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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="GENERATOR" content="Mozilla/4.77 [en] (Windows NT 5.0; U) [Netscape]">
<title>TAO Real-Time CORBA Features Documentation</title>
<!-- -->
</head>
<body>
<center>
<h3>
Features Documentation</h3></center>
This page is not a tutorial on Real-Time CORBA, but is rather a supplement
to the specification, covering all implementation-specific details. Sample
code exercising RTCORBA features can be found in
<tt>$TAO/tests/RTCORBA/</tt>.
We hope to have tutorial-style examples available in the near future.
<h3>
<a NAME="enabling"></a>Enabling Real-Time CORBA features</h3>
In order to use features from the Real-Time CORBA 1.0 specification in
TAO, a RT-CORBA client application must link with the RTCORBA library;
a RT-CORBA server application must link with the RTCORBA library and the
RTPortableServer libraries. Since some features in RT-CORBA depend on the
messaging specification, all code must be compiled with <tt>TAO_HAS_CORBA_MESSAGING</tt>
set to
<tt>1</tt>. This macros are defined in
<tt>$TAO/tao/orbconf.h</tt>
<p>By default, both Real-Time CORBA and Messaging are enabled in TAO unless
Minimum CORBA support is turned on, <i>i.e.</i>,
<tt>TAO_HAS_MINIMUM_CORBA</tt>
is set to <tt>1</tt>.
<h3>
<a NAME="mappings"></a>Priority Mappings</h3>
TAO provides three Priority Mappings: Direct, Linear, and Continuous. If
no mapping is specified, Direct Priority Mappings will be used. Note that
Continuous was previously referred to as Direct.
<dl>
<dt>
<b>Direct</b></dt>
<dd>
Maps CORBA priorities directly to native priorities.</dd>
<dt>
<b>Linear</b></dt>
<dd>
Maps each individual native priority to a contiguous range of CORBA priorities,
so that the complete CORBA priority range is used up for the mapping. See
<tt>$TAO_ROOT/tao/RTCORBA/Linear_Priority_Mapping.cpp
</tt>for
more details.</dd>
<dt>
<b>Continuous</b></dt>
<dd>
Maps the first <i>n</i> CORBA priorities to the range of native priorities,
where <i>n</i> is the number of native priorities. The lowest native priority
is mapped to CORBA priority 0, next higher native priority is mapped to
CORBA priority 1, and so on. Since in all the operating systems where TAO
is supported the native priority set contains less than 32767 priorities,
part of the CORBA priority range is left unused. Consider NT Direct priority
mapping as an example. NT native priorities -15 -2 -1 0 1 2 15 are mapped
to CORBA priorities 0 1 2 3 4 5 6, respectively, and the rest of the CORBA
priority range is not used.</dd>
</dl>
Priority mappings implement the rules for mapping CORBA priority range
(from 0 to 32767) into the native OS priority range and vice versa. However,
in some operating systems, the the native OS priority range depends on
the scheduling policy being used. That's why when specifying a priority
mapping, scheduling policy must be specified as well. Below, we describe
how to configure TAO to use a particular priority mapping and scheduling
policy. Note, in some operating systems super user privileges are required
for use of some of the scheduling policies.
<p>By default TAO uses Direct priority mapping and
<tt>SCHED_OTHER</tt>
scheduling policy. There are two ways for an application to override these
settings:
<ol>
<li>
<tt>svc.conf</tt> file can be used to select a mapping and a scheduling
policy the ORB will use. (This method does not allow the specification
of user-defined mappings.) Config file should contain the following options:</li>
<br>
<p>
<br>
<br>
<p><tt>static RT_ORB_Loader "-ORBPriorityMapping
<i>mapping_type</i> -ORBSchedPolicy
<i>sched_policy</i>"</tt>
<p>where valid values for <i>mapping_type</i> are <tt>continuous</tt>, <tt>linear</tt> and <tt>direct,</tt>
and<i> </i>valid values for <i>sched_policy</i> are <tt>SCHED_OTHER</tt>,
<tt>SCHED_FIFO</tt>
and <tt>SCHED_RR</tt>.
