One document matched: draft-rpeon-httpbis-header-compression-01.xml
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<rfc category="info" ipr="trust200902" docName="draft-rpeon-httpbis-header-compression-01">
<front>
<title abbrev="HTTP/2 Header Compression">Header Delta-Compression for HTTP/2.0</title>
<author initials="R." surname="Peon" fullname="Roberto Peon">
<organization>Google, Inc</organization>
<address>
<email>fenix@google.com</email>
</address>
</author>
<date day="12" month="Mar" year="2013" />
<area>Applications</area>
<keyword>HTTP</keyword>
<abstract>
<t>This document describes a mechanism for compressing streams of
groups of key-value pairs, often known as Headers in an HTTP session.
See <xref target="RFC2616">RFC 2616</xref> or successors for more
information about headers.</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Overview">
<t>There have been several problems pointed out with the use of the
gzip compressor in <xref target="SPDY">SPDY</xref>. 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.</t>
</section>
<section title="How it works">
<t>
The 'delta' compressor works by examining the difference between what
it is told to compress and the state that it has stored about what it
knows about the past. The previous state is encoded in two separate
pieces: An LRU of key-value pairs which the compressor 'saw' in the
past (including a static group of key-value pairs which every
compressor is assumed to have seen), and a set of references into the
LRU which is called a header-group, which the compressor uses to determine
what has changed between the current input and the past input.<vspace/>
It then encodes this difference by changing the header-group by
adding references to stored key-values, and it removes references to
key-values which should no longer be part of the output. If a
key-value exists in the to-be-compressed data, but is not present in
the LRU, then the LRU is modified by having new data added. When new
data is added, a reference to that new data is added to the
header-group. The mechanism of adding new data takes two forms:
Adding an entire new key-value, or by referring to the key part of a
stored key-value, and providing a new value. <vspace/>
When the LRU has reached its size limit, The oldest elements are
popped off the end, and, any reference to that element is removed.
<vspace/>
All keys are assumed to have been lowercased, and if not, will be.
</t>
</section>
<section title="Definitions">
<t>
<list style="hanging" hangIndent="6">
<t hangText="user-agent:"> The program or device which a human interacts with
directly and which typically initiates the transport layer
connection or session</t>
<t hangText="client:"> Synonym for user-agent</t>
<t hangText="server:"> The computer or device which typically accepts a
connection, stores, and serves data</t>
<t hangText="proxy:"> An entity acting as a server for the client, and a client
for the server</t>
<t hangText="header:"> A complete set of key-value pairs, either
request-headers, or response-headers as defined in <xref
target="RFC2616">RFC2616</xref> section 5.3 or 6.2,
respectively</t>
</list>
</t>
</section>
<section title="Header pre-processing">
<section title="Mapping the first-line">
<t> Before the data is input into the compressor (which works only on
key-value pairs), the first line of the HTTP message must be made
into key-value pairs. </t>
<t> Requests are mapped as follows:<vspace/>
"METHOD PATH VERSION" becomes:
<artwork>
[
(":method", "METHOD"),
(":path", "PATH"),
(":version", "VERSION")
]
</artwork>
</t>
<t> Responses are mapped as follows:<vspace/>
"VERSION STATUS-CODE PHRASE" becomes:
<artwork>
[
(":version", "VERSION"),
(":status", "STATUS-CODE"),
(":status-text", "PHRASE")
]
</artwork>
</t>
</section>
<section title="Mapping HTTP key-values">
<t>
The rest of the HTTP key-values are simply added to the key-values
as mapped from the first-line, with the keys made to be all
lowercase, and with cookies split into crumbs by breaking apart the
cookie string on semicolons and treating each as if it were a
separate header-line.
</t>
<t> As an example, the following key-value pairs:<vspace/>
<artwork>
Host: www.foo.com
User-Agent: Browser/1.x (FooOS; Bar) baz
Accept-Language: en-US,en;q=0.5
Cookie: foo;bar; baz
</artwork>
become:
<artwork>
[
("host", "www.foo.com")
("user-agent", "Browser/1.x (FooOS; Bar) baz"),
("accept-language", "en-US,en;q=0.5"),
("cookie", "foo"),
("cookie", "bar"),
("cookie", "baz")
]
</artwork>
</t>
</section>
</section>
<section title="Compressor and Decompressor State">
<t> The header delta de/compression scheme consists of a state machine
which executes opcodes, emits output, and modifies internal,
persistent, state. The de/compressor state consists of:</t>
<list style="hanging" hangIndent="6">
<t hangText="static_entries:"><vspace />
a number of static (unchanging) entries consisting of key-value
pairs. These are listed in appendix A.<vspace />
e.g. static_entries=[ ("key1", "val1"), ("key2", "val2), ...]
<vspace/>
an lru-idx references into the static key-value pairs if the value
of the lru-idx is < len(static-entries)
<vspace/>static_entries[lru_idx]
</t>
<t hangText="lru:"><vspace />
a queue of key-value pairs<vspace />
e.g. lru = deque([(RefCntString("key1"), "val1"),
(RefCntstring("key2", "val2")), ...])<vspace/>
<vspace/>
an lru-idx references a value in the lru if the lru-idx is >= len(static_entries).
The mapping of an lru-idx to a offset from the front of the LRU is
as follows:
<artwork>
if lru.first_idx > lru_idx:
queue_idx = 2**16 - lru.first_idx + lru_idx - len(static_entries)
else:
queue_idx = lru_idx - lru.first_idx
</artwork>
The oldest elements of the LRU are popped before inserting a new value if either:
<list>
<t> Adding a new entry would exceed the maximum allowable length</t>
<t> Adding a new entry would exceed the maximum allowable byte length</t>
</list>
</t>
<t hangText="header_groups: (default-size: 1)(max: 255)"><vspace />
a map of group-id to set of lru-idx. An lru-idx is a reference into
either the static key-value pairs or the lru's key-value pairs.
The maximum number of header-groups is limited by default to 1,
unless a higher-level of the protocol changes this. The maximum
number of header_groups is 255. It is not currently allowed to
assert that there are '0' allowed header groups.
<vspace />
e.g. header_groups = {0: set([1,4,6,15122]), 1: set([6,76,3], ...)}
</t>
<t hangText="lru.first_idx:"><vspace />
an int indicating the lru-idx of the oldest element in the queue of
key-value pairs</t>
<t hangText="max_byte_size: (default: 4k) (max:2**32-1)"><vspace />
an int indicating the maximum allowable amount of storage used by
the strings of the queue's key-value pairs. Unless a higher-level
of the protocol changes this, this is assumed to be 4k</t>
<t hangText="max_lru_entries: (default: 1024) (max:2**16-1)"><vspace />
an int indicating the maximum allowable number of key-value pairs
in the queue. Unless a higher-level of the protocol changes this,
this is assumed to be 1024</t>
<t hangText="lru.length:"><vspace />
an int indicating the total number of key-value pairs currently
stored in the lru</t>
<t hangText="lru.stored_byte_size:"><vspace />
an int indicating the total number of bytes of storage used by
strings in the queue. Note that the bytes in a ref-counted string
are counted only once, regardless of how many times that string is
referenced.</t>
</list>
</section>
<section title="Header Block Wire Format" anchor="wire_format">
<t>The decompressor is fed a header-block which may span multiple
HEADERs frames by the HTTP/2 framing layer, the format of which
follows:</t>
<artwork><![CDATA[
All ints are in network byte order.
