1. Understanding Code Mobility
Sachin Chouksey H. Qiu
Xiong

2. Distributed Applications
Problems with traditional approaches
Technologies,architectures,methodologies.
Large scale distributed settings.
Fail to provide
Configurability
Scalability
Customizability

3. Code Mobility An emerging research field. However
Lack of standard terms and concepts.
Difficult to assess and compare existing approaches.
Paper presents conceptual framework.
Classification
Technologies
Design Paradigms
Applications.

4. Development Environment
Computer Networks
Increasing size and performance
Pervasive
Ubiquitous
Mobile computing
World Wide Web

5. Problems Size of Networks (Scalability) Wireless Connectivity
Dynamic topologies
Large scale diffusion into society
Customizability
Flexibility
Extensibility
Current proposed Approaches

6. Similar Approaches Remote Job submission Process Migration
Object Migration
BUT THESE DO NOT SCALE

7. How is code mobility different ?
Internet-scale
Location Aware
Programmer controlled mobility
Mobility for
Load Balancing
Service Customization
Dynamic extension and application functionality
Autonomy
Fault tolerance
Disconnected Operation

8. 3D Classification Technologies Design Paradigms Application Domains
Languages & systems that provide mechanisms
Used in implementation stage by developer
Design Paradigms
Architectural styles used
C2, P2P, Client-Server
Application Domains
Classes of applications
E-Commerce, Distributed information retrieval

9. Mobile Code Technologies
Traditional Distributed System Layers
Core Operating System
Network Operating System
True Distributed System
For Code Mobility
Computational Environments (CE)
CE retains identity of the host
Dynamically relocate components on different hosts
CE hosts Execution units (EUs) and resources

10. Mobility Mechanisms EU = Code Segment + Execution State + Data Segment
EU moves from CE to CE
Orthogonal mechanisms
Code and execution state mobility
Data space management

11. Code and Execution State Mobility
Strong mobility
Migration
Proactive / Reactive
Remote cloning
Weak mobility
Fetch / Ship
Stand alone code / code fragment
Synchronous / Asynchronous

12. Data Space Management Rearrange EU-Resource bindings after migration
Resource = <I,V,T>
Bindings
By Identifier
By Value
By Type
Bindings constrain the data space management mechanisms
Resource Relocation
Binding reconfiguration

13. Current Mobile Code Technologies
Agent Tcl
Ara
Facile
Java
Java Aglets M0
Mole
Obliq
Safe-Tcl
Sumatra
TACOMA
Telescript

14. Design Paradigms
Design paradigms, or architectural styles, define architectural abstractions and reference structures that may be instantiated into actual software architectures

15. Why Design Paradigms?
The goal of design is the creation of a software architecture, which can be defined as the decomposition of a software system in terms of software components and interactions among them
Software architectures with similar characteristics can be represented by design paradigms

16. Describe Design Paradigms
Design paradigms are described in terms of interaction patterns that define the relocation of and coordination among the components needed to perform a service

17. Components Components are the constituents of a software architecture.
They can be further divided into:
Code components
Resource components
Computational components

18. Interactions
Interactions are events that involve two or more components, e.g., a message exchanged among two computational components

19. Sites
Sites host components and support the execution of computational components
A site represents the intuitive notion of location

20. Design Paradigms Client-Server (CS) Remote Evaluation (REV)
Code on Demand (COD)
Mobile agent (MA)

21. Comparison of the Paradigms
Before
After SA SB
Client-Server A
know-how
resource B
Remote Evaluation
Resource
Code on Demand
Mobile
Agent -

22. Outline
Add the 1st person’s
Design Paradigms
Add the 3d person’s

23. Design Paradigms
Design paradigms, or architectural styles, define architectural abstractions and reference structures that may be instantiated into actual software architectures

24. Why Design Paradigms?
The goal of design is the creation of a software architecture, which can be defined as the decomposition of a software system in terms of software components and interactions among them
Software architectures with similar characteristics can be represented by design paradigms