<li>
<i>TAO::PriorityMappingManager</i> can be used to 1) override the default
priority mapping and scheduling policy with another ORB-defined mapping/scheduling
policy combination, 2) install a user-defined priority mapping, 3) obtain
a reference to the priority mapping object used by the ORB. Code excerpts
below demonstrate how to perform each of these tasks.</li>
<br>
<p>
<br>
<br>
<p>Obtaining Priority Mapping Manager:
<br><tt>object = orb->resolve_initial_references ("PriorityMappingManager");</tt>
<br><tt>TAO::PriorityMappingManager_var mapping_manager =</tt>
<br><tt>TAO::PriorityMappingManager::_narrow (object.in ());</tt>
<p>Overriding priority mapping/policy in effect with another ORB-defined
mapping/policy combination:
<br><tt>#include "tao/RTCORBA/Continuous_Priority_Mapping.h"</tt>
<br><tt>#include "tao/RTCORBA/Linear_Priority_Mapping.h"</tt>
<br><tt>#include "tao/RTCORBA/Direct_Priority_Mapping.h"</tt>
<br><tt>...</tt>
<p><tt>RTCORBA::PriorityMapping *pm =</tt>
<br><tt>new TAO_Continuous_Priority_Mapping (policy);</tt>
<br>or
<br><tt>new TAO_Linear_Priority_Mapping (policy);</tt>
<br>or
<br><tt>new TAO_Direct_Priority_Mapping (policy);</tt>
<br><tt>mapping_manager->mapping (pm);</tt>
<br><tt>...</tt>
<br>where policy is <tt>SCHED_OTHER, SCHED_FIFO</tt> or
<tt>SCHED_RR.</tt>
Priority Mapping Manager takes the ownership of the priority mapping object.
<p>Overriding the default with user-defined priority mapping:
<br><tt>My_Mapping *foo = new My_Mapping;</tt>
<br><tt>mapping_manager->mapping (foo);</tt>
<br>where <i>My_Mapping</i> must inherit from <i>RTCORBA::PriorityMapping</i>
(a typedef for <i>TAO_Priority_Mapping</i> class) located in
<tt>$TAO/tao/Priority_Mapping.h</tt>
<p>Obtaining a pointer to the priority mapping object being used by the
ORB:
<br><tt>RTCORBA::PriorityMapping *pm =</tt>
<br><tt>mapping_manager->mapping ();</tt>
<br>Mapping manager retains the ownership of the priority mapping object.</ol>
<h3>
<a NAME="defaults"></a>ORB Default Policies</h3>
Real-Time CORBA 1.0 does not specify ORB defaults for the policies it defines,
leaving it up to implementations. Below is a summary TAO defaults.
<br>
<table BORDER CELLPADDING=7 WIDTH="100%" >
<tr>
<td ALIGN=CENTER WIDTH="31%"><b>Policy</b></td>
<td ALIGN=CENTER WIDTH="69%"><b>Default</b></td>
</tr>
<tr>
<td WIDTH="31%"><i>ServerProtocolPolicy</i></td>
<td WIDTH="69%">All protocols that are loaded by the ORB by default (e.g.,
IIOP) and any explicitly specified by the user (e.g., SHMIOP), in the order
they were loaded, with their default properties. See <a href="#protocols">Protocol
Policies</a> section for more details.</td>
</tr>
<tr>
<td WIDTH="31%"><i>ClientProtocolPolicy</i></td>
<td WIDTH="69%">None</td>
</tr>
<tr>
<td WIDTH="31%"><i>ThreadpoolPolicy</i></td>
<td WIDTH="69%">None. If no ThreadpoolPolicy policy is specified during
POA creation, the default thread-pool will be used for that POA.</td>
</tr>
<tr>
<td WIDTH="31%"><i>PriorityModelPolicy</i></td>
<td WIDTH="69%">None</td>
</tr>
<tr>
<td WIDTH="31%"><i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="69%">None</td>
</tr>
<tr>
<td WIDTH="31%"><i>PrivateConnectionPolicy</i></td>
<td WIDTH="69%">None</td>
</tr>
<tr>
<td WIDTH="31%">Priority Mapping</td>
<td WIDTH="69%">Direct mapping with <tt>SCHED_OTHER</tt> scheduling policy.
