Network Working Group Y. Nir Internet-Draft Check Point Intended status: Informational October 9, 2012 Expires: April 12, 2013 HTTP/2.0 Discussion: Compact Header Encoding draft-nir-httpbis-che-00 Abstract This document proposes an alternative encoding for HTTP headers. This encoding is considerably more compact than the uncompressed textual encoding in HTTP/1.1 and current HTTP/2.0 draft. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 12, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Nir Expires April 12, 2013 [Page 1] Internet-Draft compact-header October 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . . 3 2. The Binary Encoding . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Short Type-Value . . . . . . . . . . . . . . . . . . . . . 4 2.3. Long Type-Value . . . . . . . . . . . . . . . . . . . . . . 4 2.4. Type-Length-Value . . . . . . . . . . . . . . . . . . . . . 4 3. Header Encoding . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Custom Headers and Custom Enumerations . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. Changes from Previous Versions . . . . . . . . . . . . . . . . 6 8. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Appendix A. Additional Examples . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Nir Expires April 12, 2013 [Page 2] Internet-Draft compact-header October 2012 1. Introduction HTTP/1.x and the current draft of HTTP/2.0 encode headers using text labels and text values. HTTP/2.0 attempts to make this more efficient by compressing the textual headers. This proposes a binary-only alternative. 1.1. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. The Binary Encoding The header block is formatted as follows: +------------------------------------+ |1| version | 8 | +------------------------------------+ | Flags (8) | Length (24 bits) | +------------------------------------+ |X| Stream-ID (31bits) | +------------------------------------+ | Sequence of headers | | | +------------------------------------+ The sequence of headers is just a list of the headers in one of 5 formats: o Flags - These are headers with no associated data. The only information they convey is by their mere presence. o Short Type-Value - where the header is associated with a 16-bit value. o Long Type-Value - where the header is associated with a 32-bit value. o Type-Length-Value - where the length is specified in the header. All formats include a 16-bit header identifier (see below), and those identifiers will be allocated through a new IANA registry (see Section 5). The header identifier specifies which format applies. Nir Expires April 12, 2013 [Page 3] Internet-Draft compact-header October 2012 2.1. Flags These headers are 16-bit numbers containing the header identifier. +-----------------+ |header identifier| +-----------------+ 2.2. Short Type-Value These headers have the 16-bit identifier, and also the 16-bit value. +------------------------------------+ |header identifier| Value | +------------------------------------+ 2.3. Long Type-Value These headers have the 16-bit identifier, and also a 32-bit value. +------------------------------------+ |header identifier| Value | +-----------------+------------------+ | Value (cont) | +-----------------+ 2.4. Type-Length-Value These headers have the 16-bit identifier, and also a 24-bit length field, and a value of variable length. +------------------------------------+ |header identifier| Length | +---------+-------+------------------+ | Length | Value... | +---------+--------------------------+ 3. Header Encoding The encoding of each header is specified in the specification that describes it. For convenience, this document describes some common encodings. Specification writers SHOULD use these formats whenever they are appropriate. Unsigned integer numbers can be represented by either the short or long type-value, depending on their range. Cache ages measured in seconds, such as in HSTS should use the long type-value, whereas a Nir Expires April 12, 2013 [Page 4] Internet-Draft compact-header October 2012 header specifying an age in days should probably use a short type- value. Either way, the encoding can be called "INT". Headers that hold an enumeration (such as Method) SHOULD use a short type-value, and SHOULD reserve one value (0xffff) for custom values. Time values should be encoded as strings using the RFC3339 format. Strings such as names should use the TLV format, and SHOULD be encoded as UTF-8. String headers should be specified by their encoding, so "UTF8", or "ASCII". For headers with multiple values, the general format is always TLV, and the specification should list their type as either of three things: o Short values - a list of 16-bit values o Short strings - a sequence of strings, each prefixed by a 1-octet length field. o Long strings - a sequence of strings, each prefixed by 1 2-octet length field. 