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1573 lines (1490 loc) · 38.5 KB
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
<meta name="generator" content="AsciiDoc3 3.2.3" />
<title>ADC Recommendations</title>
<style type="text/css">
/* Shared CSS for AsciiDoc3 xhtml11 and html5 backends */
/* Default font. */
body {
font-family: Georgia,serif;
}
/* Title font. */
h1, h2, h3, h4, h5, h6,
div.title, caption.title,
thead, p.table.header,
#toctitle,
#author, #revnumber, #revdate, #revremark,
#footer {
font-family: Arial,Helvetica,sans-serif;
}
body {
margin: 1em 5% 1em 5%;
line-height: 200%;
}
a {
color: blue;
text-decoration: underline;
}
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}
em {
font-style: italic;
color: navy;
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color: #083194;
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h1, h2, h3, h4, h5, h6 {
color: #527bbd;
margin-top: 1.2em;
margin-bottom: 0.5em;
line-height: 1.3;
}
h1, h2, h3 {
border-bottom: 2px solid silver;
}
h2 {
padding-top: 0.5em;
}
h3 {
float: left;
}
h3 + * {
clear: left;
}
h5 {
font-size: 1.0em;
}
div.sectionbody {
margin-left: 0;
}
hr {
border: 1px solid silver;
}
p {
margin-top: 0.5em;
margin-bottom: 0.5em;
}
ul, ol, li > p {
margin-top: 0;
}
ul > li { color: #aaa; }
ul > li > * { color: black; }
.monospaced, code, pre {
font-family: "Courier New", Courier, monospace;
font-size: inherit;
color: navy;
padding: 0;
margin: 0;
}
pre {
white-space: pre-wrap;
}
#author {
color: #527bbd;
font-weight: bold;
font-size: 1.1em;
}
#email {
}
#revnumber, #revdate, #revremark {
}
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font-size: small;
border-top: 2px solid silver;
padding-top: 0.5em;
margin-top: 4.0em;
}
#footer-text {
float: left;
padding-bottom: 0.5em;
}
#footer-badges {
float: right;
padding-bottom: 0.5em;
}
#preamble {
margin-top: 1.5em;
margin-bottom: 1.5em;
}
div.imageblock, div.exampleblock, div.verseblock,
div.quoteblock, div.literalblock, div.listingblock, div.sidebarblock,
div.admonitionblock {
margin-top: 1.0em;
margin-bottom: 1.5em;
}
div.admonitionblock {
margin-top: 2.0em;
margin-bottom: 2.0em;
margin-right: 10%;
color: #606060;
}
div.content { /* Block element content. */
padding: 0;
}
/* Block element titles. */
div.title, caption.title {
color: #527bbd;
font-weight: bold;
text-align: left;
margin-top: 1.0em;
margin-bottom: 0.5em;
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div.title + * {
margin-top: 0;
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td div.title:first-child {
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div.content div.title:first-child {
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div.content + div.title {
margin-top: 0.0em;
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div.sidebarblock > div.content {
background: #ffffee;
border: 1px solid #dddddd;
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border: 1px solid #dddddd;
border-left: 5px solid #f0f0f0;
background: #f8f8f8;
padding: 0.5em;
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margin-left: 1.0em;
margin-right: 10%;
border-left: 5px solid #f0f0f0;
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div.verseblock > pre.content {
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div.verseblock > div.attribution {
padding-top: 0.75em;
text-align: left;
}
/* DEPRECATED: Pre version 8.2.7 verse style literal block. */
div.verseblock + div.attribution {
text-align: left;
}
div.admonitionblock .icon {
vertical-align: top;
font-size: 1.1em;
font-weight: bold;
text-decoration: underline;
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div.admonitionblock td.content {
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div.exampleblock > div.content {
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padding-left: 0.5em;
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div.imageblock div.content { padding-left: 0; }
span.image img { border-style: none; vertical-align: text-bottom; }
a.image:visited { color: white; }
dl {
margin-top: 0.8em;
margin-bottom: 0.8em;
}
dt {
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margin-bottom: 0;
font-style: normal;
color: navy;
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dd > *:first-child {
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ul, ol {
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}
ol.arabic {
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ol.loweralpha {
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}
ol.upperalpha {
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}
ol.lowerroman {
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ol.upperroman {
list-style-type: upper-roman;
