Introduction 1 Introduction 1 Part I Introduction Assignment

Introduction 1: Introduction 1

Part I: Introduction Assignment: read chapter 1 in text Our goal: Overview: r get context, r what’s the Internet overview, “feel” of networking r more depth, detail later in course r approach: m descriptive m use Internet as example r what’s a protocol? r network edge r network core r access net, physical media r performance: loss, delay r protocol layers, service models r backbones, NAPs, ISPs r history 1: Introduction 2

What’s the Internet: “nuts and bolts” view r millions of connected computing devices: hosts, end-systems m m pc’s workstations, servers PDA’s phones, toasters router server mobile local ISP running network apps r communication links m workstation regional ISP fiber, copper, radio, satellite r routers: forward packets (chunks) of data thru network company network 1: Introduction 3

“Cool” internet appliances IP picture frame http: //www. ceiva. com/ World’s smallest web server http: //www-ccs. umass. edu/~shri/i. Pic. html Web-enabled toaster+weather forecaster http: //dancing-man. com/robin/toasty/ 1: Introduction 4

What’s the Internet: “nuts and bolts” view r protocols: control sending, receiving of msgs m e. g. , TCP, IP, HTTP, FTP, PPP r Internet: “network of router server workstation mobile local ISP networks” m m loosely hierarchical public Internet versus private intranet r Internet standards m RFC: Request for comments m IETF: Internet Engineering Task Force regional ISP company network 1: Introduction 5

What’s the Internet: a service view r communication infrastructure enables distributed applications: m WWW, email, games, ecommerce, database. , voting, file (MP 3) sharing r communication services provided: m m connectionless connection-oriented 1: Introduction 6

What’s a protocol? human protocols: r “what’s the time? ” r “I have a question” r introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: r machines rather than humans r all communication activity in Internet governed by protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt 1: Introduction 7

What’s a protocol? a human protocol and a computer network protocol: Hi TCP connection req. Hi TCP connection reply. Got the time? Get http: //gaia. cs. umass. edu/index. htm 2: 00 <file> time Q: Other human protocol? 1: Introduction 8

A closer look at network structure: r network edge: applications and hosts r network core: m m routers network of networks r access networks, physical media: communication links 1: Introduction 9

The network edge: r end systems (hosts): m m m run application programs e. g. , WWW, email at “edge of network” r client/server model m m client host requests, receives service from server e. g. , WWW client (browser)/ server; email client/server r peer-peer model: m m host interaction symmetric e. g. : Gnutella, Ka. Za. A 1: Introduction 10

Network edge: connection-oriented service Goal: data transfer between end sys. r handshaking: setup (prepare for) data transfer ahead of time m m Hello, hello back human protocol set up “state” in two communicating hosts r TCP - Transmission Control Protocol m Internet’s connectionoriented service TCP service [RFC 793] r reliable, in-order byte- stream data transfer m loss: acknowledgements and retransmissions r flow control: m sender won’t overwhelm receiver r congestion control: m senders “slow down sending rate” when network congested 1: Introduction 11

Network edge: connectionless service Goal: data transfer between end systems m same as before! r UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service m unreliable data transfer m no flow control m no congestion control App’s using TCP: r HTTP (WWW), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP: r streaming media, teleconferencing, Internet telephony 1: Introduction 12

The Network Core r mesh of interconnected routers r the fundamental question: how is data transferred through net? m circuit switching: dedicated circuit per call: telephone net m packet-switching: data sent thru net in discrete “chunks” 1: Introduction 13

Network Core: Circuit Switching End-end resources reserved for “call” r link bandwidth, switch capacity r dedicated resources: no sharing r circuit-like (guaranteed) performance r call setup required 1: Introduction 14

Network Core: Circuit Switching network resources (e. g. , bandwidth) divided into “pieces” r pieces allocated to calls r dividing link bandwidth into “pieces” m frequency division m time division r resource piece idle if not used by owning call (no sharing) r dividing link bandwidth into “pieces” m frequency division m time division 1: Introduction 15

Circuit Switching: FDMA and TDMA Example: FDMA 4 users frequency time TDMA frequency time 1: Introduction 16

Network Core: Packet Switching each end-end data stream divided into packets r user A, B packets share network resources r each packet uses full link bandwidth r resources used as needed, Bandwidth division into “pieces” Dedicated allocation Resource reservation resource contention: r aggregate resource demand can exceed amount available r congestion: packets queue, wait for link use r store and forward: packets move one hop at a time m transmit over link m wait turn at next link 1: Introduction 17

Network Core: Packet Switching 10 Mbs Ethernet A B statistical multiplexing C 1. 5 Mbs queue of packets waiting for output link D 45 Mbs E 1: Introduction 18

