ARC Middleware
==============

The Advanced Resource Connector (ARC) middleware, introduced by
NorduGrid (www.nordugrid.org), is an open source software solution
enabling production quality computational and data grids.

Since the first release (May 2002) the middleware has been deployed and
been used in production environments. Emphasis is put on scalability,
stability, reliability and performance of the middleware. A growing
number of grid projects, like Swegrid, NDGF and Swiss Bio Grid has
chosen ARC as their middleware.

This release (February 2008) is a first release of a new generation of ARC 
and will be referenced as ARC1. It is based on a service container - the
Hosting Environment Daemon (HED) - and different grid capabilities are
implemented as Web Services residing in HED. Currently, an OGSA BES
compliant execution service - ARC Resource-coupled EXecution service
(A-REX) - and an echo service (for testing purposes) are included, but
the set of services is rapidly growing.



Dependencies
============

The core part of middleware is written in C/C++.
Building the software from source or installing a precompiled binary 
requires different external packages, furthermore the client and server
packages have different dependencies too. Below a list of the explicit 
requirements is shown:

  Mandatory (on client as well as server side):
    o GNU make, autotools (autoconf>=2.56) (automake>=1.8) (build)
    o C++ compiler and library (build)
    o libtool (build)
    o pkg-config (build)
    o gthread-2.0 version 2.4.7 or later (build, run)
    o glibmm-2.4 version 2.4.7 or later (build, run)
    o libxml-2.0 version 2.4.0 or later (build, run)
    o openssl version 0.9.7a or later (build, run)
    o e2fsprogs (build, run)
    o doxygen (build)
    o GNU gettext (build, run)

  Optional (mainly applicable on server side):
    o swig version 1.3.28 or later (build)
    o java sdk 1.4 or later for Java bindings (build, run)
    o python 2.4 or higher for Python bindings (build, run)
    o Grid Packaging Tools (GPT) (http://www.gridpackagingtools.org/) (build)
    o Globus Toolkit 4 (http://www.globus.org/) which contains (build, run)
      - Globus RLS client
      - Globus FTP client
      - Globus RSL
    o LHC File Catalog (LFC) (https://savannah.cern.ch/projects/jra1mdw/) (build, run)
    o CppUnit for unit testing (build)
    o Berkeley DB C++ interface (build, run)

Please note that depending on operating system distribution in order to 
build ARC1 you may need to install development versions of mentioned 
packages.



Getting the software
====================

The middleware is free to deploy anywhere by anybody. Pre-built binary
releases for a dozen of Linux platforms can be downloaded from the
NorduGrid software repository at download.nordugrid.org.

The software is released under the GNU General Public License (GPL)
(see the COPYING file).

The NorduGrid repository hosts the source code, and provides most of
the required external software which are not part of a standard Linux
distribution.

You can get the latest source code for ARC1 from the Subversion 
repository. See http://svn.nordugrid.org for more details.

There are also nightly code snapshots available at 
http://download.nordugrid.org/software/nordugrid-arc1/nightly/ .
Choose latest date available and download snapshot tarball -
for example nordugrid-arc1-200802201038-snapshot.tar.gz.



Building & Installation
=======================

Building from source is currently the recommended way to install ARC1. 
If you downloaded the tarball, unpack it and cd into the created
directory.

  tar -zxvf nordugrid-arc1-200802201038-snapshot.tar.gz
  cd nordugrid-arc1-200802201038

If you obtained the code from the Subversion repository, use the
'trunk' directory.

  cd trunk

Now configure the obtained code with

  ./autogen.sh
  ./configure --prefix=PLACE_TO_INSTALL_ARC1

Choose installation prefix wisely and according to the requirements of
your OS and personal preferences. ARC1 should function properly from
any location. By default installation goes into /usr/local if you omit
the '--prefix' option. For some modules of ARC1 to work properly you
may need to set up the environment variable after installation:

  export ARC_LOCATION=PLACE_TO_INSTALL_ARC

On some systems 'autogen.sh' may produce few warnings. Ignore them as 
long as 'configure' passes without errors. But in case of problems 
during configure or compilation, collect them and present while 
reporting problems.