header-block: group-id
( (ekvsto-opcode ekvsto-count ekvsto-field{ekvsto-count})* |
(eclone-opcode eclone-count eclone-field{eclone-count})* |
(etrang-opcode etrang-count etrang-field{etrang-count})* |
(strang-opcode etrang-count strang-field{etrang-count})* |
(etoggl-opcode etoggl-count etoggl-field{etoggl-count})* |
(stoggl-opcode stoggl-count stoggl-field{stoggl-count})* )*
(clone-opcode clone-count clone-field{clone-count})*
(kvsto-opcode kvsto-count kvsto-field{kvsto-count})*
;
group-id: UINT8;
etoggl-count: UINT8;
stoggl-count: UINT8;
etrang-count: UINT8;
strang-count: UINT8;
eclone-count: UINT8;
sclone-count: UINT8;
ekvsto-count: UINT8;
skvsto-count: UINT8;
stoggl-field: lru-idx;
etoggl-field: lru-idx;
strang-field: lru-idx lru-idx;
etrang-field: lru-idx lru-idx;
eclone-field: lru-idx string;
sclone-field: lru-idx string;
ekvsto-field: string string;
skvsto-field: string string;
stoggl-opcode: UINT8(0x00);
etoggl-opcode: UINT8(0x01);
strang-opcode: UINT8(0x02);
etrang-opcode: UINT8(0x03);
skvsto-opcode: UINT8(0x04);
ekvsto-opcode: UINT8(0x05);
sclone-opcode: UINT8(0x06);
eclone-opcode: UINT8(0x07);
lru_idx: UINT16;
string: (HUFFMAN-ENCODED-CHAR)* HUFFMAN-EOF
padding-to-nearest-byte-boundary;
padding-to-nearest-byte-boundary: 0{0-7};
]]>
</artwork>
</section>
<section title="String Encoding">
<t>Strings are <xref target="HUFF">huffman encoded</xref> using a <xref
target="CANON">canonical huffman coding</xref>. In the future, the
opcode byte will be permuted to allow alternate encodings, such as
raw text, binary, or perhaps other options.</t>
<t>The huffman code is constructed by taking the frequency-tables in
Appendix B, adding 1 to all entries, then generating a canonical
huffman coding. If/while this results in a code with a max-length of
greater than 32 bits, divide all frequencies by two, capping the
minimum frequency at '1', and regenerate until the max code-length
is 32 bits or less. The EOF symbol, when decoded, is represented as
256, which allows for any 8-bit value to be encoded and decoded.</t>
</section>
<section title="Operations">
<t> For all operations below, the 's' prefix stands for 'State
modifying', whereas the 'e' prefix stands for 'Ephemeral', and does
not modify state.</t>
<vspace />
<t>The *kvsto family of opcodes encode a new key-value entirely by
providing a new string for key and a new string for val. </t>
<t>The *clone family of opcodes encode a backreference to the key part
of a pre-existing key-value from either the static-entries or the
lru, and a new string value.</t>
<t>The *toggl family of opcodes encode a backreference to an entire
key-value from either the static-entries, or the lru.</t>
<t>The *trang family of opcodes is the same as the toggle family,
except that it encodes a range of indices instead of a single
index</t>
<vspace />
<t>With four families of opcodes, and two variations (ephemeral vs
state-changing) per family, we have eight valid opcodes:</t>
<list style="hanging" hangIndent="6">
<t hangText="skvsto: (Stateful Key-Value STOre)"> <vspace />
state-modifying kvsto. The new key and value are inserted into the
headers and also inserted into the LRU.</t>
<t hangText="ekvsto: (Ephemeral Key-Value STOre)"> <vspace />
ephemeral, non-state-modifying kvsto. The new key and value are inserted into the
headers but the LRU is untouched.</t>
<vspace />
<t hangText="sclone (Stateful key CLONE):"> <vspace />
state-modifying clone. The key part of the referenced key-value is
paired with the new value and inserted into the headers and also
inserted into the LRU</t>
<t hangText="eclone (Ephemeral key CLONE):"> <vspace />
ephemeral, non-state-modifying clone. The key part of the
referenced key-value is paired with the new value and inserted into
the headers. No persistent state is modified.</t>
<vspace />
<t hangText="stoggl (Stateful TOGGLe):"> <vspace />
state-modifying toggle. If the index exists in the current header
group, it will be turned off, else it will be turned on. </t>
<t hangText="etoggl (Ephemeral TOGGLe):"> <vspace />
ephemeral, non-state-modifying toggle. If the provided index does
not exist in the current header group after all stoggles have
modified it, then the key-value as referenced by the provided index
will be present in the output, else, that index of the current
header group will be temporarily suppressed and will not be
included in the headers</t>
<vspace/>
<t hangText="strang (Stateful Toggle RANGe):"> <vspace />
encodes a range of stoggls</t>
<t hangText="etrang (Ephemeral ToggleRANGe):"> <vspace />
encodes a range of etoggls </t>
<vspace />
</list>
</section>
<section title="Decompressor algorithm">
<t> The pseudo-code below provides a definition of how the
header-block is executed by the decompressor.</t>
<artwork><![CDATA[
ParseAndExecuteHeaderBlock(header_block):
store_later = deque()
etoggles = set()
stoggles = set()
headers = dict()
# the HTTP/2 framing layer determines when the header_block
# has finished reading.
group_id = header_block.read_uint8()
current_header_group = header_groups[group_id]
while data in header_block:
opcode = header_block.read_uint8()
num_fields = header_block.read_uint8()
if opcode == stoggl:
repeat num_fields times:
lru_idx = header_block.read_uint16()
stoggles = set_symmetric_difference(stoggles, [lru_idx])
elif opcode == etoggl:
repeat num_fields times:
lru_idx = header_block.read_uint16()
etoggles = set_symmetric_difference(etoggles, [lru_idx])
elif opcode == strang:
repeat num_fields times:
lru_idx_first = header_block.read_uint16()
lru_idx_last = header_block.read_uint16()
for lru_idx in (lru_idx_first, lru_idx_last) inclusive:
stoggles = set_symmetric_difference(stoggles, [lru_idx])
stoggles.add(lru_idx)
elif opcode == etrang:
repeat num_fields times:
lru_idx_first = header_block.read_uint16()
lru_idx_last = header_block.read_uint16()
for lru_idx in (lru_idx_first, lru_idx_last) inclusive:
etoggles = set_symmetric_difference(etoggles, [lru_idx])
elif opcode == sclone:
repeat num_fields times:
lru_idx = header_block.read_uint16()
val = header_block.read_huffman_string()
kv = lookup_idx_from_static_entries_or_lru(lru_idx)
AddToCurrentHeaders(headers, kv.key, val)
store_later.append(KV(kv.key, val))
elif opcode == eclone:
repeat num_fields times:
lru_idx = header_block.read_uint16()
val = header_block.read_huffman_string()
kv = lookup_idx_from_static_entries_or_lru(lru_idx)
AddToCurrentHeaders(headers, kv.key, val)
elif opcode == skvsto:
repeat num_fields times:
key = header_block.read_huffman_string()
val = header_block.read_huffman_string()
AddToCurrentHeaders(headers, key, val)
store_later.append(KV(key, val))
elif opcode == ekvsto:
repeat num_fields times:
key = header_block.read_huffman_string()
val = header_block.read_huffman_string()
AddToCurrentHeaders(headers, key, val)
# store the state changes to the header-group.
current_header_group = \
set_symmetric_difference(current_header_group, stoggles)
kv_references = set_symmetric_difference(current_header_group,
etoggles)
for lru_idx in sorted(kv_references):
kv = lookup_idx_from_static_entries_or_lru(lru_idx)
AddToCurrentHeaders(headers, kv.key, kv.val)
if 'cookie' in headers:
headers['cookie'] = headers['cookie'].replace('\0', '; ')
for lru_idx in sorted(current_header_group):
# sorting by idx is suboptimal when the idxs wrap 2**16.
# As a refinement, we probably want to change this in the
# future to something which sorts based on the order in
# which the elements were first mentioned, which can be
# done by a smart implementation without actually sorting.
kv = lookup_idx_from_static_entries_or_lru(lru_idx)
store_later.appendleft(kv)
# make state changes to the LRU. Note that this may remove
# items from the header-group if elements that the header-group
# refers to are removed from the LRU
for kv in store_later:
new_lru_idx = lru.store(kv.key, kv.val)
return headers
lru.clear():
while length > 0:
pop_oldest()
lru.store(key, val):
reserve_size = val.size + key.size
if max_lru_entries == 0 or
max_byte_size < reserve_size):
lru.clear()
return -1
while length + 1 >= max_lru_entries:
pop_oldest()
while true:
reserve_size = val.size
if key.refcnt == 1:
reserve_size += key.size
if stored_byte_size + reserve_size < max_byte_size:
break
pop_oldest()
push(KV(key, val))
new_lru_idx = lru.first + length
if new_lru_idx >= 2**16:
new_lru_idx -= 2**16
new_lru_idx += static_entries.size:
return new_lru_idx
lru.pop_oldest():
kv = queue.front()
length -= 1
if kv.key.refcnt == 1:
stored_byte_size -= kv.key.size
stored_byte_size -= kv.val.size
for header_group in header_groups:
if first_idx in header_group:
header_group.remove(first_idx)
first_idx = get_next_idx(first_idx)
queue.pop_front()
lru.push(kv):
length += 1
if kv.key.refcnt == 1:
stored_byte_size += kv.key.size
stored_byte_size += kv.val.size
queue.push_back(kv)
lru.get_next_idx(idx):
idx += 1
if idx >= 2**16 - 1:
return decompressor.static_entries.size
return idx
lookup_idx_from_static_entries_or_lru(lru_idx):
if lru_idx < static_entries.size:
return static_entries[lru_idx]:
if lru.first_idx > lru_idx:
queue_idx = 2**16 - lru.first_idx + lru_idx - static_entries.size
else:
queue_idx = lru_idx - lru.first_idx
return lru.queue[queue_idx]
]]>
</artwork>
</section>
<section title="Compression">
<t> The compressor generates a sequence of instructions which the
decompressor executes. There are various ways by which the compressor
can determine how to construct these operations. Pseudo-code follows
showing one approach. group_id is defined by the sender, but must
always be less than the maximum allowed number. A reasonable
implementation might assign the same group_id to a set of headers which
are likely to be similar, for instance those which go to the same
hostname or the same hostname suffix.</t>
<artwork><![CDATA[
# assumptions: headers is a dict(), where multiple key:values with
# the same key are encoded as key:value1\0value2\0value3...
# group_id is provided by some other implementation-dependent
# code
# This compressor does not use all of the opcodes and serves simply
# as an example of a workable, if suboptimal, implementation
MakeOperations(self, headers, group_id):
headers_set = set()
for (key, val) in headers:
splittoken = '\0'
if key == 'cookie':
splittoken = ';'
for partial_val in split(val, ';'):
headers_set.add( (key, partial_val) )
# Note that this discards duplicates.
# If we decide we care about that generate an 'ekvsto' or
# 'eclone' for that (duplicate) key-value here.
keep_set = set()
done_set = set()
for idx in header_groups[group_id]:
kv = lookup_idx_from_static_entries_or_lru(idx)
if kv in headers_set:
# If the KV referenced by the idx in the header-group
# is also in the to-be-compressed headers, then we
# keep using that reference (don't remove it from the
# header-group)
keep_set.add(idx) # we want to keep this one
headers_set.remove(kv)
else:
# If we're not finding the KV referenced by the idx in
# the header-group in the to-be-compressed-header, then
# this idx needs to be removed from the header-group.
done_set.add(idx) # we'll want to remove it
instructions = dict()
toggls = set()
clones = []
kvstos = []
erefs = []
for (key, val) in headers_set:
# The following 'if' block is a demonstration of an
# optimization-- since path and referer are rarely
# backreferenced, and since they are often large and
# they would, if included in the LRU, cause other entries
# to be expired from the LRU, we ensure that these don't
# get stored in the LRU by emitting an 'ephemeral' operation
if key in [":path", "referer"]:
instructions['ekvsto'].append( (key, val) )
