Lec 1: Internet Overview

Overview

1-1

Introduction Our goal:

Overview:

get “feel” and terminology ‰ more depth, detail later in course ‰ approach: ™ use Internet as example

‰

‰

‰ ‰ ‰ ‰ ‰ ‰ ‰ ‰

what’s the Internet what’s a protocol? network edge network core access net, physical media Internet/ISP structure performance: loss, delay protocol layers, service models network modeling Overview

1-2

1

Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Overview

1-3

What’s the Internet: “nuts and bolts” view ‰

‰ ‰

millions of connected computing devices: hosts

= end systems running network apps communication links ™ ™

‰

router server

workstation mobile

local ISP

fiber, copper, radio, satellite transmission rate =

regional ISP

bandwidth

routers: forward packets (chunks of data)

company network Overview

1-4

2

“Cool” internet appliances Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/

World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html

Internet phones Overview

1-5

What’s the Internet: hardware view ‰

Internet: “network of networks” ™ ™

loosely hierarchical public

‰

Intranet: private networks

‰

Internet standards ™ ™

router server

workstation mobile

local ISP

regional ISP

RFC: Request for comments IETF: Internet Engineering Task Force

company network Overview

1-6

3

What’s the Internet: a service view ‰

Distributed applications: ™

‰

Web, email, games, ecommerce, file sharing

Network protocols: used by applications to control sending, receiving of msgs: ™

‰

TCP, IP, HTTP, FTP, PPP

Communication services provided to apps: ™ ™

Connectionless unreliable connection-oriented reliable Overview

1-7

What’s a protocol? human protocols: ‰ “what’s the time?” ‰ “I have a question” ‰ introductions

network protocols: ‰ machines rather than humans ‰ all communication activity in Internet governed by protocols

protocols define: - msg format - order of msgs sent & received - actions taken on msg transmission & receipt

Overview

1-8

4

Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Overview

1-9

A closer look at network structure: ‰ network edge:

applications and hosts ‰ network core: routers ™ network of networks ™

‰ access networks,

physical media: communication links Overview

1-10

5

The network edge: ‰ end systems (hosts): ™ ™ ™

run application programs e.g. Web, email at “edge of network”

‰ client/server model ™ ™

client host requests, receives service from always-on server e.g. Web browser/server; email client/server

‰ peer-peer model: ™ ™

minimal (or no) use of dedicated servers e.g. Gnutella, KaZaA, Skype Overview

1-11

Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Overview

1-12

6

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

Overview

1-13

Network Core: Circuit Switching End-end resources reserved for “call” link bandwidth and switch capacity predetermined ‰ dedicated resources with no sharing of bandwidth ‰ guaranteed performance ‰ call setup required ‰

Overview

1-14

7

Network Core: Circuit Switching network resources (e.g., bandwidth) divided into “pieces” pieces allocated to calls ‰ resource piece idle if not used by owning call ‰

‰

dividing link bandwidth into “pieces” ™ frequency division ™ time division

(no sharing)

Overview

1-15

Circuit Switching: FDM and TDM Note: Circuit is analogous to connection

Example:

Frequency Domain Mux (FDM)

4 users/slots

bandwidth/ frequency of the link time Time Domain Mux (TDM) Transmission rate of single circuit = frame rate in frames/sec * #bits in a slot

bandwidth/ frequency of the link Slot time 4 slots/frame

Overview

1-16

8

Numerical example ‰ How long does it take to send a file of

640,000 bits (1 byte=8bits) from host A to host B over a circuit-switched network? All links are 1.536 Mbps (Mega Bits Per Second) ™ Each link uses TDM with 24 slots/sec ™ 500 msec to establish end-to-end circuit (setup time including propagation delay) ™

Single circuit speed File transmission time

= 1.536 Mbps / 24 = 64kbps = 500 msec + file size/speed = 0.5 sec + 640,000 bits / 64 kbps = 10.5 sec Overview

1-17

Network Core: Packet Switching each end-end data stream divided into packets ‰ user A, B packets share network resources ‰ each packet uses full link bandwidth ‰ resources used as needed Bandwidth division into “pieces” Dedicated allocation Resource reservation

resource contention: ‰ flow-control needed as aggregate resource demand can exceed amount available ‰ congestion control needed as packets queued and wait for link use ‰ store and forward: packets move one hop at a time Overview

1-18

9

Packet Switching: Statistical Multiplexing 10 Mb/s Ethernet

A B

statistical multiplexing

C

1.5 Mb/s queue of packets waiting for output link

D

E

Sequence of A & B packets does not have fixed pattern, on demand sharing of resources (statistical multiplexing). Overview

1-19

Packet switching versus circuit switching Packet switching allows more users to use network! Problem: 1 Mbps link and each user needs 100 kbps when “active” and is active 10% of time. N users ‰ circuit-switching FDM: ‰

™

‰

Max #users = (1,000,000 b/s)/(100,000 b/s) = 10

1 Mbps link

packet switching: ™ ™

Min #users = 10 Max is > 10 due to the probability that users are inactive 90% of time Overview

