NaradaBrokering Grid Messaging and Applications as Web Services

NaradaBrokerin

Grid Messaging and

Applications as Web Services

Geoffrey Fox

Community Grids Lab

Indiana University

NaradaBrokering might Support

•

Grid Messaging reliably in spirit of

WS-ReliableMessaging

•

Virtualize inter-service communication

•

Federate different Grids Together

•

Scalable pervasive audio-video conferencing

•

General collaborative Applications and Web services

•

Build next generation clients interacting with messages

not method-based user interrupts

•

Unify peer-to-peer networks and Grids

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 A

Web Service B

“GridMPI” v. NaradaBrokering

one needed’ for inter-node messaging

n 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

n 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”

n Jitter in latency (transit time through broker) due to routing,

processing (in NB) or packet loss recovery is important property n Grids need and can use software supported message functions and

NaradaBrokering

n

Based on a network of cooperating

broker nodes

• Cluster based architecture allows system to scale in size

n

Originally designed to provide

uniform software

multicast

to support real-time collaboration linked to

publish-subscribe for asynchronous systems.

n

Now has several core functions

• Reliable order-preserving “Optimized” Message transport

(based on performance measurement) in heterogeneous

multi-link fashion with TCP, UDP, SSL, HTTP, and will add GridFTP

• General publish-subscribe including JMS & JXTA and

support for RTP-based audio/video conferencing

• Distributed XML event selection using XPATH metaphor • QoS, Security profiles for sent and received messages

Laudable Features of NaradaBrokering

n

Is

open source

http://www.naradabrokering.org

H

as

client

“plug-in” as well as standalone brokers

Will have a

discovery service

to find nearest brokers

Does

tunnel

through most firewalls without requiring

ports to be opened

n

Supports

uniform time

across a distributed network

n

Supports

JXTA, JMS

(Java Message Service) and more

powerful native mode

n

Transit time

< 1 millisecond

per broker

n

Will have

setup

and

broker network administration

NaradaBrokering Naturally Supports

n

Filtering

of events to support different client

requirements (e.g,. PDA versus desktop, slow lines,

different A/V codecs)

n

Virtualization

of addressing, routing, interfaces

n

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

n

Monitoring

of messages for Service management and

general autonomic functions

n

Fault tolerant

data

transport

Grid Messaging Substrate

Consum

er Service

SOAP+HTT GridFT

RTP ….

Standard client-server style communication.

Substrate mediated

communication removes

transport protocol dependence.

Messaging Substrate Consum

er SOAP+HTTGridFT Service RTP ….

Any Protocol satisfying QoS

Virtualizing Communication

n Communication specified in terms of user goal and Quality of Service – not in choice of port number and protocol

n 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 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

NB Broker _{Client Filtering}

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

Architecture of Message Layer

classic publish/subscribe problem of integrating different

requests with related topics (subscribe to sports/basketball/lakers and sports)

n Related to Akamai, AOL … caching and Server optimization problem

1-> N Grid Clients

Hypercube o

NB Brokers (logical not physical)

NaradaBrokering Communication

n Applications interface to NaradaBrokering through

UserChannels which NB constructs as a set of links between NB Brokers acting as “waystations” which may need to be

dynamically instantiated

n UserChannels have publish/subscribe semantics with XML topics n 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

n Different links can have different underlying transport implementations

• Implementations in the current release include support for

TCP,UDP, Multicast, SSL, RTP and HTTP.

• GridFTP most interesting new protocol

• Supports communication through proxies and firewalls such as

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 and JMS (Java Message Service)

Low Rate; Small

NaradaBrokering and JXTA Federation

n Based on hybrid proxy that acts as both Rendezvous peer (JXTA routers) and NaradaBrokering end-point.

n No changes to JXTA core or constraints on

interactions

• Change made to Rendezvous

layer

n Peers are not aware that they interact with a

Narada-JXTA proxy or Rendezvous peer.

§ NB provides JXTA guaranteed long distance delivery

End-point Services i

Native NaradaBrokering

n

Allows you to create

Consumers

(subscribers) of events

(an event is a time stamped message where time stamp

can be empty!)

n

Allows you to create

Producers

of events (publishers)

Allows you to

discover brokers

and

initialize

communications with the broker.

n

Services available at the client side will perform

• Compression of payloads

• Computation of Message digests for Integrity

• Secure encryption of payload based on the specified keys • Fragmentation of large payloads into smaller packets

• Redundancy service which maintains active (alternate)

Event Consumer Capabilities

n Allow you to subscribe to events that conform to a certain template.

