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+<?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-06CE943B-3D6A-50D1-97C3-CCFE4D4F5864" xml:lang="en"><title>SubConnection
+Client API</title><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>This document gives an introduction to using the <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> API. </p>
+<p>The <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> API creates a channel ("subconnection")
+within a connection (<xref href="GUID-BED8A733-2ED7-31AD-A911-C1F4707C67FD.dita"><apiname>RConnection</apiname></xref>). Sockets can be attached
+to this channel and will then be bound by the properties of that channel,
+such as Quality of Service (values such as minimum bandwith, latency limits
+etc.). Depending on the state of the channel, it may not be possible to bind
+arbitary sockets into it. Attempting to bind sockets from different protocol
+families to a single channel is an error, as each channel can only be used
+by one protocol family. </p>
+<p>Note: The sub-connection can represent an end-to-end channel and/or a channel
+from this device to an intermediate device (e.g an access server such as a
+GGSN using UMTS and PDP contexts.) Properties can be specified simultaneously
+on protocol and link level. In the case of GPRS/UMTS network interfaces, sub-connections
+correspond to Primary and Secondary PDP Contexts. Before using any of these
+services, a connection to a socket server session must have been made and
+the connection must be open. </p>
+<p>An <xref href="GUID-BED8A733-2ED7-31AD-A911-C1F4707C67FD.dita"><apiname>RConnection</apiname></xref> contains one or more sub-connections
+(a default sub-connection, which is created automatically with the <xref href="GUID-BED8A733-2ED7-31AD-A911-C1F4707C67FD.dita"><apiname>RConnection</apiname></xref> plus
+any added <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> s). Each sub-connection has properties.
+To set those properties you apply an <xref href="GUID-27AA9BD2-9754-3BAE-8C2D-59937E1924CF.dita"><apiname>RSubConParameterBundle</apiname></xref> to
+the <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref>. The parameter bundle consists of families
+of parameters. A "family" is a connected set of parameters, such as QoS. At
+present only two families are defined, Quality of Service (<xref href="GUID-022ECBFB-911A-330B-B197-3BDAE6493981.dita"><apiname>KSubConQoSFamily</apiname></xref>)
+and Authorisation (<xref href="GUID-B2567E44-BD9B-39B3-BB97-385124CFD973.dita"><apiname>KSubConAuthorisationFamily</apiname></xref>). </p>
+<p>Quality of Service (QoS) in Symbian platform is implemented by setting
+parameters on the sub-connection. </p>
+<p>The <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> API provides the functionality to
+divide a Connection (provided by the <xref href="GUID-BED8A733-2ED7-31AD-A911-C1F4707C67FD.dita"><apiname>RConnection</apiname></xref> API) into
+channels that have properties such as bandwidth and latency. </p>
+<p>Each family of parameters can consist of the values you would like to have
+(<xref href="GUID-ADF08336-B43B-31CB-9548-E265E1001F27.dita"><apiname>ERequested</apiname></xref>) and the minimum you're willing to accept (<xref href="GUID-754AF65B-376E-3A75-97F0-8ECF4560BCEF.dita"><apiname>EAcceptable</apiname></xref>).
+If you don't specify the <xref href="GUID-754AF65B-376E-3A75-97F0-8ECF4560BCEF.dita"><apiname>EAcceptable</apiname></xref> then the <xref href="GUID-ADF08336-B43B-31CB-9548-E265E1001F27.dita"><apiname>ERequested</apiname></xref> will
+be used as the minimum acceptable. When the parameters have been applied and
+the sub-connection is used then the parameter family will be updated with
+a third set of values, the <xref href="GUID-12DF975A-B43E-336F-817E-FDD099F7060A.dita"><apiname>EGranted</apiname></xref> (which will be somewhere
+between the <xref href="GUID-754AF65B-376E-3A75-97F0-8ECF4560BCEF.dita"><apiname>EAcceptable</apiname></xref> and the <xref href="GUID-ADF08336-B43B-31CB-9548-E265E1001F27.dita"><apiname>ERequested</apiname></xref>)
+or an event will be raised to say that the parameters have been rejected/could
+not be granted. As this may be some time after the initial request, asynchronous
+event notification is used to tell your application what has been negotiated.
+Your application must monitor for the granted/rejected event notification. </p>
+<p>There is an overlap between the <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> API and
+the <xref href="GUID-BED8A733-2ED7-31AD-A911-C1F4707C67FD.dita"><apiname>RConnection</apiname></xref> API as both provide sub-connection management.
+The <xref href="GUID-BED8A733-2ED7-31AD-A911-C1F4707C67FD.dita"><apiname>RConnection</apiname></xref> API provides overall sub-connection management
+for an entire connection whereas the <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> API
+allows the individual setting of properties of a sub-connection as well as
+the ability to associate sockets (<xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita"><apiname>RSocket</apiname></xref>) with sub-connections.
+The sockets are then able to take advantage of the sub-connection's properties
+when they send and receive data. </p>
+<p>The <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita"><apiname>RSocket</apiname></xref> API can be created with a sub-connection
+as well as a connection. A client is able to start a sub-connection via <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> and
+associate individual <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita"><apiname>RSocket</apiname></xref> objects with that sub-connection.
+This ensures that all data flowing over those objects uses the particular
+sub-connection previously started by the application. This is implemented
+using a new <xref href="GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0.dita#GUID-D4F08503-F1EF-3531-9C3C-4AF24A6255F0/GUID-89C92445-FFCA-37F0-88D0-BF9B1B41BA2F"><apiname>RSocket::Open(…)</apiname></xref> method which takes an additional
+argument specifying the sub-connection to use for the object in question.
+The socket will not actually be added to the sub-connection until such time
+as the socket is used. </p>
+<p>As well as opening sub-connections explicitly via <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref>,
+applications may also attach to the default sub-connection (e.g. in GPRS,
+the default could be the Primary PDP context without a TFT), and modify and
+retrieve its properties. </p>
+<p>Parameters that apply to an <xref href="GUID-0AFDA357-EE44-3788-9CAB-162B874134BF.dita"><apiname>RSubConnection</apiname></xref> are grouped
+together into "families" (<xref href="GUID-5181C974-94F7-3C7D-9FFE-F38BD11001EB.dita"><apiname>CSubConParameterFamily</apiname></xref>). Each
+parameter family contains parameter sets that are either "generic" (parameters
+that are independent of the underlying technology) or "extension" (a group
+of parameters specific to a technology). There will always be one generic
+parameter set in a family and there will be zero or more extension parameter
+sets. </p>
+</conbody></concept>
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