continue
# FindEntryIdx looks for a matching key-value in the LRU, and then
# in the static-entries, recording the first matching key it finds
# while searching for the whole match. If it does find a whole
# match then v_idx will be valid. If it finds an entry with a key
# which matches, then k_idx will be valid.
(k_idx, v_idx) = FindEntryIdx(key, val)
if both k_idx and v_idx are valid:
# if we found a index for all of the kv, we'll generate
# a new toggle which backreferences that entire kv.
toggls.add(v_idx)
elif only k_idx is valid:
# Otherwise, if we did't find all of the kv pre-existing,
# but there was something that already had that key,
# generate a clone, which backreferences the key and provides
# a new value.
instructions['sclone'].append( (k_idx, val) )
else:
# Otherwise, we'll need to store a new key and value, both.
instructions['skvstos'].append( (key, val) )
full_toggl_list = union(toggls, done_set)
# convert runs of toggls into trangs
(trangs, toggls) = ComputeTrangsFromRawToggles(full_toggl_list)
instructions['stoggl'] = toggls
instructions['strang'] = trangs
header_block = SerializeInstructions(instructions, group_id)
# Execute the instructions just like you would when decompressing.
# We're throwing away the computed headers here, because all
# we care about is the side-effects to the header_groups and the
# lru from executing the generated instructions.
ParseAndExecuteHeaderBlock(header_block)
return header_block
SerializeInstructions(instructions, group_id):
outbuf.write_uint8(group_id)
for opcode in ['stoggl', 'etoggl',
'strang', 'etrang',
'eclone', 'ekvsto',
'sclone', 'skvsto']:
if not opcode in instructions:
continue
ops_idx = 0
ops_len = len(instructions[opcode])
while ops_len > ops_idx:
ops_to_go = ops_len - ops_idx
outbuf.write_uint8(OpcodeToOpcodeVal(opcode))
# a value of '0' in this field means '1'.
# a value of '255' in this field means '256',
# thus, subtract one from the actual value when
# preparing to write to the wire.
outbuf.write_uint8(min(256, ops_to_go) - 1)
orig_idx = ops_idx
for i in xrange(ops_to_go):
if opcode in ['stoggl', 'etoggl']:
outbuf.write_uint16(instructions[ops_idx])
elif opcode in ['strang', 'etrang']:
outbuf.write_uint16(instructions[ops_idx][0])
outbuf.write_uint16(instructions[ops_idx][1])
elif opcide in ['sclone', 'eclone']:
outbuf.write_uint16(instructions[ops_idx][0])
outbuf.encode_and_write_string(instructions[ops_idx][1])
elif opcode in ['skvsto', 'ekvsto']:
outbuf.encode_and_write_string(instructions[ops_idx][0])
outbuf.encode_and_write_string(instructions[ops_idx][1])
ops_idx += 1
return outbuf
]]>
</artwork>
<t> If the resulting output buffer is larger than the maximum allowed
frame size, then the buffer shall be split into
maximum-allowed-payload-size or smaller sections, and sent in
separate HEADERS frames, with only the last indicating that the frame
is finished by asserting the FRAME_FINISHED flag.</t>
</section>
<section title="Example">
<section title="Background">
<t>Here is a simple example showing an input, the changing part of
the compressor state, and an ascii-ified version of what would be
serialized on the wire.</t>
<artwork>
GET / HTTP/1.0
Host: www.foo.com
User-Agent: bar-ua baz stuff
Accept-Language: en-US,en;q=0.5
</artwork>
<t>
The first stage of processing is to break the first line into
key-value pairs. The first line becomes:</t>
<artwork>
[
(":method": "GET"),
(":path": "/"),
(":version": "HTTP/1.0")
]
</artwork>
<t>
This gets integrated with the rest of the headers, becoming:
<artwork>
[
(":method", "GET"),
(":path", "/"),
(":version", "HTTP/1.0"),
("host", "www.foo.com"),
("user-agent", "bar-ua baz stuff"),
("accept-language", "en-US,en;q=0.5"),
]
</artwork>
</t>
<t> The compressor now goes through each key-value, determining if it
is already present in the header-group, in the LRU or static state,
and determines what it needs to emit.
</t>
</section>
<section title="Example Serialization">
<t> This is sample output from a program which implements the
compression specification above. It prints out the headers to-be-compressed, followed by the instructions computed by the example (suboptimal) compressor, followed by the serialization of those instructions including the HTTP/2 framing boilerplate. </t>
<artwork>
<![CDATA[
* http2-demo: 2 req messages
################################################################################
# http1
get /http2_sample.html HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
pragma: no-cache
cache-control: no-cache
host: http2-demo
# delta2
{'opcode': 'eclone', 'index': 0, 'val': '/http2_sample.html'}
{'opcode': 'stoggl', 'index': 1}
{'opcode': 'stoggl', 'index': 3}
{'opcode': 'sclone', 'index': 38, 'val': 'no-cache'}
{'opcode': 'sclone', 'index': 10, 'val': 'ISO-8859-1,utf-8;q=0.7,*;q=0.3'}
{'opcode': 'sclone', 'index': 11, 'val': 'gzip,deflate,sdch'}
{'opcode': 'sclone', 'index': 9, 'val': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'}
{'opcode': 'sclone', 'index': 16, 'val': 'no-cache'}
{'opcode': 'sclone', 'index': 4, 'val': 'http2-demo'}
{'opcode': 'sclone', 'index': 12, 'val': 'en-US,en;q=0.8'}
{'opcode': 'sclone', 'index': 51, 'val': 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31'}
stream_id: 1234 group_id: 1
00 FE 08 01 80 00 04 D2 01 05 00 00 00 0C C8 9E | ................
9B A2 AD 5F A0 9B 32 D7 49 00 00 01 00 01 00 03 | ..._..2.I.......
04 07 00 26 6B A7 5A 97 98 C8 00 0A F6 FD 3E 33 | ...&k.Z.......>3
F3 E7 4D 73 A3 F8 D8 B1 9F 9F A3 F5 69 CD 57 F1 | ..Ms........i.W.
FF 5E 8F D5 A7 35 12 00 0B CB F6 C7 FF 18 0E 3A | .^...5.........:
28 87 F8 8E 0B CE 40 00 09 21 F2 20 CC B5 D3 F8 | (.....@..!. ....
53 DF A3 16 A2 63 9A 1E 59 96 BA 7F DF 96 BA 7F | S....c..Y.......
0A 7B F4 62 D4 4C 73 43 CB 5D 3D 1F AB 4E 6A FF | .{.b.LsC.]=..Nj.
8F FA 0F FA F4 7E AD 39 B9 C8 00 10 6B A7 5A 97 | .....~.9....k.Z.
98 C8 00 04 CC 89 E9 9F 01 D5 D2 00 0C 16 CF F6 | ................
FA 7F 02 DF 47 EA D3 9B 9C 80 00 33 F7 BB F6 CD | ....G......3....
34 50 52 63 FF B7 FC 7E 50 8F 47 FB 7B 98 DD BC | 4PRc...~P.G.{...
BF DB CB 9F 2B B9 71 FF 9F F6 EC 7B F4 1F C0 DF | ....+.q....{....
FE 98 41 4D 15 1A 84 7F B7 FC 7F AF 67 D7 DF EE | ..AM........g...
FE 3F DB 46 78 0F FB 7A C5 7E 0E FF 9F F6 EE CE | .?.Fx..z.~......
0E D4 41 3C 8C 73 23 8A 0E 64 F3 FF 6F A2 B1 54 | ..A<.s#..d..o..T
18 14 D1 51 A8 44 80 | ...Q.D.
get /http2_sample.html HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
pragma: no-cache
cache-control: no-cache
host: http2-demo
################################################################################
# http1
get /s/http2_fractal.jpg HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo
# delta2
{'opcode': 'eclone', 'index': 0, 'val': '/s/http2_fractal.jpg'}
{'opcode': 'sclone', 'index': 42, 'val': 'http://http2-demo/http2_sample.html'}
{'opcode': 'sclone', 'index': 70, 'val': '*/*'}
{'opcode': 'strang', 'index': 69, 'index_start': 67}
{'opcode': 'strang', 'index': 74, 'index_start': 71}
stream_id: 1234 group_id: 1
00 3E 08 01 80 00 04 D2 01 05 00 00 00 08 86 64 | .>.............d
4F 4D D8 C1 4B 25 68 6E AF CA 40 04 01 00 2A CC | OM..K%hn..@...*.
89 F6 00 66 44 F4 CF 80 EA E0 CC 89 E9 BA 2A D5 | ...fD.........*.
FA 09 B3 2D 74 90 00 46 FF A0 FF A9 00 02 01 00 | ...-t..F........
