Name Services Johanna Hultin Carina Hglund Name services
- Slides: 12
Name Services Johanna Hultin Carina Höglund
Name services l Introduction l General Terms l Name Services l Name Space l Name Resolution l Caching
Introduction Names l Fundamental in distributed systems Facilitates communication and resource sharing A consistent naming system is required l Adresses: locations of objects, not identifiers l l
Introduction l Name service l Translates a human-readable name into a system-internal identifier l Ex human readable names: http: //www. facebook. com /etc/passwd l URL Internet Domain Name File name Ex system-internal name: 123. 25. 7. 34 IP address
General terms l Resolution ¡ l Binding ¡ l Set of bindings Attributes: value of property of an object ¡ l Association between an object and a name Context ¡ l Translation of a name into data Ex: address Ex Name Service: ¡ Domain Name System (DNS)
Name Service A name service stores the collection of one or more naming contexts l Major operation: Look at attributes of a given name l Other operations required l ¡ ¡ ¡ l Adding/deleting bindings Listing bound names Adding/deleting context Name management is separated from other services ¡ ¡ Unification: use the same naming scheme Integration: Openness
Ex: Reaching a file from URL address l Domain Name Server ¡ Name service used by webbrowsers to interpret URL and e-mail addresses
Name spaces l All valid names recognized in a particular service ¡ l DNS name space ¡ l Ex: URL in DNS Hierarchical structure Alias ¡ Possible to use a simple name instead of a complicated one ¡ Provides for transparency. l www. example. net is an alias for www. johanna. example. net
Name Resolution l Iterative navigation ¡ DNS
Caching l Holds names that has previously been looked up l Consulted l Availability during name resolution
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