Architecture of Web Service Grids

Architecture o

Web Service Grids

Beijing

Chinese Academy of Sciences

August 28 2004

Geoffrey Fox

Community Grids Lab

Indiana University

Philosophy of Web Service Grids

•

Much of Distributed Computing was built by natural

extensions of computing models developed for sequential

machines

•

This leads to the

distributed object

(DO) model represented

by Java and

CORBA

– RPC (Remote Procedure Call) or RMI (Remote Method Invocation) for Java

•

Key people think this is not a good idea as it scales badly

and ties distributed entities together too tightly

– Distributed Objects Replaced by Services

•

Note

CORBA

was considered too complicated in both

organization and proposed infrastructure

– and Java was considered as “tightly coupled to Sun” – So there were other reasons to discard

Web services

•

Web Services

build

loosely-coupled,

distributed applications,

based on the

SOA

principles.

•

Web Services interact

by exchanging

messages in

SOAP

format

•

The contracts for the

message exchanges that

implement those

interactions are

described via

WSDL

What is a Grid?

•

You won’t find a clear description of what is Grid and how

does

differ

from a

collection of Web Services

– I see no essential reason that Grid Services have different requirements than Web Services

– Geoffrey Fox, David Walker, e-Science Gap Analysis, June 30 2003. Report UKeS-2003-01,

http://www.nesc.ac.uk/technical_papers/UKeS-2003-01/index.html.

– Notice “service-building model” is like programming language – very personal!

•

Grids were once defined as “

Internet Scale Distributed

Computing

” but this isn’t good as Grids depend as much if

not more on data as well as simulations

e-Infrastructure

 e-Infrastructure builds on the inevitable increasing performance

of networks and computers linking them together to support new flexible linkages between computers, data systems and people

• Grids and peer-to-peer networks are the technologies that build e-Infrastructure

• e-Infrastructure called CyberInfrastructure in USA

 We imagine a sea of conventional local or global connections

supported by the “ordinary Internet”

• Phones, web page accesses, plane trips, hallway conversations

• Conventional Internet technology manages billions of

broadcast or low (one client to Server) or broadcast links

 On this we superimpose high value multi-way organizations

(linkages) supported by Grids with optimized resources and system support

• Low multiplicity fully interactive real-time sessions

N plus N Community Resources

 Grid Community databases have analogy to Television and the

News Web that allow individuals to communicate instantly with each other via Web Pages and Headline News acting as proxies

Large and Small Grids

 N resources in a community (N is billions for the world and

1000-10000 for many scientific fields)

 Communities are arranged hierarchically with real work being

done in “groups” of M resources – M could be 10-100 in e-Science

 Metcalfe’s law: value of network grows like square of number of

nodes M – we call Grids where this true Metcalfe or M2 _Grids

 Nature of Interaction depends on size of M or N

• N plus N Shared Information Grids for largish N

• M2 _{Metcalfe Grids for smaller M < N}

 Technology support depends on M/N – might use a relatively

static DHT (Distributed Hash Table) for large N and a distributed shared memory for small M

 Grids must merge with peer-to-peer networks to support both N

M

2

_Interactions

• Superimpose M way “Grids” on the sea

(heatbath) of “2 by N” or N plus N

“ordinary” interactions

Implement Grid as a softwar

Information Gri

Enterprise Gri

Compute Grid

Campus Grid R2 R1

Teacher

Students

Dynamic light-weight Peer-to-peer

Collaboration Training Grid

Architecture of (Web Service) Grids



Grids built from

Web Services

communicating through

an overlay network built in SOFTWARE on the

“ordinary internet” at the application level



Grids provide the

special quality of service

(security,

performance, fault-tolerance) and customized services

needed for “distributed complex enterprises”



We need to work with Web Service community as they

debate the 60 or so proposed Web Service specifications

• Use Web Service Interoperability WS-I as “best practice”

• Must add further specifications to support high performance

• Database “Grid Services” for N plus N case

Web Services

• Java is very powerful partly due to its many “frameworks” that generalize libraries e.g.

