AMPol-Q: Adaptive Middleware Policy to support QoS

Raja Afandi, Jianqing Zhang, Carl A. Gunter

Computer Science Department,

University of Illinois Urbana-Champaign

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QoS Based Discovery

• Services are discovered and selected on the basis of functional properties (IOPE)

• Difficult to discover and compose services on the basis of non-functional features (QoS)– Complex to model QoS features– Global nature of QoS– QoS composition requires complex

calculations of aggregate and global QoS values

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Global QoS

ClientClient Service BService B

Client & Service A•Sender MUA and SMTA•Business Client and Loan Agency

Service A & Service B•SMTA and RMTA•Loan Agency & Bank

Client policies constraining Service

A & B•Message Sender requires the message to be confidential•Business client needs its loan request to be processed with in a week

Global QoS

•End-to-End QoS•Two-way QoS constraints

Service AService A

End service policies

constraining Client•Bank requires applicant credit score to be fair•RMTA requires that a message from a sender must not be greater than 10KB

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Global QoS: Discovery

• Discovery approaches:– Limited to discovering first-level immediate services– Each individual service is responsible for discovering

other services independently• Global QoS evaluation requires global

information of all the entities (Global View)

Client Service B2Service A

Service B1

Service B3

?

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QoS Policies

• Supporting QoS also requires monitoring and enforcing QoS behavior and policies

• Support for non-functional features such as security and reliability breaks the interoperability of the system – Diverse Policies– Constraints may change

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Main Objectives…

• Global QoS and dynamic discovery

• QoS Policies and Interoperability

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Strategy

• End-to-End (E2E) integrated approach– Description: Semantic modeling of QoS capabilities and

constraints (policy rules)– Global Discovery: Global service discovery and QoS analysis– Distribute Monitoring: Semantic model and distributed

enforcement– Two-Way-Specialization: entities can dynamically adapt to

the advertised requirements of each other

• Basic architecture based on three frameworks– Description framework defines QoS model and describes

declarative domain-specific policy rules– Discovery framework governs how to publish, find, and

select services on the basis of QoS– Monitoring framework provides means to adhere to and

enforce published QoS requirements and constraints

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Case Study: Messaging System

• WSEmail– Internet messaging based on web

services

SC

SS RS

RC

SS: Sender Mail ServerRS: Recipient Mail Server

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Description Framework

• Includes semantic models for describing QoS capabilities, constraints and requirements of different entities in the system:– QoS Model – Policy Model– Entity Profile Model– Messaging Domain Model

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Description Framework: QoS Model

APES

QoS Domain Ontology

QoS Base Ontology

QoS Monitoring Ontology

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Description Framework : Policy Model

• Semantic language of constraints and requirements

• Rules are defined using QoS ontology and SWRL rule format:

ampol:Encryption(?a) ampol:algoType(?a, ?b) ampol:stringValue(?b, "IBE2.3")∧ ∧

→ ampol:verified(RC_Enc_Rule1, true)

ampol:Attachment(?a) ampol:attachmentSize(?a, ?b) ampol:intValue(?b, ?c) ∧ ∧ ∧swrlb:lessThanOrEqual(?c, 1000) ampol:unit(?b, "KB") ∧

→ ampol:verified(RS_Att_Rule1, true)

• Supports • Delegation of policy enforcement • Rule prioritization to resolve conflicts• Public vs. private rules

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Description Framework : Policy Model

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Description Framework : Entity Profile Model

• Type of service description profile• Associated with a system entity and can be

advertised with OWL-S service profile• Profiles represent entity :

– Domain vocabulary– Capabilities – Constraints– Extension constraints– Service dependencies – OWL-S request templates

• Clients uses it to discover desired services• Supports global discovery better than current

approaches (based on pure OWL-S, UDDI and IOPE)

Sample Entity Profile

Sample Service Request

Sample Service Profile

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Discovery Framework

• Discover global QoS information about all the candidate services

• Select best matched services

• Binding selected parties in a QoS contract

• Consist of three components: – Service Discovery and Chaining– Global QoS Analysis– Policy Agreement and Contract Negotiation

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Discovery: Service Chain Graph

Service Chains

C: ClientB: BanksL: Loan Processing AgencyCR: Credit Reporting Agency

C1

L1

B2B1

CR1

C1 L1 B1 CR1

C1 L1 B2 CR1

B

Dependency List

Request Template

CR

Dependency List

Request Template

CR

Dependency List

Request Template

Dependency List

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Global QoS Analysis

C1 L1 CR1B1

RC1RC1 RC1 RC1

FL1 FB1 FCR1FC1

CB1

CB1

CB1 FC1

CB1 E EPC1

Agreement Agreement Value

No Agreement Penalty

R = RequirementsC = ConstraintsF = CapabilitiesE = Extension CapabilitiesEP = Extension Policy

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Monitoring Framework

• Monitoring involves measuring delivered QoS, verifying QoS constraints and taking enforcement actions

• QoS feature is associated with Monitoring Processes:– Measurement– Enforcement– Adherence

• Policy Framework control the system QoS policies– Adapts by adding or replacing pluggable components– Policy conformance and enforcement logic as extensions– Generic enough to process any complex constraints– Monitoring processes are implemented as pluggable extensions

• Extension Manager– Policies control the download and execution of extensions– Download plug-ins from secure third-party plug-in server

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AMPol-Q Middleware

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AMPol-Q Middleware Implementation

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Case Study: Policy Based WSEmail

• WSEmail: Web services based Internet messaging• Integrated AMPol-Q middleware with WSEmail

– Transparent Integration• Implemented APES features:

– Payment as Puzzle• Hashcash• RTT

– Encryption using Identity-Based Encryption (IBE)

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Case Study: Overview

• HashCash Puzzle

• IBE Encryption

SMTA (SS)Gary

RMTA (RS)

Sandy

Sender MUA (SC)afandigary@gary

Recipient MUA (RC)afandisandy@sandy

Server Egress Policies

Server Ingress Policies

Client IngressPolicies

Plugin Server

• Attachment Size

Registry Server

Entity Profiles

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AMPol-Q Contributions

• End-to-end solution for supporting non-functional constraints, capabilities & requirements– Comprehensive semantic QoS Model

– Global service discovery and global QoS analysis

– Adaptive policy framework for QoS monitoring

– Reference architecture for adaptive middleware for messaging systems

• Validation of proposed approach through a case study on WSEmail– One of the most complete studies to date of a proof-of-concept

QoS-aware policy system based on Web services

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Current and Future Work

• Formal security analysis and Improved security measures

• Policy conflict resolution and models for negotiation

• Performance testing

• Inter-Ontology relationship for heterogeneous ontologies

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Questions…

• Thanks…

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Discovery: Sample Merged Policy

SC adherence policy

SC Enforcement policy

SS Enforcement policy

RS Enforcement policy

RC Enforcement policy

Delegated Rules

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Query Matching

Service query matching constraints