See <a href="#mappings">Priority Mappings</a> section for more details.</td>
</tr>
</table>
<h3>
<a NAME="threadpools"></a>Threadpools</h3>
<ul>
<li>
ThreadPools are now fully supported. Endpoint priorities are no longer
supported.</li>
<li>
By default dynamic RTCorba threads live forever after they are created.
When using the <code>RTORBDynamicThreadIdleTimeout</code> from the
<code>RT_ORB_Loader</code> it
can be specified that the dynamic threads should end after a given
idle time. Timeout must be specified in microseconds, 0 means the threads
will stay alive forever. With <code>RTORBDynamicThreadRunTime</code> you
specify the amount of time after a dynamic thread ends itself.
</ul>
<h3>
<a NAME="valid_configurations"></a>Priority Policies</h3>
The table below lists all possible configurations of policies involving
priorities, and summarizes the semantics of each configuration.
<br>
<table BORDER CELLPADDING=4 WIDTH="100%" >
<tr>
<td ALIGN=CENTER WIDTH="33%"><b>Configuration</b></td>
<td ALIGN=CENTER WIDTH="33%"><b>Valid values</b></td>
<td ALIGN=CENTER WIDTH="34%"><b>Semantics</b></td>
</tr>
<tr>
<td WIDTH="33%">Threadpool with lanes,
<br>no <i>PriorityModelPolicy</i>,
<br>no <i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">Invalid.</td>
<td WIDTH="34%">None.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool with lanes +
<br><tt>SERVER_DECLARED</tt> model,
<br>no <i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%"><i>Server_priority</i> attribute of the <i>PriorityModelPolicy</i>
must be equal to the priority of one of the threadpool lanes. (Same goes
for priorities of all the objects registered with the target POA).</td>
<td WIDTH="34%">All processing is done at the servant's priority.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool with lanes +
<br><tt>CLIENT_PROPAGATED</tt> model,
<br>no <i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">Priority of the invoking client thread must be equal to
the priority of one of the threadpool lanes.</td>
<td WIDTH="34%">All processing is done at the client-propagated priority.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool with lanes +
<br><i>PriorityBandedConnectionPolicy</i>,
<br>no <i>PriorityModelPolicy</i></td>
<td WIDTH="33%">Invalid.</td>
<td WIDTH="34%">None.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool with lanes +
<br><tt>SERVER_DECLARED</tt> model +
<br><i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%"><i>Server_priority</i> attribute of the <i>PriorityModelPolicy</i>
must be equal to the priority of one of the threadpool lanes. (Same goes
for priorities of all the objects registered with the target POA). In addition,
each of the priority bands must cover at least one of the threadpool lane
priorities.</td>
<td WIDTH="34%">All processing is done at the servant's priority.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool with lanes +
<br><tt>CLIENT_PROPAGATED</tt> model +
<br><i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">Priority of the invoking client thread must fall into one
of the priority bands. In addition, each of the priority bands must cover
at least one of the threadpool lane priorities.</td>
<td WIDTH="34%">All processing is done at the threadpool lane priority
which matches the priority band used by the client.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool without lanes,
<br>no <i>PriorityModelPolicy</i>,
<br>no <i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">All valid CORBA priorities.</td>
<td WIDTH="34%">All processing is done at the threadpool's default priority.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool without lanes +
<br><tt>SERVER_DECLARED</tt> model,
<br>no <i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">All valid CORBA priorities.</td>
<td WIDTH="34%">Request I/O and demultiplexing processing is done at the