4. Custom Headers and Custom Enumerations For each type of header, a range will be allocated for experimental and custom headers. To avoid collisions, we define here a special header to denote what kind of header this is. The header is has identifier 49160 (0xC008), so it is TLV-formatted, and its value is formatted as follows: Custom header format +------------------------------------+ |header identifier| Flags | Name... | +---------+-------+------------------+ For example, suppose draft-nir-httpbis-copyright-notice defines a header that contains a copyright notice for the content. I will 65530 (0xFFFA). Note that the two headers don't have to be consecutive. If the sender knows that the receiver recognizes this header with this identifier, the Custom header MAY be omitted. Nir Expires April 12, 2013 [Page 5] Internet-Draft compact-header October 2012 Custom and Copyright Headers C0 08 00 00 0C FF FA 00 4C 4F 50 59 52 49 47 48 |........COPYRIGH| 54 FF FA 00 00 43 6f 70 79 72 69 67 68 74 20 28 |T....Copyright (| 63 29 20 32 30 31 32 20 49 45 54 46 20 54 72 75 |c) 2012 IETF Tru| 73 74 20 61 6e 64 20 74 68 65 20 70 65 72 73 6f |st and the perso| 6e 73 20 69 64 65 6e 74 69 66 69 65 64 20 61 73 |ns identified as| 20 74 68 65 20 64 6f 63 75 6d 65 6e 74 20 61 75 | the document au| 74 68 6f 72 73 2e 20 41 6c 6c 20 72 69 67 68 74 |thors. All right| 73 20 72 65 73 65 72 76 65 64 2e |s reserved. | For custom values in enumerations we define the Custom-Value header with identifier 49161 (0vC009), where the content is the string name of the custom value. This header MUST follow the enumeration header. 5. IANA Considerations IANA is requested to set up a new registry of header identifiers. The value is 16-bit, and the range is partitioned as follows: o 0-16383 - these values are allocated to flag headers, where the format is as in Section 2.1 o 16384-32767 - these values are allocated to short type-value headers, where the format is as in Section 2.2 o 32768-49151 - these values are allocated to long type-value headers, where the format is as in Section 2.3 o 49152-65535 - these values are allocated to type-length-value headers, where the format is as in Section 2.4 The ending quarter of each range shall be reserved for experimental and custom usage, and shall not be allocated by standards action. For example, the range 45056-49151 will be reserved for experimental and custom long type-value headers. 6. Security Considerations There are no security considerations for this draft. 7. Changes from Previous Versions First version 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Nir Expires April 12, 2013 [Page 6] Internet-Draft compact-header October 2012 Requirement Levels", BCP 14, RFC 2119, March 1997. Appendix A. Additional Examples NOTE: Most of the below examples were shamelessly copied from draft-snell-httpbis-bohe-01. Assuming the following (intentionally incomplete) header registrations: +--------------------+-------+------+---------------------------+ | HTTP Header | ID | Hex | Format | +--------------------+-------+------+---------------------------+ | Version | 16384 | 4000 | Major.Minor in 16-bit | | Method | 16385 | 4001 | Enumeration | | Host | 49152 | c000 | UTF8 | | Path (Request URI) | 49153 | c001 | UTF8 | | Status | 16386 | 4002 | uint16 | | Status-Text | 49386 | c0ea | UTF8 | | Content-Length | 32768 | 8000 | uint32 | | Content-Type | 49154 | c002 | ASCII | | Expect | 16387 | 4003 | uint16 | | Last-Modified | 49155 | c003 | RFC3339 | | ETag | 49156 | c004 | sequence of short strings | | If-None-Match | 49157 | c005 | sequence of short strings | | Allow | 49158 | c006 | sequence of uint16 | | Do-Not-Track | 58 | 003a | flag | +--------------------+-------+------+---------------------------+ And the following values representing known HTTP Methods: +---------+-------+ | Method | Value | +---------+-------+ | GET | 1 | | POST | 2 | | PUT | 3 | | DELETE | 4 | | PATCH | 5 | | HEAD | 6 | | OPTIONS | 7 | | CONNECT | 8 | +---------+-------+ Here is what the encoding looks like: Nir Expires April 12, 2013 [Page 7] Internet-Draft compact-header October 2012 Version Header: 40 00 02 00 |@...| Method Header (GET Request) 40 01 00 01 |@...| Method Header (PATCH Request) 40 01 00 05 |@...| Method Header (Custom "FOO" Method) 40 01 FF FF C0 09 00 03 46 4F 4F |@.......FOO | Do Not Track 00 3A |.:| Host Header: C0 00 00 00 0F 77 77 77 2e 65 78 61 6d 70 6c 65 |.....www.example| 2e 6f 72 67 |.org | HTTP Response Status ("200 OK") as two separate headers, one containing the status code, the other containing the status text: 40 02 00 C8 C0 EA 00 00 02 4F 4B |@........OK | Content-Length Header (value encoded as uint32): 80 00 00 00 00 C8 |......| Content-Type Header (although maybe it should become an enum: C0 02 00 00 0A 69 6d 61 67 65 2f 6a 70 65 67 |.....image/jpeg | Expect Header (Expect: 100): 40 03 00 64 |...d| Last-Modified (Using RFC3339 Format): C0 03 00 00 19 32 30 31 32 2d 30 38 2d 30 31 54 |.....2012-08-01T| 30 34 3a 32 33 3a 31 32 2e 31 32 33 34 5a |04:23:12.1234Z | Nir Expires April 12, 2013 [Page 8] Internet-Draft compact-header October 2012 ETag (Strong Entity-Tag, String-format): C0 04 00 00 06 05 61 62 63 64 65 |......abcde | If-None-Match (Multiple values) C0 05 00 00 0C 05 61 62 63 64 65 05 61 62 63 64 |......abcde.abcd| 66 |f | Allow (GET, POST, FOO): C0 06 00 00 06 00 01 00 02 FF FF C0 09 00 00 04 |................| 03 46 4f 4f |.FOO | Author's Address Yoav Nir Check Point Software Technologies Ltd. 5 Hasolelim st. Tel Aviv 67897 Israel Email: ynir@checkpoint.com Nir Expires April 12, 2013 [Page 9]