Transcript Applications as Web (Grid) Services and Related Issues Argonne 10 November 2003 PTLIU Laboratory for Community Grids Geoffrey Fox Computer Science, Informatics, Physics Indiana University, Bloomington.

Applications as Web (Grid) Services
and Related Issues
Argonne 10 November 2003
PTLIU Laboratory for Community Grids
Geoffrey Fox
Computer Science, Informatics, Physics
Indiana University, Bloomington IN 47404
http://grids.ucs.indiana.edu/ptliupages
[email protected]
1
Reporting work of
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Minjun Wang PowerPoint/OpenOffice as a WS
Xiaohong Qiu SVG as a WS
Bryan Carpenter SVG Javascript games
Sangmi Lee, Sunghoon Ko PDA and WS
Shrideep Pallickara NaradaBrokering messaging
Gurhan Gunduz Messaging performance module
Wenjun Wu and Ahmet Uyar Global-MMCS A/V
And other students not graduating in next 3 to 9
months
2
Client Applications and O/S I
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Consider applications like Word, Illustrator, Internet Explorer
These haven’t dramatically changed over the last 3 or perhaps
more years
• Some complain that such products are in fact getting worse as
they increase in size and complexity and correspondingly
decrease in usability
Microsoft has an obvious dominance in both O/S and associated
applications
Sun is trying to compete directly with StarOffice/OpenOffice
which are competitive with but not clearly better than Microsoft
products
• To be compatible with Microsoft Office requires reproducing
its bugs?
Mozilla is very competitive with Internet Explorer but not
clearly better
3
Client Applications and O/S II
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Asia – led by China – is aiming at escaping Windows
noose by developing their own (Linux) client
• For cost and desire to develop their software industry
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Palm O/S and Java are doing rather well in PDA/Cellphone industry
• Doesn’t seem one wants to run same applications on PDA’s
and desktops
• At least don’t want same user interface?
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Macintosh is doing quite well broadly as a client with a
UNIX based client
Linux (Unix?) has rather specialized CLIENT user base
4
Lessons from Web Services
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Web services are an attractive way of building service side
(Middle-tier) applications with a component model
• Expressed by using WSDL and meta-data
• All remarks here valid for Grid and Web services!
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WSRP, JSR168, Portlets, Jetspeed have taught us to distinguish
user-facing and service (resource) ports on Web services and
build a corresponding component model for user interfaces
• Jetspeed is primitive and standards WSRP, JSR168, portlets are
incomplete
• But this will surely rapidly improve as relatively obvious what to do
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So Web service based applications are significantly different
from classic desktop products like Word
• Light weight client which is relatively easily ported between client O/S
• Very easy to make collaborative using shared input port (MIMD) or
shared output port (SIMD)
• Perhaps hopelessly slow due to service-client interaction (the rule of the
millisecond?)
5
Applications as Web Services?
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Build “all” classic applications in Web service style with user
interface and “real application” interacting by (WSDL/SOAP)
messages and NOT by O/S controlled interrupts
• This is “just” MVC (Model View Control) paradigm done very explicitly
• Quite hard because MVC not actually used very systematically
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Perhaps the advantages of this architecture could be enough to
shake the Microsoft hegemony in both O/S and “productivity”
applications
• Current challenges of Microsoft applications are trying to do as well and
not easy to see how they can do better
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Immediately make a lot easier to support cross O/S applications
Form the “Next Generation Client Consortium”?
• There is quite a lot of open source (but not web service based) software
with which to begin
6
Classic MVC Paradigm
Model View Controller
Model
Controller
Mouse event
Keyboard events
Figure
View
Display
MVC Model
7
Web Service Model for Application Development
Data
Resource Facing Ports
Logic of Application
Semantic Events
Model
Messaging
System
User Facing
Ports
Events as
Messages
Rendering as
Messages
Control
Raw (UI) Events
User Interface
View
Interrupts in traditional monolithic applications become
“real messages” not directly method calls
Natural for collaboration and universal access
8
Next Generation Client?
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Access Grid (GlobalMMCS), JXTA, Mozilla (or Firebird for
browser and Thunderbird for mail), Batik SVG, OpenOffice,
Better Jetspeed …..
Support Linux, Windows, Palm, Java cellphone
Use W3C DOM and “better portlets”
What are the principles
• Split at “user interface” events (mouse clicks) or at “semantic” events
(slide change)
• What part of rendering on client (AWT, Java2D or …)
• could be different for different clients with server-side adaptors mapping
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What general support (tools) do we need?
