Collaborative Peer-to-peer Grids for Education and Research

1. Purdue 15 January 2003 Collaborative Peer-to-peer Grids for Education and Research PTLIU Laboratory for Community Grids Geoffrey Fox Computer Science, Informatics, Physics Indiana University, Bloomington IN 47404 (Technology Officer, Anabas Corporation, San Francisco) http://grids.ucs.indiana.edu/ptliupages gcf@indiana.edu uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

2. Some Basic Observations/Goals • Technology Support for e-learning is one motivation • Need Synchronous and Asynchronous Resource Sharing • Can provide universal access using collaboration technology • Grids manage and share asynchronous resources in a rather centralized fashion • Peer-to-peer networks are “just like” Grids with different implementations of services like registration and look-up • Web Services interact with messages • Everything (including applications like PowerPoint) will be a WS? • Computers are fast and getting faster. One can afford many strategies that used to be unrealistic • All messages can be publish/subscribe • Software message routing • XML will be used for most interesting data and meta-data • One will store/consider data and meta-data separately but often use same technology to manage both of them. uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

3. Deductions • The system consists of a sea of message-based Services • Services inject and extract messages whose transport and manipulation is support by a logically distinct sea of brokers/routers • They support adaptive routing, filtering, workflow … • They separate logical and actual transport • These form a federated XML database and support asynchronous collaboration • These process real-time messages in about a millisecond and support synchronous collaboration • Basic Unit of information (including events and messages) is a bunch of XML using URI’s to link to other XML or to “other technology capabilities” – Fortran programs, video files, telescopes … • This XML includes service meta-data, user profiles, H323 done right, your homework grades, update of framebuffer in shared display etc. uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

4. So what are we doing I? • We co-edited a book on Grid Computing to be published April 2003 http://www.grid2002.org • We have designed and built a messaging infrastructure NaradaBrokering embodying some of these ideas • We have shown interoperability between JXTA (Sun’s P2P environment), Java Message Service (JMS) and NaradaBrokering • We have deployed a classic (Placeware, Interwise, WebEx) synchronous collaboration environment (Garnet) using JMS or Narada (uses Anabas technology) • We have illustrated filtering/universal access by linking PDA’s to desktop collaboration • We have prototyped audio-video conferencing as a web service • We are repackaging collaborative SVG as a Web service to illustrate (explore) how wonderful it will be when all applications are Collaborative Web services • We have started HPSearch Internet Scripting Language project using “search” as access mechanism to web resources uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

5. So what are we doing II? • We have some “Architecture of Computing Portals” including concept of Grid Shell • We are building a “Application Web service toolkit” to allow any application to be made a Web service (this only manipulates metadata) • Aimed at support of classic Grid applications running on a backend supercomputer • This gives Computing Portals for various applications • We are building Jetspeed portlets of various types – including collaborative • We have thought about integration of XML with more traditional information resources and designed some XML news group technology which uses news group interface to support management and browsing of multiple XML information nuggets (instances) of general Schema • Supported by JMS/NaradaBorokering • Wizard generates interfaces to define nuggets • JSP wizard layout and browsing specification defined by annotating Schema • We continue work on HPJava (parallel computing in Java) uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

6. Database Database Classic Grid Architecture Resources Content Access Composition Middle TierBrokers Service Providers Netsolve Security Collaboration Computing Middle Tier becomes Web Services Clients Users and Devices uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

7. WSDL Application orContent source Web Service Web Services in a Nutshell • Web Services codify a clear process for deploying distributed software components representing • Data and Information Sources (Sensors, Databases) • Computers • Application Software • Learning Services like “Submit Homework”, “Grade” • System services (OGSA Open Grid Service Architecture) • Distributed Message Passing Model • We should be in some process of dividing applications (including e-learning) into components and giving them an XML “skin” defining input and output ports (data, remote procedure calls) • WSDL Web Service Definition Language Ports: Messages to and fromother web services, resourcesor users uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

8. Different Web Service Organizations • Everything is a resource (distributed object)implemented as a Web Service, whether it be: • back end supercomputers and a petabyte dataset • Microsoft PowerPoint and this file • Web Services communicate by messages ….. • Web Services are “just distributed objects” with focus on (particular) XML specified input and output messages • Grids and Peer to Peer (P2P) networks can be integrated by building both in terms of Web Services with different (or in fact sometimes the same) implementations of core services such as registration, discovery, life-cycle, collaboration and event or message transport ….. • Gives a Peer-to-Peer Grid • Roughly but not completely consistent with OGSA • Consistent with “rule”: build everything as a Web service uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

