Changeset 11107 for dotorg/trunk/html/beps/bep_0022.html

Timestamp:

05/27/2008 09:03:51 PM (6 months ago)

Author:

dave

Message:

rebuild html files.

Files:

• dotorg/trunk/html/beps/bep_0022.html (modified) (19 diffs)

dotorg/trunk/html/beps/bep_0022.html

@@ -39 +39 @@
 <tr class="field"><th class="field-name">Title:</th><td class="field-body">BitTorrent Cache Discovery Protocol</td>
 </tr>
-<tr class="field"><th class="field-name">Version:</th><td class="field-body">11087</td>
-</tr>
-<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://bittorrent.org/trac/browser/dotorg/trunk/html/beps/bep_0022.rst">2008-05-19 16:16:31 -0700 (Mon, 19 May 2008)</a></td>
+<tr class="field"><th class="field-name">Version:</th><td class="field-body">11101</td>
+</tr>
+<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://bittorrent.org/trac/browser/dotorg/trunk/html/beps/bep_0022.rst">2008-05-27 19:02:55 -0700 (Tue, 27 May 2008)</a></td>
 </tr>
 <tr class="field"><th class="field-name">Author:</th><td class="field-body">David Harrison &lt;dave&#32;&#97;t&#32;bittorrent.com&gt;, Stanislav Shalunov &lt;shalunov&#32;&#97;t&#32;bittorrent.com&gt;, Greg Hazel &lt;greg&#32;&#97;t&#32;bittorrent.com&gt;</td>
@@ -61 +61 @@
 <p class="topic-title first">Contents</p>
 <ul class="simple">
-<li><a class="reference internal" href="#motivation" id="id9">Motivation</a></li>
-<li><a class="reference internal" href="#the-discovery-mechanism" id="id10">The Discovery Mechanism</a></li>
-<li><a class="reference internal" href="#iterative-queries" id="id11">Iterative Queries</a></li>
-<li><a class="reference internal" href="#network-address-translators" id="id12">Network Address Translators</a></li>
-<li><a class="reference internal" href="#example" id="id13">Example</a></li>
-<li><a class="reference internal" href="#references" id="id14">References</a></li>
-<li><a class="reference internal" href="#copyright" id="id15">Copyright</a></li>
+<li><a class="reference internal" href="#motivation" id="id10">Motivation</a></li>
+<li><a class="reference internal" href="#the-discovery-mechanism" id="id11">The Discovery Mechanism</a></li>
+<li><a class="reference internal" href="#iterative-queries" id="id12">Iterative Queries</a></li>
+<li><a class="reference internal" href="#network-address-translators" id="id13">Network Address Translators</a></li>
+<li><a class="reference internal" href="#example" id="id14">Example</a></li>
+<li><a class="reference internal" href="#references" id="id15">References</a></li>
+<li><a class="reference internal" href="#copyright" id="id16">Copyright</a></li>
 </ul>
 </div>
@@ -86 +86 @@
 those that share the access network.  When subsequent peers transfer
 from their ISP's cache, the ISP experiences less transit traffic.</p>
+<p>The key words &quot;MUST&quot;, &quot;MUST NOT&quot;, &quot;REQUIRED&quot;, &quot;SHALL&quot;, &quot;SHALL
+NOT&quot;, &quot;SHOULD&quot;, &quot;SHOULD NOT&quot;, &quot;RECOMMENDED&quot;,  &quot;MAY&quot;, and
+&quot;OPTIONAL&quot; in this document are to be interpreted as described in
+IETF <a class="reference external" href="http://www.faqs.org/rfcs/rfc2119.html">RFC 2119</a> <a class="footnote-reference" href="#rfc-2119" id="id1">[5]</a>.</p>
 </div>
 <div class="section" id="the-discovery-mechanism">
@@ -113 +117 @@
 tracker is called a <em>cache tracker</em>, but the protocol to talk to this
 tracker is no different from the standard BitTorrent tracker protocol