If the previous commands finish without errors, compile and install ARC1

  make
  make install

On some systems You may need to use gmake instead of make.

Depending on chosen installation location you may need to run the last
command from root account. That should install the following components:

sbin/arched - server executable
bin/ - user tools and command line clients
lib/ - common libraries used by clients, server and plugins
lib/arc/ - plugins implementing Message Chain, Service and Security components
include/arc/ - C++ headers for application development
libexec/ - additional modules used by ARC1 services - currently only A-REX
share/doc/arc - configuration examples/templates and documentation
share/locale - internationalization files - curently very limited support
share/man - manual pages for various utilities



X509 Certificates
=================

Most of ARC1 planned and existing services use HTTPS as transport protocol
so they require proper setup of X509 security infrastructure. Minimal 
requirements are:
* Host certificate aka public key in PEM format
* Corresponding private key
* Certificate of the Certification Authority (CA) which was used to sign the host certificate
* Certificates of CAs of clients which are going to send requests to services. Unless
of course clients use the same CA as the server.

More information about X509 certificates and their usage in Grid environement 
can be found on http://www.nordugrid.org/documents/certificate_howto.html
and http://www.nordugrid.org/documents/ng-server-install.html#security

For testing purposes you can use the pre-generated certificates and
keys available at:

 http://svn.nordugrid.org/trac/nordugrid/browser/arc1/trunk/doc/sec/TestCA

Alternatively You may choose to use KnowARC Instant CA service available at 
https://vls.grid.upjs.sk/CA/instantCA . It is especially usefull if You 
want to test installation consisting on multiple hosts.

Please remember that it is not safe to use these keys in publicly accessible
insallations of ARC1. Make sure that even the CA certificate is removed
before making your services available to the outside world.

You can put host certificates and private keys anywhere. Common locations for
servers running from root account are /etc/grid-security/hostcert.pem and
/etc/grid-security/hostkey.pem respectively. The content of private key 
must not be encrypted and protected by password. Service has no way to
ask person about password. So make sure it is properly protected by means
of file system.

It is possible to configure ARC1 server to accept either a single CA certificate
or multiple CA certificates located in the specified directory. The latter
option is recommended. The common location is /etc/grid-security/certificates/ .
In that case names of certificate files have to follow hash values of
the certificates. These are obtainable by running the command

  openssl x509 -hash -noout -in path_to_certificate

The corresponding file name for the certificate should be <hash_value>.0 . 
The value for the pre-generated CA certificate is 4457e417. 

1. Configuration for mutual authentication
Please make sure the chosen location of certificates is correctly
configured in the service configuration file. The configuration for the
certificate for TLS MCC should look like this:  

      <KeyPath>/etc/grid-security/hostkey.pem</KeyPath>
      <CertificatePath>/etc/grid-security/hostcert.pem</CertificatePath>
      <CACertificatesDir>/etc/grid-security/certificates</CACertificatesDir>

or

      <CACertificatePath>/etc/grid-security/ca.pem</CACertificatePath>

The key file has to be without passphrase for the server side. You can also 
configure proxy certificate instead of normal certificate (See part:
Proxy certificate Generation & Usage).

The same requirements are valid for the client tools of ARC1. You may use
the pregenerated user certificate and key located at the same
place. Locations of the credentials are provided to the client tools
from the command line.

2.Configuration for no client-authentication
You can also configure only server-authentication instead of mutual 
authentication. In this case, the server will not send a client certificate 
request to the client, so the client will not send a certificate to the 
server, which means only the server's certificate is checked.

For the server side, the configuration for the certificate for TLS MCC 
should look like this:
      <KeyPath>/etc/grid-security/hostkey.pem</KeyPath>
      <CertificatePath>/etc/grid-security/hostcert.pem</CertificatePath>
      <ClientAuthn>false</ClientAuthn>
Note: here either <CACertificatePath/> or <<CACertificatesDir>/> are not needed,
because the client's certificate will not checked by server; But <ClientAuthn/>
is required here, which explicitly specify that client's certificate will not 
be checke, the default value of <ClientAuthn/> is "true" and it does not need 
to be explicitly specified.

