Basic NetworkingBasic Networking

History of the InternetHistory of the Internet

• 1957 - Soviets launch Sputnik, which leads U.S. to create the Advanced Research Projects Agency (ARPA)

• 1961 - Leonard Kleinrock: Information Flow in Large Communication Nets. First paper on packet-switching theory

• 1965 - ARPA study on "cooperative network of time-sharing computers". Linked with a dedicated 1200bps phone line!

• 1967 - First design paper on ARPANET• 1968

– PS-network presented to ARPA– Begin development of host-level protocols

History of the InternetHistory of the Internet

• 1969* - ARPANET commissioned by DoD for research into networking– Node 1: UCLA– Node 2: Stanford– Node 3: University of California Santa

Barbara– Node 4: University of Utah

• 1969 - first login (resulted in crash)

When Things Were SimplerWhen Things Were Simpler

History of the InternetHistory of the Internet• 1970 - ALOHAnet (first packet-based radio

network) developed. Connected to ARPANET in '72

• 1971 - 15 Nodes; email invented by Tomlinson based on SENDMSG

• 1972 - – the '@' sign was chosen by Tomlinson (he modified

the email program created by ARPANET).– First email mgmt system 'RD' written– First computer-to-computer chat– French try to create CYCLADES– Telnet specification created (RFC 318)

History of the InternetHistory of the Internet

• 1973– First international connections to

University College of London– Bob Metcalf creates Ethernet– Bob Kahn thinks of gateways– FTP specification– Network Voice Protocol enables

conference calls– Study shows email comprises 73% of

traffic

History of the InternetHistory of the Internet

• 1974 - TCP designed (Cerf and Kahn)• 1975

– first mailing list– First satellite link across two oceans (Hawaii

and UK)

• 1976 - Elizabeth II sends an email• 1978 - TCP splits into TCP and IP• 1979

– First MUD– USENET – Emoticons first used -) (tongue in cheek)

History of the InternetHistory of the Internet

• 1980 - ARPANET grinds to halt because of virus

• 1982 - ARPA establishes Transmission Control Protocol (TCP) and Internet Protocol (IP)

• 1983 - Nameserver developed at Univ. Wisconsin

• 1984– DNS introduced– Nodes breaks 1000

History of the InternetHistory of the Internet

• 1985 - Symbolics.com assigned first registered domain. (others were cmu.edu, perdue.edu, rice.edu, think.com, css.gov, mitre.org)

• 1987– Al Gore invents internet (actually

helped lobby the US research and education network)

– Number of hosts breaks 10,000

History of the InternetHistory of the Internet

• 1988 - Internet Worm affects ~6000 of the 60,000 hosts– IRC developed by Jarkko Oikarinen

• 1989– hosts break 100,000– CompuServe and MCIMail first commercial

email carriers

• 1990– ARPANET ceases to exist– First internet dial-up access (world.std.com)

History of the InternetHistory of the Internet

• 1991– Gopher released– World Wide Web released (Tim Berners-Lee)– PGP (Pretty good privacy) released by Paul

Zimmerman

• 1992– Hosts break 1,000,000– First audio/video multicast– "Surfing the Internet" is coined by Jean

Polly

History of the InternetHistory of the Internet

• 1993– InterNIC created by NSF– First internet talk-radio– Mosaic becomes popular (WWW grows

at 341,634% annually)

• 1994– Web traffic beats Telnet traffic– Shopping malls online– First banner ads on hotwired.com

History of the InternetHistory of the Internet

• 1995– Sun launches Java– Real Audio– WWW surpases FTP traffic– Traditional Online dialup (AOL, CompuServe)

provide Internet Access– Netscape becomes popular– Restrictions of the internet in certain

countries

• 2000 - 1 billion indexable pages– Internet2 backbone network deploys

GrowthGrowth

• As of July 2002, there are 162,128,493 hosts.

ConclusionConclusion

• The internet is popular

So What is It?So What is It?

