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UDP tracker proposal

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2014-05-27 17:54:42 +00:00
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i2p2www/pages/site/docs/applications/bittorrent.html
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@@ -1,7 +1,7 @@
{% extends "global/layout.html" %}
{% block title %}{% trans %}Bittorrent over I2P{% endtrans %}{% endblock %}
{% block lastupdated %}{% trans %}September 2012{% endtrans %}{% endblock %}
{% block accuratefor %}0.9.2{% endblock %}
{% block lastupdated %}{% trans %}May 2014{% endtrans %}{% endblock %}
{% block accuratefor %}0.9.13{% endblock %}
{% block content %}
<p>{% trans -%}
@@ -282,6 +282,47 @@ or a list of strings alone.
{%- endtrans %}</p>
<h2>{% trans %}Datagram (UDP) Trackers{% endtrans %}</h2>
<p>{% trans -%}
UDP tracker support in clients and trackers is not yet available.
Preliminary differences from
<a href="http://www.bittorrent.org/beps/bep_0015.html">BEP 15</a>
are described below, and are subject to change.
Contact the I2P developers if you wish to develop a client or tracker supporting datagram announces.
{%- endtrans %}</p>
<p>{% trans -%}
A UDP tracker listens on two ports.
The "query port" is the advertised port, and is used to receive repliable (signed) datagrams, for the connect request only.
The "response port" is used to receive unsigned (raw) datagrams, and is the source port for all replies.
The response port is arbitrary.
A client sends and receives on a single port only.
It receives only unsigned (raw) datagrams.
Raw datagrams provides increased efficiency for replies since they contain tokens sent in the query, and need not be signed.
{%- endtrans %}</p>
<p>{% trans -%}
In the announce request, the 4-byte IP is replaced by a 32-byte hash, and the port is still present,
although it may be ignored by the tracker.
In the announce response, each 4-byte IP and 2-byte port is replaced by a 32-byte hash (compact peer info), and no port is present.
The client sends the announce request and scrape request to the source port in the announce response packet.
The connect request, connect response, scrape request, scrape response, and error response are the same as in BEP 15.
{%- endtrans %}</p>
<p>{% trans -%}
Source addresses in I2P cannot be spoofed, so it is possible to use a simplified protocol
with 2 packets instead of 4, omitting the connect request and response.
In this case, the announce request would be a repliable datagram sent to the tracker's query port,
and the tracker would not require a response port.
While this is more efficient, it would be more difficult to modify an existing tracker to support this mode.
The URL for the 4-packet-mode tracker would use standard "udp://" prefix.
The URL for a modified 2-packet-mode tracker would require a different prefix if both modes are supported in I2P.
{%- endtrans %}</p>
<h2>{% trans %}Additional Information{% endtrans %}</h2>
<ul>
<li>{% trans zzz=i2pconv('zzz.i2p') -%}