-described in <a class="footnote-reference" href="#bep-3" id="id1">[1]</a>.</p>
+described in <a class="footnote-reference" href="#bep-3" id="id2">[1]</a>.</p>
 <p>When the BitTorrent client joins a swarm it announces to one or more
 of the trackers referenced in the .torrent file and announces to the
@@ -119 +123 @@
 other peers that announced the same file to the cache tracker.</p>
 <p>A cache is a BitTorrent peer.  A client MAY treat it preferentially.</p>
-<p>Reverse DNS lookups are described in <a class="reference external" href="http://www.faqs.org/rfcs/rfc1034.html">RFC 1034</a> <a class="footnote-reference" href="#rfc-1034" id="id2">[4]</a>.
-The SRV resource record type is described in <a class="reference external" href="http://www.faqs.org/rfcs/rfc2782.html">RFC 2782</a> <a class="footnote-reference" href="#rfc-2782" id="id3">[5]</a>.</p>
+<p>Reverse DNS lookups are described in <a class="reference external" href="http://www.faqs.org/rfcs/rfc1034.html">RFC 1034</a> <a class="footnote-reference" href="#rfc-1034" id="id3">[4]</a>.
+The SRV resource record type is described in <a class="reference external" href="http://www.faqs.org/rfcs/rfc2782.html">RFC 2782</a> <a class="footnote-reference" href="#rfc-2782" id="id4">[6]</a>.</p>
 </div>
 <div class="section" id="iterative-queries">
@@ -132 +136 @@
 </pre>
 <p>However, if wildcards are implemented according to the algorithm in
-section 4.3.2 in <a class="footnote-reference" href="#rfc-1034" id="id4">[4]</a> then all subdomains of pacbell.net that
+section 4.3.2 in <a class="footnote-reference" href="#rfc-1034" id="id5">[4]</a> then all subdomains of pacbell.net that
 do not have an exact label match will match the wildcard.  Thus,</p>
 <pre class="literal-block">
@@ -150 +154 @@
 _bittorrent-tracker._tcp.*.pacbell.net
 </pre>
-<p>However, section 4.3.3 in <a class="footnote-reference" href="#rfc-1034" id="id5">[4]</a> specifies that wildcards only
+<p>However, section 4.3.3 in <a class="footnote-reference" href="#rfc-1034" id="id6">[4]</a> specifies that wildcards only
 appear as the first label in a domain name.  This restriction was
-lifted in <a class="footnote-reference" href="#rfc-4592" id="id6">[6]</a>, but not with semantics applicable to our use
+lifted in <a class="footnote-reference" href="#rfc-4592" id="id7">[7]</a>, but not with semantics applicable to our use
 case.  An asterisk not at the beginning of a domain name is not
 treated like a wildcard.  Only a lookup for the exact domain name</p>
@@ -159 +163 @@
 </pre>
 <p>matches.</p>
-<p>We propose an alternative that avoids wildcards and has the advantage
-that it allows suborganizations to override the SRV records provided
-by parent organizations: the peer starts by querying using its
-fully-qualified domain name returned from the reverse DNS lookup, and
-if this fails then it queries again after removing the most specific
-(leftmost) label in the domain name.  For example, if no SRV records
-are returned when querying for</p>
+<p>We propose an alternative that avoids wildcards and allows
+suborganizations to override SRV records provided by parent
+organizations: the peer starts by querying using its fully-qualified
+domain name returned from the reverse DNS lookup, and if this fails
+then it queries again after removing the most specific (leftmost)
+label in the domain name.  For example, if no SRV records are returned