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div.compact ul, div.compact ol,
div.compact p, div.compact p,
div.compact div, div.compact div {
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margin-bottom: 0.1em;
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tfoot {
font-weight: bold;
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td > div.verse {
white-space: pre;
}
div.hdlist {
margin-top: 0.8em;
margin-bottom: 0.8em;
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div.hdlist tr {
padding-bottom: 15px;
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dt.hdlist1.strong, td.hdlist1.strong {
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td.hdlist1 {
vertical-align: top;
font-style: normal;
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color: navy;
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td.hdlist2 {
vertical-align: top;
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div.hdlist.compact tr {
margin: 0;
padding-bottom: 0;
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.comment {
background: yellow;
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.footnote, .footnoteref {
font-size: 0.8em;
}
span.footnote, span.footnoteref {
vertical-align: super;
}
#footnotes {
margin: 20px 0 20px 0;
padding: 7px 0 0 0;
}
#footnotes div.footnote {
margin: 0 0 5px 0;
}
#footnotes hr {
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border-top: 1px solid silver;
height: 1px;
text-align: left;
margin-left: 0;
width: 20%;
min-width: 100px;
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div.colist td {
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padding-bottom: 0.3em;
vertical-align: top;
}
div.colist td img {
margin-top: 0.3em;
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@media print {
#footer-badges { display: none; }
}
#toc {
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}
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color: #527bbd;
font-size: 1.1em;
font-weight: bold;
margin-top: 1.0em;
margin-bottom: 0.1em;
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div.toclevel0, div.toclevel1, div.toclevel2, div.toclevel3, div.toclevel4 {
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margin-bottom: 0;
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div.toclevel4 {
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font-size: 0.9em;
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span.black { color: black; }
span.blue { color: blue; }
span.fuchsia { color: fuchsia; }
span.gray { color: gray; }
span.green { color: green; }
span.lime { color: lime; }
span.maroon { color: maroon; }
span.navy { color: navy; }
span.olive { color: olive; }
span.purple { color: purple; }
span.red { color: red; }
span.silver { color: silver; }
span.teal { color: teal; }
span.white { color: white; }
span.yellow { color: yellow; }
span.aqua-background { background: aqua; }
span.black-background { background: black; }
span.blue-background { background: blue; }
span.fuchsia-background { background: fuchsia; }
span.gray-background { background: gray; }
span.green-background { background: green; }
span.lime-background { background: lime; }
span.maroon-background { background: maroon; }
span.navy-background { background: navy; }
span.olive-background { background: olive; }
span.purple-background { background: purple; }
span.red-background { background: red; }
span.silver-background { background: silver; }
span.teal-background { background: teal; }
span.white-background { background: white; }
span.yellow-background { background: yellow; }
span.big { font-size: 2em; }
span.small { font-size: 0.6em; }
span.underline { text-decoration: underline; }
span.overline { text-decoration: overline; }
span.line-through { text-decoration: line-through; }
div.unbreakable { page-break-inside: avoid; }
/*
* xhtml11 specific
*
* */
div.tableblock {
margin-top: 1.0em;
margin-bottom: 1.5em;
}
div.tableblock > table {
border: 3px solid #527bbd;
}
thead, p.table.header {
font-weight: bold;
color: #527bbd;
}
p.table {
margin-top: 0;
}
/* Because the table frame attribute is overriden by CSS in most browsers. */
div.tableblock > table[frame="void"] {
border-style: none;
}
div.tableblock > table[frame="hsides"] {
border-left-style: none;
border-right-style: none;
}
div.tableblock > table[frame="vsides"] {
border-top-style: none;
border-bottom-style: none;
}
/*
* html5 specific
*
* */
table.tableblock {
margin-top: 1.0em;
margin-bottom: 1.5em;
}
thead, p.tableblock.header {
font-weight: bold;
color: #527bbd;
}
p.tableblock {
margin-top: 0;
}
table.tableblock {
border-width: 3px;
border-spacing: 0px;
border-style: solid;
border-color: #527bbd;
border-collapse: collapse;
}
th.tableblock, td.tableblock {
border-width: 1px;
padding: 4px;
border-style: solid;
