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<a name="Separate-ports"></a>
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Next: <a href="Upward-negotiation.html#Upward-negotiation" accesskey="n" rel="next">Upward negotiation</a>, Up: <a href="How-to-use-TLS-in-application-protocols.html#How-to-use-TLS-in-application-protocols" accesskey="u" rel="up">How to use TLS in application protocols</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Separate-ports-1"></a>
<h4 class="subsection">3.7.1 Separate ports</h4>
<p>Traditionally <acronym>SSL</acronym> was used in application protocols by
assigning a new port number for the secure services. By doing this two
separate ports were assigned, one for the non-secure sessions, and one
for the secure sessions. This method ensures that if a user requests a
secure session then the client will attempt to connect to the secure port
and fail otherwise. The only possible attack with this method is to perform
a denial of service attack. The most famous example of this method is
“HTTP over TLS” or <acronym>HTTPS</acronym> protocol [<em>RFC2818</em>].
</p>
<p>Despite its wide use, this method has several issues. This
approach starts the <acronym>TLS</acronym> Handshake procedure just after the
client connects on the —so called— secure port. That way the
<acronym>TLS</acronym> protocol does not know anything about the client, and
popular methods like the host advertising in HTTP do not
work<a name="DOCF6" href="#FOOT6"><sup>6</sup></a>. There is no way for the client to say “I
connected to YYY server” before the Handshake starts, so the server
cannot possibly know which certificate to use.
</p>
<p>Other than that it requires two separate ports to run a single
service, which is unnecessary complication. Due to the fact that there
is a limitation on the available privileged ports, this approach was
soon deprecated in favor of upward negotiation.
</p>
<div class="footnote">
<hr>
<h4 class="footnotes-heading">Footnotes</h4>
<h3><a name="FOOT6" href="#DOCF6">(6)</a></h3>
<p>See also the Server Name Indication extension on
<a href="Server-name-indication.html#serverind">serverind</a>.</p>
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