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Naming in Distributed Systems. Lecture # 5. Overview. Pure vs impure names IDs, Addresses,Name Space, Name Resolution Implementation of a Naming Service Case Studies: Telephone System. DNS, SLP(X.500), INS Reading: Jerome, Kaashoek: Chapter 3
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Naming in Distributed Systems Lecture # 5
Overview • Pure vs impure names • IDs, Addresses,Name Space, Name Resolution • Implementation of a Naming Service • Case Studies: Telephone System. DNS, SLP(X.500), INS • Reading: • Jerome, Kaashoek: Chapter 3 • Coulouris: Distributed Systems, Addison Wesley, Chapter 9
Pure vs impure: What’s in a name • Pure Names: Uninterpreted string of bits • Independent of object location or semantics • Impure Names: • Encode object semantics and/or location • Telephone Numbers? • Descriptions • Always Search
Naming Scheme • Name Space • Syntax: Different naming conventions • 128.67.34.255 • 92-42-5722670 • StringBuffer • Naming Resolution Algorithm • Value: Destination • Frequently: Context
Examples of Naming Telephone System • Numeric name space (length dependant on the size of the city) • Hierarchical Structuring of Names • 92-42-5722670 • Hierarchical Name Resolution • Lookup: Directories • Value? • Context?
Naming Examples • Naming Variables • Naming convention • Variable Names: start with an alphabet • Class Names: start with capitalization • Value: Address of Memory Location • Pointers: Indirection • Resolution: • Symbol Tables • Context • Scoping? • Dynamic • Lexical: Static • Hierarchical Names • Java: Derived from directory structure
Naming Examples • DNS • Names as Path Names Root Root.yahoo n2 n1 k1 Root.n1.k1.lums
Closure in Naming • Names closed under composition • Using a root • Absolute Vs. Relative Paths • Context • DNS • Mailto: zahoor (from within lums) • Directory • Working directory
Name Resolution • DNS Terminology • Iterative vs. Recursive • Essentially • State management in resolution • Caching • Communication Cost
Iterative cs.lums.edu.pk root Client-side Name Resolver cs.lums.edu.pk cs.lums.edu pk cs.lums.edu cs.lums cs.lums edu cs lums IP # CS www.lums.edu.pk cs IP number
Recursive cs.lums.edu.pk root Client-side Name Resolver IP # cs cs.lums.edu cs.lums.edu pk cs.lums cs.lums edu cs IP # CS lums www.lums.edu.pk cs IP number
Recursive vs iterative • State • Caching • Communication latency