9. Database Database Event/MessageBrokers Event/MessageBrokers Event/MessageBrokers Peer to Peer Grid Peers Service FacingWeb Service Interfaces Peers User FacingWeb Service Interfaces A democratic organization Peer to Peer Grid uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

10. Education as a Web Service • “Learning Object” XML standards already exist from IMS/ADL http://www.adlnet.org – need to update architecture • Web Services for virtual university include: • Registration • Performance (grading) • Authoring of Curriculum • Online laboratories for real and virtual instruments • Homework submission • Quizzesof various types (multiple choice, random parameters) • Assessment data access and analysis • Synchronous Delivery of Curricula including Audio/Video Conferencing and other synchronous collaborative tools as Web Services • Scheduling of courses and mentoring sessions • Asynchronous access, data-mining and knowledge discovery • Learning Plan agents to guide students and teachers uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

11. Collaboration and Web Services • Collaboration has • Mechanism to set up members (people, devices) of a “collaborative sessions” • Shared generic tools such as text chat, white boards, audio-video conferencing • Shared applications such as Web Pages, PowerPoint, Visualization • b) and c) are “just shared objects” where objects could be Web Services but rarely are at moment • We can port objects to Web Services and build a general approach for making Web services collaborative • a) is a “Service” which is set up in many different ways (H323 SIP JXTA are standards supported by multiple implementations) – we can make it a WS quite easily uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

12. Web Service Architecturefor Audio Video Conferencing uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

13. XGSP: Introduction Collaboration as a WS • Registration Method registration server with its alias name and current location • Session Command Method Membership Control Commands, Session Control Commands • Query Method discover various properties about the system • Session Channel Binding Method (Specific to A/V) bind the RTP channels of a client into the media server uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

14. XGSP: Example <SessionDes> <SessionName> PervasiveTech Seminar </SessionName> <SessionID> 1234567 </SessionID> <SessionCreator> Ahmet@indiana.edu </SessionCreator> <SessionInfo> this is a meeting on the XGSP </SessionInfo> <SessionPlace> Lobby Room </SessionPlace> <SessionTime> <StartTime> (EastTime) 10:00AM </StartTime> <EndTime> (EastTime) 12:00AM </EndTime> </SessionTime> <SessionURI> http://grids.ucs.indiana.edu/~ag </SessionURI> <SessionParticipants> <Participant> Wenjun@156.56.103.129 </Participant> <Participant> Hasan@156.56.103.27 </Participant> <Participant> Shrideeper@156.56.103.111 </Participant> </SessionParticipants> <ContactInfo> wewu@indiana.edu </ContactInfo> </SessionDes> uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

15. Linking Clientsand Servers Current ImplementationPolycom (H323) Access Grid Admire (Chinese system Similar to AG)and HearMe SIP VOIPIntegration Future ProjectLink Proprietary MCU’s Illustrated for SIP (HearMe)and Access Grid Current linkage for Clients not servers uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

16. Current Status • XGSP Specification stable • Demo prototype of Polycom (H323), Access Grid, Admire, HearMe clients • H323 Gateway based on openh323 JMF (Java Media Framework) used for Media Server XGSP used Internally between audio, video and session control services Codec negotiation supported (No XGSP clients yet) Narada UDP Communication has been successfully tested XGSP MCU (Control) User Interface uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

17. H323 Client (Polycom) in XGSP Session uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

18. Comparison with other approaches uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

19. Possible A/V Web Service Futures • Productize Narada Integration – needs more testing of Narada multi-protocol interface • Will this defeat firewalls that currently spoil my lectures? • Integrate video codec shared display system with classic bimap shared display with dynamic choice • Session Control Server can be used to define collaborative sessions for other shared applications • Text chat etc. • Shared SVG, StarOffice, Internet Explorer, Word etc. (using “.net” event interface) • Integrate with JXTA interface using Narada-JXTA link • Add RealMedia (Windows Media) SIP (VOIP) and native XGSP clients • Integrate at server (MCU) level for Polycom, AccessGrid, VOIP – this is Federation uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

20. Personal View of Collaborative Systems • Originally (at Syracuse) built a collaborative environment Tango and used for online lectures and training sessions from 1997-2001 (2001 updated system) • Functionality fine but browser interface and network produced instability • Hard to build custom collaborative applications • Newer simpler (Garnet/Anabas) system addresses these issues although network issues still being addressed • Use of XML meta-data and building Education or e-learning as a set of Web Services gives interoperability • Use of Grid (as from IBM)and peer-to-peer technology will give improved infrastructure (still quiteprimitive) uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