• Event to message mapping and serialization
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When is there a performance problem?
• How “far” can server be from client?
9
Web Service Model for Application Development
Data
Resource Facing Ports
Logic of Application
Other Semantic Events
Another
version
of Model
Messaging
System
User Facing
Ports
Events as
Messages
Rendering as
Messages
Control
Some Semantic Events
Raw (UI) Events
User Interface (framebuffer)
Another View
10
What have we done in this Area?
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Most of this is work in progress ….
PowerPoint only partially as a Web Service
SVG as a Web Service and Collaborative SVG
• Example of W3C Document Object Model (DOM)
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PDA Interfaces and Collaboration using this
architecture
Universal Access
Publish-subscribe Messaging to link clients and Web
services
Global-MMCS: Collaboration as a Web Service
Looking at OpenOffice but not perfect
• Not Java and not W3C DOM compliant
11
Handling Events (Control in MVC)
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Typically events (Mouse click or change node in DOM)
are handled by setting listeners for produced events
• This is publish/subscribe intra-application
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Collaboration whether audio-video, text-chat or shared
display can be handled by collaborators subscribing to
change events published by master
• Publish/subscribe inter-clients
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Java takes about 0.75 millisecond to handle this on a
Linux server
Can handle with uniform publish/subscribe
environment
• http://www.naradabrokering.org
12
Role of Portal and User Facing Ports
Other WS
User Facing
Ports
F
I
R
O
WSDL
U
Application or
Content source
Web Service
O
F
I
Possible
Filter
Portal
Aggregate
WS-User Facing
Fragments
Other WS
User Facing
Ports
Render
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F
I
R
O
WSDL
U
Application or
Content source
Web Service
O
F
Selection
View
(NaradaBrokering)
Event Service
I
Filter
Customized View
Selector
Control Channel
Jetspeed
Portal
Customized
User-Facing
Ports
Customized View
Universal Access
With Jetspeed
Web Services,
MVC Model for applications
Asynchronous Messaging
Control Channel
User
Profile
Render
14
Shared Input Port (Replicated WS) Collaboration
Collaboration as a WS
Set up Session with XGSP
R
U
Web
F
Servic
I
I
e
O
O
F
WS
Viewer
WS
Display
Master
U
Web
F
Servic
I
I
e
O
O
F
Event
(Message)
Service
R
R
U
Web
F
Servic
I
I
e
O
O
F
WS
Viewer
WS
Display
Other
Participants
WS
Viewer
WS
Display
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Shared Output Port Collaboration
Collaboration as a WS
Set up Session with XGSP
Web Service Message
Interceptor
F
I
WSDL
R
O
Master
U
Application or
Content source
Web Service
Text Chat
Whiteboard
Multiple
masters
O
F
I
Event
(Message)
Service
WS
Viewer
WS
Display
WS
Viewer
WS
Display
Other
Participants
WS
Viewer
WS
Display
16
Collaborative SVG Web Service
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SVG is W3C 2D Vector Graphics standard and is interesting for
visualization and as a simple PowerPoint like application
• Further SVG is built on W3C DOM and one can generalize results
to all W3C DOM-based applications (“all” applications in future?)
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Apache Batik SVG is Java and open source and so it is practical
to modify it to explore
• Real Applications as a Web Service
• Collaboration as a Web Service
• MVC model and web services with implications for portlets
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We use NaradaBrokering and Global-MMCS to control
collaboration; support PDA Cell-phone and desktop clients; are
restructuring Batik as MVC Web Service
• Good progress in all areas see
• http://www.svgarena.org for SVG Games
• http://grids.ucs.indiana.edu/ptliupages/projects/carousel/ for PDA
17
Document Object Model
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DOM (Document Object Model) defines how documents to be
accessed as distributed objects – especially as a Web service
DOM has a particular tree-like specification of the Object
structure of a document
It defines
• An application programming interface (API) for documents (e.g. HTML,
XML documents) for Java, CORBA, Javascript ….