25. Describe Design Paradigms
Design paradigms are described in terms of interaction patterns that define the relocation of and coordination among the components needed to perform a service

26. Components Components are the constituents of a software architecture.
They can be further divided into:
Code components
Resource components
Computational components

27. Interactions
Interactions are events that involve two or more components, e.g., a message exchanged among two computational components

28. Sites
Sites host components and support the execution of computational components
A site represents the intuitive notion of location

29. Design Paradigms Client-Server (CS) Remote Evaluation (REV)
Code on Demand (COD)
Mobile agent (MA)

30. Comparison of the Paradigms
Before
After SA SB
Client-Server A
know-how
resource B
Remote Evaluation
Resource
Code on Demand
Mobile
Agent -

31. Mobile Code Applications(1)
They are still immature and lack of suitable methodologies.
The benefits of mobile code are appealing.(Mobile agent systems, Internet agents)
It is important to distinguish the implementation process and the paradigm.

32. Mobile Code Applications(2)
Benefits:
1. Service Customization- The interfaces or services are are not statically defined.
2. Supporting more flexible software deployment and maintenance.
3. Automatic software upgrade without human interaction on the client side.

33. Mobile Code Applications(3)
Benefits:
4. Autonomy of application components.
- heterogeneous communication infrastructure complexes the network and requires autonomic design.
Two solutions:
Or put more operations on the clients
Put more operations on the server

34. Mobile Code Applications(4)
Benefits:
5. The fault tolerance is much improved in Mobile code than the conventional client-server system.
6. A new protocol is needed to enhance the code migration among distributed systems.
7. Date management flexibility and protocol encapsulation.

35. Mobile Code Applications(5)
Application Domains for Mobile Code
Distributed Information Retrieval
Active Documents
Advanced Telecommunication Services
Remote Device Control and Configuration
Workflow Management and Cooperation
Active Networks
Electronic Commerce

36. A Case Study In Network Management (1)
Determine if mobile code is suitable for the specific application first.
Identify the corresponding paradigms.
Analyze the tradeoff for each application functionality.
Select the technology to implement the application according to the tradeoff.

37. A Case Study In Network Management (2)
The network congestion traffic problem:
1. The problem to solve: Decentralizing Network Traffic
-Both SNMP and CMIP are inefficient while the network heavy congestion.
- Some modifications have been made to solve the problem, such as the SNMPv2 with the proxy agents and the Remote Monitoring.

38. A Case Study In Network Management (3)
2. Identifying the Design Paradigms
-REV paradigm can be used, which will pack up all the SNMP operations and send them on the device for the local interaction.
-Only the useful target value will be sent back after execution.
-The capability to retain the state across several hops will also make the whole system more autonomic.

39. A Case Study In Network Management (4)
3. Evaluating the Design Tradeoffs
(details will not be discussed)
-The mobile code is only convenient when a set of SNMP instructions can be “packed” efficiently into mobile code.
-The choice of the paradigm is constrained by the actual values for the parameters of the application.

40. A Case Study In Network Management (5)
Choosing the Implementation Technology
-In principle, design paradigms and implementation are orthogonal. Sometimes, they are different.
-We also have to think about the global application development when we implement a given functionality inside it.

41. Summary and Conclusions
Mobile code is a promising solution for the design and implementation of large scale distributed applications
Little attention has been paid to the formulation of a sound conceptual framework for code mobility
Three classes of concepts in a proposed conceptual framework: applications, design paradigms and technologies

42. Strengths and Weaknesses
Systematically presenting knowledge about code mobility: motivations, concepts, principles, approaches, technologies, etc., therefore, providing a complete image
Expounding is vivid with metaphor

43. Relevance to Embedded Systems
Many embedded systems are resource-constrained
Requirements to them are higher and higher
Code mobility technology providing a possible solution
Many embedded systems are real-time systems that can not be stopped to do operations such as update