An Instantaneous Introduction to the Alliance Access Grid

1
An Instantaneous Introduction to the Alliance
Access Grid

• Michael Grobe Assistant Director
• Academic Computing Services
• The University of Kansas
• September 2000

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The Access Grid is an Internet-based model for
video conferencing developed by the Future Lab
(FL) within the Mathematics and Computer Science
(MCS) division of Argonne National Laboratories
(ANL). The Access Grid is an extension of the
Alliance Computational Grid which is a
distributed computing environment designed to
provide convenient access to high performance
computer systems to any network user.
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• As described on the Access Grid web site
• "The Access Grid is the ensemble of resources
  that can be used to support human interaction
  across the grid. It consists of
• multimedia display, presentation and interaction
  environments,
• interfaces to grid middleware,
• interfaces to visualization environments

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The Access Grid will support large-scale
distributed meetings, collaborative work
sessions, seminars, lectures, tutorials and
training. The Access Grid design point is
group-to-group communication (thus
differentiating it from desktop to desktop based
tools that are focused on individual
communication). The Access Grid includes the
notion of a "persistent" video conferencing
venue, a conferencing site operating continuously
and accessible to a wide audience of users on an
ad hoc basis
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• Basic functionality
• An Access Grid "node" will be a small conference
  room or auditorium, provisioned with the
  equipment to participate in a multipoint video
  conference. The basic functionality provided
  within the node is
• Audio encoding using one or more microphones
• Video encoding or "capture" using one or more
  cameras
• Audio presentation using one or more speakers
• Video display via one or more computer monitors
  and/or video projection techniques
• Display of PowerPoint "slides" under the control
  of a presenter located either on-site or at a
  remote site.

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To achieve this functionality the Access Grid
model relies upon the ability to send and receive
Internet Multicast traffic to and from all
conference nodes. The Access Grid is based on
software (vic and rat) developed as part of the
Internet Multicast backbone, or MBONE, which
provided multicast services over the unicast
Internet backbone (using "tunnels", or "bridges",
between multicast nexus sites).
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• Software components
• The Access Grid model revolves around two pieces
  of software
• vic the video conferencing tool, and
• rat the robust audio tool.
• and involves several other applications
• Distributed PowerPoint
• a MUD
• the Multicast Beacon
• Virtual Venue
• Virtual Network Computing

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• Video Conference (vic)
• Vic was developed by Steve McCanne and Van
  Jacobson at the Lawrence Berkeley Labs. It is
  intended to link multiple sites with multiple
  simultaneous video streams over a multicast
  infrastructure.
• vic CAN perform 2 basic functions
• take data from video capture cards in the PC to
  which cameras (or other video devices) are
  attached and send it over the network.
• receive data from the network and display it on a
  video monitor or on some other attached video
  device such as a video projector.

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Note that vic may be run in such a way that it
only receives video transmissions or only sends
transmissions it is not required to do both at
the same time. For more information about vic
see http//www-mice.cs.ucl.ac.uk/multimedia/softw
are/vic
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• Robust Audio Tool (Rat)
• rat is a recent version of the Visual Audio Tool,
  also developed by Steve McCanne and Van Jacobson
  at the Lawrence Berkely Labs. rat allows multiple
  users to engage in a audio conference over the
  Internet in multicast mode. rat can perform 2
  basic functions
• take data from the sound card in the PC to which
  microphones, headphones, or some other audio
  devices are attached and send it over the
  network.
• receive data from the network and send it to
  speakers, headphones, or other attached sound
  processing device, such as a tape recorder, etc.

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rat displays a list of connected participants and
identifies who is speaking and who is listening
at any given time. For more information about
rat see http//www-mice.cs.ucl.ac.uk/multimedia/
software/rat and the Access Grid web site.
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The Gentner AP400 Echo Canceller Within the
Access Grid model, signals from and to attached
audio equipment are funneled through an "echo
canceller" made by the Gentner Communications
Corporation, to eliminate certain kinds of echoes
produced during networked conferencing. It is
probably fair to say that the Gentner echo
canceller is the major component of the audio
conferencing system Networks of Gentners work
together to provide useful audio signal
exchanges.
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• The Gentners can use 3 different connectivity
  infrastructures
• a point-to-point telephone connection,
• a telephone connection to a telephone bridge,
• a computer network, or
• Gentner's own local area network, called G-link.
• When a Gentner uses a computer network to connect
  to other Gentners, it connects to the computer
  just as it would to a simple Codec
  (compression/decompression device).