1-20

10

Packet switching versus circuit switching Is packet switching a “slam dunk winner?” Great for bursty data ™ resource sharing ™ simpler, no call setup ‰ Excessive congestion: packet delay and loss ™ protocols needed for reliable data transfer, congestion control ‰ Q: How to provide circuit-like behavior? ™ bandwidth guarantees needed for audio/video apps ™ still an unsolved problem ‰

Overview

1-21

Packet-switching: store-and-forward L R

R

Takes L/R seconds to transmit (push out) packet of L bits on to link or R bps ‰ Entire packet must arrive at router before it can be transmitted on next link: store and ‰

R

Example: ‰ L = 7.5 Mbits (size) ‰ R = 1.5 Mbps (speed) ‰ delay = 3*7.5/1.5=15 sec

forward

‰

delay = 3L/R (assuming zero propagation delay)

more on delay shortly … Overview

1-22

11

Packet-switched networks: forwarding ‰

Goal: move packets through routers from source to

destination ‰ Packet-switched datagram network: ™ ™ ™

‰

destination address in packet determines next hop routes may change during session analogy: driving, asking directions

Packet-switched virtual circuit network: ™ ™ ™

each packet carries tag (VC ID), tag determines next hop fixed path determined at call setup time, remains fixed thru call

routers maintain per-call state

Overview

1-23

Network Taxonomy Telecommunication networks

Circuit-switched networks

FDM

TDM

Packet-switched networks Networks with VCs

Datagram Networks

(X.25,Frame relay, ATM)

(Internet)

Course Subject Overview

1-24

12

Part I summary ‰

Internet/Intranet definition: ™

‰

Intranet definition: ™

‰

msg format, order of msgs sent & received and actions taken on msg transmission & receipt

Network edge and core: ™

‰

Private Network

Network Protocol defines: ™

‰

Public loosely hierarchical Network of Networks

Hosts or end-systems and routers in the core

Circuit-switching vs Packet-switching ™ ™

FDM and TDM circuits: guaranteed constant speed, notshared and requires call setup. VCs and Datagram Networks: variable speed, shared and need resource contention management. Overview

1-25

Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models

Overview

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13

Access networks and physical media Q: How to connect end systems to edge router? residential access nets ‰ institutional access networks (school, company) ‰ mobile access networks ‰

Keep in mind: bandwidth (bits per second) of access network? ‰ shared or dedicated? ‰

Overview

1-27

Residential access: point to point access ‰

Dialup via modem ™ up to 56Kbps direct access to router (often less) ™ Can’t surf and phone at same time: can’t be “always on”

‰

ADSL: asymmetric digital subscriber line ™ up to 1 Mbps upstream (today typically < 256 kbps) ™ up to 8 Mbps downstream (today typically < 1 Mbps) ™ FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream 0 kHz - 4 kHz for ordinary telephone Overview

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14

Residential access: cable modems HFC: hybrid fiber coax ™ asymmetric: up to 30Mbps downstream, 2 Mbps upstream ‰ network of cable and fiber attaches homes to ISP router ™ homes share access to router so communication activity is visible to each other. ‰ deployment: available via cable TV companies ‰

Overview

1-29

Overview

1-30

Residential access: cable modems

Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

15

Cable Network Architecture: Overview

Typically 500 to 5,000 homes

cable headend cable distribution network (simplified)

home

Overview

1-31

Overview

1-32

Cable Network Architecture: Overview

cable headend cable distribution network (simplified)

home

16

Cable Network Architecture: Overview server(s)

cable headend cable distribution network

home

Overview

1-33

Overview

1-34

Cable Network Architecture: Overview FDM: V I D E O

V I D E O

V I D E O

V I D E O

V I D E O

V I D E O

D A T A

D A T A

C O N T R O L

1

2

3

4

5

6

7

8

9

Channels

cable headend cable distribution network

home

17

Company access: local area networks company/univ local area network (LAN) connects end system to edge router ‰ Ethernet: ™ shared or dedicated link connects end system and router ™ 10 Mbs, 100Mbps, Gigabit Ethernet ‰ LANs: chapter 5 ‰

Overview

1-35

Wireless access networks ‰

shared wireless access network connects end system to router ™

‰

wireless LANs: ™

‰

via base station aka “access point” 802.11b (WiFi): 11 Mbps

router base station

wider-area wireless access ™ ™

™

provided by telco operator 3G ~ 384 kbps • Will it happen?? WAP/GPRS in Europe

mobile hosts

Overview

1-36

18

Physical Media Twisted Pair (TP) ‰ two insulated copper wires

Bit: propagates between transmitter/rcvr pairs ‰ physical link: what lies between transmitter & receiver ‰ guided media: ‰

