Naming

1
Naming

• CSCI 4780/6780

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Names Naming System

• Names have unique importance
• Resource sharing
• Identifying entities
• Location reference
• Name can be resolved to the entity it refers to
• Naming system resolves names
• Naming system in distributed systems can itself
  be distributed

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Names, Entities Addresses

• Name is a string of bits/characters used to refer
  to an entity
• Entity can resources/users/data/processes
• Web pages, files, hosts, printers, network
  connections
• Entities permit certain operations
  (reading/writing files)
• To operate we need to access the entity
• Access Point A special kind of entity
• Host of a server
• Name of access point is called its Address
• Hosts IP address and port
• Address of access point is the address of the
  entity at that access point

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More on Entities and Addresses

• Entities can have multiple access points
• Multiple telephone numbers/email addresses
• Replicated services
• Entities might change access points
• Laptops get different IP addresses based on their
  location
• New phone number/email when switching jobs
• Can we use the address as the name of an entity?
• Difficulties in relocation/replication
  transparency
• Name that is independent of address Location
  Independent Names

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Identifiers

• An name with following properties
• Identifier refers to at most one entity
• Entity is referred to by at most one identifier
• Identifier always refers to same entity
  (persistence)
• Facilitates unambiguous reference
• Testing equality of identifiers suffices if
  entities being referred to are the same
• Addresses cannot be identifiers if they can be
  re-assigned
• Example Telephone numbers

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Flat Naming

• Identifiers are random bit strings
• No information on how to locate the entity
• Simple location resolution strategies
• Broadcasting (E.g. Address Resolution Protocol
  (ARP))
• Multicasting
• Forwarding Pointers
• A moving entity leaves behind a reference at its
  previous location
• Long chains causes inefficiency
• Maintenance costs
• Vulnerability to broken links

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Forwarding Pointers in SSP Chains

• Figure 5-1. The principle of forwarding pointers
  using (client stub, server stub) pairs.

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Redirection by Shortcuts

• Figure 5-2. Redirecting a forwarding pointer by
  storing a shortcut in a client stub.

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Shortcuts

• Figure 5-2. Redirecting a forwarding pointer by
  storing a shortcut in a client stub.

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Home Based Approaches

• Each entity has a home location
• Permanent address of the entity
• Obtains temporary address when roaming
• Home location keeps track of the current address
  of the entity
• Home agent forwards the packet to the entities
  current location
• Drawbacks?

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Home-Based Approaches

• Figure 5-3. The principle of Mobile IP.