21. Courses at Jackson State • Taught using Tango/Garnet since fall 97 over Internet twice a week from Syracuse/FSU/Indiana • Course material same style as online material for in-university classes • Curricula, Homework, Grading, Facilities done by “me” • Students get JSU NOT Syracuse/Indiana Credit • “Trivial” in that learning model identical to that in traditional courses – just changed interaction mode • Jackson State major MSI (Minority Serving) University with many computer science graduates • Do not compete with base courses but offer addon courses with “leading edge” material (Web Technology, modern scientific computing) which give JSU (under)graduates skills that are important in their career • Fall 99 Semester CPS640 offered to 40 students in 5 distant places and separately 40 at Syracuse uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

22. Lessons from Past • “True” Shared Event flexible but too much work for most cases • Shared Display – nearly always works • Shared Export – SVG PDF HTML X3D etc. can be re-used • Integrate synchronous and asynchronous collaboration • Do not build into browser as not a reliable or standard virtual machine • Build around uniform publish-subscribe style XML Event Model supporting archiving, customization, filtering – apply to all collaboration modes • Later we realized need to integrate with Peer to Peer and Web Services (straightforward as XML event model fits these architectures) uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

23. What is meant to Happen • One uses IMS/ADL to define all needed properties in XML • Such as Title of page; Address of student etc. • Ignore those sensitive to architecture; • add some XML specifications such as those to define collaborative sessions • One needs “automation”/”support tools” for process of generating meta-data • Such as prerequisites for courses; Author of web page etc. • One uses conventional authoring tools to build curricula • Uses portal technology to integrate user-interfaces to multiple Web Services • Unfortunately open approach not used in current • Hopefully industry will build needed tools as Web services and interoperability will allow picking and choosing between vendors rather than use of monolithic systems • LMS or Learning Management Systems • LCMS or Learning Content Management Systems (Use non education specific system) • Authoring/Portals (I think it is best NOT to use education specific tools) • Collaborative Environments (shared applications) • Audio-Video Conferencing uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

24. Current Status in a Nutshell • Systems such as Centra, WebEx, Garnetand Placeware offer similar functionality to our old system Tango for synchronous collaboration • Shared applications, chatroom, whiteboard, A/V conferencing • Blackboard, WebCT, Lotus offer learning management systems • Not very consistent with modern architectures but can be used effectively today • Access Grid (community e.g. classroom) and Polycom (etc.) are excellent audio-video systems • I develop research system Garnet for education portals • Features hand-held and desktop clients, integrated collaboration and some “technical advances” – major use of XML and publish/subscribe systems • Audio-Video Conferencing as a Web Service • Improving network robustness including firewall tolerance uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

25. Commercial CollaborationSystems Centra Anabas WebEx Placeware uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

26. Learning Objects • Given changing technology, need standards to protect investment in authoring and administrative data generated and stored in databases • Education community has unusually good set of community standards • Educational Environment Educause set up IMS – http://www.imsproject.org Instructional Management System with selection of companies and universities • IMS focus was changed to drop implementation work and is now “Global Learning Consortium” Inc. • Department of Defense (which has huge training needs) set up ADL Advanced Distributed Learning Initiative • www.adlnet.org whose links section includes all other useful URL’s • IEEE (Computing Community) set up P1484 Learning Technology Standards Committee LTSC uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

27. LearningServer Content Server(s) External systems: “Learning HR, E-Commerce, ERP... Management Course Interchange: System” Course LMS Structure Format (CSF), Metadata Migration Adapter Critical InterchangeCapability Services or Adapter Learning Server Server Adapter Server Side Runtime Client Side Environment: Client Launch, API, Browser Data Model AntiquatedArchitecture API Adapter Application HTML+ LMS Model used by ADL uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

28. Properties of Learning Objects • Metadata from IEEE and IMS • Roughly Properties of educational objects thought of as “documents” (author, title …) • Course Packaging, Digital Repositories from SCORM and IMS • How to form bigger units of instruction from smaller units • Called Content Packaging by IMS and Course Structure Format (CSF) by SCORM which goes in greater depth than IMS • Tests and Quizzes from IMS • Specialized CSF descriptors from SCORM (via CMI) • Such as objectives, prerequisites, completion requirements • LMS Runtime API from SCORM – I am doubtful about value • Enterprise Properties from IMS • Link to people and organization databases (training, human resource, library, student administration) • Learner Information Package from IMS • Name/Address, Goals, Skills, Grades etc. • “Competencies” from IMS • “Accessibility” (universal access guidelines) from IMS uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

