AMPol-Q: Adaptive Middleware Policy to support QoS Raja Afandi, Jianqing Zhang, Carl A. Gunter Computer Science Department, University of Illinois Urbana-Champaign

2 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

3 Global QoS Client Service 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 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

4 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 ?

5 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

6 Main Objectives… Global QoS and dynamic discovery QoS Policies and Interoperability

7 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

8 Case Study: Messaging System WS –Internet messaging based on web services SC SS RS RC SS: Sender Mail Server RS: Recipient Mail Server

9 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

10 Description Framework: QoS Model APES QoS Domain Ontology QoS Base Ontology QoS Monitoring Ontology

11 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

12 Description Framework : Policy Model

13 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

14 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

15 Discovery: Service Chain Graph B Dependency List Request Template CR Dependency List Request Template CR Dependency List Request Template Dependency List

16 Global QoS Analysis C1L1CR1B1 R C1 F L1 F B1 F CR1 F C1 C B1 C B1  F C1 C B1  E  EP C1 Agreement  Agreement Value No Agreement  Penalty R = Requirements C = Constraints F = Capabilities E = Extension Capabilities EP = Extension Policy

17 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

18 AMPol-Q Middleware

19 AMPol-Q Middleware Implementation

20 Case Study: Policy Based WS WS Web services based Internet messaging Integrated AMPol-Q middleware with WS –Transparent Integration Implemented APES features: –Payment as Puzzle Hashcash RTT –Encryption using Identity-Based Encryption (IBE)

21 Case Study: Overview HashCash Puzzle IBE Encryption SMTA (SS) Gary RMTA (RS) Sandy Sender MUA (SC) Recipient MUA (RC) Server Egress Policies Server Ingress Policies Client Ingress Policies Plugin Server Attachment Size Registry Server Entity Profiles

22 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 WS –One of the most complete studies to date of a proof-of-concept QoS-aware policy system based on Web services

23 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

24 Questions… Thanks…

25 Discovery: Sample Merged Policy SC adherence policy SC Enforcement policy SS Enforcement policy RS Enforcement policy RC Enforcement policy Delegated Rules

26 Query Matching Service query matching constraints