Fall 2011 Nassau Community College ITE153 – Operating Systems 1 Session 8 Networking & Operating Systems

Fall 2011 Nassau Community College ITE153 – Operating Systems 2

Introduction Fall 2011 Nassau Community College ITE153 – Operating Systems 3 Networking & Operating Systems

How It All Started Fall 2011 Nassau Community College ITE153 – Operating Systems

How It All Started Fall 2011 Nassau Community College ITE153 – Operating Systems

Fall 2011 Nassau Community College ITE153 – Operating Systems 6 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

Fall 2011 Nassau Community College ITE153 – Operating Systems 7 NSF and the Internet In the 1980s, NSFNet extended packet- switched 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

Fall 2011 Nassau Community College ITE153 – Operating Systems 8 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

Fall 2011 Nassau Community College ITE153 – Operating Systems 9 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

Fall 2011 Nassau Community College ITE153 – Operating Systems 10 US Internet Access Points

Fall 2011 Nassau Community College ITE153 – Operating Systems 11 Internet Addressing 32-bit global Internet address Includes network and host identifiers Dotted decimal notation (binary) (decimal)

Fall 2011 Nassau Community College ITE153 – Operating Systems 12 Internet Addressing

Fall 2011 Nassau Community College ITE153 – Operating Systems 13 Network Classes Class A: Few networks, each with many hosts All addresses begin with binary 0 Range: Class B: Medium networks, medium hosts All addresses begin with binary 10 Range: Class C: Many networks, each with few hosts All addresses begin with binary 11 Range:

Fall 2011 Nassau Community College ITE153 – Operating Systems 14 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)

Fall 2011 Nassau Community College ITE153 – Operating Systems 15 DNS Database Hierarchical database containing name, IP address, and related information for hosts Provides name-to-address directory services

Fall 2011 Nassau Community College ITE153 – Operating Systems 16 Domain Tree

IP, Protocols, Routing, Layers Fall 2011 Nassau Community College ITE153 – Operating Systems 17 Networking & Operating Systems

Private Networks Isolated to individual organizations Emergence of computer security Sharing a system Protecting data Fall 2011 Nassau Community College ITE153 – Operating Systems 18

Networking Networks start talking to each other Gateways Arpanet TCP/IP Everywhere Vinton Cerf, “IP On Everything!” Fall 2011 Nassau Community College ITE153 – Operating Systems 19

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 Fall 2011 Nassau Community College ITE153 – Operating Systems 20

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 Fall 2011 Nassau Community College ITE153 – Operating Systems 21

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 Fall 2011 Nassau Community College ITE153 – Operating Systems 22

Fall 2011 Nassau Community College ITE153 – Operating Systems 23 Protocols in a Simplified Architecture

Fall 2011 Nassau Community College ITE153 – Operating Systems 24 Protocol Data Units

Fall 2011 Nassau Community College ITE153 – Operating Systems 25 Operation of a Protocol Architecture

Fall 2011 Nassau Community College ITE153 – Operating Systems 26 TCP and UDP Headers

Fall 2011 Nassau Community College ITE153 – Operating Systems 27 IP Headers 128-bit field 32-bit field QoS max # allowable hops

Fall 2011 Nassau Community College ITE153 – Operating Systems 28 TP/IP Concepts

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. Fall 2011 Nassau Community College ITE153 – Operating Systems 29

Daemons Aren’t Evil 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 Fall 2011 Nassau Community College ITE153 – Operating Systems 30 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 processescomputer programbackgroundprocesses

Fall 2011 Nassau Community College ITE153 – Operating Systems 31 PDUs in TCP/IP TCP Header User Data IP Header User Data Network Header User Data Application Byte Stream TCP Segment IP Datagram Network-level Packet

Fall 2011 Nassau Community College ITE153 – Operating Systems 32 Some TCP/IP Protocols

Fall 2011 Nassau Community College ITE153 – Operating Systems 33 Assigned Port Numbers Sun NFS2049kerberos88 radiusauth1812http80 rip2520DNS53 isakmp500rip39 https443smtp25 ldap389telnet23 ntp123ftp21 nntp119ftp-data20 pop3110echo7 ServicePortServicePort

Fall 2011 Nassau Community College ITE153 – Operating Systems 34 Alternate Routing Diagram

Hands-on Exercises Fall 2011 Nassau Community College ITE153 – Operating Systems 35

Fall 2011 Nassau Community College ITE153 – Operating Systems 36 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

Fall 2011 Nassau Community College ITE153 – Operating Systems 37 Important URLs - the original InterNIC. This site has the “whois” database - American registry for Internet numbers. This site has a “whois” database for IP numbers - tools: traceroute, ping, nslookup, whois, dig

Homework Review the Slides Work on the Take Home Exam Due next Monday at the latest Do the Exercise: “whois and traceroute” Fall 2011 Nassau Community College ITE153 – Operating Systems 38

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. Fall 2011 Nassau Community College ITE153 – Operating Systems 39