– Java Media Framework

– Java Database Connectivity JDBC

• Web Services have a correspondingly collections of specifications that represent critical features of the distributed operating systems for “Grids of Simple Services”

– Some 60 active WS-* specifications for areas such as – a. Core Infrastructure Specifications

– b. Service Discovery

– c. Security

– d. Messaging

– e. Notification

– f. Workflow and Coordination

– g. Characteristics

– h. Metadata and State

A List of Web Services I

• a) Core Service Architecture

• XSD XML Schema (W3C Recommendation) V1.0 February 1998, V1.1 February 2004

• WSDL 1.1 Web Services Description Language Version 1.1, (W3C note) March 2001

• WSDL 2.0 Web Services Description Language Version 2.0, (W3C under development) March 2004

• SOAP 1.1 (W3C Note) V1.1 Note May 2000

• SOAP 1.2 (W3C Recommendation) June 24 2003

• b) Service Discovery

• UDDI (Broadly Supported OASIS Standard) V3 August 2003

• WS-Discovery Web services Dynamic Discovery (Microsoft, BEA, Intel …) February 2004

• WS-IL Web Services Inspection Language, (IBM, Microsoft)

A List of Web Services II

• c) Security

• SAML Security Assertion Markup Language (OASIS) V1.1 May 2004

• XACML eXtensible Access Control Markup Language (OASIS) V1.0 February 2003

• WS-Security 2004 Web Services Security: SOAP Message Security (OASIS) Standard March 2004

• WS-SecurityPolicy Web Services Security Policy (IBM, Microsoft, RSA, Verisign) Draft December 2002

• WS-Trust Web Services Trust Language (BEA, IBM, Microsoft, RSA, Verisign …) May 2004

• WS-SecureConversation Web Services Secure Conversation Language (BEA, IBM, Microsoft, RSA, Verisign …) May 2004

A List of Web Services III

• d) Messaging

• WS-Addressing Web Services Addressing (BEA, IBM, Microsoft)

March 2004

• WS-MessageDelivery Web Services Message Delivery (W3C Submission by Oracle, Sun ..) April 2004

• WS-Routing Web Services Routing Protocol (Microsoft) October 2001

• WS-RM Web Services Reliable Messaging (BEA, IBM, Microsoft, Tibco) v0.992 March 2004

• WS-Reliability Web Services Reliable Messaging (OASIS Web Services Reliable Messaging TC) March 2004

• SOAP MOTM SOAP Message Transmission Optimization Mechanism (W3C) June 2004

• e) Notification

• WS-Eventing Web Services Eventing (BEA, Microsoft, TIBCO)

January 2004

• WS-Notification Framework for Web Services Notification with WS-Topics, WS-BaseNotification, and WS-BrokeredNotification (OASIS) OASIS Web Services Notification TC Set up March 2004

A List of Web Services IV

• f) Coordination and Workflow, Transactions and Contextualization

• WS-CAF Web Services Composite Application Framework including WS-CTX,

WS-CF and WS-TXM below (OASIS Web Services Composite Application Framework TC) July 2003

• WS-CTX Web Services Context (OASIS Web Services Composite Application Framework TC) V1.0 July 2003

• WS-CF Web Services Coordination Framework (OASIS Web Services Composite Application Framework TC) V1.0 July 2003

• WS-TXM Web Services Transaction Management (OASIS Web Services Composite Application Framework TC) V1.0 July 2003

• WS-Coordination Web Services Coordination (BEA, IBM, Microsoft) September 2003

• WS-AtomicTransaction Web Services Atomic Transaction (BEA, IBM, Microsoft) September 2003

• WS-BusinessActivity Web Services Business Activity Framework (BEA, IBM, Microsoft) January 2004

• BTP Business Transaction Protocol (OASIS) May 2002 with V1.0.9.1 May 2004

• BPEL Business Process Execution Language for Web Services (OASIS) V1.1 May 2003

• WS-Choreography (W3C) V1.0 Working Draft April 2004

• WSCI (W3C) Web Service Choreography Interface V1.0 (W3C Note from BEA, Intalio, SAP, Sun, Yahoo)

A List of Web Services V

• h) Metadata and State

• RDF Resource Description Framework (W3C) Set of recommendations expanded from original February 1999 standard

• DAML+OIL combining DAML (Darpa Agent Markup Language) and OIL (Ontology Inference Layer) (W3C) Note December 2001

• OWL Web Ontology Language (W3C) Recommendation February 2004

• WS-DistributedManagement Web Services Distributed Management Framework with MUWS and MOWS below (OASIS)

• WSDM-MUWS Web Services Distributed Management: Management Using Web Services (OASIS) V0.5 Committee Draft April 2004

• WSDM-MOWS Web Services Distributed Management: Management of Web Services (OASIS) V0.5 Committee Draft April 2004

• WS-MetadataExchange Web Services Metadata Exchange (BEA,IBM, Microsoft, SAP) March 2004