• Including how to change DOM
• The logical structure of documents
• The way a document is accessed and manipulated
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DOM has a generic event model defining uniform interface for
mouse and keyboard actions
• Also defines events signifying change in DOM
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W3C DOM builds on earlier ad-hoc DOM’s of Internet Explorer
and Netscape
• Surprisingly unsuccessful so far but critical for this project as allows
general approach to user interfaces
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Example of HTML DOM
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Here is an
example of a
fragment of
HTML and
how it can be
thought of as
a tree
This is called
a “document
fragment” in
DOM
(lightweight
tree)
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Constants
The
Node
Interface
in
CORBA
IDL
Properties
Methods
20
Collaborative
SVG AsSVGAclients
Web Service
Control flow for collaborative
From
Collaboration
As a WS
Application as a Web service
Application as a Web service
Events
Rendering
From Master
NaradaBrokering
W3C DOM Events
User Interface
Participating Client
From
Collaboration
As a WS
Application as a Web service
Application as a Web service
Events
Rendering
To Collaborative Clients
W3C DOM Events
User Interface
Master Client
21
Collaborative SVG Chess Game
in Batik Browser
Players
Observers
22
Lessons from SVG Web Service
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This keeps DOM and Javascript Event Handlers on the Server;
keeps the Graphics version of DOM that interfaces with Java2D
on client; client captures raw user interface events inside SVG
frame; client captures some semantic events (zoom, change
URL) in menu-bar
We identified SIMD and MIMD model of collaboration
• Program is JavaScript implementing in our case chess or card game
• SIMD collaboration is shared output port in Web Services model
• MIMD collaboration becomes shared input port model
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Internally there are pipelines
AWT/Swing  GVT  DOM  JavaScript  new DOM for user input
new DOM  GVT  Java2D  Framebuffer
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for rendering
The Graphic Vector Toolkit (GVT) module represents a view of
the DOM tree in terms of Java objects that is more suitable for
rendering and event handling purposes.
Can share at different points of pipeline based on software
engineering issues – where is current software easiest to split
23
From the Battle Lines
Why not easy to convert legacy applications to WS
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Although many modern applications adopt MVC (Model-View-Control)
paradigm, they may not strictly follow the principles in implementation.
Not faithfully following modularized design principle the applications does
not have a clear "control" design which plays the role as the only
communication channel between "model" and "view".
• there exits direct linkage (not through "control") between Model and View
in the MVC paradigm.
• For example, some functional modules
 involve information from many stages across the pipeline rather than
just provide the linkage between the two modules
 Are instantiated in GUI/"view" but execute functions in the backend
"model" through direct methods calls
Not providing "Object Serialization"
• Object Serialization (the process of reading and writing objects) has many
uses, including remote method invocation (RMI)
• In addition to the object streams, java.io has other classes and interfaces
that define the API to help classes perform serialization for its instances.
• lacking of serializable feature of the modularized components makes it
hard to split the application into a Web service
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SIMD Collaboration
Non Web Service
Implementation
NaradaBrokering
SVG
Browser
SVG
Browser
SVG
Browser
SVG
Browser
Identical Programs receiving identical events
Token determines if browser is moving, waiting for opponent or an observer
SVG Model (DOM)
NaradaBrokering
SVG
Viewer
SVG
Viewer
SVG
Viewer
Shared Output port
SIMD Collaborative
Web Service
SVG
Viewer
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MIMD Collaboration
Shared Input port
MIMD Collaborative
Web Service
NaradaBrokering
SVG
Model
SVG
Model
SVG
Model
SVG
Model
NaradaBrokering
SVG
Viewer
SVG
Viewer
SVG
Viewer
SVG
Viewer
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PowerPoint as a Sort of Web Service
As in Access Grid Collaborative
Client
PPT as a
Web Service
NaradaBrokering Message Service
User
1
1
User
2
User
n
Master
Client
Sink
Connectable
Object
Holds meta-data
(sample of high
level semantic
events) like slide
number and title
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Semantic Events in PPT Web Service
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One can capture slide and animation semantic events such as
WindowSelectionChange WindowBeforeRightClick,
WindowBeforeDoubleClick, PresentationClose,
PresentationSave, PresentationOpen, NewPresentation,
PresentationNewSlide, WindowActivate, WindowDeactivate,
SlideShowBegin, SlideShowNextBuild, SlideShowNextSlide,
SlideShowEnd, PresentationPrint, SlideSelectionChanged,
ColorSchemeChanged, PresentationBeforeSave,
SlideShowNextClick
We don’t know how to capture
• Raw UI events such as MouseOver, MouseClicked,
MouseDoubleClicked, KeyDown, KeyUp, KeyStroke, etc.