• The specified subscription profile could topic-based strings, XPath

queries, <tag=value> pairs or integer topics.

n Event Consumers can also create Consumer constraints to specify various properties regarding the delivery of events. n Consumer constraints are different from subscriptions.

• Subscriptions (or Profiles) are evaluated in a distributed fashion by the

broker network,

• Consumer constraints are QoS related and are managed by the QoS

services running on the end-point.

n Consumer constraints can specify

• Reliable Delivery of events

• Ordered (Publisher, causal and time ordered) delivery of events • Exactly once delivery of events

Event Producer Capabilities

n

Facilitate the

generation

of events in correct format

(next slide)

n

Facilitate the

publishing

of events to brokers

n

Allow the creation of

Publisher constraints

which

facilitate specification of properties that need to be

satisfied by published events

n

Among the constraints that can be specified include

• Method of Securing message payloads

• Computing message digests

• Compressing message payloads

Native NaradaBrokering Event

• Event headers

• Content Synopsis (for selection as in JMS properties

WITHOUT reading body)

• Content Payload

• Dissemination Traces (generated on the fly as event traverses

broker network)

n This is different from structure of JMS or JXTA events

n This NBEvent structure supports the extra capabilities discussed earlier

n The event headers specify information regarding

• Security and Integrity of encapsulated payload

• Fragmentation of events

• Compression of payloads

• Correlation identifiers (to define ordering between different

streams as is needed in some collaboration applications)

• Priority

• Application Type

Based on Message Level Security Messages organized into topics

Yes No Yes end-to-end Security Yes Yes No

Support forXPath queries/ subscriptions

Yes No

Yes

Communication through proxies and firewalls

Yes No

No

Support forAudio/Video Conferencing& raw RTP clients

JXTA and later Gnutella

Yes No

Support for routing

P2P Interactions Yes Yes Yes Guaranteed Messaging (Robust) No Yes

Medium (MQ is based on the point-to-point model. There is a limit on the

effectiveness of this mode in large configurations). WebSphere MQ (formerly MQSeries) Yes No Network Performance Monitoring Yes No JMS Compliant Very large Very large Maximum number of nodes hosting the messaging

infrastructure

NaradaBrokering

Pastry

Yes No Yes Multiple transport protocolsover multiple hops.

TCP (Blocking and non-blocking), UDP, Multicast, HTTP,

SSL, RTP, (GridFTP)

TCP, UDP TCP, HTTP, Multicast, SSL, SNA etc. Transport Protocols Supported

Fair with some

“production” testing

Fair

Extremely mature,

with very robust

diagnostic information

Maturity of Software

Platforms

supporting Java 1.4 (tunneling C++)

Supported on platforms which support C#

(Microsoft) or Java

(Rice).

35 different OS/

platforms supported. Also supports the Java

Platform.

Platforms or Hosting Environments

No Yes (Squirrel)

No

Support forP2P

Autonomic Services

n In a Web (Grid) Service architecture, the state of any service is defined

by its initial condition and all the messages (including ordering) that it receives

• This how shared event model of collaboration works

n This is a “Finite State Change” model analogous to saving file and

“undo” command in many editors

n NB plus a robust store can “guarantee” to save all these messages for

(all) services

n This allows one to build both "autonomic data transport" and

"autonomic services" since these services can sustain packet losses in transport and can also sustain failures of apps/brokers

• archived messages (previous invocations, published events etc) can

be retransmitted to reconstruct state at the service or to correct a transport error.

n Further anomalies in message traffic (such as a publisher or

subscriber are silent) can be detected by NB and signal problems

n We are building examples of both scenarios using GridFTP as our

data transport example

n We will build a sample autonomic visualization service with detection

Reliable Messaging Standards

• There are 2 competing standards in the Web

Services community

–

WS-Reliability from OASIS

WS-Reliability & WS-RM

•

Specifications provide reliable delivery between two

endpoints.

•

Both the specifications use positive

acknowledgements to ensure reliable delivery

•

Both specifications include support for faults

•

WS-Reliability is a SOAP based protocol

•

WS-ReliableMessaging provides an XML schema for

reliable messaging.