• WS-RF Web Services Resource Framework including WS-ResourceProperties,

WS-ResourceLifetime, WS-RenewableReferences, WS-ServiceGroup, and

WS-BaseFaults (OASIS) Oasis TC set up April 2004 and V1.1 Framework March 2004

• ASAP Asynchronous Service Access Protocol (OASIS) with V1.0 working draft G June 2004

A List of Web Services VI

•

g) General Service Characteristics

•

WS-Policy

Web Services Policy Framework (BEA, IBM,

Microsoft, SAP)

May 2003

•

WS-PolicyAssertions

Web Services Policy Assertions

Language (BEA, IBM, Microsoft, SAP)

May 2003

•

WS-Agreement

Web Services Agreement Specification

(GGF under development)

May

2004

•

i) User Interfaces

•

WSRP

Web Services for Remote Portlets (OASIS)

OASIS Standard

August 2003

Importance of SOAP

• SOAP defines a very obvious message structure

with a

header

and a

body

• The

header

contains information used by the

“

Internet operating system

”

–

Destination, Source, Routing, Context, Sequence

Number …

• The

message body

is only used by the

application

and will never be looked at by “operating system”

except to encrypt, compress it etc.

• Much discussion in field revolves around

what is in

header!

WS-I Interoperability

•

Critical underpinning of Grids and Web Services is the

gradually growing set of specifications in the Web Service

Interoperability Profiles

•

Web Services Interoperability

(WS-I) Interoperability

Profile 1.0a." h

ttp://www.ws-i.org.

gives us

XSD,

WSDL1.1, SOAP1.1, UDDI

in basic profile and parts of

WS-Security

in their first security profile.

•

We imagine the “60 Specifications” being checked out

and evolved in the

cauldron of the real world

and

occasionally best practice identifies a new specification to

be added to

WS-I

which

gradually increases in scope

Web Services Grids and WS-I+

• WS-I Interoperability doesn’t cover all the capabilities need to support Grids

• WS-I+ is designed to minimal extension of WS-I to support “most current” Grids: it adds support for

– Enhanced SOAP Addressing (WS-Addressing) – Fault tolerant (reliable) messaging

– Workflow as in IBM-Microsoft standard BPEL

• Security and Notification best practice and support will probably get added soon

– There are Web Service frameworks here but various IBM v Microsoft v Globus differences to be resolved

• Portlet-based User Interfaces could be added

• UK OMII Open Middleware Infrastructure Institute is adopting this approach to support UK e-Science program

– Currently UK e-Science largely either uses GT2 (as in EDG) or Simple Web Services for “database Grids”

Bit

level

Internet

(OSI

Stack)

Layered Architecture for Web Services and Grids

Base Hosting Environment

Protocol HTTP FTP DNS …

Presentation XDR …

Session SSH …

Transport TCP UDP …

Network IP …

Data Link / Physical

Servic Internet

Application Specific Grids

Generally Useful Services and Grids

Workflow WSFL/BPEL

Service Management (“Context etc.”)

Service Discovery (UDDI) / Information

Service Internet Transport



Protocol

Service Interfaces WSDL

Servic Context

Higher Level

Working up from the Bottom

 We have the classic (CISCO, Juniper ….) Internet routing the

flood of ordinary packets in OSI stack architecture

 Web Services build the “Service Internet” or IOI (Internet on

Internet) with

• Routing via WS-Addressing not IP header

• Fault Tolerance (WS-RM not TCP)

• Security (WS-Security/SecureConversation not IPSec/SSL)

• Information Services (UDDI/WS-Context not DNS/Configuration files)

• At message/web service level and not packet/IP address level

 Software-based Service Internet possible as computers “fast”  Familiar from Peer-to-peer networks and built as a software

overlay network defining Grid (analogy is VPN)

 SOAP Header contains all information needed for the “Service

Consequences of Rule of the Millisecond

•

Useful to remember

critical time scales

–

1)

0.000001 ms

– CPU does a calculation

–

2a)

0.001 to 0.01 ms

– Parallel Computing MPI latency

–

2b)

0.001 to 0.01 ms

– Overhead of a Method Call

–

3)

1 ms

– wake-up a thread or process

–

4)

10 to 1000 ms

– Internet delay

•

2a), 4) implies geographically distributed

metacomputing

can’t in general compete with parallel systems

•

3) << 4) implies a software overlay network is possible

without significant overhead

–

We need to explain why it adds value of course!