• The internet (currently) is simply the physical connection between machines.– Computers– Cables– Basic Infrastructure

• The World-Wide-Web is a structure of documents that resides on machines connected to the internet

• People often confuse the two!

Network ConfigurationsNetwork Configurations• LAN - Local Area Network

– Think Clayton State

• WAN - Wide Area Network– Think University System of Georgia– Connects multiple LANs together

• Internet - system of linked networks• Intranet - a private network often used in

business• Ethernet - most popular physical layer

– Others include Token Ring, Fiber, ATM…

HardwareHardware

• Network Interface Cards (NICs) - connect a PC to the network

• Hubs - takes incoming signal and repeats it• Bridge - connects separate networks

together• Switch - examines packets before

forwarding • Router - filter out packets by protocol (or

ports) instead of packet• 802.11 - a standard for wireless networking

ProtocolsProtocols

• Simply a way of how computers identify one another on the network (TCP/IP, IPX, AppleTalk, etc)

• Also a way of establishing how information will be sent– Usually a handshake– Then data

PacketsPackets

• Also called "datagram"• TCP/IP is a "connectionless" technology• Information is sent in the form of packets

– Header information, such as srcIP and destIP– Port numbers– Sequence number– Checksum– Number of hops– Etc..

TCP/IPTCP/IP• TCP (Transmission Control Protocol)

– Make sure data gets through to other end– Rebroadcasts if necessary– Breaks large data into smaller packets (later)

and then re-assembles them again– Make sure everything arrives correctly– Puts things in order– Sits on top of IP

• IP (Internet Protocol)– Provides basic service of getting packets to their

destination– Responsible for routing individual packets

TCP vs UDPTCP vs UDP

• Two major modes:• TCP: a guaranteed protocol (receive ACKs)• UDP: a non-guaranteed protocol (why

have it?)•Simpler protocol than TCP•Good for small data•No sequence numbers

• What about UDP mail? A good idea?• Simpler protocol (ICMP doesn't even

contain port numbers!)

Ethernet LevelEthernet Level

• Broadcast medium• When you send data out, all machines on

the network receive that data• Ethernet card has a unique MAC address

on it• Only supposed to listen for it's MAC

address• Can "sniff" the network (promiscuous

mode) to pick up other people's datagrams off the network

IPsIPs

• Every computer is assigned a unique number

• IPs (AKA addresses) are very similar to URLs in structure and meaning.

• Example: 168.28.245.183 is an IP– Notice no “http” at beginning– This number directly translates to

kahuna.clayton.edu

• Use Winipcfg or ipconfig to determine your own IP

IPsIPs

• Static IPs - you have to pay for these by registering– Networksolutions.com– Domainit.com

• DHCP - Dynamically allocated IP. This means you are granted an IP temporarily!– Not guaranteed the next time– Clayton runs on DHCP

URL’sURL’sUniform Resource LocatorsUniform Resource Locators

• Tells us the path to data on the internet.• Example:

http://kahuna.clayton.edu/~chastine– “http” is protocol used (how to send info)– “www….” is location; also has numbers like

“199.77.144.111”– “~chastine” is a directory where info is kept

• A DNS (Domain Name Server) translates these IPs to names and vice-versa

• Unix and nslookup

PortsPorts

• Several thousand ports/IP• allows multiple connections on your comp• Ports 1024 and lower are “reserved”

– Web Servers (port 80)– FTP (port 21)– SSH (secure-shell: port 22)– Telnet (port 23)– Mail (port 25)– Gopher (port 70)– HTTP (port 80)

The Client/Server The Client/Server RelationshipRelationship

kahunaA vault full of important info

MeMe

YouYou User 1User 1

User 2User 2

Information PassingInformation Passing

• Requests are made for services

kahunaA vault full of important info

MeMe

YouYou User 1User 1

User 2User 2

Server SideServer Side

• Services/information passed back

kahuna

MeMe

YouYou User 1User 1

User 2User 2

Good siteGood site

• http://oac3.hsc.uth.tmc.edu/staff/snewton/tcp-tutorial/