NaradaBrokering & Reliable Delivery specifications

•

We can provide support for both these specifications

– In NaradaBrokering we provide reliable delivery from multiple points to multiple points

•

We have identified issues that will allow federation

between these specifications

– Sequence numbering, fault mappings, numbering rollovers, quality of service guarantees

•

Federation would allow

SequenceTerminated Unknown Sequence InvalidAcknowledgement MessageNumberRollover LastMessageNumberExceeded InvalidMessageHeader Invalid MessageIdentifier InvalidReferenceToMessageId InvalidTimeStamp InvalidExpiryTime InvalidReliableMessage InvalidAckRequested InvalidMessageOrder

Fault Codes supported by protocol

Relies on WS-Security and assorted specifications Relies on WS-Security and assorted specifications

Security

At most once, at least once and exactly once. Order is not necessarily tied to guaranteed delivery.

Exactly once ordered delivery, reliable delivery.

Order is always tied to guaranteed delivery and cannot be separately specified.

Delivery sequences supported

WS-Policy assertions are used to meet delivery assurances. Is initiated by the sender.

Quality of Service

Allows the specification of a RetransmissionInterval for a sequence (effects every message in the sequence). The interval can also be adjusted based on the exponential backoff algorithm. Triggered after receipt of a set of acknowledgements. In the event

an acknowledgement is not received, the message is retransmitted until a specified number of resend attempts have been made. Retransmissions

No explicit reference to UTC. Uses thedateTimeformat. Are expressed as UTC and conforms to a [XML Schema Part2: Data

Types]dateTimeelement. Timestamps

The identifier associated with the sequence of messages and the message number within that sequence.

The identifier associated with the message being acknowledged. Correlation associated with an

Acknowledgement

AckRequested is used to request the receiving entity to acknowledge the message received. This is not REQUIRED.

The AckRequested element is REQUIRED in every message for which reliable delivery needs to be ensured.

Requesting acknowledgements

Acknowledgements can be based on a range of messages, and the timing for issuing this can be advertised in a policy. An endpoint may also choose to send acknowledgements at any time.

Can be sent upon receipt of messages, as a callback or in response to a poll. Needed upon receipt of every message.

Acknowledgements

Message number is REQUIRED for every message that needs to be delivered reliably.

REQUIRED only for guaranteed ordering. Presence of numbering

information and its relation to delivery

No new sequences can be generated.

MessageRolloverfault is issued. Generate a new group identifier and begin new sequence only after

receipt of last message in old sequence. Sequence numbering rollover

Starts at 1 for the first message in a group. Starts at 0 for the first message in a group.

Sequence numbering initialization

URI based [RFC 2396]. No additional requirement. Messages within a sequence are identified based on message numbers.

URI based [RFC 2396], the syntax for the message-ID should be based on what is outlined in RFC2392.

Unique Ids

WS-Policy, WS-Security SOAP, WS-Security

Related Specifications

WSRM provides an XML schema for elements needed to support the reliable messaging framework. The specification provides a SOAP binding for the protocol.

Is a SOAP based protocol, which has an HTTP binding which facilitates acknowledgements and faults to be issued over HTTP responses.

SOAP related issues

NaradaBrokering, WS-Notification & JMS

• NaradaBrokering is JMS compliant

• Topics in NaradaBrokering could be based on XML, String(as in JMS), Plain text, Integers, and (tag=value) tuples.

– Subscriptions could be XPath queries, SQL queries, Regular expressions, Strings and integers

• Almost all the primitives needed in WS-Notification are available in NaradaBrokering

– Exception: Entities never communicate directly with each other, as proposed in WS-Notification.

– We are either allow such direct communication or mimic in NB – no performance overhead!

• We are currently building a prototype implementation of WS-Notification

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.

• NTP ensures that all entities are within 1-30 milliseconds of each other.

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

NB Time Service

• In figure on left, there is a NTP daemon running on the local machine besides the NB Time Service. NTP daemon running on the machine adjusts the underlying system clock. NB Time Service shows consistent results with NTP daemon. • Figure on right shows results on machine that does not run NTP daemon.

• The following results are obtained over a period of 48 hours.

• In these tests, NB Time Service computes offset every 30 seconds.