For the client side, the configuration for the certificate for TLS MCC 
should look like this:
      <CACertificatesDir>/etc/grid-security/certificates</CACertificatesDir>
or
      <CACertificatePath>/etc/grid-security/ca.pem</CACertificatePath>
Note: here only the ca information needs to be specified.




The set of pre-generated keys and certificates also includes a user
certificate in PKCS12 format which you can import into your browser
for accessing ARC1 services capable of producing HTML output.

ARC1 comes with utility arcproxy which generates proxy credentials
from certificate/private key pair. It provides only basic functionality 
and is meant for testing purposes only. 

IMPORTANT: If during configuration stage You see a message "OpenSSL 
contains no support for proxy credentials" that means You won't be
able to use proxy credentials generated by utilities like grid-proxy-init,
voms-proxy-init or arcproxy. Because of that all user private keys has 
to be kept unencrypted. 



Proxy certificate Generation & Usage
====================================
As metioned above, ARC1 comes with utility proxy generation utility
--arcproxy. 
arcproxy appears in ARC_LOCATION/bin. The usage of arcproxy is like:
ARC_LOCATION/bin/arcproxy -P proxy.pem -C cert.pem -K key.pem 
-c validityStart=2008-05-29T10:20:30Z
-c validityEnd=2008-06-29T10:20:30Z
-c proxyPolicyFile=delegation_policy.xml
By using argument "-c", some constraints can be specified for proxy 
certificate. 
Currently, the life time can be specified by using 
"-c validityStart=..." and "-c validityEnd=...", or "-c validityStart=..."
and "-c validityPeriod=..."; 
and the proxy policy can be specified by using "-c proxyPolicyFile=..." 
or "-c proxyPolicy=...".
Note: If the "validityStart" has not been set, the current time will 
be used as start time for proxy. 
If both "validityEnd" and "validityPeriod" have not been set, the default
validity period will be set to 12 hours.
If the "validityStart" is set, it should not be before current time.
The time unit for "validityPeriod" is second, e.g. "-c validityPeriod=86400"

If proxy certificate is used, in the configuration file for service
side or client side, the configuration for the certificate for TLS MCC 
should look like this:
      <KeyPath>./proxy.pem</KeyPath>
      <CertificatePath>./proxy.pem</CertificatePath>
      <CACertificatePath>./ca.pem</CACertificatePath>
Because normally a proxy certificate file includes the proxy certificate
and private key corresponding to the proxy certificate, <KeyPath/> and 
<CertificatePath/> are configured the same.

Alternatively, you can directly configure <ProxyPath/> instead of <KeyPath/>
and <CertificatePath/>:
      <ProxyPath>./proxy.pem</ProxyPath>
      <CACertificatePath>./ca.pem</CACertificatePath>


Proxy policy can be spefified as constraint. Proxy policy is for constraining 
identity delegation. Currently, the supported policy is Arc specific policy.
Proxy policy is inserted into proxy certificate's "proxy cert info"
extenstion in RFC3820's policy language "NID_id_ppl_anyLanguage".



ARC Server Setup & Configuration
================================

The configuration of the ARC server is specified in an XML file, the
location of which is specified as a command line argument with the -c
option of 'arched' daemon. Examples of configuration files with comments
describing various elements are available in directory share/doc/arc of
the ARC1 installation. 



The Echo Service
================

The echo service is "atomic" and has no additional dependencies other
than what is provided by the Hosting Environment Daemon (HED). An example
of an echo service configuration can be found in share/doc/arc/echo.xml.



The Echo Client
===============

The configuration of the ARC echo client is specified in an XML
file. The location of the configuration file is specified by the
environment variable ARC_ECHO_CONFIG. If there is no such environment
variable, the configuration file is assumed to be echo_client.xml in
the current working directory. An example configuration file can be
found in share/doc/arc/echo_client.xml

To use the echo client, type

  $ARC_LOCATION/bin/arcecho <message>

where <message> is the message which the echo service will return.



