OMII-UK: PAG

PAG

Summary

The Portlet Access Grid (PAG) project provides a fully functional portlet client for Access Grid Toolkit version 3 (AGTkv3). PAG enables automatic and transparent switching to unicast when multicast becomes unavailable, and allows the use of Access Grid behind restrictive firewalls and from low bandwidth connections.

Access PAG

The PAG environment can be accessed through the reference installation. The PAG service is available for use in association with the UK's National Grid Service (NGS) and Access Grid Support Centre (AGSC).

The PAG server can also be downloaded from the PAG homepage.

Status

Version 1.1. of PAG is accessed through the reference installation and can be downloaded.

System Requirements

Server

Portal server (JSR 168 standard compatible)
Java version 1.5 or higher
Apache Tomcat 5.5

User

Java version 1.5 or higher

Further information

Developers

PAG is developed by the Research Computing Services group based at the University of Manchester.

What can it do?

PAG is a complete replacement of the Venue Client provided by the AG Toolkit (AGTk). It is presented through a portal framework, allowing for easy access through any available web browser. Only minimal installation required, since the only requirement at the client side is a working instance of Java. The PAG model has the advantage that the service provider maintains the portal and the PAG portlet installation, so that the end user only need worry about their meeting.

PAG provides:

An AG client user interface accessible entirely through a portal interface.
Access to new bridging technology with minimal requirements for ports to be opened through firewalls.
An improved user experience, achieved through the introduction of 'client-level bridging'. This also allows for future AG network upgrades.
An implementation of the current node services provided by the AGTk, including, but not limited to, audio and video services. These services will use the existing node service executables, and employ Java to deliver the executable packages to the client computer.
An implementation of shared applications currently available within the AGTk, including the Shared Presentation tool and the Shared Browser.
Access to the AGTk shared data architecture.

How does it work?

Addressing the challenges of AG networking and service architecture, PAG had to break out of the ordinary portlet structure. The portlet creates only the web interface for the PAG-Client. A signed Java applet, the VenueClientController, is then used to communicate between the Portal Server and the PAG Client using asynchronous XML-RPC calls via AJAX. As all the communication is embedded in HTTP, PAG avoids problems with firewalls and proxy servers.

The Java applet starts a Java Application, the VenueClient, on the client machine through Java Web Start. The VenueClient controls the AG services. These services are packaged as Java Web Start applications hosted on the PAG servlet. XML-RPC is used between the VenueClient and the VenueClientController as a straightforward communication method. The communication between the VenueClient and the AGServices is based on the SOAP interfaces provided by the AGTk.

The UDP traffic from the services themselves is tunnelled through a client bridge. This is a UDP bridge that passes the traffic between the service and the AG, either using multicast directly or through a bridge. PAG includes an interface for allowing additional bridge types to be defined over the standard set provided.

Add new attachment

Only authorized users are allowed to upload new attachments.

List of attachments

Kind	Attachment Name	Size	Version	Date Modified	Author	Change note
png	PAGcommunication_trans.png	69.4 kB	2	04-Sep-2008 14:39	SimonHettrick

« This page (revision-18) was last changed on 08-Jul-2009 11:12 by SimonHettrick