Building PSE’s with th

Rule of the Millisecond I

n Typical Web Services are used in situations with interaction delays (network transit)

of 100’s of milliseconds

n But basic message-based interaction architecture only incurs fraction of a

millisecond delay

n Thus use Web Services to build ALL PSE components

• Use messages and NOT method/subroutine call or RPC

n This “rule” OFTEN violated – people use “Java Interfaces” and so cannot distribute

services

Interaction

Nugget

1 Nugget2

Nugget

Building PSE’s with th

Rule of the Millisecond II

n Messaging has several advantages over scripting languages

• Collaboration trivial by sharing messages

• Software Engineering due to greater modularity

• Web Services do/will have wonderful support

n “Loose” Application coupling uses workflow technologies

n Find characteristic interaction time (millisecond programs; microseconds MPI and

particle) and use best supported architecture at this level

• Two levels: Web Service (Grid) and C/C++/C#/Fortran/Java/Python

n Major difficulty in frameworks is NOT building them but rather in supporting them

• IMHO only hope is to always minimize life-cycle support risks

• Science is too small a field to support much!

n Expect to use DIFFERENT technologies at each level even though possible to do

everything with one technology

Streams and Workflow

n

Grids

need to consider

streams

and

Services

• Topics in NB are streams not just individual messages

n

There is

service-oriented workflow

where streams are

typically implicit.

n

For

stream-oriented workflow

, the streams are explicit.

We have built a sophisticated system GlobalMMCS for

audio-video conferencing, which we will discuss next

• Media Industry and sensor based science are different

examples

n

We are building a

stream control engine for

NaradaBrokering

when streams are “just” message

flows on the Grid. Here one would use NB discovery

services – find streams – and monitor

UNIX-style Workflow Example

n

`flow: x &> (y1|z1 &> p,(q|storage1)), (y2|z2|storage2)`

n

Note this approach allows for example all workflow

streams to use RMI, GridFTP, RTP – your or rather

NaradaBrokering’s choice

x

y1 z1 p

y2 z2 storage2

q storage1

Stream–oriented Workflow

n

As in audio-video conferencing and multimedia file

delivery where it’s the media streams that are the

“point”

n

Services generate and transform streams but one thinks

of

streams going through services

rather than

services

generating streams

n

Multi-cast streams where video from one client sent to

all other participants in a collaborative session common

n

One thinks of a stream being published and

participants subscribing to it.

Pub/Sub Queue

Publish

InterGrids Federated Grid using NB

n Build a P2P Network where each component (cell or Gridlet) is itself a Grid

n If cell is a single computer, reduces to using NB to build

communication infrastructure between nodes of P2P network n If cell is a JXTA peer group, then InterGrids includes previous

federation of JXTA Peer Groups

Gridlets NB Brokers

InterGrids Mediation Architecture

n NB acts as a Mediation agent in such a Cellular Grid

n Using federated security model constructs a VPN like Virtual Private Grid (NB could support VPN protocol and combine with Grid Security)

n Mediation includes more than routing (as in current JXTA) as

can map between Interface standards

n Each Gridlet can use different Service standards

n Services register interfaces with mediator giving ways to map

using perhaps OGSA as a common intermediate form

n Allows integration of OGSI WSRF WS-GAF and “pure web service” or Jini or JXTA based Grids where each Grid uses its natural service architecture

n Support interoperable (like Job Submission) and federated

(like registry or metadata catalog) services

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

• We can port objects to Web Services and build a general

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 updates of all kinds as

messages

• “Event service” for collaboration is similar to Grid notification service

and we effectively define SDE’s (service data elements) in OGSI

n Group (Session) communication service is needed for the delivery of the update events

Collaborative SVG Web Service

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” in future?)

n 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

n We use NaradaBrokering and XGSP 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

Applications as Web Services?

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

n 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

n Immediately make a lot easier to support cross O/S applications n Form the “Next Generation Client Consortium”?

• There is quite a lot of open source (but not web service based) software

Web Service Model for Application Development

W3C DOM User Interface W3C DOM Raw (UI) Events

Application as a Web service

W3C DOM Semantic Events Data

User Facin Ports

Resource Facing Ports

Events as Message s Rendering as Messages View Control Model Narad Brokering

Interrupts in traditional monolithic applications becom “real messages” not directly method calls

Natural for collaboration and universal access

Collaborative SVG As A Web Service

Collaborative SVG Chess

Game in Batik Browser

Players

W Displa y W Viewe r WS Displa y WS Viewe r Even (Message Service Master W Displa y WS Viewe r

Web Service Message Interceptor

Collaboration as a W Set up Session with XGSP

Application o Content source WSD L Web Service F I U O F I R O

SV Browse r SV Browse r SV Browse r SV Browse r

Identical Programs receiving identical event

Token determines if browser is moving, waiting for opponent or an observer

SIMD Collaboration

SV

Viewer ViewerSV ViewerSV ViewerSV

SVG Model

(DOM)

NaradaBrokeri ng

Shared Output por

SIMD Collaborativ

Web Service

Non Web Service Implementation

W Displa y W Viewe r WS Displa y WS Viewe r Even (Message Service Master W Displa y WS Viewe r