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The Distributed PowerPoint software The Argonne
Distributed PowerPoint software allows a single
presenter at one node to control PowerPoint
applications running on computer systems located
at other Access Grid nodes. For example, a
conference speaker can run PowerPoint along with
the Distributed PowerPoint master software on her
laptop computer at the podium of one of the AG
sites. When the speaker changes slides, the
master will notify the DPPT server, which will
notify DPPT clients running on systems at other
nodes which will, in turn, direct their local
PowerPoint programs to change slides.
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Note that this approach requires that some
PowerPoint features be removed or disabled prior
to presentation, because Distributed PowerPoint
cannot deal with them. (See later discussions of
VNC and "scan conversion" for alternatives.)
The DPPT clients can operate on PowerPoint
slidesets published on a Web server, or on local
copies of the slidesets.
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The MUD software Operators at each site
involved in an Access Grid conference typically
keep in touch by using software originally
developed for online "role-playing" games
generically called Multi-User dragons and
Dungeons" games, or "MUDs". (MUD functionality is
similar to that of Inter net Relay Chat operating
with access control.) Argonne runs a MUD server
for use by Access Grid operators who run MUD
clients on their desktop systems. tkMOO-lite is
currently the recommended MUD client for this
purpose, but others, such as Tiny-Fugue in the
Unix environment can be used as well. tkMOO will
run on both Windows and Linux systems, so it may
be be run on any of the AG component systems
described below.
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• The Multicast Beacon
• To help diagnose multicast network problems
  during conferences, Argonne promotes the use of
  the NLANR multicast "Beacon" monitoring system,
  which includes three pieces of software
• a Beacon to be run at each AG node,
• a server to collect transmission statistics from
  a collection of Beacons, and
• a Beacon viewer that displays data collected by
  the server.

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The Beacon at each node connects to a Multicast
group and collects latency, loss, and packet
misordering statistics from all other beacons
connected to that Multicast group and sends them
to the Beacon server. The Beacon viewer displays
these traffic statistics as a matrix showing
traffic to and from each Beacon attached to the
server. (There is also a web-based Beacon.) At
KU the Beacon is running on the AG node's video
capture system.
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• The Virtual Venue software
• Coordinating multiple group conferences can be
  complicated. Argonne has developed a collection
  of web pages and Java applications that can
  simplify the process.
• The Virtual Venue is basically a web-page that
  lets users select a "conference" to attend. In
  this context a "conference" is composed of
• a vic multicast address,
• a rat multicast address, and
• a MUD identifier.

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If your systems are Virtual Venue-enabled, the
display system operator can click on a conference
room name and the vic, rat and MUD applications
running on the video display, video capture and
audio processing systems will all be started with
target addresses and settings appropriate to the
selected conference room. This coordination is
accomplished by running an "event server" and the
event controller on the display system, along
with "event listeners" on the video capture and
audio processing systems.
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Virtual Network Computing (VNC) VNC allows users
to share monitor screens over the Internet in a
variety of modes. In the Access Grid environment,
VNC allows a speaker to share his/her podium
laptop with Access Grid display systems which can
then project it at remote nodes. This is useful
when a speaker wishes to give real-time
demonstrations or present PowerPoint slides that
include "fancy" features, such as animations,
that cannot be displayed using Distributed
PowerPoint. VNC employs a client server
architecture, and there are clients and servers
available for Windows98/NT/2000 and Unix
operating systems.
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Although not part of the original Access Grid
canon, VNC has been employed during several
Access Grid conferences, and shows promise for
future applications. VNC eliminates the
coordination effort required to display
Distributed PowerPoint slide sets. (No files need
to be downloaded ahead of time and no slide
synchronization is required.) In general, update
times are a function of the number of pixels
changed and the number of remote viewers (as well
as avaible bandwidth), so VNC will not be
appropriate for all applications. Instructions
for setting up a VNC relay, are presented in
Using Unix-based VNC to relay other VNC traffic.
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Basic system configurations The AG model uses a
collection of commodity components to provide
various services. To assure optimal
responsiveness individual functions (video
capture, video display, audio capture and
presentation) are placed on separate computer
systems. There is a variety of hardware and
software configurations that can provide the
required video conferencing functionality
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• This section shows one such configuration
• 1 computer system running Linux for audio capture
  and presentation
• 1 computer system running Linux for video capture
  
• 1 computer running Windows2000 video display
  through 1 or more video cards controlling one or
  more video projectors illuminating 1 or more
  screens.
• 1 computer system running Win98 for controlling
  the audio echo-canceller/mixer
• 1 speaker's podium computer running Windows2000
  or NT to control remote PowerPoint displays
  and/or give real-time demonstrations using some
  Windows application

