HTTPbis Working Group R. Peon
Internet-Draft Google, Inc
Intended status: Informational Mar 18, 2013
Expires: September 19, 2013
Header Delta-Compression for HTTP/2.0
draft-rpeon-httpbis-header-compression-03
Abstract
This document describes a mechanism for compressing streams of groups
of key-value pairs, often known as Headers in an HTTP session. See
RFC 2616 [RFC2616] or successors for more information about headers.
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. How it works . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Header pre-processing . . . . . . . . . . . . . . . . . . . . 4
4.1. Mapping the first-line . . . . . . . . . . . . . . . . . . 4
4.2. Mapping HTTP key-values . . . . . . . . . . . . . . . . . 4
5. Compressor and Decompressor State . . . . . . . . . . . . . . 5
6. Header Block Wire Format . . . . . . . . . . . . . . . . . . . 6
7. String Encoding . . . . . . . . . . . . . . . . . . . . . . . 8
8. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9. Decompressor algorithm . . . . . . . . . . . . . . . . . . . . 9
10. Compression . . . . . . . . . . . . . . . . . . . . . . . . . 12
11. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 15
11.2. Example Serialization . . . . . . . . . . . . . . . . . . 16
12. Unfinished components . . . . . . . . . . . . . . . . . . . . 25
13. Security Considerations . . . . . . . . . . . . . . . . . . . 25
14. Requirements Notation . . . . . . . . . . . . . . . . . . . . 25
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
16. Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . 25
17. Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . 27
18. Appendix C . . . . . . . . . . . . . . . . . . . . . . . . . . 32
19. Normative References . . . . . . . . . . . . . . . . . . . . . 38
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 38
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1. Overview
There have been several problems pointed out with the use of the gzip
compressor in SPDY [SPDY]. The biggest of these problems is that it
is possible for a smart attacker to inject content into the
compressor, and then to test hypotheses about the prior contents of
the compressor by examining the output size after each such content
injection. The other issue is that gzip often consumes more CPU than
many would like, especially in situations where one is doing forward
or reverse proxying. The compressor proposed here intends to solve
the first issue and significantly mitigate the second, while
providing compression that is not too much worse than gzip.
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