2003-05-15 21:40:35 +02:00
|
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
|
|
|
<html>
|
|
|
|
|
<head>
|
|
|
|
|
<title>Shorewall and ECN</title>
|
|
|
|
|
<meta http-equiv="content-type"
|
|
|
|
|
content="text/html; charset=ISO-8859-1">
|
|
|
|
|
<meta name="author" content="Tom Eastep">
|
|
|
|
|
</head>
|
2003-12-03 00:51:46 +01:00
|
|
|
<body>
|
|
|
|
|
<br>
|
|
|
|
|
<h1 style="text-align: center;">ECN<br>
|
|
|
|
|
</h1>
|
|
|
|
|
Explicit Congestion Notification (ECN) is described in RFC 3168 and is
|
|
|
|
|
a proposed internet standard. Unfortunately, not all sites support ECN
|
|
|
|
|
and when
|
|
|
|
|
a TCP connection offering ECN is sent to sites that don't support it,
|
|
|
|
|
the
|
2003-07-16 20:59:33 +02:00
|
|
|
result is often that the connection request is ignored.<br>
|
2003-12-03 00:51:46 +01:00
|
|
|
<br>
|
|
|
|
|
To allow ECN to be used, Shorewall allows you to enable ECN on your
|
|
|
|
|
Linux systems then disable it in your firewall when the destination
|
|
|
|
|
matches a list that you create (the /etc/shorewall/ecn file).<br>
|
|
|
|
|
<br>
|
|
|
|
|
You enable ECN by<br>
|
|
|
|
|
<br>
|
|
|
|
|
<blockquote>
|
2003-05-15 21:40:35 +02:00
|
|
|
<pre><b><font color="#009900">echo 1 > /proc/sys/net/ipv4/tcp_ecn</font></b></pre>
|
2003-12-03 00:51:46 +01:00
|
|
|
</blockquote>
|
|
|
|
|
You must arrange for that command to be executed at system boot. Most
|
|
|
|
|
distributions have a method for doing that -- on RedHat, you make an
|
|
|
|
|
entry in /etc/sysctl.conf.<br>
|
|
|
|
|
<br>
|
|
|
|
|
<blockquote>
|
2003-05-15 21:40:35 +02:00
|
|
|
<pre><b><font color="#009900">net.ipv4.tcp_ecn = 1<br><br></font></b></pre>
|
2003-12-03 00:51:46 +01:00
|
|
|
</blockquote>
|
|
|
|
|
Entries in /etc/shorewall/ecn have two columns as follows:<br>
|
|
|
|
|
<br>
|
|
|
|
|
INTERFACE - The name of an interface on your system<br>
|
|
|
|
|
<br>
|
|
|
|
|
HOST(S) - An address (host or
|
|
|
|
|
subnet) of a system or group of systems accessed through the
|
|
|
|
|
interface in the first column. You may include a comma-separated
|
|
|
|
|
list of such addresses in this column. <br>
|
|
|
|
|
<br>
|
|
|
|
|
Example: Your external interface is eth0 and you want to disable ECN
|
|
|
|
|
for tcp connections to 192.0.2.0/24:<br>
|
|
|
|
|
<br>
|
|
|
|
|
In /etc/shorewall/ecn:<br>
|
|
|
|
|
<br>
|
|
|
|
|
<blockquote>
|
2003-05-15 21:40:35 +02:00
|
|
|
<table cellpadding="2" cellspacing="0" border="1">
|
2003-12-03 00:51:46 +01:00
|
|
|
<tbody>
|
|
|
|
|
<tr>
|
|
|
|
|
<td valign="top"><b>INTERFACE<br>
|
|
|
|
|
</b></td>
|
|
|
|
|
<td valign="top"><b>HOST(S)<br>
|
|
|
|
|
</b></td>
|
|
|
|
|
</tr>
|
|
|
|
|
<tr>
|
|
|
|
|
<td valign="top">eth0<br>
|
|
|
|
|
</td>
|
|
|
|
|
<td valign="top">192.0.2.0/24<br>
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
</tbody>
|
2003-05-15 21:40:35 +02:00
|
|
|
</table>
|
2003-12-03 00:51:46 +01:00
|
|
|
<br>
|
|
|
|
|
</blockquote>
|
|
|
|
|
<font size="2">Last updated 3/28/2003 - <a href="support.htm">Tom
|
|
|
|
|
Eastep</a></font>
|
2003-05-15 21:40:35 +02:00
|
|
|
<p><a href="copyright.htm"><font size="2">Copyright</font> © <font
|
|
|
|
|
size="2">2001, 2002, 2003 Thomas M. Eastep.</font></a><br>
|
2003-12-03 00:51:46 +01:00
|
|
|
</p>
|
|
|
|
|
<br>
|
2003-05-15 21:40:35 +02:00
|
|
|
</body>
|
|
|
|
|
</html>
|