45 00 43 00 4A 00 47 | E.C.J.G
get /s/http2_fractal.jpg HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo
size time | ratio min max std
http1 826 0.00 | 1.00 1.00 1.00 0.00
delta2 334 0.01 | 0.40 0.17 0.63 0.32
* http2-demo: 2 res messages
################################################################################
# http1
HTTP/1.1 200 ?
content-length: 797
content-encoding: gzip
accept-ranges: bytes
expires: Fri, 1 Jan 2100 12:00:00 GMT
vary: Accept-Encoding
server: Apache/2.2.22 (Ubuntu)
last-modified: Thu, 08 Nov 2012 17:24:16 GMT
cache-control: public, max-age=3600000000
date: Tue, 12 Mar 2013 23:12:44 GMT
content-type: text/html
# delta2
{'opcode': 'stoggl', 'index': 6}
{'opcode': 'sclone', 'index': 16, 'val': 'public, max-age=3600000000'}
{'opcode': 'sclone', 'index': 27, 'val': 'Fri, 1 Jan 2100 12:00:00 GMT'}
{'opcode': 'sclone', 'index': 18, 'val': 'gzip'}
{'opcode': 'sclone', 'index': 13, 'val': 'bytes'}
{'opcode': 'sclone', 'index': 52, 'val': 'Accept-Encoding'}
{'opcode': 'sclone', 'index': 19, 'val': '797'}
{'opcode': 'sclone', 'index': 34, 'val': 'Thu, 08 Nov 2012 17:24:16 GMT'}
{'opcode': 'sclone', 'index': 24, 'val': 'Tue, 12 Mar 2013 23:12:44 GMT'}
{'opcode': 'sclone', 'index': 44, 'val': 'Apache/2.2.22 (Ubuntu)'}
{'opcode': 'sclone', 'index': 23, 'val': 'text/html'}
stream_id: 1234 group_id: 1
00 99 08 01 80 00 04 D2 01 00 00 00 06 04 09 00 | ................
10 C3 3D BC 6D AE 60 E5 0F 39 E1 BE 3A 91 40 88 | ..=.m.`..9..:.@.
88 88 8C 80 00 1B EC C6 D9 80 83 B6 17 01 90 88 | ................
11 B8 45 C2 21 4D 4F 90 00 12 DF FB B7 09 00 00 | ..E.!MO.........
0D DB E9 94 79 C8 00 34 D7 5D 71 C3 29 FA EE AE | ....y..4.]q.)...
FB 2D BB 7C 80 00 13 5B 57 20 00 22 7F 0C E6 01 | .-.|...[W ."....
60 77 5F E2 06 24 60 4B 71 A5 C5 40 53 53 E4 00 | `w_..$`Kq..@SS..
18 7E 71 98 08 C2 A8 62 06 24 80 34 38 8D C9 48 | .~q....b.$.48..H
53 53 E4 00 2C D7 84 2B E1 1E 83 D2 7A 4C C3 D7 | SS..,..+....zL..
F5 DB 9D D9 67 EC 90 00 17 CA 3E 79 74 70 CB 97 | ....g.....>ytp..
19 00 | ..
HTTP/1.1 200 ?
content-length: 797
content-encoding: gzip
accept-ranges: bytes
expires: Fri, 1 Jan 2100 12:00:00 GMT
vary: Accept-Encoding
server: Apache/2.2.22 (Ubuntu)
last-modified: Thu, 08 Nov 2012 17:24:16 GMT
cache-control: public, max-age=3600000000
date: Tue, 12 Mar 2013 23:12:44 GMT
content-type: text/html
################################################################################
# http1
HTTP/1.1 200 ?
content-length: 365
accept-ranges: bytes
expires: Fri, 1 Jan 2100 12:00:00 GMT
server: Apache/2.2.22 (Ubuntu)
last-modified: Tue, 23 Oct 2012 02:26:33 GMT
cache-control: public, max-age=3600000000
date: Tue, 12 Mar 2013 23:12:44 GMT
content-type: image/jpeg
# delta2
{'opcode': 'stoggl', 'index': 69}
{'opcode': 'sclone', 'index': 75, 'val': 'image/jpeg'}
{'opcode': 'sclone', 'index': 71, 'val': '365'}
{'opcode': 'sclone', 'index': 72, 'val': 'Tue, 23 Oct 2012 02:26:33 GMT'}
{'opcode': 'strang', 'index': 67, 'index_start': 66}
{'opcode': 'strang', 'index': 74, 'index_start': 73}
stream_id: 1234 group_id: 1
00 35 08 01 80 00 04 D2 01 00 00 00 45 04 02 00 | .5..........E...
4B B7 94 37 C7 A3 F1 84 77 C8 00 47 45 0A 90 00 | K..7....w..GE...
48 7E 71 98 0D 01 DF 5E 40 62 46 02 6E 3A 1C 84 | H~q....^@bF.n:..
05 35 3E 40 02 01 00 43 00 42 00 4A 00 49 | .5>@...C.B.J.I
HTTP/1.1 200 ?
content-length: 365
accept-ranges: bytes
expires: Fri, 1 Jan 2100 12:00:00 GMT
server: Apache/2.2.22 (Ubuntu)
last-modified: Tue, 23 Oct 2012 02:26:33 GMT
cache-control: public, max-age=3600000000
date: Tue, 12 Mar 2013 23:12:44 GMT
content-type: image/jpeg
size time | ratio min max std
http1 614 0.00 | 1.00 1.00 1.00 0.00
delta2 224 0.00 | 0.36 0.22 0.49 0.19
* http2-demo1: 107 req messages
################################################################################
# http1
get /s/0.png HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo1
# delta2
{'opcode': 'eclone', 'index': 0, 'val': '/s/0.png'}
{'opcode': 'sclone', 'index': 92, 'val': 'http2-demo1'}
{'opcode': 'strang', 'index': 91, 'index_start': 86}
{'opcode': 'strang', 'index': 96, 'index_start': 93}
stream_id: 1234 group_id: 2
00 20 08 01 80 00 04 D2 02 05 00 00 00 08 81 CC | . ..............
F6 E5 20 04 00 00 5C CC 89 E9 9F 01 D5 C8 90 02 | .. ...\.........
01 00 5B 00 56 00 60 00 5D | ..[.V.`.]
get /s/0.png HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo1
################################################################################
# http1
get /s/6.png HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo1
# delta2
{'opcode': 'eclone', 'index': 0, 'val': '/s/6.png'}
{'opcode': 'stoggl', 'index': 107}
stream_id: 1234 group_id: 2
00 0E 08 01 80 00 04 D2 02 05 00 00 00 08 87 23 | ...............#
3D B9 48 00 00 00 6B | =.H...k
get /s/6.png HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo1
################################################################################
# http1
get /s/12.png HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo1
# delta2
{'opcode': 'eclone', 'index': 0, 'val': '/s/12.png'}
stream_id: 1234 group_id: 2
00 0B 08 01 80 00 04 D2 02 05 00 00 00 08 82 12 | ................
67 B7 29 00 | g.).
get /s/12.png HTTP/1.1
accept-language: en-US,en;q=0.8
accept-encoding: gzip,deflate,sdch
accept: */*
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.28 Safari/537.31
:scheme: http
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
referer: http://http2-demo/http2_sample.html
pragma: no-cache
cache-control: no-cache
host: http2-demo1
]]>
</artwork>
</section>
</section>
<section title="Unfinished components">
<t>These are components that must be added in the future.</t>
<list>
<t>Encoding of raw or ascii bytes</t>
<t>Describing safe mechanisms for changing the allowable compressor
state size downwards.</t>
<t>The frequency table used to generate the huffman encoding should
be updated with a more comprehensive analysis of header-character
frequency. </t>
</list>
</section>
<section title="Security Considerations">
<t> The compressor algorithm described here is expected to be immune to
the current attacks against encrypted stream-based compressors such
as TLS+gzip, but more scrutiny is warranted. The reason that it is
believed that the algorithm(s) expressed here is immune is that any
backreference to a header key or value always requires a whole-text
match, and thus any probe of the compression context confirms no
hypothesis unless the attacker has guessed the entire plaintext key
and value simultaneously. </t>
</section>
<section title="Requirements Notation">
<t>
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
<xref target="RFC2119"/>.
</t>
</section>
<section title="Acknowledgements">
</section>
<section title="Appendix A">
<artwork><![CDATA[
Appendix A (static-entries) :
