Internet Resources Discovery (IRD)

1
Internet Resources Discovery (IRD)

• Introduction to the Internet/WWW

2
Introduction to the Internet

• Internet Resources/Services
• What is the Internet
• Standards/Protocols

3
Internet Resources/Services

• Electronic Mail (E-Mail)
• News (Usenet)
• File Transfer (FTP)
• Remote Login (Telnet)
• Information Browsing (Gopher)
• Automated Title Search (Archie, Veronica)
• Automatic Content Search (WAIS)
• Advanced Browsing (WWW)

4
Internet Resources Discovery (IRD)

• Resources discovery - locating unfamiliar
  resources.
• Resources can be documents, files, users and
  services, both textual and multimedia.
• IRD is resource discovery on the internet and in
  the Web.

5
What is the Internet?

• Internet is a Multi-Network Architecture
• Internet Interconnected Network
• Internet is based on TCP/IP Protocol Set
• IP Internet Protocol
• TCP Transmission Control Protocol
• Based on former ARPANET by DOD

6
Whats the Internet nuts and bolts view

• millions of connected computing devices hosts,
  end-systems
• pcs workstations, servers
• PDAs phones, toasters
• running network apps
• communication links
• fiber, copper, radio, satellite
• routers forward packets (chunks) of data thru
  network

7
Internet Infrastructure
LAN
WAN
LAN
Campus Ethernet
Corporate Network
Regional and National Providers (ISP)
Router
Router
Router
Router
Router
8
Interconnected Network
PrivateDedicated
PublicCircuit Switched
Router
Local Area
ISDN
Bridge
Router
MetropolitanArea
Local Area
Gateway
Gateway
Public Packet Switched
9
Who Runs the Internet?

• nobody
• StandardsInternet Engineering Task Force
  (later)
• Numbers IANA (Internet Assigned Numbers
  Authority)
• Names Internic (US), RIPE (Europe),
• Network ISPs (Internet Service Providers), NAPs
  (Network Access Points),
• Fibers telephone companies (mostly)
• Content thousands of companies, universities,
  individuals,

10
Whats a protocol?

• human protocols
• whats the time?
• I have a question
• introductions
• specific messages sent
• specific actions taken when messages received,
  or other events

• network protocols
• machines rather than humans
• all communication activity in Internet governed
  by protocols

protocols define format, order of
messages sent and received among network
entities, and actions taken on message
transmission, receipt
11
Whats a protocol?

• a human protocol and a computer network protocol

Hi
TCP connection req.
Hi
Q Other human protocol?
12
TCP/IP

• TCP breaks the message data into pieces

Data
IP Packet
13
TCP/IP

• TCP takes a long message and breaks it up
• Each piece has a sequence number.
• Each piece is sent using IP
• Destination has enough info to reassemble
  message.
• Will request missing piece until all is there.

TCP
TCP
IP
Internet
IP
14
IP Packet
Packet Data
From 192.112.36.5
To 128.174.5.6
IP Address
Packet Envelope
15
IP Properties
Network Delay is Variable

• IP will get it there, but
• Message might be lost, or sent out of order.
• Message cant be too long (about 1K max).
• For email, web, want reliable transfer of big
  files.
• Still doesnt say for which process a packet is
  intended
• Message come to a machine, but are handled by a
  process.
• Like a house with many people in it.
• Solution is TCP.

16
Protocols in the TCP/IP Model
Protocols
Application Transport Network Physicaldata
link
TELNET
FTP
SMTP
DNS
TCP
UDP
IP
ARPANET
SATNET
Packetradio
LAN
Networks
17
Internet/WWW Standards

• Internet
• Domain Name System (DNS)
• WWW
• Uniform Resource Locator (URL)
• Hypertext Markup Language (HTML)
• Hypertext Transfer Protocol (HTTP)

18
Domain Name Service (DNS)
cs.biu.ac.il www.netscape.com
www.cmu.edu

• Map Domain Name to IP Address
• Domain Names must be Unique
• Domain Names have many Parts
• Suffix of Domain Names Significant

19
Domain Names
cs.biu.ac.il
il
ac
biu
tau
cs
20
DNS - Domain Name Lookup

• Search in cache
• Search in local repository
• If the name is in the same domain
• If the name was retrieved lately
• Ask other servers

21
DNS - Domain Name Lookup
Domain name server in Israel
Users computer in Israel
Users computer in USA
Name
Internet
IP Address
22
DNS - Domain Name Lookup
Domain name server in Israel
Domain name server in USA
Users computer in Israel
Users computer in USA
Name
Name
Internet
IP Address
IP Address
23
Uniform Resource Locator (URL)
URL is an address of a Web page in the
Internet.
Protocol//domain-nameport/directory/file-name

• Protocol http, ftp, gopher...
• Domain-Name (or IP-address)
• Port (for security purposes)
• Directory
• File-Name

Example http//www.cs.biu.ac.il8080/taly/mm/ind
ex.html