Reflective Middleware for Mobile Environments

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Reflective Middleware for Mobile Environments

• Nalini Venkatasubramanian
• Distributed Systems Middleware Group
• UCI

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QoS Aware Information Infrastructure
Electronic Commerce
Distance Learning
QoS Enabled Wide Area Network
Collaborative Multimedia (Telemedicine)
Collaborative task Clients
Requirements - Availability, Reliability,
Quality-of-Service,
Cost-effectiveness, Security
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Global Information Infrastructure

• Proliferation of devices
• System support for multitude of smart devices
  that
• attach and detach from a distribution
  infrastructure
• produce large volume of information at a high
  rate
• limited by communication and power constraints
• Require a customizable global networking
  backbone.
• Explore effective middleware infrastructures
  which can be used to support efficient QoS-based
  resource provisioning algorithms in a highly
  dynamic environment
• Complex interactions
• risks include non-termination, information loss,
  inconsistencies and incorrect execution semantics

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Composable Middleware

• In providing such an environment, interactions
  between various components as well as
  system-level correctness must be maintained
• Incorporate effective mechanisms into a
  composable middleware framework to ensure safety
  and QoS enforcement in distributed and mobile
  environments.
• Customizable, Composable Middleware Frameworks
• Provide for dynamic network and system
  customization, dynamic invocation/revocation/insta
  llation of services
• To adapt to the above dynamic changes in modern
  applications and manage distributed components

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Reflection

• Provides a plug-and-play environment for enabling
  run-time modification of policies
• An efficient technique to build composable
  middleware
• Features
• Separation of concerns
• Introspection
• Flexibility, Adaptability
• Composition
• Implies concurrent execution of multiple resource
  management policies

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Why Reflective Middleware?

• Wireless communication, mobile computing and
  real-time applications demand
• High adaptability
• dynamic customization of systems, services and
  communication protocols
• Safe flexibility
• constrain composition of services and protocols
  in order to prevent functional interference that
  could lead to an inconsistent state of the system
• required to protect the system from security
  threats and failure
• Cost-effective QoS guarantees
• In achieving these goals, one must be careful to
  maintain consistency and correctness need a
  semantic model (TLAM)

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A New Paradigm for ODS

• Two Level Actor Machine (TLAM) for ODS
• Separate enforcement of system level requirements
  from application level activities to permit
  customizability
• Basis for CompOSEQ implementation
• Layered Specifications
• End-to-end service specification
• System-level architecture specification
• Local behavior specification
• Isolate complex interactions in well understood
  core services for managing composition

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Core Services
Applying Core Services
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QoS Broker

• Composability is essential in ensuring
  cost-effective QoS in distributed multimedia
  systems
• Safe composability of resource management
  services
• QoS Brokers coordinate multiple activities in
  such systems
• interactions between multiple QoS sessions
• interactions with multiple system services
• Functions of a QoS broker
• Deal adaptively with incoming requests
• Re(configure) data to service requests
• Must maintain resource allocation invariants

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The CompOSE/Q Framework
QoS Broker
Request Mgmt
Data Mgmt
Data Placement
De-replication
Message Scheduling
Request Scheduling
Application Objects
Clock Sync
Migration
Replication
Core Services
Remote Creation
Distributed Snapshot
Directory Services
Interaction with Core Services
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Communication Model

• Extension of TLAM model consisting of a
  composable reflective communication framework
  (CRCF) to support customizable communication
  services.
• Distinguishes and handles different types of
  messages and communication protocols
• Integrates QoS parameters into resource
  management and message handling processes. It
  provides
• High-level communication services through
  composition of basic protocols
• Dynamic installation of protocols
• 4 levels of message customization
• Efficient implementation

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CRCF Architecture
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ComposeQ Architecture (cont)
query
register
NodeManager
CommunicationManager
NodeInfoManager
query
start
SendPot
Outgoing messages
Router
MessageQManager
RemoteMessageReceiver
Postman
spawn
ReceivePot
Incoming messages
DedicatedMessageReceiver
Node
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QoS-based Resource Provisioning

• Degree of network awareness that middleware and
  applications must have to deal with network
  conditions
• Resource provisioning algorithms utilize current
  system resource availability information to
  ensure that applications meet their QoS
  requirements
• Additional Challenges
• In highly dynamic (e.g. mobile) environments,
  system conditions are constantly changing

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QoS-provisioning in Mobile Environments

• Directory Service as a core service For QoS Based
  Resource Management in Mobile Environments
• State information enables decision making for
  resource provisioning - e.g. Routing, Scheduling
  and Placement
• Maintaining accurate and current system
  information is important to efficient execution
  of resource provisioning algorithms
• Global Approximations of System State
• Information Acquisition
• Directory Organization and Manipulation
• Scalability Hierarchical directory organization
  Caching
• Goal Ensure effective utilization of network and
  server resources while tolerating imprecision

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Resource Management Tasks

• Scheduling
• Given a client requests R(Ci, Vi, Qi), schedule
  the request to the server node that satisfies the
  QoS constrains.
• Routing
• For an OD pair, choose a path among feasible
  paths to satisfy the QoS requirements, maximize
  the overall network throughput.
• Placement
• Predict the future requests based on history and
  locality, reallocate resources to the server node
  to maximize the overall throughput.

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Combined Path and Server Selection
s1
s1
O
s2
O
s2
CD
s3
s3
Left Graph GltN,Egt with the client requesting at
point O and a set of feasible servers S
s1,s2,s3. Right Graph GltN,Egt extended from
G, adding a point CD and artificial edges e1,e2
and e3
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Dynamic Service Brokering for Mobile Environments

• Goal
• To provide information good enough for resource
  provisioning tasks such as admission control,
  load balancing etc.
• Need an information collection mechanism that is
  
• is aware of multiple levels of imprecision in
  data
• is aware of quality requirements of applications
• makes optimum use of the system (network and
  server) resources
• Collected Parameters
• Network link status, Data server capacity (Remote
  disk bandwidth, Processor capacity)

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AutoSeC Framework
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Data Placement in Mobile Environments

• Design load management mechanisms that
• Provide fault tolerance, i.e. a high degree of
  data availability and
• Ensure effective resource management
• Ensure QoS for admitted clients
• Data availability provided via replication and
  intelligent data placement mechanisms.
• Predictive Fault Tolerant Data Placement
  Mechanisms

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Future Work (cont)

• Further study on the use of Directory Services
• Scalability analysis/techniques
• Security issues, service discovery, store for
  binaries, data etc.
• Provision of an Access Control Model for
  security
• Capability-based architecture
• Object-level granularity with flexibility in
  implementing custom policies depending on the
  applications being supported
• Inter-domain security based on various security
  levels.
• Composability issues with existing core services
  (Remote Creation, Snapshot, etc.), semantic
  model.
• Support for Real-time applications
• Soft real-time guarantees for actors with such
  requirements