# (key, val)
# Order does matter...
static_entries = [
(':path', '/'),
(':scheme', 'http'),
(':scheme', 'https'),
(':method', 'get'),
(':host', ''),
('cookie', ''),
(':status', '200'),
(':status-text', 'OK'),
(':version', '1.1'),
('accept', ''),
('accept-charset', ''),
('accept-encoding', ''),
('accept-language', ''),
('accept-ranges', ''),
('allow', ''),
('authorizations', ''),
('cache-control', ''),
('content-base', ''),
('content-encoding', ''),
('content-length', ''),
('content-location', ''),
('content-md5', ''),
('content-range', ''),
('content-type', ''),
('date', ''),
('etag', ''),
('expect', ''),
('expires', ''),
('from', ''),
('if-match', ''),
('if-modified-since', ''),
('if-none-match', ''),
('if-range', ''),
('if-unmodified-since', ''),
('last-modified', ''),
('location', ''),
('max-forwards', ''),
('origin', ''),
('pragma', ''),
('proxy-authenticate', ''),
('proxy-authorization', ''),
('range', ''),
('referer', ''),
('retry-after', ''),
('server', ''),
('set-cookie', ''),
('status', ''),
('te', ''),
('trailer', ''),
('transfer-encoding', ''),
('upgrade', ''),
('user-agent', ''),
('vary', ''),
('via', ''),
('warning', ''),
('www-authenticate', ''),
('access-control-allow-origin', ''),
('content-disposition', ''),
('get-dictionary', ''),
('p3p', ''),
('x-content-type-options', ''),
('x-frame-options', ''),
('x-powered-by', ''),
('x-xss-protection', ''),
]
]]>
</artwork>
</section>
<section title="Appendix B">
<t>Appendix B huffman code-table for requests</t>
<artwork><![CDATA[
For Requests
( 0) |11111111|11111111|11110111|100 [27] 7ffffbc [27]
( 1) |11111111|11111111|11110111|101 [27] 7ffffbd [27]
( 2) |11111111|11111111|11110111|110 [27] 7ffffbe [27]
( 3) |11111111|11111111|11110111|111 [27] 7ffffbf [27]
( 4) |11111111|11111111|11111000|000 [27] 7ffffc0 [27]
( 5) |11111111|11111111|11111000|001 [27] 7ffffc1 [27]
( 6) |11111111|11111111|11111000|010 [27] 7ffffc2 [27]
( 7) |11111111|11111111|11111000|011 [27] 7ffffc3 [27]
( 8) |11111111|11111111|11111000|100 [27] 7ffffc4 [27]
( 9) |11111111|11111111|11111000|101 [27] 7ffffc5 [27]
( 10) |11111111|11111111|11111000|110 [27] 7ffffc6 [27]
( 11) |11111111|11111111|11111000|111 [27] 7ffffc7 [27]
( 12) |11111111|11111111|11111001|000 [27] 7ffffc8 [27]
( 13) |11111111|11111111|11111001|001 [27] 7ffffc9 [27]
( 14) |11111111|11111111|11111001|010 [27] 7ffffca [27]
( 15) |11111111|11111111|11111001|011 [27] 7ffffcb [27]
( 16) |11111111|11111111|11111001|100 [27] 7ffffcc [27]
( 17) |11111111|11111111|11111001|101 [27] 7ffffcd [27]
( 18) |11111111|11111111|11111001|110 [27] 7ffffce [27]
( 19) |11111111|11111111|11111001|111 [27] 7ffffcf [27]
( 20) |11111111|11111111|11111010|000 [27] 7ffffd0 [27]
( 21) |11111111|11111111|11111010|001 [27] 7ffffd1 [27]
( 22) |11111111|11111111|11111010|010 [27] 7ffffd2 [27]
( 23) |11111111|11111111|11111010|011 [27] 7ffffd3 [27]
( 24) |11111111|11111111|11111010|100 [27] 7ffffd4 [27]
( 25) |11111111|11111111|11111010|101 [27] 7ffffd5 [27]
( 26) |11111111|11111111|11111010|110 [27] 7ffffd6 [27]
( 27) |11111111|11111111|11111010|111 [27] 7ffffd7 [27]
( 28) |11111111|11111111|11111011|000 [27] 7ffffd8 [27]
( 29) |11111111|11111111|11111011|001 [27] 7ffffd9 [27]
( 30) |11111111|11111111|11111011|010 [27] 7ffffda [27]
( 31) |11111111|11111111|11111011|011 [27] 7ffffdb [27]
' ' ( 32) |11111111|0110 [12] ff6 [12]
'!' ( 33) |11111111|0111 [12] ff7 [12]
'"' ( 34) |11111111|111010 [14] 3ffa [14]
'#' ( 35) |11111111|1111100 [15] 7ffc [15]
'$' ( 36) |11111111|1111101 [15] 7ffd [15]
'%' ( 37) |100110 [6] 26 [6]
'&' ( 38) |1110000 [7] 70 [7]
''' ( 39) |11111111|1111110 [15] 7ffe [15]
'(' ( 40) |11111111|1000 [12] ff8 [12]
')' ( 41) |11111111|1001 [12] ff9 [12]
'*' ( 42) |11111111|1010 [12] ffa [12]
'+' ( 43) |11111111|1011 [12] ffb [12]
',' ( 44) |11111110|00 [10] 3f8 [10]
'-' ( 45) |100111 [6] 27 [6]
'.' ( 46) |00110 [5] 6 [5]
'/' ( 47) |0000 [4] 0 [4]
'0' ( 48) |00111 [5] 7 [5]
'1' ( 49) |01000 [5] 8 [5]
'2' ( 50) |01001 [5] 9 [5]
'3' ( 51) |101000 [6] 28 [6]
'4' ( 52) |1110001 [7] 71 [7]
'5' ( 53) |101001 [6] 29 [6]
'6' ( 54) |1110010 [7] 72 [7]
'7' ( 55) |101010 [6] 2a [6]
'8' ( 56) |1110011 [7] 73 [7]
'9' ( 57) |101011 [6] 2b [6]
':' ( 58) |101100 [6] 2c [6]
';' ( 59) |11110100|0 [9] 1e8 [9]
'<' ( 60) |11111111|11111111|10 [18] 3fffe [18]
'=' ( 61) |101101 [6] 2d [6]
'>' ( 62) |11111111|11111110|0 [17] 1fffc [17]
'?' ( 63) |11110100|1 [9] 1e9 [9]
'@' ( 64) |11111111|11100 [13] 1ffc [13]
'A' ( 65) |11101100 [8] ec [8]
'B' ( 66) |11101101 [8] ed [8]
'C' ( 67) |11101110 [8] ee [8]
'D' ( 68) |11101111 [8] ef [8]
'E' ( 69) |11110101|0 [9] 1ea [9]
'F' ( 70) |1110100 [7] 74 [7]
'G' ( 71) |11110101|1 [9] 1eb [9]
'H' ( 72) |11110110|0 [9] 1ec [9]
'I' ( 73) |11110110|1 [9] 1ed [9]
'J' ( 74) |11111110|01 [10] 3f9 [10]
'K' ( 75) |11111111|010 [11] 7fa [11]
'L' ( 76) |11110111|0 [9] 1ee [9]
'M' ( 77) |11110111|1 [9] 1ef [9]
'N' ( 78) |11111000|0 [9] 1f0 [9]
'O' ( 79) |11111000|1 [9] 1f1 [9]
'P' ( 80) |11111001|0 [9] 1f2 [9]
'Q' ( 81) |11111110|10 [10] 3fa [10]
'R' ( 82) |11111001|1 [9] 1f3 [9]
'S' ( 83) |11111010|0 [9] 1f4 [9]
'T' ( 84) |11111010|1 [9] 1f5 [9]
'U' ( 85) |11111011|0 [9] 1f6 [9]
'V' ( 86) |11111011|1 [9] 1f7 [9]
'W' ( 87) |11111100|0 [9] 1f8 [9]
'X' ( 88) |11111100|1 [9] 1f9 [9]
'Y' ( 89) |11111110|11 [10] 3fb [10]
'Z' ( 90) |11111111|00 [10] 3fc [10]
'[' ( 91) |11111111|111011 [14] 3ffb [14]
'\' ( 92) |11111111|11111111|11111011|100 [27] 7ffffdc [27]
']' ( 93) |11111111|111100 [14] 3ffc [14]
'^' ( 94) |11111111|111101 [14] 3ffd [14]
'_' ( 95) |101110 [6] 2e [6]
'`' ( 96) |11111111|11111111|110 [19] 7fffe [19]
'a' ( 97) |01010 [5] a [5]
'b' ( 98) |101111 [6] 2f [6]
'c' ( 99) |01011 [5] b [5]
'd' (100) |110000 [6] 30 [6]
'e' (101) |0001 [4] 1 [4]
'f' (102) |110001 [6] 31 [6]
'g' (103) |110010 [6] 32 [6]
'h' (104) |110011 [6] 33 [6]
'i' (105) |01100 [5] c [5]
'j' (106) |1110101 [7] 75 [7]
'k' (107) |11110000 [8] f0 [8]
'l' (108) |110100 [6] 34 [6]
'm' (109) |110101 [6] 35 [6]
'n' (110) |01101 [5] d [5]
'o' (111) |01110 [5] e [5]
'p' (112) |01111 [5] f [5]
'q' (113) |11111101|0 [9] 1fa [9]
'r' (114) |10000 [5] 10 [5]
's' (115) |10001 [5] 11 [5]
't' (116) |0010 [4] 2 [4]
'u' (117) |110110 [6] 36 [6]
'v' (118) |11110001 [8] f1 [8]
'w' (119) |110111 [6] 37 [6]
'x' (120) |11110010 [8] f2 [8]
'y' (121) |11110011 [8] f3 [8]
'z' (122) |11111101|1 [9] 1fb [9]
'{' (123) |11111111|11111110|1 [17] 1fffd [17]
'|' (124) |11111111|1100 [12] ffc [12]
'}' (125) |11111111|11111111|0 [17] 1fffe [17]
'~' (126) |11111111|1101 [12] ffd [12]
(127) |11111111|11111111|11111011|101 [27] 7ffffdd [27]
(128) |11111111|11111111|11111011|110 [27] 7ffffde [27]
(129) |11111111|11111111|11111011|111 [27] 7ffffdf [27]