Packet switching versus circuit switching Packet switching allows more users to use network! r 1 Mbit link r each user: m 100 Kbps when “active” m active 10% of time r circuit-switching: m 10 users r packet switching: m with 35 users, probability > 10 active less than. 0004 (See Slide 42 for more details) N users 1 Mbps link 1: Introduction 19

Packet-switched networks: routing r Goal: move packets among routers from source to destination m we’ll study several path selection algorithms (chapter 4) r datagram network: m destination address determines next hop m routes may change during session m analogy: driving, asking directions r virtual circuit network: m each packet carries tag (virtual circuit ID), tag determines next hop m fixed path determined at call setup time, remains fixed thru call m routers maintain per-call state 1: Introduction 20

Access networks and physical media Q: How to connection end systems to edge router? r residential access nets m Cable modem r institutional access networks (school, company) m Local area networks r mobile access networks Physical media r r coax, fiber Radio 1: Introduction 21

Delay in packet-switched networks packets experience delay on end-to-end path r four sources of delay at each hop transmission A r nodal processing: m check bit errors m determine output link r queueing m time waiting at output link for transmission m depends on congestion level of router propagation B nodal processing queueing 1: Introduction 22

Delay in packet-switched networks Transmission delay: r R=link bandwidth (bps) r L=packet length (bits) r time to send bits into link = L/R transmission A Propagation delay: r d = length of physical link r s = propagation speed in medium (~2 x 108 m/sec) r propagation delay = d/s Note: s and R are very different quantities! propagation B nodal processing queueing 1: Introduction 23

Queueing delay (revisited) r R=link bandwidth (bps) r L=packet length (bits) r a=average packet arrival rate traffic intensity = La/R r La/R ~ 0: average queueing delay small r La/R -> 1: delays become large r La/R > 1: more “work” arriving than can be serviced, average delay infinite! 1: Introduction 24

“Real” Internet delays and routes traceroute (or tracert): routers, rt delays on sourcedest path also: pingplotter, various windows programs 1 cs-gw (128. 119. 240. 254) 1 ms 2 border 1 -rt-fa 5 -1 -0. gw. umass. edu (128. 119. 3. 145) 1 ms 2 ms 3 cht-vbns. gw. umass. edu (128. 119. 3. 130) 6 ms 5 ms 4 jn 1 -at 1 -0 -0 -19. wor. vbns. net (204. 147. 132. 129) 16 ms 11 ms 13 ms 5 jn 1 -so 7 -0 -0 -0. wae. vbns. net (204. 147. 136) 21 ms 18 ms 6 abilene-vbns. abilene. ucaid. edu (198. 32. 11. 9) 22 ms 18 ms 22 ms 7 nycm-wash. abilene. ucaid. edu (198. 32. 8. 46) 22 ms 8 62. 40. 103. 253 (62. 40. 103. 253) 104 ms 109 ms 106 ms 9 de 2 -1. de. geant. net (62. 40. 96. 129) 109 ms 102 ms 104 ms 10 de. fr 1. fr. geant. net (62. 40. 96. 50) 113 ms 121 ms 114 ms 11 renater-gw. fr 1. fr. geant. net (62. 40. 103. 54) 112 ms 114 ms 112 ms 12 nio-n 2. cssi. renater. fr (193. 51. 206. 13) 111 ms 114 ms 116 ms 13 nice. cssi. renater. fr (195. 220. 98. 102) 123 ms 125 ms 124 ms 14 r 3 t 2 -nice. cssi. renater. fr (195. 220. 98. 110) 126 ms 124 ms 15 eurecom-valbonne. r 3 t 2. ft. net (193. 48. 50. 54) 135 ms 128 ms 133 ms 16 194. 211. 25 (194. 211. 25) 126 ms 128 ms 126 ms 17 * * * 18 * * * 19 fantasia. eurecom. fr (193. 55. 113. 142) 132 ms 128 ms 136 ms 1: Introduction 25

Protocol “Layers” Networks are complex! r many “pieces”: m hosts m routers m links of various media m applications m protocols m hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks? 1: Introduction 26

Internet protocol stack r application: supporting network applications m ftp, smtp, http application r transport: host-host data transfer m tcp, udp transport r network: routing of datagrams from network source to destination m ip, routing protocols r link: data transfer between neighboring network elements m link physical ppp, ethernet r physical: bits “on the wire” 1: Introduction 27

Layering: logical communication Each layer: r distributed r “entities” implement layer functions at each node r entities perform actions, exchange messages with peers application transport network link physical application transport network link physical 1: Introduction 28

Layering: logical communication E. g. : transport r r r take data from app addressing, reliability check info to form “datagram” send datagram to peer wait for peer to ack receipt analogy: post office data application transport network link physical ack data network link physical application transport network link physical data application transport network link physical 1: Introduction 29

Layering: physical communication data application transport network link physical application transport network link physical data application transport network link physical 1: Introduction 30

