Name Services - Distributed Operating Systems - Lecture Slides, Slides for Computer Science. All India Institute of Medical Sciences
ekana
ekana27 March 2013

Name Services - Distributed Operating Systems - Lecture Slides, Slides for Computer Science. All India Institute of Medical Sciences

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These are the Lecture Slides of Distributed Operating Systems which includes Neumann Bottleneck, Networked Information, Memory Hierarchy, Evidence, Latency, Communication, Intelligent Service, Communication Latency, Rout...
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Name Services

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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

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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

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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

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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

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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)

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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

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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

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Features

• Name services look up attributes of an object by providing an object’s name.

• Hierarchical in structure

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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

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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

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GNS Features & Structure

• Names – Directory names = ab/cd/ef/qwm – Value names = jessie.crane/password

• Replication and caching essential

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X500 Features & Structure

• Directory services return attributes that match specified attr.

• Yellow pages service • Directory Information

Tree (DIT) • Replication and

caching Docsity.com

Jini Features & Structure

• Registers the services provided in a spontaneous networking environment

• Look-up service & Jini • Print from laptop

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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

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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

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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

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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

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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

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Discovery Service Application

• Google – finds pages that are openly available on the Web.

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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

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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

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