threadpool's default priority. Application level processing is done at
the servant's priority.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool without lanes + <tt>CLIENT_PROPAGATED</tt> model,
<br>no <i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">All valid CORBA priorities.</td>
<td WIDTH="34%">Request I/O and demultiplexing processing is done at the
threadpool's default priority. Application level processing is done at
the client-propagated priority.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool without lanes +
<br><i>PriorityBandedConnectionPolicy</i>,
<br>no <i>PriorityModelPolicy</i></td>
<td WIDTH="33%">Invalid.</td>
<td WIDTH="34%">None.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool without lanes +
<br><tt>SERVER_DECLARED</tt> model +
<br><i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%"><i>Server_priority</i> attribute of the <i>PriorityModelPolicy</i>
must fall into one of the priority bands. (Same goes for priorities of
all the objects registered with the target POA).</td>
<td WIDTH="34%">Request I/O and demultiplexing processing is done at the
threadpool's default priority. Application level processing is done at
the servant's priority. In this case, <i>PriorityBandedConnectionPolicy</i>
is used to restrict the allowed priority values for the servant.</td>
</tr>
<tr>
<td WIDTH="33%">Threadpool without lanes +
<br><tt>CLIENT_PROPAGATED</tt> model +
<br><i>PriorityBandedConnectionPolicy</i></td>
<td WIDTH="33%">Priority of the invoking client thread must fall into one
of the priority bands.</td>
<td WIDTH="34%">Request I/O and demultiplexing processing is done at the
threadpool's default priority. Application level processing is done at
the client-propagated priority. In this case, <i>PriorityBandedConnectionPolicy</i>
is used to restrict the allowed priority values for the client.</td>
</tr>
</table>
<h3>
<a NAME="explicit_bind"></a>Explicit Binding</h3>
<tt>Object::_validate_connection ()</tt> method establishes a connection,
if one doesn't already exist, and verifies policy overrides for the <i>invoking
thread/ its priority/ target object</i> combination. To establish all connections
ahead of time, application must call <tt>_validate_connection ()</tt> for
<b>all</b><i>thread/
priority/ object</i> combinations that will be used.
<h3>
<a NAME="protocols"></a>Protocol Policies</h3>
In addition to <i>TCPProtocolProperties</i> defined by the Real-Time CORBA
specification, TAO provides configurable properties for each protocol it
supports. Below is a summary of all protocol properties available in TAO.
<ul>
<li>
<b>IIOP</b></li>
<br>Protocol <i>ProfileId</i>: 0
<br>Transport properties interface name: <i>RTCORBA::TCPProtocolProperties</i>
(standard)
<br>Implementation class name: <i>TAO_TCP_Properties</i>
<table BORDER CELLPADDING=4 HEIGHT="150" >
<tr>
<td ALIGN=CENTER HEIGHT="19"><b>Protocol Properties Attribute</b></td>
<td ALIGN=CENTER HEIGHT="19"><b>Default Value</b></td>
</tr>
<tr>
<td HEIGHT="19">long <i>send_buffer_size</i></td>
<td ALIGN=LEFT HEIGHT="19"><tt>ACE_DEFAULT_MAX_SOCKET_BUFSIZ</tt></td>
</tr>
<tr>
<td HEIGHT="19">long <i>recv_buffer_size</i></td>
<td ALIGN=LEFT HEIGHT="19"><tt>ACE_DEFAULT_MAX_SOCKET_BUFSIZ</tt></td>
</tr>
<tr>
<td HEIGHT="19">boolean <i>keep_alive</i> (not yet supported)</td>
<td ALIGN=LEFT HEIGHT="19"><tt>1</tt></td>
</tr>
<tr>
<td HEIGHT="19">boolean <i>dont_route</i> (not yet supported)</td>
<td ALIGN=LEFT HEIGHT="19"><tt>0</tt></td>
</tr>
<tr>
<td HEIGHT="19">boolean <i>no_delay</i></td>
<td ALIGN=LEFT HEIGHT="19"><tt>1</tt></td>
</tr>
</table>
<li>
<b>UIOP</b></li>
<br>Protocol <i>ProfileId</i>: 0x54414f00U
<br>Transport properties interface name: <i>RTCORBA::UnixDomainProtocolProperties</i>
(TAO-specific)
<br>Implementation class name: <i>TAO_Unix_Domain_Properties</i>