• Sound events such as SoundClipPlayed, SoundFilePlayed, etc.
• Some animation events such as AnimationClipPlayed,
MoviesPlayed, AnimationFilePlayed
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Integration of PDA, Cell phone and Desktop Grid Access
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Real-time Community Collaboration
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Desktop PC, local wireless (802.11b) and the rest of the world (Sprint
PCSVision as glimpse of next generation cell phones)
Reconcile different protocols, different display areas, different O/S and
different network bandwidths
Text Chat
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Real-time Community Collaboration
PowerPoint via “Shared Pixels”
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Real-time Community Collaboration
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Scalable Vector Graphics (SVG) via “Shared Web Service”
4500
4000
Performance of PDA Client
Latency over successive iterations
Time (milliseconds)
3500
3000
2500
2000
1500
1000
Publishing Event from PDA to Server
Subscribing to Event from PDA
500
0
• Treo 300 Sprint PCS Vision Java MIDP on Palm O/S
• 50 Kbit/sec bandwidth both directions
• Developing optimized protocol (HHMP) to be built into
NaradaBrokering for fault-tolerance and latency hiding
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(pre-start HTTP connection)
Application Web Services
and Universal Access
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NaradaBrokering can link lightweight clients (V in
MVC) to Web Services holding as a Web service the
“guts of an application” (M in MVC)
• This allows customizable user interfaces gotten by mapping
between client profile protocols at NB
• Supports collaboration between diverse clients
Map P to P1
P1
Agent1
Client1
Web Service
NB
M
Profiles
P
Client2
Map P to P2
P2
Agent2
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Collaboration Personal Server and EventFlow
Web Service B
Topic set B
(does not need
content adaption)
SVG Web Service A
Topic set A
(needs content adapting)
Subscribe/Publish to
Topic set A
Subscribe/Publish to
Topic set B
( Subscribe to Topic set A
instead of mobile devices
and adapt the content
to give Topic Set C)
JMS
Collaboration
Personal Server
Topic set C
Subscribe
/Publish to
Topic set A,C
NB
NB
HTTP
RTP
HHMP
Subscribe/Publish to
Topic set A,B
HTTP/HHMP
Interface
(for current
3G phone service)
Subscribe/Publish to
Topic set B,C
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Web Service to Client Pipeline
IB M
computation unit
Generating user presentation
real time
multimedia
Database
DAT
M&L
DTX
PCL
MCL
User event transmit
Universal user devices
• DAT (Data) stage: Data source (facing remote resources)
• M&L (Model and Logic) stage: Semantic processing of the data
• DTX (Data Transformer) stage: Process of filtering the object for
heterogeneous devices
• PCL (Presentation client) stage: Generating abstract presentation for each
client
• MCL (Minimal client) stage: Actual drawing onto user device
• PDA would “just” have MCL
• Desktop might have PDA and MCL
• Such diagrams can be analysed formally using Petri nets
Page. 36
Event Processing in Web Service to Client Pipeline
• Events allow Client and service to interact
– Transformations in each module MUST be invertible
• Two directions of dataflow
– Event transmission
– Presentation Generation
User Event Transmission
DAT
M&L
DTX
PCL
MCL
<?xml vers
<!DOCTYPE
<!--local DT
<svg width=
<desc>This
SVG document
with the original
size of 1200 x 2000
DOM tree of
SVG
document
Rendered Image
with CSS for PDAs
(resolution of
160 x 160)
SVG browser
for PDAs
Generating Presentation View
Actual Display
on PDA
Page. 37
Some Simple Principles
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One must use invertible transformations so that can propagate
information to AND from the client
Don’t ever send a position (x,y) for say a mouse click – rather
send position and coordinate system specified by some
transformation (as in affine transformations used in graphics)
• Or send semantic meaning of click – e.g. open URL
Accumulate mouse-move events into arrays or cumulative events
to avoid too many messages
Choose “cutting point” between M and V to support interactivity
and performance
Jetspeed is just aggregating lots of different “Views”
All messages MUST go through messaging system – it must
support all needed protocols such as those needed to minimize
latency for cellphones
• Messaging system has routing optimization/firewalls built in
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NaradaBrokering
Audio/Video
Conferencing Client
Computer
Modem
Minicomputer
Server
NaradaBrokering Broker
Network
Brokers
ONLY
process
messages
Firewall
Workstation
Peers
Laptop computer
Peers
PDA
Audio/Video
Conferencing Client
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“GridMPI” v. NaradaBrokering
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In parallel computing, MPI and PVM provided “all the features
one needed’ for inter-node messaging
NB aims to play same role for the Grid but the requirements and
constraints are very different
• NB is not MPI ported to a Grid/Globus environment
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Typically MPI aiming at microsecond latency but for Grid, time
scales are different
• 100 millisecond quite normal network latency
• 30 millisecond typical packet time sensitivity (this is one audio or video
frame) but even here can buffer 10-100 frames on client (conferencing to
streaming)
• <1 millisecond is time for a Java server to “think”
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Jitter in latency (transit time through broker) due to routing,
processing (in NB) or packet loss recovery is important property
Grids need and can use software supported message functions and
trade-offs between hardware and software routing different from
parallel computing
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NaradaBrokering
Based on a network of cooperating broker nodes
• Cluster based architecture allows system to scale in size
• Grid routing topologies are open research issue?
