Course Information. Details. Topics. Network Examples. Overview. Walrand Lecture 1. EECS 228a. EECS 228a Lecture 1 Overview: Networks

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1 Walrad Lecture 1 Course Iformatio Lecture 1 Overview: Networks Jea Walrad Istructor: Jea Walrad Office Hours: M-Tu 1:00-2:00 Time/Place: MW 2:00-3:30 i 285 Cory Home Page: Fall 2002 EECS228a - Walrad 2 Topics Overview [1 week] Ecoomics of Networks [4] Routig [4] Cogestio Cotrol [2.5] Traffic Models [2.5] Review [1] Theoretical backgroud State of the art Details Gradig: I class presetatios: 50% Project: 50% - Origial research o selected topic Material: Lecture Slides ad Notes Research Papers EECS228a - Walrad 3 EECS228a - Walrad 4 Overview Teleglobe Commuicatios Corporatio Fiber + Satellite Network Compoets Iteretworkig Iteret Other Networks Packets Trasport Web Browsig Telephoe Call Resource Sharig Multiplexig Protocols IETF EECS228a - Walrad 5 EECS228a - Walrad 6

2 Walrad Lecture 1 Global Crossig Corporatio KPNQWEST EECS228a - Walrad 7 EECS228a - Walrad 8 Williams Commuicatios Palo lto Network EECS228a - Walrad 9 EECS228a - Walrad 10 Network Compoets Lik: carry bits from oe place to aother (or maybe to may other places) Switch/router: move bits betwee liks, formig iteretwork Host: commuicatio edpoit (workstatio, PD, cell phoe, toaster, tak) Network Compoets Liks Fibers Cat5 Ushielded Twisted Pairs Coaxial Cable Wireless EECS228a - Walrad 11 EECS228a - Walrad 12

3 Walrad Lecture 1 Network Compoets Etheret Network Iterface Card Network Compoets Etheret EECS228a - Walrad 13 EECS228a - Walrad 14 Network Compoets Lik: Etheret Network Compoets Telephoe Switch Large Router Etheret is a broadcast-capable, multiaccess LN EECS228a - Walrad 15 EECS228a - Walrad 16 Network with Routers LNs itercoected by routers LN1 LN3 R1 R3 LN2 R2 R4 Iteret EECS228a - Walrad 17 Iteretworkig Provides message delivery betwee multiple etworks: Subet 1 ISP 1 ISP 2 Subet 2 Example: Subet 1 = etwork of LNs of previous slide ISP 1 = Sprit, ISP 2 = MCI Subet 2 = UCB etwork EECS228a - Walrad 18

4 Walrad Lecture 1 The Iteret global etwork of etworks all usig a commo protocol (IP, the Iteret Protocol) Focus of this class challege to uderstad: large scale (10 s of millios of users, 10 s of thousads of etworks) heterogeeity, irregular topology, decetralized maagemet EECS228a - Walrad 19 Scale of Iteret Data from EECS228a - Walrad 20 Other Networks The Telephoe Network Processor Itercoectio Networks TM Networks Cable-TV Networks EECS228a - Walrad 21 Packets B... B B... B 3 B port 2 EECS228a - Walrad 22 Packets: Mai Ideas The switches have o memory of packets: scalability The etwork is idepedet of the applicatios: flexibility The packet formats ad addresses are idepedet of the techology: extesibility Trasport Packets EECS228a - Walrad 23 CKs EECS228a - Walrad 24

5 Walrad Lecture 1 Web Browsig Example Locatig Resource: DNS Coectio Ed-to-ed Packets Bits Poits to remember EECS228a - Walrad 25 Web: Example Click Lik or URL get cotet from local or remote computer URL: Specifies - Protocol: http - Computer: - Strig Computer (server) selects cotets based o strig EECS228a - Walrad 26 Web: Locatig Resource is the ame of a computer Network uses IP addresses To fid the IP address, the applicatio uses a hierarchical directory service called the Domai Name System host local com IP = a.b.c.d EECS228a - Walrad IP = a.b.c.d 27 Web: Coectio The protocol (http) sets up a coectio betwee the host ad c.com to trasfer the page The coectio trasfers the page as a byte Host stream, without errors: pacig + error cotrol c.com coect OK get page page; close EECS228a - Walrad 28 Web: Ed-to-ed The byte stream flows from ed to ed across may liks ad switches: routig (+ addressig) That stream is regulated ad cotrolled by both eds: retrasmissio of erroeous or missig bytes; flow cotrol host Ed-to-edpacig ad flow cotrol EECS228a - Walrad 29 Routig Web: Packets The etwork trasports bytes grouped ito packets The packets are selfcotaied ad routers hadle them oe by oe The ed hosts worry about errors ad flow cotrol: Destiatio checks packet for errors (usig error detectio code CKS) ad seds CKs with sequece umber # Source retrasmits packets that were ot Host IP address: B IP address: B #,CKS bytes EECS228a - Walrad 30 C Destiatio B C Next Hop