29. Learning Management Systems • Most education and training stresses asynchronous or web support for conventional delivery • WebCT Blackboard Lotus(IBM) and others offer LMS systems with limited synchronous capability • Support typical educational needs like grading, quizzes, homework, glossaries, group email • Varying database backend and • Varying authoring support • Popular with colleges as supports not so expert faculty • DoD use less clear as need for homework and other tools less critical than for University classes • No built in support for areas like “programming labs” (VPL from NPAC did this) uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

30. Hierarchical Delivery Model • One could teach to 1000 different students – each at a separate workstation but … • No real opportunity for questions so better to use broadcast technology – not conferencing • Further could better deliver to 40 classrooms – each with an average of 25 students • Each classroom has central high quality A/V conferencing, displays and • A Mentor monitoring and helping students • Each student could have wireless laptop or PDA • So synchronous systems must support simultaneously disparate clients – high end display to PC to PDA uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

31. Authoring of Curriculum • Possible Market pressures push to high end authoring • Authoring approaches for the Web can include • Basic HTML • Macromedia/Adobe/etc. packages like Fireworks, Dreamweaver, Illustrator • PowerPoint and Word exported • Also can include RealNetworks or Microsoft or .. format Multimedia • Note Streaming multimedia formats have larger buffers than A/V conferencing formats • Certainly use XML to specify content and render this into attractive portal • SVG and SMIL are important 2D vector graphics and multimedia standards • HTMLdoes not give reproducible pages • Flash can be thought of as “proprietary SVG” uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

32. Application as a WSGeneral Application PortsInterface with other WebServices WSDL W S Application orContent source R P Web Service User Face ofWeb ServiceWSRP Ports define WS as a Portlet Web Services as a Portlet • Each Web Service naturally has a user interface specified as “just another port” • Customizable for universal access • This gives each Web Service a Portlet view specified (in XML as always) by WSRP (Web services for Remote Portals) • So component model for resources “automatically” gives a component model for user interfaces • When you build your application, you define portletat same time WSRP isWeb Services for Remote Portals1st Meeting OASIS March 18 2002 uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

33. WSDL W S Application orContent source R P ClientRender Web Service Integration of Portlets • Portals integrate Portlets into a complete user interface • Apache Jetspeed seems good open source technology supporting this model Application as a WSGeneral Application PortsInterface with other WebServices PortalUser ProfileAggregateUI Fragments Integrate Multiple Portlets User Customizationat either Portal or if complicated at WS User Face ofWeb ServiceWSRP Ports define WS as a Portlet uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

34. Online Knowledge Center built from Portlets A set of UIComponents • Web Services provide a component model for the middleware (see large “common component architecture” effort in Dept. of Energy) • Should match each WSDL component with a corresponding user interface component • Thus one “must use” a component model for the portal with again an XML specification (portalML) of portal component uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

35. 4 available portletslinking to Web ServicesI choose two Jetspeed Computing Portal: Choose Portlets uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

36. uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

37. Object Viewer Object Display Object Object’ Object’’ Collaboration: Shared Display • Sharing can be done at any point on “object” or Web Service pipeline Shared Web Service SharedDisplay Shared Export Shared Event Master Shared Display shares framebuffer with eventscorresponding to changedpixels in master client. Event(Message)Service Object Display As long as pipeline uses messages, easy tomake collaborativeWindows framebuffers and in fact most applications do NOT expose a message based update interface Object Display uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

38. R R R U U U WSViewer WSDisplay F F F F F F I I I I I I WebService WebService WebService O O O O O O WS Viewer WS Display WS Viewer WSDisplay Shared Input Port (Replicated WS) Collaboration Collaboration as a WSSet up Session with XGSP Master Event(Message)Service OtherParticipants uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

39. Shared Output Port Collaboration WSDL R U Application orContent source F F WSViewer WSDisplay I I O O Web Service Collaboration as a WSSet up Session with XGSP Web Service Message Interceptor Master WS Viewer WS Display Text Chat Whiteboard Multiple masters Event(Message)Service OtherParticipants WS Viewer WSDisplay uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

40. NaradaBrokering • Based on a network of cooperating broker nodes • Cluster based architecture allows system to scale to arbitrary size • Originally designed to provide uniform software multicast to support real-time collaboration linked to publish-subscribe for asynchronous systems. • Now has four major core functions • Message transport (based on performance measurement) in heterogeneous multi-link fashion • General publish-subscribe including JMS & JXTA and support for RTP-based audio/video conferencing • Filtering for heterogeneous clients • Federation of multiple instances of Grid services uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

