Safe Dynamic Adaptation

1
Safe Dynamic Adaptation
Department of Computer Science Engineering
Ji Zhang and Zhenxiao Yang Advisor Prof. Betty
H.C. Cheng Software Engineering and Network
Systems (SENS) Laboratory

• Dependency invariants The relationships among
  the components that should be held true
  throughout the programs execution.
• A system configuration is safe if the
  configuration does not violate any dependency
  invariants.
• Safe adaptation process definition
• The process does not interrupt atomic
  communication.
• The process does not violate dependency
  invariants.
• Safe Adaptation Process
• Constructing minimum adaptation path (Figure 2)
• Construct safe configuration set The set of
  safe configurations.
• Construct safe adaptation graph Vertices are
  safe confi-gurations and arcs are adaptive
  actions. Each action is as-signed a application
  specific cost value .
• Search for minimum adaptation path (MAP) The
  path with minimum cost from one configuration
  (source) to another (target).

• Motivation
• Dynamic adaptation is the trend Increasingly,
  computer software systems and applications must
  adapt to changing con-ditions in both the
  supporting computing and communication
  infrastructure, as well as in the surrounding
  physical environ-ment.
• Examples warranting dynamic adaptations
• Dynamic introductions of new strategies.
• Quick responses to security threats.
• Switching to certain execution mode to save
  battery life.
• Insertions of encryption layers to network
  protocol stack.
• Existing research efforts include
• Supports in programming languages
• Framework supporting adaptation
• Adaptive middleware
• Adaptable and extensible operating systems
• Separation of concerns These techniques
  separates the adaptation behavior from the base
  program behavior.
• Safe dynamic adaptation

• Filter schemas Two forward error correction
  schemes are available for data processing DES
  64-bit encoding/decoding, and DES 128-bit
  enco-ding/decoding.
• The server has two components E1 ( a DES 64-bit
  encoder) and E2 ( a DES 128-bit encoder).
• The hand-held client has three components D1 ( a
  DES 64-bit de-coder), D2 ( a DES 128/64-bit
  compatible decoder), and D3 (a DES 128-bit
  decoder).
• The laptop client has two components D4 (a DES
  64-bit decoder) and D5 (a DES 128-bit decoder).
• Adaptations and adaptive actions
• The overall adaptation objective is to
  reconfigure the system from running the DES
  64-bit encoder/decoders to running the DES
  128-bit encoder/decoders to "harden" security at
  run time.
• Available adaptation actions are inserting,
  removing, and replacing filter(s)

In the example, we use a 7-bit vector
(D5,D4,D3,D2,D1,E2,E1) to represent a
configuration. The source configuration is
(0100101) and the target configuration is
(1010010).
May. 10, 2004