Originally designed to provide uniform software multicast to
support real-time collaboration linked to publish-subscribe for
asynchronous systems.
Perhaps better thought of as stream not message handler
Now has several core functions
• Reliable order-preserving “Optimized” Message transport
(based on performance measurement) in heterogeneous multilink fashion with TCP, UDP, SSL, HTTP, and will add GridFTP
• General publish-subscribe including JMS & JXTA and
support for RTP-based audio/video conferencing
• General software routing to avoid network problem
• Distributed XML event selection using XPATH metaphor
• QoS, Security profiles for sent and received messages
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• Interface with reliable storage for persistent events
Grid Messaging Substrate
SOAP+HTTP
GridFTP
RTP ….
Standard client-server
style communication.
Substrate mediated
communication removes
transport protocol
dependence.
Consumer
Consumer
Service
SOAP+HTTP
GridFTP
RTP ….
Service
Messaging Substrate
Any Protocols satisfying QoS
Messaging Substrate has “intelligence” “any desired fault tolerance” “logging” etc.
Hope to demonstrate with multicast fault tolerant GridFTP
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Laudable Features of NaradaBrokering
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Is open source http://www.naradabrokering.org available now;
major new release for SC03
Will have end-point “plug-in” as well as standalone brokers
• end-point is service or user-interface machine
Will have a discovery service to find nearest brokers
Does tunnel through most firewalls without requiring ports to be
opened
Links to NWS (Network Weather Service) style performance
estimation systems
Supports JXTA (peer-to-peer network), JMS (Java Message
Service) and more powerful native mode
Transit time < 1 millisecond per broker
Will have setup and broker network administration module
43
NaradaBrokering Naturally Supports
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Filtering of events (streams) to support different end-point
requirements (e.g,. PDA versus desktop, slow lines, different A/V
codecs)
Virtualization of addressing, routing, interfaces (OGSI versus
pure Web services for example)
Federation and Mediation of multiple instances of Grid services
as illustrated by
• Composition of Gridlets into full Grids (Gridlets are single computers in
P2P case)
• JXTA with peer-group forming a Gridlet
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Monitoring of messages for Service management and general
autonomic functions
Fault tolerant data transport
Virtual Private Grid with fine-grain Security model
44
Virtualizing Communication
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Communication specified in terms of user goal and Quality of
Service – not in choice of port number and protocol
Protocols have become overloaded e.g. MUST use UDP for A/V
latency requirements but CAN’t use UDP as firewall will not
support ………
A given communication can involve multiple transport protocols
and multiple destinations – the latter possibly determined
dynamically
NB Brokers
A
Satellite
UDP
Firewall
HTTP
Software Multicast
NB Broker
Client Filtering
Fast
Link
B1
Hand-Held
Protocol
Dial-up
Filter
B2
B3
45
Performance Monitoring
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Every broker incorporates a Monitoring service that
monitors links originating from the node.
Every link measures and exposes a set of metrics
• Average delays, jitters, loss rates, throughput.
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Individual links can disable measurements for
individual or the entire set of metrics.
Measurement
Broker
Broker
Monitoring
intervals can
Node
Node
Service
also be varied
Link
Link
Monitoring Service,
Data
Data
returns measured
Aggregates info
metrics to
Control Message
from nodes in a
Exchange
Performance
certain domain
Aggregator.