+when querying for</p>
 <pre class="literal-block">
 _bittorrent-tracker._tcp.adsl-69-107-0-14.dsl.pltn13.pacbell.net
@@ -177 +181 @@
 _bittorrent-tracker.pltn13.pacbell.net
 </pre>
-<p>The search removes one domain at a time terminating when one or more
+<p>The search removes one label at a time terminating when one or more
 resource records are found or before querying the root domain or
 top-level domains that are not ccTLDs, e.g., .com, .org, .net. We
-avoid querying the root or global top-level domains given the low
-likelihood that caches would be defined globally, and thus clients
-would unnecessarily burden the root domain name servers with queries
+avoid querying the root or top-level domains given the low likelihood
+that caches would be defined globally, and thus clients would
+unnecessarily burden the root domain name servers with queries
 generating negative results. We considered stopping before querying
 country-level domains, but a country providing public infrastructure
@@ -197 +201 @@
 address.  This globally-routable address is the host's <em>external IP
 address</em>.</p>
-<p>When finding a cache, the BitTorrent client must use its host's
-external IP address.  A BitTorrent client can obtain its host's
-external IP either from the <em>external ip</em> key returned from a tracker
-implementing BEP 24 <a class="footnote-reference" href="#bep-24" id="id7">[3]</a> or from peers using the <em>yourip</em>
-extension defined for the <em>Extension Protocol</em> proposed in <a class="footnote-reference" href="#bep-10" id="id8">[2]</a>.</p>
+<p>The BitTorrent client must use its host's external IP address.  A
+BitTorrent client MAY obtain its host's external IP either from the
+<em>external ip</em> key returned from a tracker implementing BEP 24
+<a class="footnote-reference" href="#bep-24" id="id8">[3]</a> or from peers implementing the <em>yourip</em> extension defined
+for the <em>Extension Protocol</em> proposed in <a class="footnote-reference" href="#bep-10" id="id9">[2]</a>.</p>
 </div>
 <div class="section" id="example">
 <h1>Example</h1>
-<p>In our example, we used AT&amp;T's PacBell network.  AT&amp;T could implement
+<p>In our example, we use AT&amp;T's PacBell network.  AT&amp;T could implement
 cache discovery by adding the following lines to the zone file for
 pacbell.net,</p>
@@ -214 +218 @@
 <p>Now when a client performs cache discovery, it performs three DNS
 queries removing labels before reaching the domain name pacbell.net,
-at which point the SRV record would be returned and the client would
-then query tracker.pacbell.net to obtain caches.</p>
+at which point the SRV record is returned and the client queries
+tracker.pacbell.net to obtain the domain names of caches.</p>
 <p>In Python, the cache tracker's port and domain can be obtained using
 PyDNS using the following code:</p>
@@ -226 +230 @@
 names = name.split('.')
 while names and names[0] not in tlds:
-   name = &quot;_bittorrent._tcp.&quot; + &quot;.&quot;.join(names)
+   name = &quot;_bittorrent-tracker._tcp.&quot; + &quot;.&quot;.join(names)
    req = DNS.Request( name=name, qtype=&quot;SRV&quot;, protocol=&quot;udp&quot;)
    response = req.req()
@@ -243 +247 @@
 ;; flags: qr aa rd ra; Ques: 1, Ans: 1, Auth: 2, Addit: 3
 ;; QUESTIONS:
-;;      _bittorrent._tcp.pacbell.net, type = SRV, class = IN
+;;      _bittorrent-tracker._tcp.pacbell.net, type = SRV, class = IN
 