border-color: #527bbd;
}
table.tableblock.frame-topbot {
border-left-style: hidden;
border-right-style: hidden;
}
table.tableblock.frame-sides {
border-top-style: hidden;
border-bottom-style: hidden;
}
table.tableblock.frame-none {
border-style: hidden;
}
th.tableblock.halign-left, td.tableblock.halign-left {
text-align: left;
}
th.tableblock.halign-center, td.tableblock.halign-center {
text-align: center;
}
th.tableblock.halign-right, td.tableblock.halign-right {
text-align: right;
}
th.tableblock.valign-top, td.tableblock.valign-top {
vertical-align: top;
}
th.tableblock.valign-middle, td.tableblock.valign-middle {
vertical-align: middle;
}
th.tableblock.valign-bottom, td.tableblock.valign-bottom {
vertical-align: bottom;
}
/*
* manpage specific
*
* */
body.manpage h1 {
padding-top: 0.5em;
padding-bottom: 0.5em;
border-top: 2px solid silver;
border-bottom: 2px solid silver;
}
body.manpage h2 {
border-style: none;
}
body.manpage div.sectionbody {
margin-left: 3em;
}
@media print {
body.manpage div#toc { display: none; }
}
</style>
<script type="text/javascript">
/*<+'])');
// Function that scans the DOM tree for header elements (the DOM2
// nodeIterator API would be a better technique but not supported by all
// browsers).
var iterate = function (el) {
for (var i = el.firstChild; i != null; i = i.nextSibling) {
if (i.nodeType == 1 /* Node.ELEMENT_NODE */) {
var mo = re.exec(i.tagName);
if (mo && (i.getAttribute("class") || i.getAttribute("className")) != "float") {
result[result.length] = new TocEntry(i, getText(i), mo[1]-1);
}
iterate(i);
}
}
}
iterate(el);
return result;
}
var toc = document.getElementById("toc");
if (!toc) {
return;
}
// Delete existing TOC entries in case we're reloading the TOC.
var tocEntriesToRemove = [];
var i;
for (i = 0; i < toc.childNodes.length; i++) {
var entry = toc.childNodes[i];
if (entry.nodeName.toLowerCase() == 'div'
&& entry.getAttribute("class")
&& entry.getAttribute("class").match(/^toclevel/))
tocEntriesToRemove.push(entry);
}
for (i = 0; i < tocEntriesToRemove.length; i++) {
toc.removeChild(tocEntriesToRemove[i]);
}
// Rebuild TOC entries.
var entries = tocEntries(document.getElementById("content"), toclevels);
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var entry = entries[i];
if (entry.element.id == "")
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div.className = "toclevel" + entry.toclevel;
toc.appendChild(div);
}
if (entries.length == 0)
toc.parentNode.removeChild(toc);
},
/////////////////////////////////////////////////////////////////////
// Footnotes generator
/////////////////////////////////////////////////////////////////////
/* Based on footnote generation code from:
* http://www.brandspankingnew.net/archive/2005/07/format_footnote.html
*/
footnotes: function () {
// Delete existing footnote entries in case we're reloading the footnodes.
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var noteholder = document.getElementById("footnotes");
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entriesToRemove.push(entry);
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<body class="article">
<div id="header">
<h1>ADC Recommendations</h1>
<span id="author">version 1.2.0, UNRELEASED</span><br />
<div id="toc">
<div id="toctitle">Table of Contents</div>
<noscript><p><b>JavaScript must be enabled in your browser to display the table of contents.</b></p></noscript>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_abstract">1. Abstract</h2>
<div class="sectionbody">
<div class="paragraph"><p>These are the official recommendations to ADC. This document is based on the information contained in the ADC documents, ADC wiki and ADC blog. Information is this document should be taken as guide lines to implementations.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_version_history">2. Version history</h2>
<div class="sectionbody">
<div class="paragraph"><p>The latest draft of the next version of this document as well as intermediate
and older versions can be downloaded from
$URL: <a href="https://github.com/dc-protocols/adc/blob/main/ADC-REC.txt">https://github.com/dc-protocols/adc/blob/main/ADC-REC.txt</a> $.</p></div>
<div class="paragraph"><p>This version corresponds to $Revision: 1 $.</p></div>
<div class="sect2">
<h3 id="_version_1_2_0_unreleased">2.1. Version 1.2.0, UNRELEASED</h3>
<div class="ulist"><ul>
<li>
<p>
Added client and hub implementation outlines
</p>
</li>
</ul></div>
</div>
<div class="sect2">
<h3 id="_version_1_1_0_2013_12_21">2.2. Version 1.1.0, 2013-12-21</h3>
<div class="paragraph"><p>Fredrik Ullner, <<a href="mailto:ullner@gmail.com">ullner@gmail.com</a>></p></div>
<div class="ulist"><ul>
<li>
<p>
Added ZLIB recommendation
</p>
</li>
<li>
<p>
Added SID recommendations/considerations.
