One document matched: draft-snell-httpbis-bohe-02.xml
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<rfc category="info" ipr="trust200811" docName="draft-snell-httpbis-bohe-02">
<front>
<title abbrev="application/merge-patch">
HTTP/2.0 Discussion: Binary Optimized Header Encoding
</title>
<author initials="J.M." surname="Snell" fullname="James M Snell">
<address>
<email>jasnell@gmail.com</email>
</address>
</author>
<date month="February" year="2013" />
<keyword>I-D</keyword>
<keyword>http</keyword>
<keyword>spdy</keyword>
<abstract>
<t>This memo describes a proposed alternative encoding for
headers within SPDY SYN_STREAM, SYN_REPLY and HEADERS
frames.</t>
</abstract>
</front>
<middle>
<section title="Binary Optimized Header Encoding">
<t>Binary Optimized Header Encoding is a proposed
alternative serialization for headers within SPDY SYN_STREAM,
SYN_REPLY and HEADERS frames that is designed to optimize
generation, consumption and processing of the most commonly
used HTTP headers.</t>
<figure><preamble>Alternate Header Block Serialization:</preamble><artwork>
+-------+---------+
| NUM | Headers |
+-------+---------+
</artwork></figure>
<t>'NUM' is a single unsigned 8-bit value indicating the total number
of distinct headers contained in the encoded block.</t>
<t>'Headers' consists of the complete set of encoded headers. The format
for each header is determined by whether the header name (the key) and
the header value are included in the static "default dictionary"
defined by this specification. The first two bits of each encoded
header record identify the specific header format used.</t>
<figure><preamble>Registered Key + Registered Value Pair</preamble><artwork>
+--+---+--+
|00|FLG|ID|
+--+---+--+
</artwork></figure>
<t>If the header name and value are both included in the default
dictionary, the header is encoded using only three distinct fields:
the two-bit opcode (00) followed by six unused flag bits, followed
by the index of the header key+value pair as provided by the default
dictionary, encoded as a variable-length, unsigned integer.</t>
<figure><preamble>Registered Key + Unregistered Value</preamble><artwork>
+--+---+--+---+---+
|01|FLG|ID|LEN|VAL|
+--+---+--+---+---+
</artwork></figure>
<t>If the header name is included in the default dictionary, but the
value given is not, the header is encoded using five fields: the two-bit
opcode (01) followed by six flag bits as defined below, followed by the
numerically lowest index of the named header as provided by the default
dictionary encoded as a variable-length, unsigned integer, followed by
another variable-length, unsigned integer specifying the length of the
value, followed by the encoded value.</t>
<figure><preamble>Unregistered Key + Value Pair</preamble><artwork>
+--+---+------+---+------+---+
|10|FLG|LENkey|key|LENval|val|
+--+---+------+---+------+---+
</artwork></figure>
<t>If the header name and value are not included in the default dictionary,
the header is encoded using six distinct fields: the two-bit opcode (10)
followed by six flag bits as defined below, followed by a variable-length,
unsigned integer specifying the key length, followed by the ISO-8859-1
encoded key name, followed by a variable-length, unsigned integer specifying
the value length, followed by the encoded value.</t>
<figure><preamble>Flags:</preamble><artwork>
FLG = 000000
||||||
||||Reserved
|||Numeric (val is one or more uvarints)
||Huffman-encoded
|UTF-8 or ISO8859-1 (1 or 0)
Binary | Text (1 or 0)
</artwork></figure>
<t>When the opcode is either 01 or 10, the six-bit FLG field is used to specify
additional properties about the header value. When the opcode is 00, the FLG
bits are unused and MUST NOT be set.</t>
<t>Moving from the most significant bit to the least, the flags are:
<list style="symbols">
<t>Binary or Text (0x32) - When set, the value is to be interpreted as
binary data. When unset, the value is to be interpreted as encoded-text.</t>
<t>UTF-8 or ISO-8859-1 (0x16) - When set, indicates that the text-encoded
value is UTF-8 encoded. Otherwise, ISO-8859-1 is assumed. Only used if the
Binary or Text bit is unset.</t>
<t>Huffman-encoded (0x08) - When set, indicates that the text-encoded
value has been static huffman encoded. The static dictionary used for the
encoding is dependent on whether the text is UTF-8 or ISO-8859-1 encoded.
