Basic Computer NetworkWeeSan Lee weesan@cs.ucr.edu

BandwidthData rate measured in bits (not bytes) per secondsKbps (Kilobits per seconds)125 chars/secMbps (Megabits per seconds)1,250 chars/secGbps (Gigabits per seconds)12,500 chars/sec

Connecting to the InternetRequirementA computer or PDA or cell phoneAn account with an ISP (Internet Service Provider)A modem (modulator/demodulator) for dial-up services or a NIC (Network Interface Card) for DSL/Cable services

Home Network (single machine)USB/Ethernet CableDSL/Cable ModemWall Jack

Home Network (multiple machines)USB/Ethernet CableDSL/Cable ModemWall JackHub/Switch/Router

Home Network (multiple machines)Ethernet CableDSL/Cable ModemWall JackHub/Switch/Router

Home Wireless NetworkEthernet CableDSL/Cable ModemWall JackHub/Switch/Router

Connection TypesLANWLANDial-up ServicesBroadband ServicesWAN

LAN (Local Area Network)A network of computers that are in the same physical location, such as home or buildingUsually connected using EthernetA standard on how computers communicate over a shared media (cable)http://en.wikipedia.org/wiki/Image:Ethernet_RJ45_connector_p1160054.jpghttp://en.wikipedia.org/wiki/Image:BNC_connector.jpgOld: BNC connector for coaxial cableNew: RJ45 for twisted pair cable

LAN (Local Area Network)Ethernet Standard10BaseT10Mbps (Mega bits per second)100BaseT100Mbps1000BaseT1000Mbps or 1GbpsCorrection from the book (pg. 10)Why do we get faster connection at work or on campus than at home?

LAN (Local Area Network)Question: Can 2 computers communicate by connecting each other using an Ethernet cable back-to-back?

WLAN (Wireless LAN)Wi-Fi (Wireless Fidelity)A wireless technology that connects computers without cablesAccess Point (AP)A device (base station) that connects wireless devices togetherUsually connected to a wired-networkESSID (Extended Service Set ID)A name for the AP, eg. mobilenetHotspotThe area covered by wireless access points

WLAN (Wireless LAN)Standard802.11b - 11Mbps802.11g - 54Mbps802.11a - 54MbpsSecurityWEP (Wired Equivalen Privacy)WPA (Wi-Fi Protected Access)To prevent wardriving

2.4G5G

Dial-up ServicesModemModulator/demodulatorA device that converts analog signal to digital (modulation) and vice versa (demodulation)Speed1200/2400/9600 bps14.4/28.8/33.6 Kbps56 Kbps

Dial-up ServicesISDNIntegrated Services Digital Network2 data channel (56K each)1 voice channel

Broadband ServicesxDSL (Digital Subscriber Line)A technology that provides digital data transmission over unused frequencies on traditional telephone linesFor example, ADSL (Asymmetric DSL): DL > ULSpeedDownlink128Kbps - 4MbpsUplink64Kbps - 800KbpsNeed a DSL modemSplitters are needed to separate the voice and data signal

Broadband ServicesCableA technology that provides digital data transmission over cable TV infrastructureSpeedDownlink128Kbps - 3~5MbpsUplink64Kbps - 128Kbps~1MbpsNeed a cable modem

Broadband ServicesSatelliteA technology that provide digital data transmission over satellitesSpeedDownlink500Kbps - 1MbpsUplink50Kbps - 100KbpsNeed a satellite dish

WAN (Wide Area Network)A LAN spans a large geographic area, such as connections between citiesUsually connected using leased lineT1 (1.5Mbps)T3 (45Mbps)OC3 (155Mbps)OC12 (622Mbps)OC48 (2.4Gbps)

Fiber optic linesTelecommunication lines

Hub/Switch/RouterTo connect multiple segments of networks into a larger oneHubA multiport repeater to enhance signal within the same LANSwitchLike hub but with intelligentBetter performanceRouterForward packets from one LAN to another

Intranet vs. InternetIntranetA private network that is contained within an enterpriseCould be LANs and WANsInternetA public network of networksBoth are using TCP/IP

TCP/IPA family of protocols that makes the Internet worksThe Robustness PrincipleBe liberal in what you accept, and conservative in what you send - Jon Postel

TCP/IP (cont)SegmentsPacketsFramesBitsData

Application LayerEg. WWW, FTP, IRC, Email, telnet, Transport LayerEg. TCP, UDPNetwork LayerEg. IPLink LayerEg. Ethernet, WiFiPhysical LayerEg. Ethernet Cable, fiber-optics

PacketsA small chunk of data transmitted over the InternetAlice

The InternetBob

VPN (Virtual Private Network)A secure tunnel to a private network through a public networkOnce established, local node appears to be a node in the private network in a secure mannerCorrection from the book (pg. 11):VPN does not mean using telephone line connection!!!

Host & IP AddressCorrection from the book:A host is a computer connected directly to the InternetYou home computer is not a hostEach host needs an IP addressIP addressA 32-bit number, arranged in 4 numbers seperated by .Eg. 74.125.19.147

DNS (Domain Name System)Domain name to IP address conversionEg. www.google.com ??.???.??.??Domain name or IP address lookuphttp://cqcounter.com/whois/

Top-level DomainsgTLDs (generic TLDs).com, .edu, .net, .org, .gov, .mil.aero, .biz, .coop, .info, .museum, .name, .proccTLDs (country code TLDs).au, .ca, .br, .de, .fi, .fr, .jp, .hk, .cn, .tw, .my, .us

Second-level DomainsDomains that are directly below a TLDEg.ucr.edugoogle.comsony.co.jpMust apply to a registrar for the appropriate TLD

Domain Names & RegistrarsProfitable domain namesCreditCards.com - $2.75MLoans.com $3MBusiness.com - $7.5MNetwork Solutions, Inc used to monopolize the name registrationNow, ~500 registrars

How To Register A Domain Name?Come up a new name2 name servers IP addresses1 administrative contact1 technical contactRegister the name to an Internet domain registrarEg. www.netsol.com, www.godaddy.comUsed to be done via email or fax, now all web-based!

PoliciesAUP (Acceptable Use Policies)A legal document, written to protect the ISP from unlawful use of its service, and outlines prohibited uses of the service and possible consequences of misusePrivacy PoliciesA document describes an ISPs policy for protecting users information

ConclusionDescribed how to get connected to the InternetTalked about the related network technologies and components

ReferencesInternet Effectively (Ch 1-2)Modemhttp://en.wikipedia.org/wiki/ModemDSLhttp://en.wikipedia.org/wiki/Digital_subscriber_lineHow DSL works?http://electronics.howstuffworks.com/dsl.htmVPNhttp://en.wikipedia.org/wiki/Vpn

References (cont)RFC1122: Requirements for Internet Hostsftp://ftp.rfc-editor.org/in-notes/rfc1122.txtDomain Nameshttp://www.icann.org/topics/new-gtld-strategy-faq.htmhttp://www.iana.org/root-whois/index.html

Homework 2Read Stealing your neighbor's Nethttp://money.cnn.com/2005/08/08/technology/personaltech/internet_piracy/index.htmRead Is stealing wireless wrong?http://news.bbc.co.uk/2/hi/uk_news/magazine/6960304.stmPost your own comment in 100-150 words to Homework 2 Forum by next Mon (10/8) @ 23:55pmReply one of the comments from others by next Tue (10/9) @ 23:55pm.