1 06/00 questions 10/6/2015 qos in dos ecoop 2000john zinky bbn technologies ecoop 2000 workshop on...

1 06/00 Questions 04/19/23 QoS in DOS ECOOP 2000 John Zinky BBN Technologies

ECOOP 2000 Workshop onQuality of Service in Distributed Object Systems

http://www.vsb.informatik.uni-frankfurt.de/misc/QoSDOS

June 13, 2000Cannes, France

Christian [email protected]

John Zinky [email protected]


Distributed Object Middleware has Emerged to Solve Heterogeneity and Distribution Problems

Middleware makes programming distributed applications easier

• Standard programming interfaces hide platform and system dependencies

• Standard protocols, e.g., message formats, allow applications on different systems to interoperate

• Middleware provides higher level, application oriented programming building blocks

Host 2

Impl

Host 1

Impl

Applications

Host 2

Simulation

Distributed ObjectMiddleware

Impl

IDLIDL

CollaborativePlanning

IDL

Hosts/Systems

Workflow


The Problem: Wide-Area Distributed Applications Are (Still) Hard to Build and Maintain

• WANs resources are dynamic, unpredictable, and unreliable

• Different user communities have different usage patterns

• Quality of Service (QoS) requirements change

• Administrative constraints on resources change

• The same function can be done in multiple ways that use different resource mix

Host1

Client1

Host2

Client2

Host4

Client3

ObjectResource Constrained

Wide Area Network LANHost3

Client4


PPP

The Simple Abstraction of TCP/IP Networks Allowed Networks and Applications to Grow Independently

FTP TelnetWWW

X.25

New Networking Technologies were added without the need to understand anything about applications beyond their use of TCP/IP

New Types of Applications were added without the need to understand anything about networks beyond the Sockets API

Ethernet

TCP/IP

*Dave Clark from a talk at MIT circa 1996


But Applications and Networks could be Implemented More Efficiently, if More Information were Available

Ethernet

TCP/IP QoS

Video Conference

ATM

RSVP

Multicast

Some Applications need guarantees on the Quality of Service (QoS) from the network

Networks could make better optimizations if they knew the application’s requirements.

Research is ongoing on how to widen TCP/IP choke point to exchange QoS information


Distributed Objects with QoS Extensions is a Powerful Abstraction Layer on which to Build Applications

DOS + QoS

Collaborative Planning

WorkFlow

Simulation Application’s beyond Multimedia

Distributed Objects are the first abstraction layer that unifies CPU, Storage, and Communications

QoS Communication interface needs to be hidden from applications.

•It is too complicated•It is changing too quickly

Multimedia

QoS issues are also being addressedfor CPU and Storage

Unix QoSCPU

RealtimeSQL QoSStorage

RealtimeTCP/IP QoSComm

WinSock


• QoS is well-controlled Client and Object are at the same location

• QoS is unruly across the network

• How can we resolve this?

Who is Responsible for the The QoS Problem?

Client Object

Client Object Network

Client Object

Client Object

Client Object QoS Gateway


Current ORBs Must be Extended for Adaptive QoS Interface and Control

Logical Method Calls

BandwidthControl

StatusCollection

ConfigurationManagement

Client Host Network

Operating System

Middleware

ApplicationsClient

Servant Host

Operating System

Middleware

ApplicationsObject

ResourceManagers

ResourceManagers

Network Based Services

PropertyManagers

PolicyManagers

...

Event Services

Name Services ...

QoS Adaptive LayerQoS Adaptive Layer

Distributed ObjectsCOTS ORBSchedulers

Distributed ObjectsCOTS ORBSchedulers

Specialized ProtocolsGroup Communications

Specialized ProtocolsGroup Communications


What Support Should be Given to Different Roles

Client Network Server

ApplicationDeveloper

MechanismDeveloper

Client

ORB Proxy

Specialized ORB

Object

ORB Proxy

Specialized ORB

Network

Mechanism/PropertyManager

Logical Method Call

QoS Developer?


• Organize System Properties– Observe

– Summarize imperfect observations

– Translate

– Actively negotiate

• Alternative Behavior– Change policy

– Control resources

• Emit Events– Reevaluate observations

– Change reservations

• Recover From Errors– Mask undesirable behavior

Dispatch

XBehavior

YBehavior

ZBehavior

Enforce

Enforce

Object

Resources

SystemProperties

UserClient

Managing QoS is a Feedback Loop for ChangingBehavior Based on System Properties

Environment

Server


Questions

• What kind of QoS is being handled?– Realtime, Dependability, Security, Resource Management

• What roles are supported?– Application programmer, Mechanism Designer, System Administrator

• How is QoS adaptability reused?– Service, Library, OS extension, Programming Language

• How is QoS requirements specified?– Specialized Language, QoS Translation,

• Where does QoS adaptability occur?– Above, In, or Below the Middleware/ORB

• What time horizons does Adaptability occur?– Design time, System Configuration, Connection time, Invocation time


Workshop Objectives

• Collect a common understanding of QoS

• Discuss dependencies of QoS on different layers,– e.g. below, in, above ORBs

• The QoSDOS Reference Model for Provisioning QoS in Middleware?


Sessions

9:00 Overview

9:15 QoS Support in and below ORBs

10:00 Break

10:15 QoS Specifications

12:00 Lunch

1:00 QoS Frameworks "above the ORB“

2:15 Break

2:30 QoS Frameworks "above the ORB“ (cont)

4:00 Break

4:15 QoS Streaming in OO, QoS enabled applications

5:15 Close

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