<table BORDER CELLPADDING=4 >
<tr>
<td ALIGN=CENTER><b>Protocol Properties Attribute</b></td>
<td ALIGN=CENTER><b>Default Value</b></td>
</tr>
<tr>
<td>long <i>send_buffer_size</i></td>
<td><tt>ACE_DEFAULT_MAX_SOCKET_BUFSIZ</tt></td>
</tr>
<tr>
<td>long <i>recv_buffer_size</i></td>
<td><tt>ACE_DEFAULT_MAX_SOCKET_BUFSIZ</tt></td>
</tr>
</table>
<li>
<b>SHMIOP</b></li>
<br>Protocol <i>ProfileId</i>: 0x54414f02U
<br>Transport properties interface name: <i>RTCORBA::SharedMemoryProtocolProperties</i>
(TAO-specific)
<br>Implementation class name: <i>TAO_SMEM_Properties</i>
<table BORDER CELLPADDING=4 >
<tr>
<td ALIGN=CENTER><b>Protocol Properties Attribute</b></td>
<td ALIGN=CENTER><b>Default Value</b></td>
</tr>
<tr>
<td>long <i>preallocate_buffer_size</i></td>
<td>not yet supported</td>
</tr>
<tr>
<td>string <i>mmap_filename</i></td>
<td>not yet supported</td>
</tr>
<tr>
<td>string <i>mmap_lockname</i></td>
<td>not yet supported</td>
</tr>
</table>
</ul>
Real-Time CORBA 1.0 does not define how protocol properties are created.
<i>TAO_Protocol_Factory</i>
class can be used to create default <i>ProtocolProperties</i> for a particular
protocol given its <i>ProfileId</i>:
<p><tt>class TAO_Protocol_Properties_Factory</tt>
<br><tt>{</tt>
<br><tt>public:</tt>
<p><tt>static RTCORBA::ProtocolProperties*</tt>
<br><tt>create_transport_protocol_property (IOP::ProfileId id);</tt>
<p><tt>static RTCORBA::ProtocolProperties*</tt>
<br><tt>create_orb_protocol_property (IOP::ProfileId id);</tt>
<br><tt>};</tt>
<p>Alternatively, concrete <i>ProtocolProperties</i> implementation classes
can be instantiated directly as needed.
<p>The table below summarizes how protocol policies overrides affect protocol
selection and configuration in TAO.
<br>
<table BORDER CELLPADDING=4 >
<tr>
<td ALIGN=CENTER><b>Policy</b></td>
<td ALIGN=CENTER><b>ORB default</b></td>
<td ALIGN=CENTER><b>Override levels that have impact on protocol selection</b></td>
<td ALIGN=CENTER><b>Override levels that have impact on protocol configuration</b></td>
</tr>
<tr>
<td><i>ServerProtocolPolicy</i></td>
<td>All protocols loaded into the ORB, in the order they were loaded.</td>
<td>ORB
<br>POA</td>
<td>ORB
<br>(If no protocol properties are specified at the ORB level, default
protocol configurations are used.)</td>
</tr>
<tr>
<td><i>ClientProtocolPolicy</i></td>
<td>None</td>
<td>ORB
<br>Current
<br>Object</td>
<td>ORB
<br>(If no protocol properties are specified at the ORB level, default
protocol configurations are used.)</td>
</tr>
</table>
<p>NOTE: <tt>-ORBSndSock</tt> and <tt>-ORBRcvSock</tt> ORB options have
no effect when RTCORBA is enabled.
<p>Protocol policies do not depend on any other Real-Time CORBA features
and can be used alone. In fact, we plan to make protocol policies available
outside RTCORBA, and better integrate them with the Pluggable Protocols
framework in the near future.
<br>
<hr>
<h3>
<a NAME="diffserv"></a>Diffserv Support</h3>
<p>Though the RT-CORBA specification details the real-time ORB, thread
priorities, and application scheduling requirements, it is less
explicit about the communication transport and the underlying
network priorities. Our research involved using Differentiated Services
technology to prioritize the RT-CORBA traffic in the network. This
effort required two essential enhancements to the TAO ORB. First, we
provided an efficient and flexible way of setting the DSCP codepoints
in the data packets, which is done by extending the ORB protocol
properties. DSCP codepoints can dynamically change, based on many
factors like QoS feedback received from external QoS monitoring
resources or even a change in the application policy. Second, we
provide a mechanism to map the RT-CORBA priorities to the Diff-Serv
network priorities. The detials of the implementation follows.