Performance Aggregation
Service
46
Transit Delay (Milliseconds)
Mean transit delay for message samples in
NaradaBrokering: Different communication hops
9
8
7
6
5
4
3
2
1
0
hop-2
hop-3
hop-5
hop-7
100
1000
Message Payload Size (Bytes)
Pentium-3, 1GHz,
256 MB RAM
100 Mbps LAN
47
JRE 1.3 Linux
Standard Deviation for message samples in NaradaBrokering
Different communication hops - Internal Machines
0.8
hop-2
hop-3
hop-5
hop-7
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1000
1500
2000
2500
3000
3500
Message Payload Size
(Bytes)
4000
4500
5000
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Transit delays for Content Payloads.
Broker at Cardiff, Clients at Indiana
114.5
Delay
114
113.5
113
112.5
112
111.5
100 200 300 400 500 600 700 800 900 1000
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Content Payload Size in Bytes
Standard deviation for Content Payloads.
Broker at Cardiff, Clients at Indiana
2.6
Standard Deviation
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
100 200 300 400 500 600 700 800 900 1000
50
Content Payload Size in Bytes
Architecture of Message Layer
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Need to optimize not only routing of particular messages but
classic publish/subscribe problem of integrating different
requests with related topics (subscribe to sports/basketball/lakers
and sports)
Related to Akamai, AOL … caching and Server optimization
problem
Hypercube of
NB Brokers (logical
not physical)
N≈100
clients
per leaf node
for A/V
conferencing
1-> N Grid Clients
Scale using
NB broker
network
51
Global-MMCS 2.0 XGSP based MCU
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We are building an open source protocol independent Web
Service “MCU” which will scale to an arbitrary number of users
and provide integrated thousands of simultaneous users
collaboration services.
We will deploy it globally and hope to test with later this year.
The function of A/V media server will be distributed using
NaradaBrokering architecture.
• Media Servers mix and convert A/V streams and are built as
Web Services
Open Global-MMCS MCU based on the following open source
projects
• openh323 is basis of H323 Gateway
• NIST SIP stack is basis of SIP Gateway
• NaradaBrokering is open source messaging from Indiana
• Java Media Framework basis of Media Servers
52
XGSP Web Service MCU Architecture
Use Multiple Media servers to scale to many codecs and many
versions of audio/video mixing
Session Server
XGSP-based Control
NaradaBrokering
All Messaging
NB Scales as
distributed
Admire
Web
Services
SIP
H323
Media Servers
Filters
High Performance (RTP)
and XML/SOAP and ..
Access Grid
Native XGSP
Gateways convert to uniform XGSP Messaging
NaradaBrokering
53
Polycom, Access Grid
and RealVideo views of
multiple streams using
A/V Web Service
integrating SIP and H323
54
Performance Test : GlobalMMCS1.0
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We conducted extensive performance tests on audio and video
servers.
Video:
• The test shows that our video server is capable of supporting
100-300 clients if there is only one video sender.
• Video Server Machine : 1.2GHz Intel Pentium III dual CPU, 1GB
MEM, RedHat Linux 7.3
Audio:
• Our tests show that audio server can support 5 concurrent
sessions (250 participants in total) without any packet droppings.
• Audio Server Machine: 2.5GHz Pentium 4 CPU, 512MB
Windows XP machine

memory,
Scale with logarithmic Broker network
55
Average delays per packet for 50 video-clients
NaradaBrokering Avg=2.23 ms, JMF Avg=3.08 ms
60
NaradaBrokering-RTP
JMF-RTP
Delay (Milliseconds)
50
40
30
20
10
0
0
200 400 600 800 1000 1200 1400 1600 1800 2000
Packet Number
56
Average jitter (std. dev) for 50 video clients.
NaradaBrokering Avg=0.95 ms, JMF Avg=1.10 ms
8
NaradaBrokering-RTP
JMF-RTP
Jitter (Milliseconds)
7
6
5
4
3
2
1
0
0
200 400 600 800 1000 1200 1400 1600 1800 2000
Packet Number
57
4.5
NaradaBrokering-RTP
900 audio clients
JMF-RTP
4
3.5
3
2.5
2
1.5
1
0.5
0
0
200 400 600 800 1000 1200 1400 1600 1800 2000
Packet Number
58