The A-REX Service
=================

ARC1 comes with OGSA BES compliant Grid job management service called A-REX.
To deploy A-REX use example configuration files available in share/doc/arc :
 * arex.xml - configuration for arched server. Read comments inside this file
and edit it to fit your installation. This file defines WS interface of A-REX.
 * arc-arex.conf - legacy configuration for Grid Manager part of A-REX. This
file defines how jobs are managed by A-REX locally. Read and edit it. For more
detailed information please read Grid Manager documentation available in SVN
repository
http://svn.nordugrid.org/trac/nordugrid/browser/arc1/trunk/doc/a-rex/arex_tech_doc.pdf?format=raw

Grid Manager runs as part of A-REX service. There is no need to run any additional
executable. But you still need to setup its infrastructure as long as you are 
going to have anything more sophisticated than described in the example configuration.
For more information read the previously mentioned document.

Currently, a proper functioning A-REX requires environment variable ARC_LOCATION
to be set to the installation prefix of ARC1.

A-REX uses HTTPS as transport protocol (although You can reconfigure it to use 
plain HTTP) so it requires proper setup of X509 security infrastructure. See
above for instructions.

Copy example configuration files to some location and edit them. Make sure all paths
to X509 certificates and Grid Manager configuration are set correctly. Start server 
with command

  $ARC_LOCATION/sbin/arched -c path_to_edited_arex.xml

Look into log file specified in arex.xml for possible errors. You can safely ignore 
messages like "Not a '...' type plugin" and "Unknown element ... - ignoring".

If You compiled ARC1 with Globus support and You see complaints about "libglobus..." 
and that it cannot open a shared object file, try to add "/opt/globus/lib" to your
LD_LIBRARY_PATH:

  export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/globus/lib



Testing and Using A-REX (clients)
================================

Now You may use the command line utility 'arcinfo' to obtain a service description.
You can do something like

 ./arcinfo -c ARC1:https://localhost:60000/arex -l

This should produce a description list of the resources A-REX represents. Below
you can see an example of proper output.

---
Cluster: localhost
 Health State: ok

Location information:

Domain information:

Service information:
 Service Name: MINIMAL Computing Element
 Service Type: org.nordugrid.arex