<dl>
<dt>
<b>Modifications to RTCORBA.pidl</b></dt>
<br>
<ul>
<li>
<b>TCP Protocol Properties extension</b></li>
<br>
<dd>
The TCP protocol properties interface was extended to add a flag, enable_network_priority.
When this flag is set to 1 the RTCORBA priority is mapped to network priority
(diffserv codepoint - DSCP) and this priority is set on the GIOP requests
and replies. When the flag is not set no network priorities are set on
the GIOP requests and replies and are hence best effort.</dd>
<p><tt>local interface TCPProtocolProperties : ProtocolProperties</tt>
<br><tt>{</tt>
<br><tt>attribute long send_buffer_size;</tt>
<br><tt>attribute long recv_buffer_size;</tt>
<br><tt>attribute boolean keep_alive;</tt>
<br><tt>attribute boolean dont_route;</tt>
<br><tt>attribute boolean no_delay;</tt>
<br><tt>attribute boolean enable_network_priority;</tt>
<br><tt>};</tt>
<br>
<li>
<b>Network Priority Mapping Interfaces</b></li>
<dd>
<p>Support was added for mapping RTCORBA priority to Network Priority. It
is similar to the RTCORBA to native thread priority mapping.</dd>
<p><tt>typedef long NetworkPriority;</tt>
<br><tt>native NetworkPriorityMapping;</tt></ul><br>
<dt>
<b>Usage</b></dt>
<br>
<ul>
<li>
<b>Client - Setting DSCP on the GIOP Requests</b></li>
<br><br>
<dd>
1. <i>Create TCP protocol properties</i> - The enable_network_priority
flag implies the setting/unsetting of the network priority.</dd>
<p><tt>RTCORBA::TCPProtocolProperties_var tcp_properties =</tt>
<br><tt> rt_orb->create_tcp_protocol_properties (send_buffer_size,</tt>
<br><tt>
recv_buffer_size,</tt>
<br><tt>
1, //keep alive</tt>
<br><tt>
0, //don't route</tt>
<br><tt>
1, //no delay</tt>
<br><tt>
enable_network_priority);</tt>
<p>2. <i>Create TCP Protocol Properties Policy</i>
<p><tt>RTCORBA::ProtocolList protocols;</tt>
<br><tt>protocols.length (1);</tt>
<br><tt>protocols[0].protocol_type = 0; //IIOP</tt>
<br><tt>protocols[0].transport_protocol_properties =</tt>
<br><tt> RTCORBA::ProtocolProperties::_duplicate (tcp_properties.in
());</tt>
<br><tt>protocols[0].orb_protocol_properties =</tt>
<br><tt> RTCORBA::ProtocolProperties::_nil ();</tt>
<p><tt>CORBA::PolicyList policy_list;</tt>
<br><tt>policy_list.length (1);</tt>
<br><tt>policy_list[0] =</tt>
<br><tt> rt_orb->create_client_protocol_policy (protocols);</tt>
<p>3.<i> Set TCP Protocol Properties Policy</i>
<p><b>ORB Level</b> - This implies that the tcp protocol properties set
will apply to every invocation made with this ORB.
<p><tt>CORBA::Object_var object =</tt>
<br><tt>orb->resolve_initial_references ("ORBPolicyManager");</tt>
<br><tt>CORBA::PolicyManager_var policy_manager =</tt>
<br><tt> CORBA::PolicyManager::_narrow (object.in ());</tt>
<br><tt>policy_manager->set_policy_overrides (policy_list,</tt>
<br><tt>
CORBA::SET_OVERRIDE);</tt>
<p><b>THREAD Level</b> - This implies that the tcp protocol properties
set will apply to all the invocations made in the corresponding thread
only. All other invocations will have the TCP protocol properties set at
the ORB level.