•

2b) versus 3) and 4) describes regions where

method

and

Linking Modules

n

From method based to RPC to message based to event-based

publish-subscribe Message Oriented Middleware

Module A Module

B

Method Call .001 to 1 millisecond

Service A Service

B Message_s

0.1 to 1000 millisecond latency

Coarse Grain Service Model

Closely coupled Java/Python …

Service B Service A

Publisher Post Events “Listener

Subscribe to Events

What is a Simple Service?

– We can implement each functionality as an independent distributed service

– Or we can bundle multiple functionalities in a single service • Whether functionality is an independent service or one of many

method calls into a “glob of software”, we can always make them as Web services by converting interface to WSDL

• Simple services are gotten by taking functionalities and making as small as possible subject to “rule of millisecond”

– Distributed services incur messaging overhead of one (local) to

100’s (far apart) of milliseconds to use message rather than method call

– Use scripting or compiled integration of functionalities ONLY when require <1 millisecond interaction latency

• Apache web site has many projects that are multiple functionalities presented as (Java) globs and NOT (Java) Simple Services

Grids of Grids of Simple Services

• Link via methods  messages  streams • Services and Grids are linked by messages

• Internally to service, functionalities are linked by methods • A simple service is the smallest Grid

• We are familiar with method-linked hierarch

Lines of Code  Methods  Objects  Programs  Packages

Overlay and Compose

Grids of Grids Methods Services Component Grids

CPUs Clusters Compute

Resource Grids MPPs

Databases _DatabasesFederated

Sensor Sensor Nets

Data

Component Grids?

• So we build collections of Web Services which we

package as

component Grids

–

Visualization Grid

–

Sensor Grid

–

Utility Computing Grid

–

Person (Community) Grid

–

Earthquake Simulation Grid

–

Control Room Grid

–

Crisis Management Grid

• We build bigger Grids by

composing component

Critical Infrastructure (CI) Grids built as Grids of Grids

Gas Service and Filters

Physical Network Registr

y Metadata

Flood Service and Filters

Flood CIGrid

_…

CIGrid

…

Data

Access/Storage Securit

y Notification Workflow Messaging Portal

s Visualization_Grid Collaboration

Grid

Sensor Grid Compute

Grid GIS Grid

Database Database Analysis and Visualizatio Portal Repositorie Federated Databases Data Filte Services

Field Trip Data

Streaming Data Sensor s

?

Geoscience Research and Education Grids

GI Grid

Sensor Grid Database Grid

IOI and CIE

• Let us study the two layers IOI (Service Internet On the Bit Internet) and CIE (Context and Information Environment)

• IOI is most “straightforward” as it is providing reasonably well understood capabilities at a new “level”

• CIE is roughly the inter-service “shared memory” used to manage and control them at “distributed operating system level

– Critical is “shared” (a database service) versus message based CIE

IOI

Application Specific Grids

Generally Useful Services and Grids

Workflow WSFL/BPEL

Service Management (“Context etc.”)

Service Discovery (UDDI) / Information

Service Internet Transport



Protocol

Service Interfaces WSDL

CIE Higher Level

Minicompute r Firewall Compute r Serve r PDA Mode m Laptop computer Workstatio n Peer s Peer s Audio/Video Conferencing Client Audio/Video Conferencing Client NaradaBrokering Broker Network

NaradaBrokering

Web Service B

Stream

Server-enhance Messaging

NB supports messages and streams

Prototype implementation of WS-ReliableMessaging Web Service reliability

NaradaBrokering enhanced Grid-FTP. Bridge to the Globus TK3. Grid Application Support

Java Message Service (JMS) 1.0.2b compliant Support for routing P2P JXTA interactions. Messaging Related

Compliance

Compression and Decompression of payloads Fragmentation a nd Coalescing of payloads Message Payload options

Message-level WS-Security compatible security Security

Recovery from failures and disconnects. Replay of events/messages at any time. Recovery and Replay

Producer Order and Total Order over a message type

Time Ordered delivery using Grid-wide NTP based absolute time Ordered delivery

Robust and exactly-once delivery of messages in presence of failures

Reliable delivery

Subscription can be Strings, Integers, XPath queries, Regular Expressions, SQL and tag=value pairs.

Subscription Formats

Transport protocols supported include TCP, Parallel TCP streams, UDP, Multicast, SSL, HTTP and HTTPS.

