Name & Directory Name & Directory ServicesServices

Yang WangYang Wang

OutlineOutline

• Why and What?

• Some important Terms.

• How to do?

• History and Implementation.

• Example and Experiment

• References

Why We Need It?Why We Need It?

• Making a request to a service or accessing an object by means of inter-process communication requires that must one first locate the service or object.[1]

• Look-up operations.

• [1].Randy Chow,Theodore Johnson, “Distributed Operating Systems & Algorithms”, 1998

What Is It?What Is It?

• Name Service or Directory Service: Describing how a named object can be addressed and subsequently located by using its address.[1]

Resolution processResolution process

• The operation of locating an object.

• Two stages:

• Name resolution maps names to logical addresses. (who the object is.)

Address resolution that maps logical addresses to network routes.(where the object can be found.)[1]

PurposePurpose

• Enable user to reference network resources with short names instead of real addresses.

• Locate object by attributes.

• Provide a layer of transparency so that the network resources can be managed independently.[3]

OutlineOutline

• Why and What?

• Some important Terms.

• How to do?

• History and Implementation.

• Example and Experiment

• References

Name SpaceName Space

• Object attributes

• Focus on name and address.

• Collection of names ,with their corresponding attributes and addresses.

Name StructuresName Structures

• 1.flat structure <attributes> Physical

• 2.hierachical <name,attributes,address>

(DNS) Organizational

• 3.structure-free <name,type,attributes,address>

Functional

OutlineOutline

• Why and What?

• Some important Terms.

• How to do?

• History and Implementation.

• Example and Experiment

• References

Storage model(x.500)Storage model(x.500)

• X.500 DIB directory information base.• DIT Directory Information Tree.• Naming domain: a sub-name space for which

there is a single administrative authority for name management.

• Naming Context: basic units for distributing the info base to Directory Service Agents.

• DSA: The server for the name service.• DUA: directory user agent[1]

ResulotionResulotion

• DSA

• DUA initiate the resolution.

3 kinds

Enhancement Enhancement

• Caching (DNS)

• Replication

OutlineOutline

• Why and What?

• Some important Terms.

• How to do?

• History and Implementation.

• Example and Experiment

• References

History of Name ServiceHistory of Name Service

1. In 60s and early in 70s, hosts file and other files used to store parameters and information for locating.

Drawbacks: modify frequently, larger and larger.[7]

[7].Larry Gouthier, 1998, Directory-enabled computing: the directory's expanding role.

hostshosts

DNSDNS

• Domain Name Service replaced.

• Dynamic and based on server.

• The first standard directory and the most successful one.

• At the same time, people developed Directory for Novel Netware, MS LAN manager,SNA etc.[7]

X.500X.500

• DNS only contains host, domain and address, not enough.

• In the 80s, X.500

• Drawback: too complicated, not support by MS.Mainly In unix -> LDAP[7]

• [7].Larry Gouthier, 1998, Directory-enabled computing: the directory's expanding role.

ImplementationImplementation

• Active Directory for Windows 2000, Server 2003

• Apple Open Directory in Mac OS X Server

• Novell eDirectory - formerly called Novell Directory Services (NDS) for Novell NetWare version 4.x-5.x

• OpenLDAP

• Sun Directory Services

OutlineOutline

• Why and What?

• Some important Terms.

• How to do?

• History and Implementation.

• Example and Experiment

• References

ExampleExample

• DNS

• Domain Name System

Name spaceName spaceRoot DomainRoot Domain

SubdomainsSubdomains

Second-Level DomainSecond-Level Domain

Top-Level DomainTop-Level Domain

FQDN:server1.sales.south.nwtraders.com

FQDN:server1.sales.south.nwtraders.com

southsouth

nwtradersnwtraders

comcom

salessales

westwest easteast

orgorgnetnet

Host: server1Host: server1

DNSDNS Locating ProcessLocating Process

Computer1Computer1

Local DNS Server

Local DNS Server

nwtraders.comnwtraders.com

Root Hint (.)Root Hint (.)

.com.com

Recu

rsive

que

ry fo

r

mail

1.nw

trade

rs.co

m17

2.16

.64.

11

Iterative Query

Iterative Query

Iterative Query

Ask .com

Ask nwtraders.com

Authoritative Response33

22

11

Some new researchSome new research

• Load distribution.[6]

• Web Content distribution.[6]

• [6]. James E Kurose, Keith W.Ross, 2007,Computer Networking, 4th Edition.

ReferencesReferences

• 1.Randy Chow,Theodore Johnson, “Distributed Operating Systems & Algorithms”, 1998

• 2. Jeff Hodges,"Introduction to Directories and LDAP", June 1997

• 3. http://en.wikipedia.org/wiki/Directory_service • 4. http://en.wikipedia.org/wiki/X.500• 5.

http://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol

• 6. James E Kurose, Keith W.Ross, 2007,Computer Networking, 4th Edition.

continuecontinue

• 7.Larry Gouthier, 1998, Directory-enabled computing: the directory's expanding role.

• 8.Akamai 2007,http://www.akamai.com

• 9.RFC 1034, RFC 1035