Name & Directory Services Yang Wang

Outline Why and What? Some important Terms. How to do? History and Implementation. Example and Experiment References

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

Resolution 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]

Purpose 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]

Outline Why and What? Some important Terms. How to do? History and Implementation. Example and Experiment References

Name Space Object attributes Focus on name and address. Collection of names,with their corresponding attributes and addresses.

Name Structures 1.flat structure Physical 2.hierachical (DNS) Organizational 3.structure-free Functional

Outline Why and What? Some important Terms. How to do? History and Implementation. Example and Experiment References

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]

Resulotion DSA DUA initiate the resolution. 3 kinds

Enhancement Caching (DNS) Replication

Outline Why and What? Some important Terms. How to do? History and Implementation. Example and Experiment References

History 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.

hosts

DNS 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.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.

Implementation 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

Outline Why and What? Some important Terms. How to do? History and Implementation. Example and Experiment References

Example DNS Domain Name System

Name space Root Domain Subdomains Second-Level Domain Top-Level Domain FQDN: server1.sales.south.nwtraders.com FQDN: server1.sales.south.nwtraders.com south nwtraders com sales west east org net Host: server1

DNS Locating Process Computer1 Local DNS Server Local DNS Server nwtraders.com Root Hint (.).com Recursive query for mail1.nwtraders.com Iterative Query Ask.com Ask nwtraders.com Authoritative Response

Some new research Load distribution.[6] Web Content distribution.[6] [6]. James E Kurose, Keith W.Ross, 2007,Computer Networking, 4 th Edition.

References 1.Randy Chow,Theodore Johnson, “Distributed Operating Systems & Algorithms”, Jeff Hodges,"Introduction to Directories and LDAP", June s_Protocol s_Protocol 6. James E Kurose, Keith W.Ross, 2007,Computer Networking, 4 th Edition.

continue 7.Larry Gouthier, 1998, Directory-enabled computing: the directory's expanding role. 8.Akamai 2007, 9.RFC 1034, RFC 1035