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• Audio capture and presentation computer
• The audio capture computer
• Converts analog audio from mixers and mics to
  digital form for transmission by rat over the
  multicast network
• Converts digital audio to analog audio for
  distribution to room speakers and/or headsets .
• Software
• RedHat Linux version 6.1
• rat
• AudioResourceManager from the Virtual Venue suite
  

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• Video capture computer
• The video capture computer system converts analog
  video from cameras and/or VCRs, etc. to digital
  for transmission by vic over the multicast
  network.
• Software
• RedHat Linux version 6.1
• Stock kernel with the BTTV drivers
• vic
• VideoResourceMonitor from the Virtual Venue suite
  

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• Video display computer
• Receives video content over the network and
  displays it on the PC monitor as well as one or
  more other monitors and/or video projectors if
  desirable (using the ability of Win2K to display
  its console screen across multiple video cards)
• Decodes Video streams
• Runs collaboration applications such as
  Distributed PowerPoint and the VNC viewer

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• Software
• Windows 2000
• vic
• PowerPoint
• Argonne Distributed PowerPoint client
• EventServerMonitor and DisplayResourceManager
  from the Virtual Venue suite
• VNC viewer

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Echo canceller control computer The audio
control computer runs Windows 98 and uses custom
Genter Control Software to control the Gentner
mixer/echo canceller. See http//www.gentner.com
for more details. Within the KU ACS node, this
function is provided by a 133MHz PC.
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• Speaker's podium computer
• The speaker's podium computer runs
• Windows98/NT/2000
• PowerPoint
• the Argonne Distributed PowerPoint master
  software, and the
• VNC server
• Configuration suggested by Argonne Some laptop
  powerful enough to run PowerPoint

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The KU ACS Podium laptop is connected to a "scan
converter" that can convert the VGA/SVGA signal
generated by the laptop to NTSC video expected by
video capture cards. The CORIOscan Select from
TVONE is lists for around 495, and can be used
to produce a reasonably high-resolution image
(1280x860).
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• Alternatives for displaying speaker slidesets
• As mentioned earlier, the Access Grid provides
  several methods for displaying speaker slidesets.
  
• use Distributed PowerPoint.
• This is the "standard" method and provides high
  quality representation at every site with very
  little network traffic. Using DPPT means getting
  each slide set prior to use, stripping it of
  special PPT features and publishing it on a Web
  server for distribution to each remote site.
  This approach may not work well if the speaker
  relies on special features (such as fancy
  animations) or launches other applications during
  the talk.

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• use a VNC server running on the Podium laptop and
  a VNC relay (as discussed earlier).

This approach provides high quality video
including simple animations and all PowerPoint
features, but introduces some update delay, and
generates much more network traffic than the
other alternatives. (If a version of VNC were
produced to employ Multicast for image
distribution network traffic would be
significantly reduced.)
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• split the Podium laptop video output, send one
  channel to a local projector for the local
  audience, and one to a scan converter and then to
  a video capture card for distribution over vic
  from the video capture machine.
• This will give excellent update speed both
  locally and remotely, but relatively poor image
  quality at remote sites. Text smaller than 20
  points is usually not legible, but animations and
  videos present well (as long as high resolution
  is not necessary). This approach could be a very
  effective, general solution IF vic could be used
  with a higher quality codec than the usual H.261.
  An MPEG-1 codecs is apparently under development
  and should provide a significant improvement.

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• use commercial streaming video package.
• For example, during the Kansas issue of Alliance
  Chautauqua 2000, Cisco IPTV was employed to
  present full-motion animations at high
  resolution. However, setting up for IPTV
  broadcasts is complex and requires access to an
  IPTV server, so this alternative will not be
  available to all.

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• Ancillary Servers
• You may need to run some of the ancillary servers
  mentioned earlier on separate computer systems.
  For example, you may need boxes to run a
• Distributed PowerPoint server,
• VNC relay server,
• MUD, and/or a
• Virtual Venue server (should you wish to define
  your own Virtual Venues).

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• Operators
• You will need from 1 to 4 operators, depending on
  how you apportion duties, to run an Access Grid
  node. With one operator per basic function you
  will need an operator for
• video display,
• video capture,
• audio control, and
• network monitoring.
• To some degree there is a trade-off between
  system costs and operator costs, and the staffing
  requirements will vary with the complexity of the
  presentations being offered at a site.

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Additional Info The Access Grid web
site http//www.fp.mcs.anl.gov/fl/accessgrid/ Fo
r a more detailed version of this talk see
http//www.cc.ukans.edu/acs/docs/access-grid-nod
e/ Acknowledgments Some of the material for
this web page has been taken from the Argonne
Labs web site listed above, or from documents
provided via that site.