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Name Services

Name Services. Jessie Crane CPSC 550. History. ARPAnet – experimental computer network (late 1960s) hosts.txt – a file that contained all the information about every host on the network Single management domain. History.

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Name Services

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  1. Name Services Jessie Crane CPSC 550

  2. History • ARPAnet – experimental computer network (late 1960s) • hosts.txt – a file that contained all the information about every host on the network • Single management domain

  3. History • TCP/IP standardized connectivity to ARPAnet for all computers (early 1980s) • hosts.txt – traffic and load problems • – file consistency problems • Increasing number of users • NIC had no control over host names

  4. History • NIC called for a replacement of the current system • Centralized system • Single-host bottleneck • Paul Mockapertis created the Domain Name Service (DNS) in 1984. • Distributed database • Hierarchical structure

  5. Name Services • Domain Name Service (DNS) • Maps domain names to IP addresses • Global Name Service (GNS) • Maps global names to their attributes • X500 directory service • Stores collections of bindings between names and attributes • Looks up entries that match attribute-based specs • Jini discovery service • Looks up objects according to attributes

  6. Goals • Objective – look up attributes of an object by providing the object’s name • Handle very large name spaces • Have a long life • Have high availability • Fault tolerance • Tolerance of mistrust (GNS)

  7. Definitions • Names – refer to resources in a distributed system • Name service – stores a collection of naming contexts • Resolves names, which makes communication and resource sharing possible • Different resources use the same naming scheme, such as a URL

  8. Definitions • Replication – the process of copying data from one computer to another • Caching – storing previously looked up information • Resolver – a library routine that creates queries and sends them to a name server

  9. Features • Name services look up attributes of an object by providing an object’s name. • Hierarchical in structure

  10. DNS Features • Maps domain names to IP addresses • Mostly for host names and email addresses • Elements of that allow worldly lookup • Hierarchical partitioning of the name database • Replication of the naming data • Caching

  11. DNS Structure • This method ensures subdirectories or files do not have the same name • Similar to Unix file system • Tree with root set to null • Each node = root of subtree • Subtree = partition of overall database • Decentralize administration

  12. GNS Features & Structure • Names • Directory names = ab/cd/ef/qwm • Value names = jessie.crane/password • Replication and caching essential

  13. X500 Features & Structure • Directory services return attributes that match specified attr. • Yellow pages service • Directory Information Tree (DIT) • Replication and caching

  14. Jini Features & Structure • Registers the services provided in a spontaneous networking environment • Look-up service & Jini • Print from laptop

  15. How to Use DNS • Register a new domain – need to submit a DNS server name and address • Register with current DNS server • Configure new DNS server • /etc/named.boot or /etc/named.conf • URLs and email clients

  16. How to Use Directory Services • Done through and application interface • Examples: • User logging into a system enters a name and password. • User invoking a spell check on a document

  17. How to Use Discovery Services • Jini can go on a home computer • Storage for devices can run directly on the PC • Digital cameras – store pictures • Cell phones – backup the phone book • Answering machine – store long messages • VCR – store video on hard disk

  18. DNS Application • BIND • Resolves Internet host names into IP addresses and vice versa • Most name servers on the Internet run BIND • Old versions of BIND allow DNS spoofing attacks

  19. Directory Service Application • Active Directory Service Interfaces (ASDI) • Compose of interfaces used to access directory services from different networks • adding new users • managing printers • locating resources in a distributed environment • Setting permissions on network resources

  20. Discovery Service Application • Google – finds pages that are openly available on the Web.

  21. Significance of Points • Use a distributed peer-to-peer system instead of DNS • Main reason: do not have to worry about a server being down. • Pros: • Computing power • Storage space • Example: Napster

  22. Summary • DNS is very good and will probably be faster on average than a peer-to-peer system • DNS not have as many security issues • Peer-to-peer no availability issue

  23. References • Albitz, Paul and Liu Crickel, “DNS and BIND.” O’Reilly & Associates, Inc., 2001. • Blanchfield, Sean, An Anonymous and Scaleable Distributed Peer-to-Peer System.” University of Dublin, 2002. • Galli, Doreen L., “Distributed Operating Systems.” Prentice Hall, 2000. • Hauben, Micheal, “History of ARPAnet.” http://www.dei.isep.ipp.pt/docs/arpa.html, 2000. • Yuan, Fei and Li, Xuhui, “Hybrid Searching Algorithm for Loosely-Controlled Peer-to-Peer System.” University of Waterloo, 2002.

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