Collaboration as a W Set up Session with XGSP

We Servic e F I U O F I R O

Shared Input Port (Replicated WS) Collaboration

MIMD Collaboration

SV

Viewer ViewerSV ViewerSV ViewerSV

NaradaBrokering

Shared Input por

MIMD Collaborativ

Web Service

SVG Mode

l

SVG Mode

l

SVG Mode

l

SVG Mode

l

Global-MMCS 2.0 XGSP MCU

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

collaboration services.

n We will deploy it globally and hope to test with later this year. n The function of A/V media server will be 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 from Indiana • Java Media Framework basis of Media Servers

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

A/V Collaboration Systems

n

H323

• H.323 is defined as an umbrella standard specifying the

components to be used within an H.323-based environment.

n

SIP

• The Session Initiation Protocol (SIP) defines how to establish,

maintain and terminate Internet sessions including multimedia conferences

n

Access Grid

• enhanced Mbone A/V tools ( VIC, RAT ) • Internet 2 network ( Multicast support

n

RealStreaming

XGSP Collaboration Framework

n

To integrate heterogeneous systems into one

collaboration system

• A unified, scalable, robust “overlay” network is needed to

support A/V and data group communication over heterogeneous networking environments.

• A common A/V signaling protocol has to be designed to

support interactions between different A/V collaboration endpoints.

• Different A/V endpoints should collaborate in the same

Group Communication in Collaboration

n

Collaboration applications usually need a group

communication service for both multipoint data and

control information delivery

• Centralized conferencing systems usually depend upon a

single conference server

• Distributed conferencing systems use IP multicast

Access Grid uses Internet2 multicast for audio/video transmission.

• Problems: Centralized conferencing systems don’t have good

scalability and IP multicast has not become ubiquitously available

n

We use distributed NaradaBrokering to provide this

A/V Collaboration over publish/subscribe Middleware

n

video streams (VS) VS {v

, v

, … v

}

audio streams (AS) AS { a

, a

, … a

}

A/V endpoints: E

, E

, … E

Each endpoint may send a single or multiple video

streams, but only send an audio stream

n

Different types of A/V endpoints have different

collaboration capabilities.

• Multicast endpoints are able to receive multiple video and

audio streams, display all the video streams in their screens, and mix all the audio streams by themselves

• Unicast endpoints like Polycom Via Video can only receive

Publish/subscribe of A/V

n

A stream in VS and AS is regarded as a “topic”

n

Each RTP packet from this stream is regarded as an

“event” for this topic

n

Only the sender of this stream can “publish” A/V

events to this topic

n

Other endpoints need to subscribe to this topic in order

to receive the stream data

n

Create mixed video and audio stream topics for unicast

RTP packets encapsulation

n

RTPLink: RTP Packets map to Narada Brokering

Event

n

Every legacy A/V client needs one corresponding

RTPLink to be set up at a broker within broker

network.

n

Unicast RTPLink:

Integer Topic Numbers for RTP and RTCP

n

Multicast RTPLink:

A reflector between NaradaBrokers and multicast groups,

encapsulating raw RTP packets from a multicast IP address to RTP events, publishing these events to NaradaBrokers, and

Audio Mixer, Video Mixer, Image Grabber

n Audio Mixing

The audio mixer creates a mixed audio stream from all the audio streams in the session

n Video Mixing

Video mixing makes the unicast users watch the pictures of multiple participants in a meeting through one video stream

n Video Thumbnail

visualize the VS set in the session, embedded into the control panel of each endpoint, which

Image grabbers capture video streams and save them as static JPEG files.

n All the media processing components can be distributed among the pool of the media servers connected to NaradaBrokering infrastructures.

H.323, SIP Gateway Servers, A/V Session Server

n

H.323 and SIP gateway transform these protocol

specific messages into XGSP signaling messages so that

H.323 and SIP A/V endpoints could communicate with

the XGSP A/V session server

n

The session server implements session management

logics

• creating/destroying A/V sessions

• allowing endpoints to join/leave session

• Allowing users to make audio/video selection, managing A/V

application components

n

Note Session Server very similar to Context Server in

Streaming Subsystem Servers

n Integration of RealNetwork Streams requires multiple services

Stream Conversion Handler manages and forwards H261 streams

SMIL is W3C standard for synchronizing media streams

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

Application Web Service

and Universal Access

n

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

Client1

Client2 M

Agent1

Agent2 Profiles NB

P1

P2 P

Map P to P1

Map P to P2