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Naming

Naming. Naming. Access point & address Location independent naming Identifier It refers to at most one entity Each entity has at most one id An id always refers to the same entity Name-to-address binding Name resolution vs message routing Flat naming Broadcasting and multicasting.

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Naming

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  1. Naming

  2. Naming • Access point & address • Location independent naming • Identifier • It refers to at most one entity • Each entity has at most one id • An id always refers to the same entity • Name-to-address binding • Name resolution vs message routing • Flat naming • Broadcasting and multicasting

  3. Naming versus Locating Entities • Direct, single level mapping between names and addresses. • T-level mapping using identities.

  4. Forwarding Pointers • The principle of forwarding pointers using (proxy, skeleton) pairs.

  5. Forwarding Pointers • Redirecting a forwarding pointer, by storing a shortcut in a proxy.

  6. Home-Based Approaches • The principle of Mobile IP.

  7. Distributed Hash Tables • CHORD • FT_p[i] = first node in range [p+2^(i-1), p+2^i). • Enhance by storing r nodes in the range and during lookup use closest to query

  8. Chord Searching for 26 from 1 Searching for 12 from 28

  9. Hierarchical Approaches • Hierarchical organization of a location service into domains, each having an associated directory node.

  10. Hierarchical Approaches • An example of storing information of an entity having two addresses in different leaf domains.

  11. Hierarchical Approaches • Looking up a location in a hierarchically organized location service.

  12. Hierarchical Approaches • An insert request is forwarded to the first node that knows about entity E. • A chain of forwarding pointers to the leaf node is created.

  13. Pointer Caches • Caching a reference to a directory node of the lowest-level domain in which an entity will reside most of the time.

  14. Pointer Caches • A cache entry that needs to be invalidated because it returns a nonlocal address, while such an address is available.

  15. Scalability Issues • The scalability issues related to uniformly placing subnodes of a partitioned root node across the network covered by a location service.

  16. Structured Name Spaces • A general naming graph with a single root node. Absolute vs relative path names

  17. Name Spaces • The general organization of the UNIX file system implementation on a logical disk of contiguous disk blocks.

  18. Linking and Mounting • The concept of a symbolic link vs a hard link explained in a naming graph.

  19. Linking and Mounting • Mounting remote name spaces through a specific process protocol. • Mount point vs mounting point

  20. Linking and Mounting • Organization of the DEC Global Name Service

  21. Name Space Distribution • An example partitioning of the DNS name space, including Internet-accessible files, into three layers.

  22. Name Space Distribution • A comparison between name servers for implementing nodes from a large-scale name space partitioned into a global layer, as an administrational layer, and a managerial layer.

  23. Implementation of Name Resolution • The principle of iterative name resolution.

  24. Implementation of Name Resolution • The principle of recursive name resolution.

  25. Implementation of Name Resolution • Recursive name resolution of <nl, vu, cs, ftp>. Name servers cache intermediate results for subsequent lookups.

  26. Implementation of Name Resolution • The comparison between recursive and iterative name resolution with respect to communication costs.

  27. The DNS Name Space • The most important types of resource records forming the contents of nodes in the DNS name space.

  28. DNS Implementation • An excerpt from the DNS database for the zone cs.vu.nl.

  29. DNS Implementation • Part of the description for the vu.nl domain which contains the cs.vu.nl domain.

  30. Attribute-based naming • Describe an entity via (attribute,value) pairs • Partial match queries in DB lingo • LDAP and X.500 • Scalability issues • Decrentralized implementations • Attribute-value tree: hash-index for all paths to nodes in XML-like tree

  31. The X.500 Name Space • A simple example of a X.500 directory entry using X.500 naming conventions.

  32. The X.500 Name Space (2) • Part of the directory information tree.

  33. The X.500 Name Space (3) • Two directory entries having Host_Name as RDN.

  34. The Problem of Unreferenced Objects • An example of a graph representing objects containing references to each other.

  35. Reference Counting (1) • The problem of maintaining a proper reference count in the presence of unreliable communication.

  36. Reference Counting (2) • Copying a reference to another process and incrementing the counter too late • A solution.

  37. Advanced Referencing Counting (1) • The initial assignment of weights in weighted reference counting • Weight assignment when creating a new reference.

  38. Advanced Referencing Counting (2) • Weight assignment when copying a reference.

  39. Advanced Referencing Counting (3) • Creating an indirection when the partial weight of a reference has reached 1.

  40. Advanced Referencing Counting (4) • Creating and copying a remote reference in generation reference counting.

  41. Tracing in Groups (1) • Initial marking of skeletons.

  42. Tracing in Groups (2) • After local propagation in each process.

  43. Tracing in Groups (3) • Final marking.

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