 ;; ANSWERS:
-_bittorrent._tcp.pacbell.net    600    SRV     (5, 0, 6969, 'cache.pacbell.net')
+_bittorrent-tracker._tcp.pacbell.net    600    SRV     (5, 0, 6969, 'cache.pacbell.net')
 
 ;; AUTHORITY RECORDS:
@@ -272 +276 @@
 <colgroup><col class="label" /><col /></colgroup>
 <tbody valign="top">
-<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>BEP_0003. The BitTorrent Protocol Specification, Cohen
-(<a class="reference external" href="http://www.bittorrent.org/beps/bep_0003.html">http://www.bittorrent.org/beps/bep_0003.html</a>)</td></tr>
+<tr><td class="label"><a class="fn-backref" href="#id2">[1]</a></td><td>BEP_0003. The BitTorrent Protocol Specification, Cohen.
+<a class="reference external" href="http://www.bittorrent.org/beps/bep_0003.html">http://www.bittorrent.org/beps/bep_0003.html</a></td></tr>
 </tbody>
 </table>
@@ -279 +283 @@
 <colgroup><col class="label" /><col /></colgroup>
 <tbody valign="top">
-<tr><td class="label"><a class="fn-backref" href="#id8">[2]</a></td><td>BEP_0010.  Extension Protocol. Norberg, Strigeus, Hazel
-(<a class="reference external" href="http://www.bittorrent.org/beps/bep_0010.html">http://www.bittorrent.org/beps/bep_0010.html</a>)</td></tr>
+<tr><td class="label"><a class="fn-backref" href="#id9">[2]</a></td><td>BEP_0010.  Extension Protocol. Norberg, Strigeus, Hazel.
+<a class="reference external" href="http://www.bittorrent.org/beps/bep_0010.html">http://www.bittorrent.org/beps/bep_0010.html</a></td></tr>
 </tbody>
 </table>
@@ -286 +290 @@
 <colgroup><col class="label" /><col /></colgroup>
 <tbody valign="top">
-<tr><td class="label"><a class="fn-backref" href="#id7">[3]</a></td><td>BEP_0024.  Tracker Returns External IP.  Harrison
-(<a class="reference external" href="http://www.bittorrent.org/beps/bep_0024.html">http://www.bittorrent.org/beps/bep_0024.html</a>)</td></tr>
+<tr><td class="label"><a class="fn-backref" href="#id8">[3]</a></td><td>BEP_0024.  Tracker Returns External IP.  Harrison.
+<a class="reference external" href="http://www.bittorrent.org/beps/bep_0024.html">http://www.bittorrent.org/beps/bep_0024.html</a></td></tr>
 </tbody>
 </table>
@@ -293 +297 @@
 <colgroup><col class="label" /><col /></colgroup>
 <tbody valign="top">
-<tr><td class="label">[4]</td><td><em>(<a class="fn-backref" href="#id2">1</a>, <a class="fn-backref" href="#id4">2</a>, <a class="fn-backref" href="#id5">3</a>)</em> <a class="reference external" href="http://www.faqs.org/rfcs/rfc1034.html">RFC-1034</a>.  DOMAIN NAMES - CONCEPTS AND FACILITIES. Mockapetris,
-November 1987. (<a class="reference external" href="http://tools.ietf.org/html/rfc1034">http://tools.ietf.org/html/rfc1034</a>)</td></tr>
+<tr><td class="label">[4]</td><td><em>(<a class="fn-backref" href="#id3">1</a>, <a class="fn-backref" href="#id5">2</a>, <a class="fn-backref" href="#id6">3</a>)</em> <a class="reference external" href="http://www.faqs.org/rfcs/rfc1034.html">RFC-1034</a>.  DOMAIN NAMES - CONCEPTS AND FACILITIES. Mockapetris,
+November 1987. <a class="reference external" href="http://tools.ietf.org/html/rfc1034">http://tools.ietf.org/html/rfc1034</a></td></tr>
+</tbody>
+</table>
+<table class="docutils footnote" frame="void" id="rfc-2119" rules="none">
+<colgroup><col class="label" /><col /></colgroup>
+<tbody valign="top">
+<tr><td class="label"><a class="fn-backref" href="#id1">[5]</a></td><td><a class="reference external" href="http://www.faqs.org/rfcs/rfc2119.html">RFC-2119</a>. <a class="reference external" href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a></td></tr>
 </tbody>
 </table>
@@ -300 +310 @@
 <colgroup><col class="label" /><col /></colgroup>
 <tbody valign="top">
-<tr><td class="label"><a class="fn-backref" href="#id3">[5]</a></td><td><a class="reference external" href="http://www.faqs.org/rfcs/rfc2782.html">RFC-2782</a>.  A DNS RR for specifying the location of services (DNS
+<tr><td class="label"><a class="fn-backref" href="#id4">[6]</a></td><td><a class="reference external" href="http://www.faqs.org/rfcs/rfc2782.html">RFC-2782</a>.  A DNS RR for specifying the location of services (DNS
 SRV). Gulbrandsen, Vixie, Esibov. February 2000.
-(<a class="reference external" href="http://tools.ietf.org/html/rfc2782">http://tools.ietf.org/html/rfc2782</a>)</td></tr>
+<a class="reference external" href="http://tools.ietf.org/html/rfc2782">http://tools.ietf.org/html/rfc2782</a></td></tr>
 </tbody>
 </table>
@@ -308 +318 @@
 <colgroup><col class="label" /><col /></colgroup>
 <tbody valign="top">
-<tr><td class="label"><a class="fn-backref" href="#id6">[6]</a></td><td><a class="reference external" href="http://www.faqs.org/rfcs/rfc4592.html">RFC-4592</a>. The Role of Wildcards in the Domain Name System. Lewis
-(<a class="reference external" href="http://www.faqs.org/rfcs/rfc4592.html">http://www.faqs.org/rfcs/rfc4592.html</a>)</td></tr>
+<tr><td class="label"><a class="fn-backref" href="#id7">[7]</a></td><td><a class="reference external" href="http://www.faqs.org/rfcs/rfc4592.html">RFC-4592</a>. The Role of Wildcards in the Domain Name
+System. Lewis.  <a class="reference external" href="http://www.faqs.org/rfcs/rfc4592.html">http://www.faqs.org/rfcs/rfc4592.html</a></td></tr>
 </tbody>
 </table>