(130) |11111111|11111111|11111100|000 [27] 7ffffe0 [27]
(131) |11111111|11111111|11111100|001 [27] 7ffffe1 [27]
(132) |11111111|11111111|11111100|010 [27] 7ffffe2 [27]
(133) |11111111|11111111|11111100|011 [27] 7ffffe3 [27]
(134) |11111111|11111111|11111100|100 [27] 7ffffe4 [27]
(135) |11111111|11111111|11111100|101 [27] 7ffffe5 [27]
(136) |11111111|11111111|11111100|110 [27] 7ffffe6 [27]
(137) |11111111|11111111|11111100|111 [27] 7ffffe7 [27]
(138) |11111111|11111111|11111101|000 [27] 7ffffe8 [27]
(139) |11111111|11111111|11111101|001 [27] 7ffffe9 [27]
(140) |11111111|11111111|11111101|010 [27] 7ffffea [27]
(141) |11111111|11111111|11111101|011 [27] 7ffffeb [27]
(142) |11111111|11111111|11111101|100 [27] 7ffffec [27]
(143) |11111111|11111111|11111101|101 [27] 7ffffed [27]
(144) |11111111|11111111|11111101|110 [27] 7ffffee [27]
(145) |11111111|11111111|11111101|111 [27] 7ffffef [27]
(146) |11111111|11111111|11111110|000 [27] 7fffff0 [27]
(147) |11111111|11111111|11111110|001 [27] 7fffff1 [27]
(148) |11111111|11111111|11111110|010 [27] 7fffff2 [27]
(149) |11111111|11111111|11111110|011 [27] 7fffff3 [27]
(150) |11111111|11111111|11111110|100 [27] 7fffff4 [27]
(151) |11111111|11111111|11111110|101 [27] 7fffff5 [27]
(152) |11111111|11111111|11111110|110 [27] 7fffff6 [27]
(153) |11111111|11111111|11111110|111 [27] 7fffff7 [27]
(154) |11111111|11111111|11111111|000 [27] 7fffff8 [27]
(155) |11111111|11111111|11111111|001 [27] 7fffff9 [27]
(156) |11111111|11111111|11111111|010 [27] 7fffffa [27]
(157) |11111111|11111111|11111111|011 [27] 7fffffb [27]
(158) |11111111|11111111|11111111|100 [27] 7fffffc [27]
(159) |11111111|11111111|11111111|101 [27] 7fffffd [27]
(160) |11111111|11111111|11111111|110 [27] 7fffffe [27]
(161) |11111111|11111111|11111111|111 [27] 7ffffff [27]
(162) |11111111|11111111|11100000|00 [26] 3ffff80 [26]
(163) |11111111|11111111|11100000|01 [26] 3ffff81 [26]
(164) |11111111|11111111|11100000|10 [26] 3ffff82 [26]
(165) |11111111|11111111|11100000|11 [26] 3ffff83 [26]
(166) |11111111|11111111|11100001|00 [26] 3ffff84 [26]
(167) |11111111|11111111|11100001|01 [26] 3ffff85 [26]
(168) |11111111|11111111|11100001|10 [26] 3ffff86 [26]
(169) |11111111|11111111|11100001|11 [26] 3ffff87 [26]
(170) |11111111|11111111|11100010|00 [26] 3ffff88 [26]
(171) |11111111|11111111|11100010|01 [26] 3ffff89 [26]
(172) |11111111|11111111|11100010|10 [26] 3ffff8a [26]
(173) |11111111|11111111|11100010|11 [26] 3ffff8b [26]
(174) |11111111|11111111|11100011|00 [26] 3ffff8c [26]
(175) |11111111|11111111|11100011|01 [26] 3ffff8d [26]
(176) |11111111|11111111|11100011|10 [26] 3ffff8e [26]
(177) |11111111|11111111|11100011|11 [26] 3ffff8f [26]
(178) |11111111|11111111|11100100|00 [26] 3ffff90 [26]
(179) |11111111|11111111|11100100|01 [26] 3ffff91 [26]
(180) |11111111|11111111|11100100|10 [26] 3ffff92 [26]
(181) |11111111|11111111|11100100|11 [26] 3ffff93 [26]
(182) |11111111|11111111|11100101|00 [26] 3ffff94 [26]
(183) |11111111|11111111|11100101|01 [26] 3ffff95 [26]
(184) |11111111|11111111|11100101|10 [26] 3ffff96 [26]
(185) |11111111|11111111|11100101|11 [26] 3ffff97 [26]
(186) |11111111|11111111|11100110|00 [26] 3ffff98 [26]
(187) |11111111|11111111|11100110|01 [26] 3ffff99 [26]
(188) |11111111|11111111|11100110|10 [26] 3ffff9a [26]
(189) |11111111|11111111|11100110|11 [26] 3ffff9b [26]
(190) |11111111|11111111|11100111|00 [26] 3ffff9c [26]
(191) |11111111|11111111|11100111|01 [26] 3ffff9d [26]
(192) |11111111|11111111|11100111|10 [26] 3ffff9e [26]
(193) |11111111|11111111|11100111|11 [26] 3ffff9f [26]
(194) |11111111|11111111|11101000|00 [26] 3ffffa0 [26]
(195) |11111111|11111111|11101000|01 [26] 3ffffa1 [26]
(196) |11111111|11111111|11101000|10 [26] 3ffffa2 [26]
(197) |11111111|11111111|11101000|11 [26] 3ffffa3 [26]
(198) |11111111|11111111|11101001|00 [26] 3ffffa4 [26]
(199) |11111111|11111111|11101001|01 [26] 3ffffa5 [26]
(200) |11111111|11111111|11101001|10 [26] 3ffffa6 [26]
(201) |11111111|11111111|11101001|11 [26] 3ffffa7 [26]
(202) |11111111|11111111|11101010|00 [26] 3ffffa8 [26]
(203) |11111111|11111111|11101010|01 [26] 3ffffa9 [26]
(204) |11111111|11111111|11101010|10 [26] 3ffffaa [26]
(205) |11111111|11111111|11101010|11 [26] 3ffffab [26]
(206) |11111111|11111111|11101011|00 [26] 3ffffac [26]
(207) |11111111|11111111|11101011|01 [26] 3ffffad [26]
(208) |11111111|11111111|11101011|10 [26] 3ffffae [26]
(209) |11111111|11111111|11101011|11 [26] 3ffffaf [26]
(210) |11111111|11111111|11101100|00 [26] 3ffffb0 [26]
(211) |11111111|11111111|11101100|01 [26] 3ffffb1 [26]
(212) |11111111|11111111|11101100|10 [26] 3ffffb2 [26]
(213) |11111111|11111111|11101100|11 [26] 3ffffb3 [26]
(214) |11111111|11111111|11101101|00 [26] 3ffffb4 [26]
(215) |11111111|11111111|11101101|01 [26] 3ffffb5 [26]
(216) |11111111|11111111|11101101|10 [26] 3ffffb6 [26]
(217) |11111111|11111111|11101101|11 [26] 3ffffb7 [26]
(218) |11111111|11111111|11101110|00 [26] 3ffffb8 [26]
(219) |11111111|11111111|11101110|01 [26] 3ffffb9 [26]
(220) |11111111|11111111|11101110|10 [26] 3ffffba [26]
(221) |11111111|11111111|11101110|11 [26] 3ffffbb [26]
(222) |11111111|11111111|11101111|00 [26] 3ffffbc [26]
(223) |11111111|11111111|11101111|01 [26] 3ffffbd [26]
(224) |11111111|11111111|11101111|10 [26] 3ffffbe [26]
(225) |11111111|11111111|11101111|11 [26] 3ffffbf [26]
(226) |11111111|11111111|11110000|00 [26] 3ffffc0 [26]
(227) |11111111|11111111|11110000|01 [26] 3ffffc1 [26]
(228) |11111111|11111111|11110000|10 [26] 3ffffc2 [26]
(229) |11111111|11111111|11110000|11 [26] 3ffffc3 [26]
(230) |11111111|11111111|11110001|00 [26] 3ffffc4 [26]
(231) |11111111|11111111|11110001|01 [26] 3ffffc5 [26]
(232) |11111111|11111111|11110001|10 [26] 3ffffc6 [26]
(233) |11111111|11111111|11110001|11 [26] 3ffffc7 [26]
(234) |11111111|11111111|11110010|00 [26] 3ffffc8 [26]
(235) |11111111|11111111|11110010|01 [26] 3ffffc9 [26]
(236) |11111111|11111111|11110010|10 [26] 3ffffca [26]
(237) |11111111|11111111|11110010|11 [26] 3ffffcb [26]
(238) |11111111|11111111|11110011|00 [26] 3ffffcc [26]
(239) |11111111|11111111|11110011|01 [26] 3ffffcd [26]
(240) |11111111|11111111|11110011|10 [26] 3ffffce [26]
(241) |11111111|11111111|11110011|11 [26] 3ffffcf [26]
(242) |11111111|11111111|11110100|00 [26] 3ffffd0 [26]
(243) |11111111|11111111|11110100|01 [26] 3ffffd1 [26]
(244) |11111111|11111111|11110100|10 [26] 3ffffd2 [26]
(245) |11111111|11111111|11110100|11 [26] 3ffffd3 [26]
(246) |11111111|11111111|11110101|00 [26] 3ffffd4 [26]
(247) |11111111|11111111|11110101|01 [26] 3ffffd5 [26]
(248) |11111111|11111111|11110101|10 [26] 3ffffd6 [26]
(249) |11111111|11111111|11110101|11 [26] 3ffffd7 [26]
(250) |11111111|11111111|11110110|00 [26] 3ffffd8 [26]
(251) |11111111|11111111|11110110|01 [26] 3ffffd9 [26]
