Shepherd for this document is Patrick Meenan. The
Responsible Area Director is Francesca Palombini.