Communications through authenticating proxies/firewalls & NATs. Network QoS based Routing

Multiple transport support In publish-subscribe

Paradigm with different Protocols on each link

NaradaBrokering and IOI

• Support for Multiple Transport protocols • Support for multiple delivery mechanisms

– Reliable Delivery

– Exactly-once Delivery – Ordered Delivery

– Optional Delivery optimization modules for different modes • Compression/Decompression of payloads with optional module • Coalescing/Fragmentation of payloads with optional module • NTP Time Service

• Security Service

• Performance Monitoring

• Performance optimized routing with optional module

Virtualizing Communication

n Communication specified in terms of user goal and Quality of

Service – not in choice of port number and protocol

n Bit Internet Protocols have become overloaded e.g. MUST use

UDP for A/V latency requirements but CAN’t use UDP as firewall will not support ………

n A given “Service Internet” communication can involve multiple

transport protocols and multiple destinations – the latter possibly determined dynamically

Dial-u Filter Satellit

UDP

Firewal HTTP

A

B1

Hand-Hel Protocol Fas

Link

Software Multicast B2

B3

Performance Monitoring

n

Every broker

incorporates a

Monitoring service

that

monitors links

originating from the node.

n

Every link measures and exposes a set of

metrics

• Average delays, jitters, loss rates, throughput.

n

Individual links can

disable

measurements for

individual or the entire set of metrics.

n

Measurement

intervals can

also be varied

n

Monitoring Service,

returns measured

metrics to

Pentium-3, 1GHz, 256 MB RAM

100 Mbps LAN

JRE 1.3 Linux

hop-3 0 1 2 3 4 5 6 7 8 9 100 1000 Transit Delay (Milliseconds)

Message Payload Size (Bytes)

Mean transit delay for message samples in NaradaBrokering: Different communication hops

hop-2

NaradaBrokering Service Integration

S1 P1 P2 S2

S1 _S2

Proxy Messaging

Handler Messaging

S? Service _{P? Proxy}

Transport Controlled by Overlay Network

Internal to Service: SOAP Handlers/Extensions/Plug-ins Java (JAX-RPC) .NET Indigo and special cases: PDA's gSOAP, Axis C++

Mechanisms for Reliable Messaging I

•

There are essentially sequence numbers on each message

•

Unreliable transmission detected by non-arrival of a

message with a particular sequence number

•

Remember this is “just some TCP reliability” built at

application level

•

One can either use ACK’s – Receiver (service B) positively

acknowledges messages when received

– Service A fully responsible for reliability

•

Or NAK’s – Service B is partially responsible and tracks

message numbers – sends a NAK if sequence number

missing

Service B Service A

Mechanisms for Reliable Messaging II

•

Each message has a retransmission time; messages are

retransmitted if ACK’s not received in time

– Uses some increasing time delay if retransmit fails

•

Note need to be informed (eventually) that OK to throw

away messages at sender; pure NAK insufficient

•

Note this is reliability from final end-point to beginning

end-point: TCP reliability is for each link and has different

grain size and less flexible reliability mechanisms

•

There are several efficiency issues

– Divide messages into groups and sequence within groups

– Do not ACK each message but rather sequences of messages

Custom Message Reliability

Narada Broker

Filter 1 Filter

2

WS-RM Wireless

Optimized WS-RM

WS-Reliability

2 second PDA reply latency!

Different endpoints may well need different

reliability schemes. Another reason to use application layer.

NaradaBrokering and Fault Tolerance

•

As well as reliable messaging, NaradaBrokering supports

performance based dynamic routing

– Choose both route and protocol (UDP, Parallel TCP ..)

•

It will also support automatic fail-over among replicated

services subscribing to same message stream

•

Provides scriptable control of streams for custom

management schemes

•

Saves ALL messages in faul

tolerant storage for eithe

session replay or recovery

•

Will support reliable

BitTorrent

P2P file swapping model

(better than GridFTP?)

Fast Web Service Communication I

• IOI Application level Internet allows one to optimize

message streams at the cost of “startup time”,

Web Services

can deliver the fastest possible interconnections

with or

without reliable messaging

• Typical results from Grossman (UIC) comparing Slow

SOAP over TCP with binary and UDP transport (latter

gains a factor of

1000

)

Pure SOAP SOAP over UDP Binary over UDP

Fast Web Service Communication II

• Mechanism only works for

streams

– sets of related

messages

• SOAP header in streams is constant

except for

sequence number (Message ID), time-stamp ..

