Distributed Systems: Naming Continued

1
Distributed SystemsNaming (Continued)

• CS 654Lecture 10October 19, 2006(Makeup day)

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Merging Namespaces

• How can we merge namespaces? Are there any
  issues?
• Mounting
• Can be used to merge namespaces.
• In the hierarchical case, what is needed is a
  special directory node that jumps to the other
  namespace.

3
Mounting

• Mounting remote name spaces through a specific
  process protocol.
• How do you access steens mbox from Machine A?

4
GNS Mounting

• Organization of the DEC Global Name Service

5
Name Space Implementation

• Name spaces always map names to something.
• DNS maps what to what?
• Can be divided into three layers
• Global layer Doesnt change very often.
• Administrational layer Single organization
• Managerial layer Change regularly

6
Name Space Distribution

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

7
Name Server Characteristics

• 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.

8
Name Resolution

• A name resolver looks up names.
• How about a simple hash table?
• Overload if just one.
• Replicate?
• How do you update a record?
• The idea is that you want to distribute the load,
  but do it in the right way.
• Assume that we use a hierarchical name space.

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Iterative Name Resolution

• Consider the name rootltnl, vu, cs, ftp, pub,
  globe, index.txtgt.

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Recursive Name Resolution

• The principle of recursive name resolution.

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Recursion and Caching

• Recursive name resolution of ltnl, vu, cs, ftpgt.
  Name servers cache intermediate results for
  subsequent lookups.
• Is iterative or recursive better for caching?

12
Name Resolution Communication Costs

• The comparison between recursive and iterative
  name resolution with respect to communication
  costs.