<p>orb->orb_core ()->policy_current ().set_policy_overrides (policy_list,
<br>
CORBA::SET_OVERRIDE);
<p><b>OBJECT Level</b> - This implies that the tcp protocol properties
set will apply to the invocations made on the corresponding object only.
<p><tt>CORBA::Object_var object = server->_set_policy_overrides (policy_list,</tt>
<br><tt>
CORBA::SET_OVERRIDE);</tt>
<p><tt>server = Test::_narrow (object.in ()); //server is the CORBA Object</tt>
<p>The above steps can be applied repeatedly to create and set TCP protocol
properties on the client to enable/disable network priority on the GIOP
requests. Since the TCP protocol properties are updated per invocation
the most recently set policy will apply.
<br>
<li>
<b>Server - Setting DSCP on the GIOP Replies</b></li>
<br>
<dd>
1. <i>Create the TCP protocol properties</i> - The enable_network_priority
flag implies the setting/unsetting of the network priority.</dd>
<p><tt>RTCORBA::TCPProtocolProperties_var tcp_properties =</tt>
<br><tt> rt_orb->create_tcp_protocol_properties (send_buffer_size,</tt>
<br><tt>
recv_buffer_size,</tt>
<br><tt>
1, //keep alive</tt>
<br><tt>
0, //don't route</tt>
<br><tt>
1, //no delay</tt>
<br><tt>
enable_network_priority);</tt>
<p>2. <i>Create TCP Protocol Properties Policy</i>
<p><tt>RTCORBA::ProtocolList protocols;</tt>
<br><tt>protocols.length (1);</tt>
<br><tt>protocols[0].protocol_type = 0; //IIOP</tt>
<br><tt>protocols[0].transport_protocol_properties =</tt>
<br><tt> RTCORBA::ProtocolProperties::_duplicate (tcp_properties.in
());</tt>
<br><tt>protocols[0].orb_protocol_properties =</tt>
<br><tt> RTCORBA::ProtocolProperties::_nil ();</tt>
<br>
<p><tt>CORBA::PolicyList policy_list;</tt>
<br><tt>policy_list.length (1);</tt>
<br><tt>policy_list[0] =</tt>
<br><tt> rt_orb->create_server_protocol_policy (protocols);</tt>
<p>3. <i>Create POA with Diffserv enabled</i>
<p><tt>CORBA::PolicyList poa_policy_list;</tt>
<br><tt>poa_policy_list.length (1);</tt>
<br><tt>poa_policy_list [0] =</tt>
<br><tt> rt_orb->create_server_protocol_policy (protocols);</tt>
<p><tt>PortableServer::POA_var poa_with_ds =</tt>
<br><tt>root_poa->create_POA ("POA_WITH_DS",</tt>
<br><tt>
poa_manager.in (),</tt>
<br><tt>
poa_policy_list );</tt>
<p>All the servants that want network priority set on their replies should
register with this POA.
<p>NOTE - The POA policy can be set only once. This implies that all replies
sent from the POA that has the network priority set will have the DSCP
set on them. In order to unset the network priority one has to use a different
POA without the network priority set on it.
<br> </ul>
<dt>
<b>Network Priority Mapping</b></dt>
<br>
<ul>
<li>
<b>NetworkPriorityMapping interface</b></li>
<br>
<dd>
The RTCORBA to network priority mapping framework is similar to the RTCORBA
to native thread priority mapping framework. As mentioned in section 2.1.2
this is implemented by providing the native interface NetworkPriorityMapping.
The native interface is implemented in the RTCORBAC.h as:
<p><tt>typedef TAO_Network_Priority_Mapping
NetworkPriorityMapping;</tt></dd>
<p><tt>Where TAO_Network_Priority_Mapping is defined as:</tt>
<p><tt>class TAO_Network_Priority_Mapping</tt>
<br><tt>{</tt>
<br><tt>public:</tt>
<br><tt> virtual CORBA::Boolean to_network (RTCORBA::Priority
corba_priority,</tt>
<br><tt>
RTCORBA::NetworkPriority &network_priority) = 0;</tt>
<br><tt> virtual CORBA::Boolean to_CORBA (RTCORBA::NetworkPriority
network_priority,</tt>
<br><tt>
RTCORBA::Priority &corba_priority) = 0;</tt>
<br><tt>};</tt>
<p>The methods to_network (…) and to_corba (…) can be implemented differently
for different mapping algorithms that can be defined by the application.