41. Role of Event/Message Brokers • We will use events and messages interchangeably • An event is a time stamped message • Our systems are built from clients, servers and “event brokers” • These are logical functions – a given computer can have one or more of these functions • In P2P networks, computers typically multifunction; in Grids one tends to have separate function computers • Event Brokers “just” provide message/event services; servers provide traditional distributed object services as Web services • There are functionalities that only depend on event itself and perhaps the data format; they do not depend on details of application and can be shared among several applications • NaradaBrokering is designed to provide these functionalities • MPI provided such functionalities for all parallel computing uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

42. Engineering Issues Addressedby Event / Messaging Service • Application level Quality of Service – e.g. give audio highest priority • Tunnel through firewalls & proxies • Filter messages to slow (collaborative/real-time) clients • Choose Hardware or Software multicast • Scaling of software multicast • Efficient calculation of destinations and routes. • Integrate synchronous and asynchronous collaboration with same messaging, control, archiving for all functions • Supports local broker accesses • Transparently replace single server JMS systems with a distributed solution. • Provides reliable inter-peer group messaging for JXTA uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

43. Destination Source Matching Routing Filter workflow Web Service 1 Web Service 2 (Virtual)Queue WSDLPorts WSDLPorts Broker NaradaBrokering implements an Event Service • Filter is mapping to PDA or slow communication channel (universal access) – see our PDA adaptor • Workflow implements message process • Routing illustrated by JXTA and includes firewall • Destination-Source matching illustrated by JMS using Publish-Subscribe mechanism • These use Security model (being designed) based on WS-Sec uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

44. Features of Event Service • MPI nowadays aims at a microsecond latency • The Event Web Service aims at a millisecond (computer) latency • Typical distributed system travel times are many milliseconds (to seconds for Geosynchronous satellites) • Different performance/functionality trade-off • Messages are not sent directly from P to S but rather from P to Broker B and from Broker B (via other brokers) to subscriber S. • Synchronous systems: B acts as a real-time router/filterer • Messages can be archived and software multicast • Asynchronous systems: B acts as a database & workflow engine • Subscription is in each case, roughly equivalent to a database query • Company X sets up a firewall • The event service sets up brokers either side of firewall to optimize transport through the firewall. uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

45. Data base Narada Broker Network (P2P) Community For message/events service Broker Broker (P2P) Community Resource Hypercube topology for brokers? Tree for distance education with teacher at root Broker Broker Broker (P2P) Community Software multicast Broker (P2P) Community uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

46. FastLink FirewallHTTP B1 SatelliteUDP A Hand-HeldProtocol Software Multicast Dial-upFilter Performance in Message-based Architecture I • Useful analogies with transportation gridsand parallel computing • In traveling from cities A to B (say 3 separate passengers), one chooses between and changes transport mechanism at waystations to optimize cost, time, comfort, scenic beauty … • Waystations are now NB brokers where one chooses transport protocol • Able to choose between car, type of car, plane, train etc • Able to dynamically create waystations to cope with problems and acts as hubs for multicast messages • Knows about traffic jams and can assign the “HOV lane” B2 B3 uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

47. Performance in Message-based Architecture II • Application level QoS – can optimize among managed streams (audio versus video) using performance subsystem • This is just a variant of the NP complete load balancing problem of parallel computing where all reasonable heuristics worked • Load-balance in Space-time (strings) not just Space (particles) • “Performance” needs to measured carefully as includes QoS • I delayed shared application update to ensure audio quality and filtered image to lower resolution • So “application” has changed to satisfy performance constraints uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

48. NaradaBrokering Communication • Applications interface to NaradaBrokering through UserChannels which NB constructs as a set of links between NB Broker waystations which may need to be dynamically instantiated • UserChannels have publish/subscribe semantics with XML topics • Links implement a single conventional “data” protocol. • Interface to add new transport protocols within the Framework • Administrative channel negotiates the best available communication protocol for each link • Different links can have different underlying transport implementations • Implementations in the current release include support for TCP,UDP, Multicast, SSL and RTP. HTTP, HTTPS support will be available in Feb 2003 release. • Supports communication through proxies such as iPlanet, Netscape and Apache. • Supports communication through firewalls such as Microsoft ISA, Checkpoint. uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

49. Note on Optimization • Note in parallel computing, couldn’t do much dynamic optimization as aiming at microsecond latency • Natural to use hardware routing • In 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” • Jitter in latency (transit time) due to routing, processing (in NB) or packet loss recovery is important property • Grid needs and can tolerate significant dynamic optimization uri="http://www.naradabrokering.org" email="gcf@indiana.edu"

50. Sender/receiver/broker - (Pentium-3, 1 GHz, 256 MB RAM). 100 Mbps LAN. JDK-1.3, Red Hat Linux 7.3 uri="http://www.naradabrokering.org" email="gcf@indiana.edu"