Transcript Sess_08 - Vin Costa`s Wiki

Session 8
Networking & Operating Systems
Fall 2011
Nassau Community College
ITE153 – Operating Systems
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Networking & Operating
Systems
Introduction
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How It All Started
1969
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How It All Started
1969
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Internet History
Evolved from ARPANet (Defense
Department’s Advanced Research Projects
Agency Network)
ARPANet was developed in 1969, and was
the first packet-switching network
Initially, included only four nodes: UCLA,
UCSB, Utah, and SRI
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NSF and the Internet
In the 1980s, NSFNet extended packetswitched networking to non-ARPA
organization; eventually replaced ARPANet
Instituted Acceptable Use Policies to control
use
CIX (Commercial Internet eXchange) was
developed to provide commercial
internetworking
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The World Wide Web
Concept proposed by Tim Berners-Lee in
1989, prototype WWW developed at CERN in
1991
First graphical browser (Mosaic) developed
by Mark Andreessen at NCSA
Client-server system with browsers as clients,
and a variety of media types stored on
servers popped up everywhere
Uses HTTP (Hyper Text Transfer Protocol) for
retrieving files
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Connecting to the Internet
End users get connectivity from an ISP
(Internet Service Provider)
Home users use dial-up, ADSL, cable
modems, satellite, wireless
Businesses use dedicated circuits
connected to LANs
ISPs use “wholesalers” called network
service providers and high speed (T-3 or
higher) connections
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US Internet Access Points
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Internet Addressing
32-bit global Internet address
Includes network and host identifiers
Dotted decimal notation
11000000 11100100 00010001 00111001
(binary)
192.228.17.57 (decimal)
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Internet Addressing
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Network Classes
Class A: Few networks, each with many hosts
All addresses begin with binary 0
Range: 1-126
Class B: Medium networks, medium hosts
All addresses begin with binary 10
Range: 128-191
Class C: Many networks, each with few hosts
All addresses begin with binary 11
Range: 192-223
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Domain Name System
32-bit IP addresses have two drawbacks
Routers can’t keep track of every network path
Users can’t remember dotted decimals easily
Domain names address these problems by
providing a name for each network domain
(hosts under the control of a given entity)
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DNS Database
Hierarchical database containing name, IP
address, and related information for hosts
Provides name-to-address directory
services
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Domain Tree
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Networking & Operating
Systems
IP, Protocols, Routing, Layers
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Private Networks
Isolated to individual organizations
Emergence of computer security
Sharing a system
Protecting data
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Networking
Networks start talking to each
other
Gateways
Arpanet
TCP/IP Everywhere
Vinton Cerf,
“IP On Everything!”
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Maturing of the Internet
Telephones used by 50% of worlds
population
Internet attained similar level of growth in
2010 – approaching max growth
Connecting computers and programmable
devices
More devices than people
Internet of Things
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Early Hacking
Cap’n Crunch cereal prize
Giveaway whistle produces
2600 MHz tone
Blow into receiver – free
phone calls
“Phreaking” encouraged by
Abbie Hoffman
Doesn’t hurt anybody
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Captain Crunch
John Draper
`71: Bluebox built by many
Jobs and Wozniak were early
implementers
Developed “EasyWriter” for first
IBM PC
High-tech hobo
Whitehat hacker
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Protocols in a Simplified
Architecture
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Protocol Data Units
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Operation of a Protocol
Architecture
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TCP and UDP Headers
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IP Headers
32-bit field
QoS
max # allowable hops
128-bit field
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TP/IP Concepts
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Client-Server Model
The client–server model of computing is a
distributed application that partitions tasks or
workloads between the providers of a resource
or service, called servers (daemons), and
service requesters, called clients.
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Daemons Aren’t Evil
Daemon is a computer program
that runs in the background,
rather than under the direct
control of a user; they are usually
initiated as background processes
Developers began to use the word daemon
to describe background processes which
worked tirelessly to perform system chores
ftpd, httpd, smtpd – look for the “d” suffix
Windows calls these services
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PDUs in TCP/IP
TCP
Header
IP
Header
Network
Header
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User
Data
Application
Byte Stream
User
Data
TCP
Segment
User
Data
IP
Datagram
User
Data
Network-level
Packet
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Some TCP/IP Protocols
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Assigned Port Numbers
Port
Service
Port
Service
7
echo
110
pop3
20
ftp-data
119
nntp
21
ftp
123
ntp
23
telnet
389
ldap
25
smtp
443
https
39
rip
500
isakmp
53
DNS
520
rip2
80
http
1812
radiusauth
88
kerberos
2049
Sun NFS
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Alternate Routing Diagram
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Hands-on
Exercises
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Hands-On
Examine some sites using whois and
traceroute for the domain name and
the IP address. See how much you can
find out about a site
Try: whois ncc.edu
Try: traceroute www.google.com
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Important URLs
http://www.networksolutions.com/whois/index.jhtml the original InterNIC. This site has the “whois”
database
http://www.arin.net - American registry for Internet
numbers. This site has a “whois” database for IP
numbers
http://network-tools.com/ - tools: traceroute, ping,
nslookup, whois, dig
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Homework
Review the Slides
Work on the Take Home Exam
Due next Monday at the latest
Do the Exercise: “whois and traceroute”
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The Internet Highway
…a parting thought
There is a road, no simple highway,
Between the dawn and the dark of night,
And if you go no one may follow,
That path is for your steps alone.
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