Only used if the Binary or Text bit is unset.</t>
<t>Numeric (0x04) - When set, indicates that the value is encoded as a
variable-length unsigned integer. Only used if the Binary or Text bit is
set (indicating a binary value).</t>
<t>The final two bits (0x02 and 0x01) are reserved.</t>
</list>
</t>
<section title="Example Headers">
<t>Assuming the following (incomplete) default dictionary:</t>
<texttable>
<ttcol>ID</ttcol>
<ttcol>Key</ttcol>
<ttcol>Value</ttcol>
<c>0</c><c>date</c><c></c>
<c>1</c><c>:scheme</c><c></c>
<c>2</c><c>:scheme</c><c>http</c>
<c>3</c><c>:scheme</c><c>https</c>
<c>4</c><c>:scheme</c><c>ftp</c>
<c>5</c><c>:method</c><c></c>
<c>6</c><c>:method</c><c>get</c>
<c>7</c><c>:method</c><c>post</c>
<c>8</c><c>:method</c><c>put</c>
<c>9</c><c>:method</c><c>delete</c>
<c>10</c><c>:method</c><c>options</c>
<c>11</c><c>:method</c><c>connect</c>
<c>12</c><c>:method</c><c>patch</c>
<c>13</c><c>:method</c><c>link</c>
<c>14</c><c>:path</c><c></c>
<c>15</c><c>:path</c><c>/</c>
<c>16</c><c>:host</c><c></c>
<c>17</c><c>cookie</c><c></c>
<c>18</c><c>:status</c><c></c>
<c>19</c><c>:status</c><c>200</c>
<c>20</c><c>:status</c><c>201</c>
<c>21</c><c>:status</c><c>202</c>
<c>22</c><c>:status</c><c>204</c>
<c>23</c><c>:status</c><c>205</c>
<c>24</c><c>:status-text</c><c></c>
<c>25</c><c>:status-text</c><c>OK</c>
<c>26</c><c>:version</c><c></c>
<c>27</c><c>:version</c><c>1.0</c>
<c>28</c><c>:version</c><c>1.1</c>
<c>29</c><c>:version</c><c>2.0</c>
<c>30</c><c>accept</c><c></c>
<c>31</c><c>accept-charset</c><c></c>
<c>32</c><c>accept-encoding</c><c></c>
<c>33</c><c>accept-language</c><c></c>
<c>34</c><c>accept-ranges</c><c></c>
<c>35</c><c>allow</c><c></c>
<c>36</c><c>authorizations</c><c></c>
<c>37</c><c>cache-control</c><c></c>
<c>38</c><c>content-base</c><c></c>
<c>39</c><c>content-encoding</c><c></c>
<c>40</c><c>content-length</c><c></c>
<c>41</c><c>content-location</c><c></c>
<c>42</c><c>content-md5</c><c></c>
<c>43</c><c>content-range</c><c></c>
<c>44</c><c>content-type</c><c></c>
<c>45</c><c>etag</c><c></c>
<c>46</c><c>expect</c><c></c>
<c>47</c><c>expires</c><c></c>
<c>48</c><c>from</c><c></c>
<c>49</c><c>if-match</c><c></c>
<c>50</c><c>if-modified-since</c><c></c>
<c>51</c><c>if-none-match</c><c></c>
<c>52</c><c>if-range</c><c></c>
<c>53</c><c>if-unmodified-since</c><c></c>
<c>54</c><c>last-modified</c><c></c>
<c>55</c><c>location</c><c></c>
<c>56</c><c>max-forwards</c><c></c>
<c>57</c><c>origin</c><c></c>
<c>58</c><c>pragma</c><c></c>
<c>59</c><c>proxy-authenticate</c><c></c>
<c>60</c><c>proxy-authorization</c><c></c>
<c>61</c><c>range</c><c></c>
<c>62</c><c>referer</c><c></c>
<c>63</c><c>retry-after</c><c></c>
<c>64</c><c>server</c><c></c>
<c>65</c><c>set-cookie</c><c></c>
<c>66</c><c>status</c><c></c>
<c>67</c><c>te</c><c></c>
<c>68</c><c>trailer</c><c></c>
<c>69</c><c>transfer-encoding</c><c></c>
<c>70</c><c>transfer-encoding</c><c>gzip</c>
<c>71</c><c>upgrade</c><c></c>
<c>72</c><c>user-agent</c><c></c>
<c>73</c><c>vary</c><c></c>
<c>74</c><c>via</c><c></c>
<c>75</c><c>warning</c><c></c>
<c>76</c><c>www-authenticate</c><c></c>
<c>77</c><c>access-control-allow-origin</c><c></c>
<c>78</c><c>content-disposition</c><c></c>
<c>79</c><c>get-dictionary</c><c></c>
<c>80</c><c>p3p</c><c></c>
<c>81</c><c>x-content-type-options</c><c></c>
<c>82</c><c>x-frame-options</c><c></c>
<c>83</c><c>x-powered-by</c><c></c>
<c>84</c><c>x-xss-protection</c><c></c>
<c>85</c><c>connection</c><c></c>
<c>86</c><c>connection</c><c>keep-alive</c>
</texttable>
<figure><preamble>The header :version=2.0 would be encoded as:</preamble><artwork>
00 1D |..|
</artwork></figure>
<figure><preamble>The header :method=GET would be encoded as:</preamble><artwork>
00 06 |..|
</artwork></figure>
<figure><preamble>The header :method=foo would be encoded as:</preamble><artwork>
01 76 05 05 00 03 66 6F |......fo|
6F |o|
</artwork></figure>
<figure><preamble>The header foo=bar would be encoded as:</preamble><artwork>
b6 03 66 6f 6f 05 00 |..foo...|
03 62 61 72 |.bar|
</artwork></figure>
</section>
</section>
<section title="Security Considerations">
<t>TBD</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc2119;
</references>
</back>
</rfc>
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