--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Symbian3/PDK/Source/GUID-6A78F618-09A9-56A7-8C58-98C353BF0788.dita	Fri Jan 22 18:26:19 2010 +0000
@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-6A78F618-09A9-56A7-8C58-98C353BF0788" xml:lang="en"><title>Domain
+Name Server</title><shortdesc>The Domain Name Server (DNS) identifies the Internet servers based
+on the host names. This topic describes the concept of the DNS. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>Internet communication is based on IP addresses, the DNS maps the host
+names to IP addresses. The DNS supports International Domain Names that contain
+ASCII and non-ASCII characters. </p>
+<section id="GUID-4592BB90-B123-4B0E-86BF-DB7EA3C49639"><title>Domain Name Server Proxy</title> <p>DNS Proxy server is a
+partial implementation of the DNS Server that runs on the standard DNS Server,
+port number 53. When DNS Proxy server is implemented on the Symbian platform,
+it forwards DNS requests or queries to the network DNS server for mapping
+the host names to IP addresses. DNS Proxy server resolves local names on the
+private network using the local DNS database. For standard internet domain
+names it uses external DNS server in the public network. </p> <p>The local
+name resolution is done using the local DNS database and the DNS. The DNS
+queries for standard internet domain name resolution are sent to the external
+DNS on one of the available uplinks. The Dynamic Host Configuration Protocol
+(DHCP) server updates the local database when the DHCP server assigns an IP
+address to the connecting local host on the private network. </p> </section>
+<section id="GUID-BAB306E6-5ABF-40A5-A938-3EC214A55558"><title>International Domain Names</title> <p>International Domain
+Names (IDN) can contain non-ASCII characters, the DNS uses a Punycode conversion
+library to resolve these domain names. When the Domain Name Daemon receives
+a domain name that contains non-ASCII characters it converts the domain name
+to Punycode. For more information about how the domain name is converted to
+Punycode see RFC 3492. By default, the support for IDN resolution is turned
+off. The library only converts UCS2.0 encoded domain names. </p> </section>
+<section id="GUID-B3928F70-373C-4971-A4D2-D7DBA9CA7477"><title>Top Level Domain (TLD) Whitelists and Backlists</title> <p>The
+support of International Domain Names threatens system security with homograph
+attacks, also known as phishing. The Symbian platform whitelist/blacklist
+URI service supports a whitelist/blacklist service for TLDs and a list of
+allowed characters for each TLD. This list is initialised when the system
+starts and can be edited using a sis package. </p> </section>
+</conbody><related-links>
+<link href="GUID-7510C121-A23F-50E0-8130-16AF552BC497.dita"><linktext>Dynamic Host
+Configuration Protocol</linktext></link>
+</related-links></concept>
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