Endpoint information:
 URL: https://localhost:60000/arex
 Capabilities:
  executionmanagement.jobexecution
 Technology: webservice
 Interface Name: OGSA-BES
 Supported Profiles:
  WS-I 1.0
  HPC-BP
 Implementor: NorduGrid
 Implementation Name: A-REX
 Implementation Version: 0.9
 QualityLevel: development
 Health State: ok
 Serving State: production
 Issuer CA: /O=Grid/O=NorduGrid/CN=NorduGrid Certification Authority
 Trusted CAs:
  /C=BE/O=BELNET/OU=BEGrid/CN=BEGrid CA/emailAddress=gridca@belnet.be
  /C=FR/O=CNRS/CN=CNRS2-Projets
  /DC=org/DC=ugrid/CN=UGRID CA
  /C=BR/O=ICPEDU/O=UFF BrGrid CA/CN=UFF Brazilian Grid Certification Authority
  /C=DE/O=DFN-Verein/OU=DFN-PKI/CN=DFN-Verein PCA Grid - G01
  /C=PT/O=LIPCA/CN=LIP Certification Authority
  /C=FR/O=CNRS/CN=GRID-FR
  /C=FR/O=CNRS/CN=CNRS2
  /C=TR/O=TRGrid/CN=TR-Grid CA
  /C=NL/O=NIKHEF/CN=NIKHEF medium-security certification auth
  /DC=org/DC=DOEGrids/OU=Certificate Authorities/CN=DOEGrids CA 1
  /DC=ch/DC=cern/CN=CERN Trusted Certification Authority
  /C=AU/O=APACGrid/OU=CA/CN=APACGrid/emailAddress=camanager@vpac.org
  /C=IE/O=Grid-Ireland/CN=Grid-Ireland Certification Authority
  /O=Grid/O=NorduGrid/CN=NorduGrid Certification Authority
  /DC=RO/DC=RomanianGRID/O=ROSA/OU=Certification Authority/CN=RomanianGRID CA
  /DC=bg/DC=acad/CN=BG.ACAD CA
  /C=MX/O=UNAMgrid/OU=UNAM/CN=CA
  /C=GR/O=HellasGrid/OU=Certification Authorities/CN=HellasGrid Root CA 2006
  /C=CL/O=REUNACA/CN=REUNA Certification Authority
  /DC=org/DC=balticgrid/CN=Baltic Grid Certification Authority
  /C=IT/O=INFN/CN=INFN CA
  /DC=me/DC=ac/DC=MREN/CN=MREN-CA
  /C=FR/O=CNRS/CN=CNRS-Projets
  /C=DE/O=DFN-Verein/OU=DFN-PKI/CN=DFN-Verein User CA Grid - G01
  /C=UK/O=eScienceCA/OU=Authority/CN=UK e-Science CA
  /C=RS/O=AEGIS/CN=AEGIS-CA
  /C=SI/O=SiGNET/CN=SiGNET CA
  /C=VE/O=Grid/O=Universidad de Los Andes/OU=CeCalCULA/CN=ULAGrid Certification Authority
  /DC=ORG/DC=SEE-GRID/CN=SEE-GRID CA
  /C=CH/O=Switch - Teleinformatikdienste fuer Lehre und Forschung/CN=SWITCH Personal CA
  /C=RU/O=RDIG/CN=Russian Data-Intensive Grid CA
  /C=HU/O=KFKI RMKI CA/CN=KFKI RMKI CA
  /C=JP/O=KEK/OU=CRC/CN=KEK GRID Certificate Authority
  /DC=EDU/DC=UTEXAS/DC=TACC/O=UT-AUSTIN/CN=TACC Root CA
  /C=AT/O=AustrianGrid/OU=Certification Authority/CN=Certificate Issuer
  /C=IL/O=IUCC/CN=IUCC/emailAddress=ca@mail.iucc.ac.il
  /DC=TW/DC=ORG/DC=NCHC/CN=NCHC CA
  /C=KR/O=KISTI/O=GRID/CN=KISTI Grid Certificate Authority
  /DC=LV/DC=latgrid/CN=Certification Authority for Latvian Grid
  /DC=NET/DC=PRAGMA-GRID/CN=PRAGMA-UCSD CA
  /C=CH/O=SwissSign/CN=SwissSign CA (RSA IK May 6 1999 18:00:58)/emailAddress=ca@SwissSign.com
  /C=MA/O=MaGrid/CN=MaGrid CA
  /C=MK/O=MARGI/CN=MARGI-CA
  /C=GR/O=HellasGrid/OU=Certification Authorities/CN=HellasGrid CA 2006
  /C=TH/O=NECTEC/OU=GOC/CN=NECTEC GOC CA
  /C=PL/O=GRID/CN=Polish Grid CA
  /C=UK/O=eScienceRoot/OU=Authority/CN=UK e-Science Root
  /DC=cz/DC=cesnet-ca/CN=CESNET CA
  /C=TW/O=AS/CN=Academia Sinica Grid Computing Certification Authority Mercury
  /DC=es/DC=irisgrid/CN=IRISGridCA
  /C=JP/O=AIST/OU=GRID/CN=Certificate Authority
  /C=JP/O=National Research Grid Initiative/OU=CGRD/CN=NAREGI CA
  /DC=BR/DC=UFF/DC=IC/O=UFF LACGrid CA/CN=UFF Latin American and Caribbean Catch-all Grid CA
  /C=CY/O=CyGrid/O=HPCL/CN=CyGridCA
  /DC=CN/DC=Grid/CN=Root Certificate Authority at CNIC
  /C=AR/O=e-Ciencia/OU=UNLP/L=CeSPI/CN=PKIGrid
  /C=CN/O=HEP/CN=gridca-cn/emailAddress=gridca@ihep.ac.cn
  /C=CA/O=Grid/CN=Grid Canada Certificate Authority
  /CN=SWITCH CA/emailAddress=switch.ca@switch.ch/O=Switch - Teleinformatikdienste fuer Lehre und Forschung/C=CH
  /DC=CN/DC=Grid/DC=SDG/CN=Scientific Data Grid CA
  /C=HU/O=NIIF/OU=Certificate Authorities/CN=NIIF Root CA
  /C=IR/O=IPM/O=IRAN-GRID/CN=IRAN-GRID CA
  /C=FR/O=CNRS/CN=CNRS
  /C=CH/O=Switch - Teleinformatikdienste fuer Lehre und Forschung/CN=SWITCHgrid Root CA
  /C=AM/O=ArmeSFo/CN=ArmeSFo CA
  /C=FR/O=CNRS/CN=GRID2-FR
  /DC=net/DC=ES/O=ESnet/OU=Certificate Authorities/CN=ESnet Root CA 1
  /DC=ch/DC=cern/CN=CERN Root CA
  /DC=IN/DC=GARUDAINDIA/CN=Indian Grid Certification Authority
  /C=DE/O=GermanGrid/CN=GridKa-CA
  /C=SK/O=SlovakGrid/CN=SlovakGrid CA
  /CN=SwissSign Bronze CA/emailAddress=bronze@swisssign.com/O=SwissSign/C=CH
  /DC=EDU/DC=UTEXAS/DC=TACC/O=UT-AUSTIN/CN=TACC Classic CA
  /C=BE/OU=BEGRID/O=BELNET/CN=BEgrid CA
  /CN=SwissSign Silver CA/emailAddress=silver@swisssign.com/O=SwissSign/C=CH
  /C=CH/O=Switch - Teleinformatikdienste fuer Lehre und Forschung/CN=SWITCH Server CA
  /C=PK/O=NCP/CN=PK-GRID-CA
  /C=DE/O=DFN-Verein/OU=DFN-PKI/CN=DFN-Verein Server CA Grid - G01
  /C=HR/O=edu/OU=srce/CN=SRCE CA
 Staging: staginginout
 Job Descriptions:
  ogf:jsdl:1.0