<br>
<li>
<b>Default Network Priority Mappings</b></li>
<br>
<dd>
TAO implements the default Linear Mapping from RTCORBA to Diffserv Codepoint
mapping. Further mappings may be added to TAO. The application can choose
these TAO supported mappings through the Service Configurator (svc.conf)
files with the following entry:</dd>
<p>static RT_ORB_Loader "-ORBSchedPolicy SCHED_FIFO -ORBScopePolicy PROCESS
-ORBPriorityMapping direct <i>-RTORBNetworkPriorityMapping Linear</i>"
<br>
<li>
<b>Network Priority Mapping Manager</b></li>
<br>
<dd>
A NetworkPriorityMappingManager is defined in TAO to manage the Network
Priority Mapping.</dd>
<p><tt>typedef TAO_Network_Priority_Mapping_Manager NetworkPriorityMappingManager;</tt>
<p><tt>Where TAO_Network_Priority_Mapping_Manager is:</tt>
<p><tt>class TAO_RTCORBA_Export TAO_Network_Priority_Mapping_Manager :</tt>
<br><tt>{</tt>
<br><tt>public:</tt>
<br><tt> TAO_Network_Priority_Mapping_Manager (RTCORBA::NetworkPriorityMapping
* mapping);</tt>
<br><tt> void mapping (RTCORBA::NetworkPriorityMapping
* mapping);</tt>
<br><tt> RTCORBA::NetworkPriority_Mapping *mapping (void);</tt><tt></tt>
<p><tt>private:</tt>
<br><tt> TAO_Network_Priority_Mapping *mapping_;</tt>
<br><tt>};</tt>
<p>The application developer can add his custom network priority mappings
as described in section 2.3.3 using the NetworkPriorityMappingManager.
<br>
<li>
<b>Custom Network Priority Mapping</b></li>
<br>
<dd>
In order to implement a custom network priority mapping the application
developer should implement the methods of the TAO_Network_Priority_Mapping
class. E.g:</dd>
<p><tt>class TAO_Custom_Network_Priority_Mapping :</tt>
<br><tt>public TAO_Network_Priority_Mapping</tt>
<br><tt>{</tt>
<br><tt> virtual CORBA::Boolean to_network (RTCORBA::Priority
corba_priority,</tt>
<br><tt>
RTCORBA::NetworkPriority &network_priority);</tt>
<br><tt> virtual CORBA::Boolean to_CORBA (RTCORBA::NetworkPriority
network_priority,</tt>
<br><tt>
RTCORBA::Priority &corba_priority);</tt>
<br><tt>};</tt>
<p>This custom Network Priority Mapping can then be loaded into the Network
Priority Mapping Manager as follows:
<p><tt># Resolve the Network priority Mapping Manager</tt>
<br><tt>CORBA::Object_var object = orb->resolve_initial_references ("NetworkPriorityMappingManager");</tt>
<br><tt>RTCORBA::NetworkPriorityMappingManager_var mapping_manager = RTCORBA::NetworkPriorityMappingManager::_narrow
(object.in ());</tt>
<p><tt># Initialize the custom priority mapping</tt>
<br><tt>TAO_Custom_Network_Priority_Mapping *cnpm = 0;</tt>
<br><tt>ACE_NEW (cnpm,</tt>
<br><tt> TAO_Custom_Network_Priority_Mapping);</tt>
<p><tt>#Load the custom network priority mapping object in the network
priority</tt>
<br><tt>#mapping manager. The user can thus add his own priority mapping.</tt>
<br><tt>mapping_manager->mapping (cnpm);</tt>
<p>This ensures that the Custom Network Priority Mapping will be used to
map the RTCORBA priority to the network priority.
</ul>
<br>
</dl>
</body>
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