</p>
</li>
</ul></div>
</div>
<div class="sect2">
<h3 id="_version_1_0_0_2010_07_01">2.3. Version 1.0.0, 2010-07-01</h3>
<div class="paragraph"><p>Fredrik Ullner, <<a href="mailto:ullner@gmail.com">ullner@gmail.com</a>></p></div>
<div class="ulist"><ul>
<li>
<p>
Initial release
</p>
</li>
</ul></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_general_recommentations">3. General recommentations</h2>
<div class="sectionbody">
<div class="paragraph"><p>Message length
Messages can be constructed to be long or short with varying complexity. All messages that contain a positional parameter can also contain additional named parameters. This mean that implementations must be able to read enough data to accuratley be aware of additional data. This also means that it may be in the implementations' interest to stop processing after an excessive amount of data, but implementations should strive to be as resiliant as possible. Certain messages that require parsing of specific parts, their context and content (e.g. regular expressions) may very well be short but nontheless pose a security issue if not dealt with appropriately.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_sta_recommendations">4. STA recommendations</h2>
<div class="sectionbody">
<div class="paragraph"><p>Clients should display text messages appropriately depending on context, severity and error code. It is recommended to display the error message regardless of the error code. Hubs must not depend on where clients display error codes.</p></div>
<div class="paragraph"><p>While STA messages require a severity to accompany the error code, the severity may not be of importance to some error codes or are simply implied by the actual error code. However, it is important that the severity is sent as appropriate and is accurate. STA messages with 0 (success) for severity can usually be regarded by implementations that the information require little or no counter-action.
The following list include error codes that make no or little sense in one or many severities, and a description why they are best used in one or only some severities. The descriptive text for the error codes can be seen in the STA specification, but may be re-stated as part of the description why they can have severity restriction(s).</p></div>
<div class="tableblock">
<table rules="all"
frame="border"
cellspacing="0" cellpadding="4">
<col />
<col />
<tbody>
<tr>
<td align="left" valign="top"><p class="table">11</p></td>
<td align="left" valign="top"><p class="table">If the hub is full, it makes little sense in keeping the client in some "connected" state. The recommended severity is to use 2 (fatal) to force the client to reconnect at a later time.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">12</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 11.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">21</p></td>
<td align="left" valign="top"><p class="table">While potentially fatal, the client may resend its INF with a new NI field. The recommended severity for hubs is to use 2 (fatal) but they can use 1 (recoverable).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">22</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 21.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">23</p></td>
<td align="left" valign="top"><p class="table">An invalid password depend on whether the hub wish to allow the client to resend its password (say, if the transmission became garbled). However, the recommended severity is to use 2 (fatal) unless under special circumstances, for some clients or for some users.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">24</p></td>
<td align="left" valign="top"><p class="table">The recommended severity is to use 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">25</p></td>
<td align="left" valign="top"><p class="table">Can be 1 (recoverable) or 2 (fatal) but generally not 0 (sucess).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">26</p></td>
<td align="left" valign="top"><p class="table">If the user is not registered in the hub, it makes little sense to try to reconnect immediately. The recommended severity is to use 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">27</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 24.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">30</p></td>
<td align="left" valign="top"><p class="table">The recommended severity is to use 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">31</p></td>
<td align="left" valign="top"><p class="table">Must be 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">32</p></td>
<td align="left" valign="top"><p class="table">Must be 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">43</p></td>
<td align="left" valign="top"><p class="table">Information that is missing or is bad is generally grounds for a disconnect but may be recoverable under certain states. The recommended severity is to use 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">44</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 43.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">45</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 43.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">46</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 43.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">47</p></td>
<td align="left" valign="top"><p class="table">Must be 2 (fatal).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">50</p></td>
<td align="left" valign="top"><p class="table">May be cause for a disconnect but is generally recoverable. The recommended severity is to use 1 (recoverable).</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">51</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 50.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">52</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 50.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">53</p></td>
<td align="left" valign="top"><p class="table">Similar to error code 11.</p></td>
</tr>
<tr>
<td align="left" valign="top"><p class="table">54</p></td>
<td align="left" valign="top"><p class="table">Must be 2 (fatal).</p></td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_zlib_compression">5. ZLIB compression</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_generic">5.1. Generic</h3>
<div class="ulist"><ul>
<li>
<p>
Try to keep constant and almost constant named parameters together, that way there is a higher likelyhood for a longer parameter match.
