Transcript Overview of Computer Networks

CPET 355
Data Communications & Networking
7. The Application Layer:
Domain Name System
Paul I-Hai Lin, Professor
Electrical and Computer Engineering
Technology
Purdue University, Fort Wayne Campus
April 5, 2004
Prof. Paul Lin
1
The Application Layer
(TCP/IP-based)






Introduction
TCP/IP Application Suites
DSN – The Domain Name System
Electronics Mail
The World Wide Web
Other TCP/IP applications?
April 5, 2004
Prof. Paul Lin
2
Web Site References for
Standards






W3C World Wide Web Consortium - http://www.w3.org/
Internet Architecture Board (IAB) of Internet
Society (http://ww.isoc.org/index.html)
Internet Engineering Task Force - http://www.ietf.org/
RFC Pages -http://www.ietf.org/rfc.html
International Organization for Standardization http://www.iso.org/iso/en/ISOOnline.frontpage
Internet Corporation for Assigned Names and Numbers http://www.icann.org/
April 5, 2004
Prof. Paul Lin
3
Request For Comments




<http://ietf.cnri.reston.va.us/rfc/>
Working notes of the Internet
research and development
community
A RFC may be recommended by the
IETF to become a standard
Web site that hold archives relate to
the Internet and IETF
April 5, 2004
Prof. Paul Lin
4
TCP/IP Applications




Telnet: Remote Login (RFC 854)
TFTP: Trivial File Transfer Protocol
FTP: File Transfer Protocol (RFC 959)
File Access using NFS (Network File
Systems) and RPC (Remote Procedure
Call)
April 5, 2004
Prof. Paul Lin
5
TCP/IP Applications




Telnet: Remote Login (RFC 854)
TFTP: Trivial File Transfer Protocol
FTP: File Transfer Protocol (RFC 959)
File Access using NFS (Network File
Systems) and RPC (Remote Procedure
Call)
April 5, 2004
Prof. Paul Lin
6
The Domain Name System

The Need for Unique Name Spaces
• Binding the names and IP addresses
• Flat name space (no structure, a flat table)
• Hierarchical name space (tree type: root, node)

The DNS Purpose:
• mapping host names and e-mail destinations to IP
addresses
• Map domain names onto resource records

Resource Record (five-tuple)
Domain_name
April 5, 2004
Time_to_live Class Type Value
Prof. Paul Lin
7
The Domain Name System




A hierarchical, domain-based naming
scheme, and a distributed database
system
A distributed Internet directory service
RFC 1034 – Domain Name: Concepts &
Facilities, 1987
RFC 1035 – Domain Name:
Implementation and Specification, 1987
April 5, 2004
Prof. Paul Lin
8
Domain Name Space




Each node in the DNS tress has a “Label”
A domain is a subtree of the domain name
space
Each node has a “Domain Name”
ICANN (www.icann.org) Internet
Corporation for Assigned Names and
Numbers
April 5, 2004
Prof. Paul Lin
9
Distribution of Domain Name


Two Top Level Domains before year 2000:
Generic and Countries
In Nov. 2000, ICANN approved
• Four new general purpose top-level domains:

biz (business), info (information), name (people’s
name), pro (professions)
• Three specialized top-level domains:

April 5, 2004
aero (aerospace industry), coop (co-operatives),
and museum
Prof. Paul Lin
10
Domain Name Space


The Country Domain - ISO 3166
Top-Level Domain Name Examples (Generic)
•
•
•
•
•
•
•
com
- commercial
edu
- educational institutions
org
- nonprofit organizations
net
- network providers
gov
- the U.S. federal government
mil
- the U.S. armed forces
int
- certain international organizations,
www.un.int
April 5, 2004
Prof. Paul Lin
11
Domain Name Space

Top-Level Countries Domain
(http://www.iana.org/cctld/cctld-whois.htm)
•
•
•
•
•
•
•
us
mx
tw
kr
Jp
nl
br
April 5, 2004
- U.S.
- Mexico
- Taiwan
- Korean
- Japan
- Netherlands
- Brazil
Prof. Paul Lin
12