Queue information:
 Mapping Queue: default
 Max Total Jobs: 100
 Max Running Jobs: 10
 Max Waiting Jobs: 99
 Max Pre LRMS Waiting Jobs: 0
 Max User Running Jobs: 5
 Max Slots Per Job: 1
 Doesn't Support Preemption
 Total Jobs: 0
 Running Jobs: 0
 Waiting Jobs: 0
 Suspended Jobs: 0
 Staging Jobs: 0
 Pre-LRMS Waiting Jobs: 0
 Free Slots: 10
 Free Slots With Duration:
  P68Y1M5DT3H14M7S: 10
 Used Slots: 0
 Requested Slots: 0

Manager information:
 Resource Manager: torque
 Doesn't Support Advance Reservations
 Doesn't Support Bulk Submission
 Total Physical CPUs: 10
 Total Logical CPUs: 10
 Total Slots: 10
 Non-homogeneous Resource
 Working area is nor shared among jobs
 Working Area Total Size: 15
 Working Area Free Size: 4
 Working Area Life Time: P7D
 Cache Area Total Size: 15
 Cache Area Free Size: 4

Execution Environment information:
 Execution environment is a physical machine
 Execution environment does not support inbound connections
 Execution environment does not support outbound connections
---

Please note that you can run similar arcinfo request against any ARC1 service
except echo service.

A-REX accepts jobs described in JSDL language. Example JSDL jobs are provided
in $ARC_LOCATION/share/doc/ in files 'jsdl_simple.xml' and 'jsdl_stage.xml'. To 
submit job to A-REX service one may use the 'arcsub' command:

$ARC_LOCATION/bin/arcsub -c ARC1:https://localhost:60000/arex -f /usr/local/share/doc/arc/jsdl_simple.xml -j id.xml

If everything goes properly somewhere in it's output there should be a message
"Job submitted!", and a job identifier is obtained which will be stored
in 'id.xml' file. One can then query job state with the 'arcstat' utility:

 $ARC_LOCATION/bin/arcstat id.xml
 Job status: Running/Submitting

 $ARC_LOCATION/bin/arcstat id.xml
 Job status: Running/Finishing

 $ARC_LOCATION/bin/arcstat id.xml
 Job status: Finished/Finished

Some of the of A-REX client tools consists of arcsub, arcstat, arckill, arcget 
and arcclean commands. For more information please see the man pages of those utilities.