Protocol layering and data Each layer takes data from above r adds header information to create new data unit r passes new data unit to layer below source M Ht M Hn Ht M Hl Hn Ht M application transport network link physical destination application Ht transport Hn Ht network Hl Hn Ht link physical M message M segment M datagram M frame 1: Introduction 31

Internet structure: network of networks r roughly hierarchical r national/international local ISP backbone providers (NBPs) m m e. g. BBN/GTE, Sprint, AT&T, IBM, UUNet interconnect (peer) with each other privately, or at public Network Access Point (NAPs) r regional ISPs m connect into NBPs r local ISP, company m connect into regional ISPs regional ISP NBP B NAP NBP A regional ISP local ISP 1: Introduction 32

National Backbone Provider e. g. Sprint US backbone network 1: Introduction 33

Internet History 1961 -1972: Early packet-switching principles r r 1961: Kleinrock - queueing theory shows effectiveness of packetswitching 1964: Baran - packetswitching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational r 1972: m ARPAnet demonstrated publicly m NCP (Network Control Protocol) first host protocol m first e-mail program m ARPAnet has 15 nodes 1: Introduction 34

Internet History 1972 -1980: Internetworking, new and proprietary nets r r r 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s Ph. D thesis proposes Ethernet 1974: Cerf and Kahn architecture for interconnecting networks late 70’s: proprietary architectures: DECnet, SNA, XNA late 70’s: switching fixed length packets (ATM precursor) 1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: m minimalism, autonomy no internal changes required to interconnect networks m best effort service model m stateless routers m decentralized control define today’s Internet architecture 1: Introduction 35

Internet History 1980 -1990: new protocols, a proliferation of networks r 1983: deployment of r r TCP/IP 1982: smtp e-mail protocol defined 1983: DNS defined for name-to-IP-address translation 1985: ftp protocol defined 1988: TCP congestion control r new national networks: Csnet, BITnet, NSFnet, Minitel r 100, 000 hosts connected to confederation of networks 1: Introduction 36

Internet History 1990’s: commercialization, the WWW r r r Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990 s: WWW m hypertext [Bush 1945, Nelson 1960’s] m HTML, http: Berners-Lee m 1994: Mosaic, later Netscape m late 1990’s: commercialization of the WWW Late 1990’s: r est. 50 million computers on Internet r est. 100 million+ users r backbone links running at 1 Gbps 1: Introduction 37

Introduction: Summary Covered a “ton” of material! r Internet overview r what’s a protocol? r network edge, core, access network m packet-switching versus circuit-switching r performance: loss, delay r layering and service models r backbones, NAPs, ISPs r history You now have: r context, overview, “feel” of networking r more depth, detail later in course 1: Introduction 38

References How does the Internet work? https: //www. youtube. com/watch? v=x 3 c 1 ih 2 NJEg r A Packet’s Tale: How does the Internet Work? https: //www. youtube. com/watch? v=ewr. Bal. T_e. BM r How the Internet Works in 5 Minutes? https: //www. youtube. com/watch? v=7_LPdtt. KXPc r The Internet: IP Addresses and DNS https: //www. youtube. com/watch? v=5 o 8 Cwaf. Cxn. U r Internet Abstraction Layers https: //www. youtube. com/watch? v=Q 6 ix. Ze 6 if. HI r OSI Model https: //www. youtube. com/watch? v=vv 4 y_u. One. C 0 r Packet Transmission across the Internet https: //www. youtube. com/watch? v=nomy. RJehhn. M r Internet of Things (Io. T) Architecture https: //www. youtube. com/watch? v=FRx. RT 0 Dj. E 7 A r History of the Internet https: //www. youtube. com/watch? v=9 h. IQjr. MHTv 4 r 1: Introduction 39

Questions of Class 1 (for attendance) r Why do you take CSE 3461? r What Internet protocols have you heard of? 1: Introduction 40

Questions of Class 2 (for feedback) r Which topics on computer networking are you most interested in? r Any suggestions to this course (content, assignments and teaching etc. )? 1: Introduction 41

Slide 19: Packet Switching Efficiency function combinations(n, r) { if (n==r) { return 1; } else { r=(r < n-r) ? n-r : r; return product_Range(r+1, n)/product_Range(1, n-r); }} function product_Range(a, b) { var prd = a, i = a; while (i++< b) { prd*=i; } return prd; }function combinations(n, r) { if (n==r) { return 1; } else { r=(r < n-r) ? n -r : r; return product_Range(r+1, n)/product_Range(1, n-r); }} prob = + Math. pow(0. 1, 0)*Math. pow(0. 9, 35); for (i=1; i<=10; i++) prob = prob + Math. pow(0. 1, i)*Math. pow(0. 9, 35 i)*combinations(35, i); 1 -prob= 0. 0004242975954498185 1: Introduction 42