• One needs two types of new Web Service

Specification

• “

WS-StreamNegotiation

” to define how one can use

WS-Policy to send messages at start of a stream to

define the methodology for treating remaining

messages in stream

Fast Web Service Communication III

•

Then use “WS-StreamNegotiation” to

negotiate stream

in

Tortoise SOAP – ASCII XML over HTTP and TCP –

–

Deposit basic SOAP header through connection – it is part of

context for stream (linking of 2 services)

–

Agree on firewall penetration, reliability mechanism, binary

representation and fast transport protocol

–

Naturally transport UDP plus WS-RM

•

Use “WS-FlexibleRepresentation” to define encoding of a

Fast

transport

(On a different port) with messages just having

“FlexibleRepresentationContextToken”, Sequence Number,

Time stamp if needed

–

RTP packets have essentially this structure

–

Could add stream termination status

•

Can monitor and control with original negotiation stream

CIE: Common Service Information and Metadata

– Workflow tells you how to specify service interaction but more basically there is shared information or context

specifying/controlling collection

• WS-RF and WS-GAF have different approaches to contextualization – supplying a common “context” which at its simplest is a token to represent state

• More generally core shared information includes dynamic service metadata and the equivalent of configuration information.

• One can supports such a common context either as pool of messages or as message-based access to a “database” (Context Service)

• Two services linked by a stream are perhaps simplest example of a collection of services needing context

• Note that there is a tension between storing metadata in messages and services.

Web Service Metadata and State I

•

The Semantic Grid and Semantic Web are important

frameworks for metadata but handicapped by lack of

“compelling” tools

•

RDF

Resource Description Framework (W3C) Set of

recommendations expanded from original February 1999

standard h

ttp://www.w3.org/RDF/

and the heart of the

Semantic Web and Grid h

ttp://www.semanticgrid.org

•

DAML+OIL

combining DAML (Darpa Agent Markup

Language) and OIL (Ontology Inference Layer) (W3C)

Note December 2001 ht

tp://www.w3.org/TR/daml+oil-reference

Web Service Metadata and State II

Management Framework with MUWS and MOWS below (OASIS) http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=wsdm

• Management includes issues like monitoring quality of service, enforcing service level agreements, controlling tasks and managing life-cycles.

• WSDM-MUWS Web Services Distributed Management:

Management Using Web Services (OASIS) V0.5 Committee Draft April 2004 ht

tp://www.oasis-open.org/committees/download.php/6234/cd-wsdm-muws-0.5.pdf • WSDM-MOWS Web Services Distributed Management:

Management of Web Services (OASIS) V0.5 Committee Draft April 2004 htt p://www.oasis-open.org/committees/download.php/6255/cd-wsdm-mows-0.5-20040402.pdf

• WS-MetadataExchange Web Services Metadata Exchange (BEA,IBM, Microsoft, SAP) March 2004 http

://www-106.ibm.com/developerworks/library/specification/ws-mex/

– Describes how metadata can be exchanged between services rather than by looking it up in registries like UDDI or higher level metadata catalogs; the old OGSI standard used such service-resident metadata extensively

Web Service Metadata and State III

ResourceProperties, ResourceLifetime,

WS-RenewableReferences, WS-ServiceGroup, and WS-BaseFaults

(OASIS)

http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=wsrf with Oasis TC set up April 2004 and V1.1 Framework March 2004 http://www-

106.ibm.com/developerworks/library/ws-resource/ws-modelingresources.pdf

– Uses rich metadata to define stateful interactions – its use of SOAP header creates interoperability problems

• ASAP Asynchronous Service Access Protocol (OASIS)

• http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=asap with V1.0 working draft G June 2004 htt

p://www.oasis-open.org/committees/download.php/7151/wd-asap-spec-01g.pdf – Another approach to issues discussed in WSDM and WSRF

• WS-GAF Web Service Grid Application Framework (Arjuna, Newcastle University) http://www.neresc.ac.uk/ws-gaf/

Database SDE SDE Servic e SDE SDE Servic e SDE SDE Servic e SDE SDE Servic e SDE SDE Servic e SDE SDE Servic e SDE SDE Servic e Individual Services Web Service Ports

Grid or Domain Specific Metadata Catalogs System or Federated Registry or Metadata

Catalog

Database1 Database2 Database3

Four Metadata Architectures

Messages

Stateful Interactions

•

There are (at least) four approaches to specifying

state

– OGSI use factories to generate separate services for each session in standard distributed object fashion

– Globus GT-4 and WSRF use metadata of a resource to identify state associated with particular session