(252) |11111111|11111111|11110110|10 [26] 3ffffda [26]
(253) |11111111|11111111|11110110|11 [26] 3ffffdb [26]
(254) |11111111|11111111|11110111|00 [26] 3ffffdc [26]
(255) |11111111|11111111|11110111|01 [26] 3ffffdd [26]
(256) |10010 [5] 12 [5]
]]>
</artwork>
</section>
<section title="Appendix C">
<t>Appendix C huffman code-table for responses</t>
<artwork><![CDATA[
For Responses
( 0) |11111111|11111111|11101111|10 [26] 3ffffbe [26]
( 1) |11111111|11111111|11101111|11 [26] 3ffffbf [26]
( 2) |11111111|11111111|11110000|00 [26] 3ffffc0 [26]
( 3) |11111111|11111111|11110000|01 [26] 3ffffc1 [26]
( 4) |11111111|11111111|11110000|10 [26] 3ffffc2 [26]
( 5) |11111111|11111111|11110000|11 [26] 3ffffc3 [26]
( 6) |11111111|11111111|11110001|00 [26] 3ffffc4 [26]
( 7) |11111111|11111111|11110001|01 [26] 3ffffc5 [26]
( 8) |11111111|11111111|11110001|10 [26] 3ffffc6 [26]
( 9) |11111111|11111111|11110001|11 [26] 3ffffc7 [26]
( 10) |11111111|11111111|11110010|00 [26] 3ffffc8 [26]
( 11) |11111111|11111111|11110010|01 [26] 3ffffc9 [26]
( 12) |11111111|11111111|11110010|10 [26] 3ffffca [26]
( 13) |11111111|11111111|11110010|11 [26] 3ffffcb [26]
( 14) |11111111|11111111|11110011|00 [26] 3ffffcc [26]
( 15) |11111111|11111111|11110011|01 [26] 3ffffcd [26]
( 16) |11111111|11111111|11110011|10 [26] 3ffffce [26]
( 17) |11111111|11111111|11110011|11 [26] 3ffffcf [26]
( 18) |11111111|11111111|11110100|00 [26] 3ffffd0 [26]
( 19) |11111111|11111111|11110100|01 [26] 3ffffd1 [26]
( 20) |11111111|11111111|11110100|10 [26] 3ffffd2 [26]
( 21) |11111111|11111111|11110100|11 [26] 3ffffd3 [26]
( 22) |11111111|11111111|11110101|00 [26] 3ffffd4 [26]
( 23) |11111111|11111111|11110101|01 [26] 3ffffd5 [26]
( 24) |11111111|11111111|11110101|10 [26] 3ffffd6 [26]
( 25) |11111111|11111111|11110101|11 [26] 3ffffd7 [26]
( 26) |11111111|11111111|11110110|00 [26] 3ffffd8 [26]
( 27) |11111111|11111111|11110110|01 [26] 3ffffd9 [26]
( 28) |11111111|11111111|11110110|10 [26] 3ffffda [26]
( 29) |11111111|11111111|11110110|11 [26] 3ffffdb [26]
( 30) |11111111|11111111|11110111|00 [26] 3ffffdc [26]
( 31) |11111111|11111111|11110111|01 [26] 3ffffdd [26]
' ' ( 32) |0000 [4] 0 [4]
'!' ( 33) |11111111|1010 [12] ffa [12]
'"' ( 34) |1101000 [7] 68 [7]
'#' ( 35) |11111111|111010 [14] 3ffa [14]
'$' ( 36) |11111111|1111100 [15] 7ffc [15]
'%' ( 37) |11110101|0 [9] 1ea [9]
'&' ( 38) |11111110|00 [10] 3f8 [10]
''' ( 39) |11111111|11100 [13] 1ffc [13]
'(' ( 40) |11110101|1 [9] 1eb [9]
')' ( 41) |11110110|0 [9] 1ec [9]
'*' ( 42) |11111111|1011 [12] ffb [12]
'+' ( 43) |11111110|01 [10] 3f9 [10]
',' ( 44) |100110 [6] 26 [6]
'-' ( 45) |100111 [6] 27 [6]
'.' ( 46) |1101001 [7] 69 [7]
'/' ( 47) |11101000 [8] e8 [8]
'0' ( 48) |0001 [4] 1 [4]
'1' ( 49) |0010 [4] 2 [4]
'2' ( 50) |0011 [4] 3 [4]
'3' ( 51) |01000 [5] 8 [5]
'4' ( 52) |01001 [5] 9 [5]
'5' ( 53) |01010 [5] a [5]
'6' ( 54) |101000 [6] 28 [6]
'7' ( 55) |01011 [5] b [5]
'8' ( 56) |01100 [5] c [5]
'9' ( 57) |01101 [5] d [5]
':' ( 58) |01110 [5] e [5]
';' ( 59) |11110110|1 [9] 1ed [9]
'<' ( 60) |11111111|11111100 [16] fffc [16]
'=' ( 61) |1101010 [7] 6a [7]
'>' ( 62) |11111111|111011 [14] 3ffb [14]
'?' ( 63) |11111111|1100 [12] ffc [12]
'@' ( 64) |11111111|11111110|0 [17] 1fffc [17]
'A' ( 65) |1101011 [7] 6b [7]
'B' ( 66) |11110111|0 [9] 1ee [9]
'C' ( 67) |11101001 [8] e9 [8]
'D' ( 68) |11101010 [8] ea [8]
'E' ( 69) |11101011 [8] eb [8]
'F' ( 70) |11101100 [8] ec [8]
'G' ( 71) |101001 [6] 29 [6]
'H' ( 72) |11110111|1 [9] 1ef [9]
'I' ( 73) |11111000|0 [9] 1f0 [9]
'J' ( 74) |11101101 [8] ed [8]
'K' ( 75) |11111110|10 [10] 3fa [10]
'L' ( 76) |11111000|1 [9] 1f1 [9]
'M' ( 77) |101010 [6] 2a [6]
'N' ( 78) |11101110 [8] ee [8]
'O' ( 79) |11101111 [8] ef [8]
'P' ( 80) |11111001|0 [9] 1f2 [9]
'Q' ( 81) |11111001|1 [9] 1f3 [9]
'R' ( 82) |11111010|0 [9] 1f4 [9]
'S' ( 83) |1101100 [7] 6c [7]
'T' ( 84) |01111 [5] f [5]
'U' ( 85) |11111010|1 [9] 1f5 [9]
'V' ( 86) |11111011|0 [9] 1f6 [9]
'W' ( 87) |11110000 [8] f0 [8]
'X' ( 88) |11111110|11 [10] 3fb [10]
'Y' ( 89) |11111111|00 [10] 3fc [10]
'Z' ( 90) |11111111|01 [10] 3fd [10]
'[' ( 91) |11111111|1101 [12] ffd [12]
'\' ( 92) |11111111|111100 [14] 3ffc [14]
']' ( 93) |11111111|100 [11] 7fc [11]
'^' ( 94) |11111111|1111101 [15] 7ffd [15]
'_' ( 95) |11111011|1 [9] 1f7 [9]
'`' ( 96) |11111111|11111111|10 [18] 3fffe [18]
'a' ( 97) |10000 [5] 10 [5]
'b' ( 98) |1101101 [7] 6d [7]
'c' ( 99) |101011 [6] 2b [6]
'd' (100) |101100 [6] 2c [6]
'e' (101) |10001 [5] 11 [5]
'f' (102) |1101110 [7] 6e [7]
'g' (103) |1101111 [7] 6f [7]
'h' (104) |1110000 [7] 70 [7]
'i' (105) |101101 [6] 2d [6]
'j' (106) |11111100|0 [9] 1f8 [9]
'k' (107) |11111100|1 [9] 1f9 [9]
'l' (108) |1110001 [7] 71 [7]
'm' (109) |1110010 [7] 72 [7]
'n' (110) |101110 [6] 2e [6]
'o' (111) |101111 [6] 2f [6]
'p' (112) |110000 [6] 30 [6]
'q' (113) |11111101|0 [9] 1fa [9]
'r' (114) |110001 [6] 31 [6]
's' (115) |1110011 [7] 73 [7]
't' (116) |110010 [6] 32 [6]
'u' (117) |110011 [6] 33 [6]
'v' (118) |11110001 [8] f1 [8]
'w' (119) |11110010 [8] f2 [8]
'x' (120) |11110011 [8] f3 [8]
'y' (121) |11110100 [8] f4 [8]
'z' (122) |11111101|1 [9] 1fb [9]
'{' (123) |11111111|11111110|1 [17] 1fffd [17]
'|' (124) |11111111|111101 [14] 3ffd [14]
'}' (125) |11111111|11111111|0 [17] 1fffe [17]
'~' (126) |11111111|11111101 [16] fffd [16]
(127) |11111111|11111111|11110111|10 [26] 3ffffde [26]
(128) |11111111|11111111|11110111|11 [26] 3ffffdf [26]
(129) |11111111|11111111|11111000|00 [26] 3ffffe0 [26]
(130) |11111111|11111111|11111000|01 [26] 3ffffe1 [26]
(131) |11111111|11111111|11111000|10 [26] 3ffffe2 [26]
(132) |11111111|11111111|11111000|11 [26] 3ffffe3 [26]
(133) |11111111|11111111|11111001|00 [26] 3ffffe4 [26]
(134) |11111111|11111111|11111001|01 [26] 3ffffe5 [26]
(135) |11111111|11111111|11111001|10 [26] 3ffffe6 [26]
(136) |11111111|11111111|11111001|11 [26] 3ffffe7 [26]
(137) |11111111|11111111|11111010|00 [26] 3ffffe8 [26]
(138) |11111111|11111111|11111010|01 [26] 3ffffe9 [26]
(139) |11111111|11111111|11111010|10 [26] 3ffffea [26]
(140) |11111111|11111111|11111010|11 [26] 3ffffeb [26]
(141) |11111111|11111111|11111011|00 [26] 3ffffec [26]
(142) |11111111|11111111|11111011|01 [26] 3ffffed [26]
(143) |11111111|11111111|11111011|10 [26] 3ffffee [26]
(144) |11111111|11111111|11111011|11 [26] 3ffffef [26]
(145) |11111111|11111111|11111100|00 [26] 3fffff0 [26]
(146) |11111111|11111111|11111100|01 [26] 3fffff1 [26]
(147) |11111111|11111111|11111100|10 [26] 3fffff2 [26]
(148) |11111111|11111111|11111100|11 [26] 3fffff3 [26]
(149) |11111111|11111111|11111101|00 [26] 3fffff4 [26]
(150) |11111111|11111111|11111101|01 [26] 3fffff5 [26]
(151) |11111111|11111111|11111101|10 [26] 3fffff6 [26]
(152) |11111111|11111111|11111101|11 [26] 3fffff7 [26]