Security and Authorization
==========================

ARC1 implements security related features through set of Security Handler and 
Policy Decision Point components. Security Handler components are attached to 
message processing components. Each Security Handler takes care of processing
own part of security information. Currently ARC1 comes with 2 Security Handlers:
 * identity.map - associates client's identity with local (UNIX) identity. It 
   uses PDP components to choose local isentity and/or identity mapping algorithm.
 * arc.authz - calls PDP components and combines obtained authorization
   decisions.
 * delegation.collector - parses proxy policy from remote proxy certificate.
                          this Security Handler should be configured under tls
                          mcc component.
 * usernametoken.handler - implement the functioanlity ofws-security usernametoken 
                          profile. It will generate usernametoken into soap header,
                          or extract usernametoken outof soap header and do 
                          authentication based on the extracted usernametoken.

Among available PDP components there are
 * allow - always returns positive result
 * deny - always returns negative result 
 * simplelist.pdp - compares DN of user to those stored in a file.
 * arc.pdp - compares request information parsed from message and policy 
             information specified in this pdp.
 * pdpservice.invoker -  it composes the request, puts request into soap message,
             and invokes the remote pdp service to get the response soap which includes
             authorization decision. the pdp service has similar functionality
             with arc.pdp.
 * delegation.pdp - compares request information parsed from message and policy
             information specified in proxy certificate from remote side.

There are examples of A-Rex service and echo service with Security Handlers being used.
They may be found at $ARC_LOCATION/share/doc/arc/arex_secure.xml and 
$ARC_LOCATION/share/doc/arc/echo.xml

There is also a pdp service which implements the same functionality as arc.pdp. See 
src/service/pdp/README.
Specifically for arc.pdp and pdpservice, a formatted policy with specific schema
should be managed, see $ARC_LOCATION/share/doc/arc/pdp_policy.xml.example and 
$ARC_LOCATION/share/doc/arc/Policy.xsd for details.

For usernametoken handler, there is example about configuration on service side in 
$ARC_LOCATION/share/doc/arc/echo.xml, you can run echo service by using this configuration
file with usernametoken sechandler configuered. For client side, the echo client 
(src/client/echo)can use usernametoken sechandler to authenticate against echo service 
(see README under src/client/echo); there is also a test program in 
src/tests/echo/test_clientinterface.cpp which can be compiled and tested against echo
service with usernametoken sechandler configured.


Finding more information
========================

Many information about functionality and configuration of various components
may be found inside corresponding configuratrion XML schemas.

There is an API document 


Contributing
============

The open source development of the ARC middleware is coordinated by
the NorduGrid Collaboration. Currently, the main contributor is the
KnowARC project (www.knowarc.eu), but the Collaboration is open to new
members. Contributions from the community to the software and the
documentation is welcomed. Sources can be downloaded from the software
repository at download.nordugrid.org or the Subversion code repository at
svn.nordugrid.org.

The technical coordination group defines outstanding issues that have
to be addressed in the framework of the ARC development. Feature
requests and enhancement proposals are recorded in the Bugzilla bug
tracking system at bugzilla.nordugrid.org. For a more detailed
description, write access to the code repository and further
questions, write to the nordugrid-discuss mailing list (see
www.nordugrid.org for details). Ongoing and completed Grid Research
projects and student assignments related to the middleware are listed
on the NorduGrid Web site as well.



Support, documentation, mailing lists, contact
==============================================

User support and site installation assistance is provided via the
request tracking system available at nordugrid-support@nordugrid.org.
In addition, NorduGrid runs a couple of mailing lists, among which the
nordugrid-discuss mailing list is a general forum for all kind of
issues related to the ARC middleware.

NorduGrid deploys the Bugzilla problem tracking system
(bugzilla.nordugrid.org). Feature and enhancement requests, as well as
discovered problems, should be reported there.

Research papers, overview talks, reference manuals, user guides,
installation instructions, conference presentations, FAQ and even
tutorial materials can be fetched from the documentation section of
www.nordugrid.org

Contact information is kept updated on the www.nordugrid.org web site.