– WS-GAF uses WS-Context to provide abstract context

defining state. Has strength and weakness that reveals less about nature of session

– WS-I+ “Pure Web Service” leaves state specification the application – e.g. put a context in the SOAP body

Explicit and Implicit Factories

• Stateful interactions are typified by amazon.com where messages carry correlation information allowing multiple messages to be linked together

– Amazon preserves state in this fashion which is in fact preserved in its database permanently

• Stateful services have state that can be queried outside a particular interaction

• Also note difference between implicit and explicit factories

– Some claim that implicit factories scale as each service manages its own instances and so do not need to worry about registering instances and lifetime management

Notification Architecture

• Point-to-Poin

• Or Brokere

• NaradaBrokering will support both WS-Eventing

and WS-Notification as well as Java Message

Service JMS that is Java Notification standard

Service B Service A

Bro

ker Publish

Subscribe

Queues Messages Supports creation and subscription of topics

Service B Service A

NaradaBrokering and NTP

• NaradaBrokering includes an implementation of the Network Time Protocol (NTP)

• All entities within the system use NTP to communicate with atomic time servers maintained by organizations like NIST and USNO to compute offsets

– Offset is the computed difference between global time and the local time.

– The offset is computed based on the time returned from multiple atomic time servers.

• The NTP algorithms weighs results from individual time clocks based on the distance of the atomic server from the entity.

• This ensures that all entities are within 1 millisecond of each other.

• The timestamps account for clock drifts that take place on machines

Collaboration and Web Services

n

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, maps, (medical) instruments ….

n

b)

and

c)

are “just shared objects” where objects

could be Web Services but rarely are at moment

approach for making Web services collaborative

n

a)

is a “Service” which is set up in many different

Shared Event Collaboration

n All collaboration is about sharing events defining state changes

• Audio/Video conferencing shares events specifying in

compressed form audio or video

• Shared display shares events corresponding to change in

pixels of a frame buffer

• Instant Messengers share updates to text message streams • Microsoft events for shared PowerPoint (file replicated

between clients) as in Access Grid

n Finite State Change NOT Finite State Machine architecture n Using Web services allows one to expose update events of all

kinds as message streams

n Need publish/subscribe approach to share messages (NB) plus n System to control “session” – who is collaborating and rules

• XGSP is XML protocol for controlling collaboration building

XGSP Web Service MCU Architecture

SIP H323 Access_Grid Native_XGSP Admire

Gateways convert to uniform XGSP Messaging

High Performance (RTP and XML/SOAP and ..

Media Servers

Filters Session Server

XGSP-based Control

NaradaBrokerin g

All Messaging

Use Multiple Media servers to scale to many codecs and many versions of audio/video mixing

NB Scales a distributed

We Services

Global-MMCS Community Grid

Service “MCU” which will scale to an arbitrary number of users and provide integrated thousands of simultaneous users

collaboration services.

n The function of A/V media server is distributed using

NaradaBrokering architecture.

• Media Servers mix and convert A/V streams

n Open XGSP 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

• Java Media Framework basis of Media Servers

• Helix Community http://www.helixcommunity.org for Real

Media

n http://www.globalmmcs.org open source “non advertised”

Break up into Web Services

• Session Control

• Thumbnail “image” grabber

• Audio Mixer

• Video Mixer

• Codec Conversion • Helix Real Streaming • PDA Conversion

• H323/SIP Gateways

n As independent can replicate particular services as needed

• Codec conversion might require 20 services for 20 streams

spread over 5 machines

n 1000 simultaneous users could require:

• 1 session controller, 1 audio mixer, 10 video mixers, 20 codec

converters, 2 PDA converters and 20 NaradaBrokers

n Support with a stream optimized Grid Farm in the sky

• Future billion way “Video over IP” serving 3G Phones and home media

GlobalMMCS and NaradaBrokering

n All communication – both control and “binary” codecs are

handled by NaradaBrokering

n Control uses SOAP and codecs use RTP transport n Each stream is regarded as a “topic” for NB

n Each RTP packet from this stream is regarded as an “event” for

this topic

n Can use replay and persistency support in NB to support

archiving and late clients

n Can build customized stream management to administer replay,

and who gets what stream in what codec

n NaradaBrokering supports unicast and multicast

n Use firewall penetration and network monitoring services in NB

0 1 0 2 0 3 0 4 0 5 0 6 0

0 20

0 400 600 800 1000 1200 1400 1600 1800 2000

Delay (Milliseconds)

Packet Number

Average delays per packet for 50

video-clients_{NaradaBrokering Avg=2.23 ms, JMF Avg=3.08}

ms

NaradaBrokering-RTP

0 1 2 3 4 5 6 7 8

0 20

0 400 600 800 1000 1200 1400 1600 1800 2000

Jit

ter

(Milliseconds)

Packet Number

Average jitter (std. dev) for 50 video clients.