(153) |11111111|11111111|11111110|00 [26] 3fffff8 [26]
(154) |11111111|11111111|11111110|01 [26] 3fffff9 [26]
(155) |11111111|11111111|11111110|10 [26] 3fffffa [26]
(156) |11111111|11111111|11111110|11 [26] 3fffffb [26]
(157) |11111111|11111111|11111111|00 [26] 3fffffc [26]
(158) |11111111|11111111|11111111|01 [26] 3fffffd [26]
(159) |11111111|11111111|11111111|10 [26] 3fffffe [26]
(160) |11111111|11111111|11111111|11 [26] 3ffffff [26]
(161) |11111111|11111111|11000000|0 [25] 1ffff80 [25]
(162) |11111111|11111111|11000000|1 [25] 1ffff81 [25]
(163) |11111111|11111111|11000001|0 [25] 1ffff82 [25]
(164) |11111111|11111111|11000001|1 [25] 1ffff83 [25]
(165) |11111111|11111111|11000010|0 [25] 1ffff84 [25]
(166) |11111111|11111111|11000010|1 [25] 1ffff85 [25]
(167) |11111111|11111111|11000011|0 [25] 1ffff86 [25]
(168) |11111111|11111111|11000011|1 [25] 1ffff87 [25]
(169) |11111111|11111111|11000100|0 [25] 1ffff88 [25]
(170) |11111111|11111111|11000100|1 [25] 1ffff89 [25]
(171) |11111111|11111111|11000101|0 [25] 1ffff8a [25]
(172) |11111111|11111111|11000101|1 [25] 1ffff8b [25]
(173) |11111111|11111111|11000110|0 [25] 1ffff8c [25]
(174) |11111111|11111111|11000110|1 [25] 1ffff8d [25]
(175) |11111111|11111111|11000111|0 [25] 1ffff8e [25]
(176) |11111111|11111111|11000111|1 [25] 1ffff8f [25]
(177) |11111111|11111111|11001000|0 [25] 1ffff90 [25]
(178) |11111111|11111111|11001000|1 [25] 1ffff91 [25]
(179) |11111111|11111111|11001001|0 [25] 1ffff92 [25]
(180) |11111111|11111111|11001001|1 [25] 1ffff93 [25]
(181) |11111111|11111111|11001010|0 [25] 1ffff94 [25]
(182) |11111111|11111111|11001010|1 [25] 1ffff95 [25]
(183) |11111111|11111111|11001011|0 [25] 1ffff96 [25]
(184) |11111111|11111111|11001011|1 [25] 1ffff97 [25]
(185) |11111111|11111111|11001100|0 [25] 1ffff98 [25]
(186) |11111111|11111111|11001100|1 [25] 1ffff99 [25]
(187) |11111111|11111111|11001101|0 [25] 1ffff9a [25]
(188) |11111111|11111111|11001101|1 [25] 1ffff9b [25]
(189) |11111111|11111111|11001110|0 [25] 1ffff9c [25]
(190) |11111111|11111111|11001110|1 [25] 1ffff9d [25]
(191) |11111111|11111111|11001111|0 [25] 1ffff9e [25]
(192) |11111111|11111111|11001111|1 [25] 1ffff9f [25]
(193) |11111111|11111111|11010000|0 [25] 1ffffa0 [25]
(194) |11111111|11111111|11010000|1 [25] 1ffffa1 [25]
(195) |11111111|11111111|11010001|0 [25] 1ffffa2 [25]
(196) |11111111|11111111|11010001|1 [25] 1ffffa3 [25]
(197) |11111111|11111111|11010010|0 [25] 1ffffa4 [25]
(198) |11111111|11111111|11010010|1 [25] 1ffffa5 [25]
(199) |11111111|11111111|11010011|0 [25] 1ffffa6 [25]
(200) |11111111|11111111|11010011|1 [25] 1ffffa7 [25]
(201) |11111111|11111111|11010100|0 [25] 1ffffa8 [25]
(202) |11111111|11111111|11010100|1 [25] 1ffffa9 [25]
(203) |11111111|11111111|11010101|0 [25] 1ffffaa [25]
(204) |11111111|11111111|11010101|1 [25] 1ffffab [25]
(205) |11111111|11111111|11010110|0 [25] 1ffffac [25]
(206) |11111111|11111111|11010110|1 [25] 1ffffad [25]
(207) |11111111|11111111|11010111|0 [25] 1ffffae [25]
(208) |11111111|11111111|11010111|1 [25] 1ffffaf [25]
(209) |11111111|11111111|11011000|0 [25] 1ffffb0 [25]
(210) |11111111|11111111|11011000|1 [25] 1ffffb1 [25]
(211) |11111111|11111111|11011001|0 [25] 1ffffb2 [25]
(212) |11111111|11111111|11011001|1 [25] 1ffffb3 [25]
(213) |11111111|11111111|11011010|0 [25] 1ffffb4 [25]
(214) |11111111|11111111|11011010|1 [25] 1ffffb5 [25]
(215) |11111111|11111111|11011011|0 [25] 1ffffb6 [25]
(216) |11111111|11111111|11011011|1 [25] 1ffffb7 [25]
(217) |11111111|11111111|11011100|0 [25] 1ffffb8 [25]
(218) |11111111|11111111|11011100|1 [25] 1ffffb9 [25]
(219) |11111111|11111111|11011101|0 [25] 1ffffba [25]
(220) |11111111|11111111|11011101|1 [25] 1ffffbb [25]
(221) |11111111|11111111|11011110|0 [25] 1ffffbc [25]
(222) |11111111|11111111|11011110|1 [25] 1ffffbd [25]
(223) |11111111|11111111|11011111|0 [25] 1ffffbe [25]
(224) |11111111|11111111|11011111|1 [25] 1ffffbf [25]
(225) |11111111|11111111|11100000|0 [25] 1ffffc0 [25]
(226) |11111111|11111111|11100000|1 [25] 1ffffc1 [25]
(227) |11111111|11111111|11100001|0 [25] 1ffffc2 [25]
(228) |11111111|11111111|11100001|1 [25] 1ffffc3 [25]
(229) |11111111|11111111|11100010|0 [25] 1ffffc4 [25]
(230) |11111111|11111111|11100010|1 [25] 1ffffc5 [25]
(231) |11111111|11111111|11100011|0 [25] 1ffffc6 [25]
(232) |11111111|11111111|11100011|1 [25] 1ffffc7 [25]
(233) |11111111|11111111|11100100|0 [25] 1ffffc8 [25]
(234) |11111111|11111111|11100100|1 [25] 1ffffc9 [25]
(235) |11111111|11111111|11100101|0 [25] 1ffffca [25]
(236) |11111111|11111111|11100101|1 [25] 1ffffcb [25]
(237) |11111111|11111111|11100110|0 [25] 1ffffcc [25]
(238) |11111111|11111111|11100110|1 [25] 1ffffcd [25]
(239) |11111111|11111111|11100111|0 [25] 1ffffce [25]
(240) |11111111|11111111|11100111|1 [25] 1ffffcf [25]
(241) |11111111|11111111|11101000|0 [25] 1ffffd0 [25]
(242) |11111111|11111111|11101000|1 [25] 1ffffd1 [25]
(243) |11111111|11111111|11101001|0 [25] 1ffffd2 [25]
(244) |11111111|11111111|11101001|1 [25] 1ffffd3 [25]
(245) |11111111|11111111|11101010|0 [25] 1ffffd4 [25]
(246) |11111111|11111111|11101010|1 [25] 1ffffd5 [25]
(247) |11111111|11111111|11101011|0 [25] 1ffffd6 [25]
(248) |11111111|11111111|11101011|1 [25] 1ffffd7 [25]
(249) |11111111|11111111|11101100|0 [25] 1ffffd8 [25]
(250) |11111111|11111111|11101100|1 [25] 1ffffd9 [25]
(251) |11111111|11111111|11101101|0 [25] 1ffffda [25]
(252) |11111111|11111111|11101101|1 [25] 1ffffdb [25]
(253) |11111111|11111111|11101110|0 [25] 1ffffdc [25]
(254) |11111111|11111111|11101110|1 [25] 1ffffdd [25]
(255) |11111111|11111111|11101111|0 [25] 1ffffde [25]
(256) |10010 [5] 12 [5]
]]>
</artwork>
</section>
</middle>
<back>
<references title="Normative References">
&RFC2119;
&RFC2616;
<reference anchor="HUFF" target="">
<front>
<title>A Method for the Construction of Minimim Redundancy Codes</title>
<author surname="Huffman, D. A." fullname="David A. Huffman">
</author>
<date month="Proceedings of the Institute of Radio Engineers, September 1952, Volume 40, Number 9, pp. 1098-1101"/>
</front>
</reference>
<reference anchor="CANON" target="">
<front>
<title>Generating a canonical prefix encoding</title>
<author surname="Schwartz, E. S."> </author>
<author surname="Kallick, B."> </author>
<date month="Comm. ACM, 7,3 (March 1964), pp 166-169"/>
</front>
</reference>
<reference anchor="SPDY" target="http://tools.ietf.org/html/draft-mbelshe-httpbis-spdy">
<front>
<title>SPDY PROTOCOL</title>
<author initials="M" surname="Belshe" fullname="Mike Belshe">
<organization>Twist</organization>
</author>
<author initials="R" surname="Peon" fullname="Roberto Peon">
<organization>Google</organization>
</author>
</front>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-24 06:58:16 |