6 Walrad Lecture 1 Web: Bits Web: Poits to remember Separatio of tasks Equipmet i each ode seds the packets as a strig of bits That equipmet is ot aware of the meaig of the bits Trasmitter Physical Medium Scalability Receiver Optical Copper Wireless EECS228a - Walrad sed bits o a lik: trasmitter/receiver [clock, modulatio, ] sed packet o each hop [framig, error detectio, ] sed packet ed to ed [addressig, routig] pace trasmissios [detect cogestio] retrasmit erroeous or missig packets [acks, timeout] fid destiatio address from ame [DNS] 31 Telephoe Call routers do t kow about coectios ames ad addresses are hierarchical EECS228a - Walrad 32 Telephoe Network Telephoe Network Dialig a Number Settig up a Circuit Phoe Coversatio Releasig the Circuit 5ESS (Lucet) DMS100 (Nortel) EECS228a - Walrad 33 Telephoe Network EECS228a - Walrad 34 Telephoe Network Logic Diagram: EECS228a - Walrad 35 EECS228a - Walrad 36

7 Walrad Lecture 1 Dialig a Number Settig Up a Circuit S1 B rig B Off-Hook S1 Listes dials S1 Registers EECS228a - Walrad 37 Circuit = capacity to carry oe phoe call (show by thi lies) Circuit is allocated to the call betwee ad B Circuits are ot shared; they are dedicated. EECS228a - Walrad 38 Phoe Coversatio Release Circuits B B Voice sigals use the reserved circuits EECS228a - Walrad 39 or B goes Off-Hook Circuits get released EECS228a - Walrad 40 Resource Sharig - Multiplexig Networks are shared resources Sharig via multiplexig Fudametal Questio: how to achieve cotrolled sharig Multiplexig Methods for sharig a commuicatio chael Tradeoff betwee utilizatio ad predictability Commo pproaches: TDM (time-divisio multiplexig) Statistical Multiplexig EECS228a - Walrad 41 EECS228a - Walrad 42

8 Walrad Lecture 1 Time Divisio Multiplexig (also called STDM --Sychroous Time Divisio Multiplexig) Statistical Multiplexig liks rate r bps each Multiplexer 1 lik, rate r bps liks ay rate Multiplexer 1 lik, ay rate Trace Frame: Excerpt: bps = bits per secod Time slots are reserved EECS228a - Walrad 43 Variable-sized packets of data are iterleaved based o the statistics of the seders EECS228a - Walrad 44 alysis of STDM/FDM TDM, FDM (frequecy divisio multiplexig), ad WDM (wavelegth) may uder-utilize chael with idle seders pplicable oly to fixed umbers of flows Requires precise timer (or oscillator ad guard bads for FDM) Resources are guarateed alysis of Statistical Mux ig Traffic is set o demad, so chael is fully utilized if there is traffic to sed y umber of flows Need to cotrol sharig: packets are limited i size prevets domiatio of sigle seder Resources are ot guarateed EECS228a - Walrad 45 EECS228a - Walrad 46 Protocols greemet dictatig the form ad fuctio of data exchaged betwee two (or more) parties to effect a commuicatio Two parts: sytax ad sematics sytax: where bits go sematics: what they mea ad what to do with them Protocol Example Iteret Protocol (IP) if you ca geerate ad uderstad IP, you ca be o the Iteret media, OS, data rate idepedet TCP ad HTTP if you ca do these, you are o the web EECS228a - Walrad 47 EECS228a - Walrad 48

9 Walrad Lecture 1 Protocol Stadards New fuctios require ew protocols Thus there are may (e.g. IP, TCP, UDP, HTTP, RIP, OSPF, IS-IS, SMTP, SNMP, Telet, FTP, DNS, NNTP, NTP, BGP, PIM, DVMRP, RP, NFS, ICMP, IGMP) Specificatios do ot chage frequetly Orgaizatios: IETF, IEEE, ITU The IETF Specifies Iteret-related protocols Produces RFCs ( Quotatio from IETF T-shirt: We reject kigs, presidets ad votig. We believe i rough cosesus ad ruig code. --- David Clark EECS228a - Walrad 49 EECS228a - Walrad 50