RFC 3229 (rfc3229) - Page 2 of 49
Delta encoding in HTTP
Alternative Format: Original Text Document
RFC 3229 Delta encoding in HTTP January 2002
Table of Contents
1 Introduction.................................................... 3
1.1 Related research and proposals........................... 4
2 Goals........................................................... 5
3 Terminology..................................................... 6
4 The HTTP message-generation sequence............................ 8
4.1 Relationship between deltas and ranges................... 11
5 Basic mechanisms................................................ 13
5.1 Background: an overview of HTTP cache validation......... 13
5.2 Requesting the transmission of deltas.................... 14
5.3 Choice of delta algorithm and format..................... 16
5.4 Identification of delta-encoded responses................ 16
5.5 Guaranteeing cache safety................................ 17
5.6 Transmission of delta-encoded responses.................. 18
5.7 Examples of requests combining Range and delta encoding.. 19
6 Encoding algorithms and formats................................. 22
7 Management of base instances.................................... 23
7.1 Multiple entity tags in the If-None-Match header......... 24
7.2 Hints for managing the client cache...................... 25
8 Deltas and intermediate caches.................................. 27
9 Digests for data integrity...................................... 28
10 Specification.................................................. 28
10.1 Protocol parameter specifications....................... 28
10.2 IANA Considerations..................................... 30
10.3 Basic requirements for delta-encoded responses.......... 30
10.4 Status code specifications.............................. 30
10.4.1 226 IM Used...................................... 31
10.5 Header specifications................................... 31
10.5.1 Delta-Base....................................... 31
10.5.2 IM............................................... 32
10.5.3 A-IM............................................. 33
10.6 Caching rules for 226 responses......................... 35
10.7 Rules for deltas in the presence of content-codings..... 36
10.7.1 Rules for generating deltas in the presence of
content-codings.................................. 37
10.7.2 Rules for applying deltas in the presence of
content-codings.................................. 37
10.7.3 Examples for using A-IM, IM, and content-codings. 38
10.8 New Cache-Control directives............................ 40
10.8.1 Retain directive................................. 40
10.8.2 IM directive..................................... 40
10.9 Use of compression with delta encoding.................. 41
10.10 Delta encoding and multipart/byteranges................ 42
11 Quantifying the protocol overhead.............................. 42
12 Security Considerations........................................ 44
13 Acknowledgements............................................... 44
14 Intellectual Property Rights................................... 44
Mogul, et al. Standards Track