Process MigrationOutlineWhat is process Migration?MotivationSlide 5Process Migration MechanismsExample:What is migratedSlide 8What is migrated?Slide 10Slide 11Slide 12Slide 13Secure Process MigrationSandbox modelJAVA Security MechanismReference1Process MigrationGroup A4:Min FangBryan MadenChris Sun2Outline•Definition•Motivation•Mechanisms•Security – Sand box model3What is process Migration?•Transfer of sufficient amount of the state of a process from one machine to another•The process executes on the target machine.4Motivation•Load sharing–Move processes from heavily loaded system to lightly loaded system.•Communication performance–Processes that interact intensively can be moved to the same node to reduce communication cost5Motivation•Availability–long-running process may need to move because the machine it is running on will be down6Process Migration Mechanisms•Who initiates the migration?•What happens to outstanding messages and signals?•What “portion” of the process is migrated?7Example:What is migrated8Example:What is migrated9What is migrated?•Eager (all): Transfer entire address space–No trace of process is left behind–It could be unnecessarily expensive, if address space is large and the process does not need most of it.10What is migrated?•Precopy: Process continues to execute on the source code while the address space is copied–Pages modified on the source node have to be copied a second time–reduce the process frozen time11What is migrated?•Eager (dirty): Transfer only portion of the address space that is in main memory and have been modified–Any additional blocks of the virtual address space are transferred on demand–The source machine is involved throughout the life of the process12What is migrated?•Copy-on-reference: Pages are only brought over on reference.–Variation of eager (dirty)–Has lowest initial cost of process migration13What is migrated?•Flushing: Pages are cleared from main memory by flushing dirty pages to disk–Relieves the source of holding any pages of the migrated process in main memory.14Secure Process Migration•Protect the migrating process–Impossible to fully protect all kinds of attacks–Possible to detect modifications: Ajanta system–Read only state–Append-only logs–Selective revealing•Protect the target–Sand box model–Playground model15Sandbox model•Provide a restricted environment to confine the behavior of a process instead of eliminating process execution failures.•Each instruction of the migrated process can be fully controlled.16JAVA Security Mechanism•The Class Loader: download into correct name space tagged with security info•The byte code verifier: check if the un-trusted code obey the security rules of the sandbox.•The security manager: authenticate the mobile code and makes the decision17Reference•Tanenbaum and Steen, Distributed Systems: Principles and Paradigms.•Stallings, Operating Systems 4th
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