NaradaBrokering Avg=0.95 ms, JMF Avg=1.10

ms

NaradaBrokering-RTP

Polycom, Access Grid

and RealVideo views of

Integration of PDA, Cell phone and Desktop Grid Access

Grids and e-globalcommunity

Peer-to-peer networks

already are a good example of

value of Information Technology supporting broad

global communities

• File sharing, text chats, bulletin boards

n

Grids must include these capabilities and extend in

terms of increased

functionality

and

quality of service

n

This will support business and cultural interactions

between nations

n

Several interesting applications can be supported by

• Replacing files by multi-media streams so can collaborate in

real-time

• Adding traditional tools like audio-video conferencing and shared applications to P2P set

n

This integration of P2P and Grid to give M

Grids

Streaming M

2

_Grids

 e-Textilemanufacturing involves Clothes designers in USA and

manufacturers in Hong Kong exchanging designs which are

streams of images

 e-Sports is a possible collaboration between Indiana University and

Beijing Sport University

• Basket ball coaches (teacher) interact with aspiring NBA players in China

• Martial Arts masters in China train neophytes in Indiana

• Faculty recreational sports adviser works from university with faculty exercising at home

• Hope to have working incredibly well by the 2008 Olympics

 Interactive TV Grid: allows anybody to discuss professional or

home video (of sports or other events) within a custom Grid

 Multi-player distributed games which should be supported with

exactly the same overlay Grid

 Video Game Production Grid links artistic direction (design) in one

country with digital animation (manufacturing) in another

 e-Science: Physics and Environmental Science Sensors

 Surveillance Grid enables security personnel to annotate and

Some Technology for Streaming M

_Grids



Basic capability is

collaborative annotatable multimedia

tool

for images, sensors and real-time video streams

•

Allow Grid participants to view real-time streams,

rewind on the fly and add text and graphical

comments

•

Similar to instant replay on TV but far more flexible



Need rich

metadata system

to label and correlate

streams, images and annotations



Extend

Grid and P2P file access

paradigms to

stream

storage, browsing and access



Core Technologies shared with

distance education

Using http:/

/www.globalmmcs.org for mu

ltimedia

GlobalMMCS Futures I

– SVG game ( stable ) – Whiteboard ( stable ) – e-Sport ( prototype)

– Jabber IM client ( prototype)

• 2. JMF Audio/Video client ( stable)

– performance enhancement finished

– new codec ( MPEG4 finished; try H.264) – support different platform ( Linux, Mac ) – support NAT/firewall

– screen codec for shared display ( prototype )

• 3. Replay & Archive (prototype)

– Replay Engine based on NaradaBroker Storage Service – XGSP-RTSP gateway

– Extend RTSP and NaradaBrokering for Instant Replay

• 4. Web Server ( stable)

GlobalMMCS Futures II

•

5. Conferencing Media Processing Service ( Stable)

– Fix the bugs and add scheduling – Support new codec ( MPEG4 )

•

6. H.323 Gateway ( Stable)

– Import it to Linux platform

•

7. RealStreaming Gateway ( Stable )

– Import it to Linux

– Support Mobile clients

•

8. Global-MMCS deployment & test

– Test under the setting of multiple NaradaBroker and NAT/Firewall

– support deployment for AFRL, NASA, DOE portals – test with remote sites

P2P and Server based solutions

n Peer-to-peer architectures have advantage that they can be deployed

just using client resources and no system commitment is needed

n Typically clients do not have good network QoS and it is hard for

example to support rich multi-point audio video conferencing in this way

n M2 Grids typically require multicast so average load in P2P case on

client legs goes like O(M)

• Server-side multicast puts O(M) load on backbone and O(1) load

on clients and can lead to much better scaling and performance

• N plus N Grids may not see such large improvements with server

side support

n So Grids should support initial P2P deployment with a seamless

upgrade to add better QoS using Servers.

n Extend familiar P2P paradigms like BitTorrent to Grids and

Streaming

n Grid and peer-to-peer linkage combines scalable performance with

ease of deployment P2P

Grid Farm in the Sky (clouds)