</p>
</li>
<li>
<p>
When possible try to keep similar commands no more than a window size (usually 32 bits if highest rate is used) away, that ensures you will benefit from the redundancy provided by these (this may be particularly important when sending large strings like MOTDs or help and configuration values intertwined with other commands).
</p>
</li>
<li>
<p>
Syncing is important to keep the clients updated but when you sync some bytes are sent (the sync ones and the ones for the Huffman tree of the new packet if it is a type 2 packet) as such it may make sense to keep in different queues commands depending on how much latency matters for them, for example you may want to keep low latency for MSG commands and send them frequently but may prefer to send searches or passive results together each half second or so. Also latencies matter depending on the type of network, on a LAN users expect most things to happen almost inmediately (especially things like MSGs) whilst clients connecting over a classic DSL line may not care that much for higher latencies.
</p>
</li>
</ul></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_sid_generation">6. SID generation</h2>
<div class="sectionbody">
<div class="paragraph"><p>The following are different algorithms for hubs to allocate and assign session IDs (SIDs) to clients.</p></div>
<div class="sect2">
<h3 id="_background">6.1. Background</h3>
<div class="paragraph"><p>In ADC the Session ID (or SID) uniquely identifies a user while connected to a hub, and the user will be assigned a SID at the time of login. Once assigned, the SID cannot be changed without a reconnect.</p></div>
<div class="paragraph"><p>The SID is a 4 byte sequence of Base32 characters consisting of 32 possible characters, A-Z and 2-7. This means there can be 32^4 different SIDs (slightly over 1 million).</p></div>
</div>
<div class="sect2">
<h3 id="_algorithms">6.2. Algorithms</h3>
<div class="paragraph"><p>The following algorithms are ways one can manage the SIDs that are assigned.</p></div>
<div class="sect3">
<h4 id="_random_sid_allocation">6.2.1. Random SID allocation</h4>
<div class="olist arabic"><ol class="arabic">
<li>
<p>
When client logs in: SID = random number between 1 and 1048576.
</p>
</li>
<li>
<p>
if (SID in use) go to 1.
</p>
</li>
<li>
<p>
Assign SID to user.
</p>
</li>
</ol></div>
<div class="paragraph"><p>Advantages:</p></div>
<div class="ulist"><ul>
<li>
<p>
Very simple to implement.
</p>
</li>
</ul></div>
<div class="paragraph"><p>Disadvantages:</p></div>
<div class="ulist"><ul>
<li>
<p>
Theoretically, if a hub has close to the maximum allowed users (1 million), the algorithm of generating a unique SID becomes very costly. On a hub consiting of a few thousand users this is negligible if looking up users based on SID is fast.
</p>
</li>
</ul></div>
<div class="paragraph"><p>Notes:</p></div>
<div class="ulist"><ul>
<li>
<p>
The algorithm requires that lookup of users must be as cheap as possible.
</p>
</li>
</ul></div>
</div>
<div class="sect3">
<h4 id="_incremental_sid_allocation">6.2.2. Incremental SID allocation</h4>
<div class="olist arabic"><ol class="arabic">
<li>
<p>
When hub starts, set: counter = 0
</p>
</li>
<li>