™

‰

™

™

signals propagate in solid media: copper, fiber, coax

Category 3: traditional phone wires, 10 Mbps Ethernet Category 5: 100Mbps Ethernet

unguided media: ™

signals propagate freely, e.g., radio

Overview

1-37

Physical Media: coax, fiber Coaxial cable:

two concentric copper conductors ‰ bidirectional ‰ baseband: ‰

™ ™

‰

single channel on cable legacy Ethernet

broadband: ™ ™

multiple channels on cable HFC

Fiber optic cable: glass fiber carrying light pulses, each pulse a bit ‰ high-speed operation: ‰

™

‰

high-speed point-to-point transmission (e.g., 10’s100’s Gps)

low error rate: repeaters spaced far apart ; immune to electromagnetic noise

Overview

1-38

19

Physical media: radio signal carried in electromagnetic spectrum ‰ no physical “wire” ‰ bidirectional ‰ propagation environment effects: ‰

™ ™ ™

reflection obstruction by objects interference

Radio link types: ‰

terrestrial microwave ™

‰

LAN (e.g., Wifi) ™

‰

2Mbps, 11Mbps, 54 Mbps

wide-area (e.g., cellular) ™

‰

e.g. up to 45 Mbps channels

e.g. 3G: hundreds of kbps

satellite ™ ™ ™

Kbps to 45Mbps channel (or multiple smaller channels) 270 msec end-end delay geosynchronous versus low altitude Overview

1-39

Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Overview

1-40

20

Internet structure: network of networks roughly hierarchical ‰ at center: “tier-1” ISPs or Internet backbone networks ‰

(e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage, connect to large tier-2 ISPs and to all tier-1 ISPs and many customer networks. Tier-1 providers interconnect (peer) privately

Tier 1 ISP

Tier 1 ISP

Tier-1 providers also interconnect at public Network Access Points (NAPs).

NAP

Tier 1 ISP

Overview

1-41

Tier-1 ISP: e.g., Sprint Sprint US backbone network

DS3 (45 Mbps) OC3 (155 Mbps) OC12 (622 Mbps) OC48 (2.4 Gbps)

Seattle Tacoma

Stockton San Jose

Cheyenne Kansas City

New York Pennsauken Relay Wash. DC

Chicago Roachdale

Anaheim Atlanta Fort Worth Orlando Overview

1-42

21

Internet structure: network of networks ‰

“Tier-2” ISPs: smaller (often regional) ISPs ™

Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

NAPs (Network Access Points) are complex high-speed switching networks often concentrated at a single building. Operated by 3rd party telecom or Internet backbone ISP-1. ‰ PoPs (Points of Presence) are private group of routers within each ISP and used to connect it (peer it) with other up/down/equal ISPs and is the new trend in connectivity. Tier-2 ISPs also peer privately with each other, Tier-2 ISP Tier-2 ISP pays Tier-2 ISP interconnect at tier-1 ISP for public NAPs or connectivity to private POPs. ‰

Tier 1 ISP

rest of Internet, tier-2 ISP is customer of tier-1 provider

Tier 1 ISP

Tier 1 ISP Tier-2 ISP

NAP

Tier-2 ISP

Tier-2 ISP Overview

1-43

Internet structure: network of networks ‰

“Tier-3” ISPs and local ISPs ™

last hop (“access”) network (closest to end systems) local ISP

Local and tier3 ISPs are customers of higher tier ISPs connecting them to rest of Internet

Tier 3 ISP Tier-2 ISP

local ISP

local ISP

local ISP Tier-2 ISP

Tier 1 ISP

Tier 1 ISP

Tier-2 ISP local local ISP ISP

NAP

Tier 1 ISP Tier-2 ISP local ISP

Tier-2 ISP local ISP Overview

1-44

22

Internet structure: network of networks ‰

a packet passes through many networks! local ISP

Tier 3 ISP Tier-2 ISP

local ISP

local ISP

local ISP Tier-2 ISP

Tier 1 ISP

Tier 1 ISP local ISP

Tier-2 ISP local ISP

NAP

Tier 1 ISP Tier-2 ISP local ISP

Tier-2 ISP local ISP Overview

1-45

MichNet: Statewide Backbone Nation’s longestrunning regional network ‰ An 2.5 Gigabit (OC48c) backbone, with 24 backbone nodes ‰ Two diverse 2.5 gigabit (2x OC48) to chicago ‰ www.merit.edu/mn ‰

Overview

1-46

23

Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Overview

1-47

How do loss and delay occur? packets queue in router buffers packet arrival rate to link exceeds output link capacity ‰ packets queue, wait for turn ‰

packet being transmitted (delay)

A B

packets queueing (delay) free (available) buffers: arriving packets dropped (loss) if no free buffers

Overview

1-48

24

Four sources of packet delay ‰

1. Processing delay at router: ™ ™

‰

check bit errors determine output link

2. Queueing delay at router ™ ™

time waiting at output link for transmission depends on congestion level of router

transmission

A

propagation

B

nodal processing

queueing Overview

1-49

Delay in packet-switched networks 3. Transmission delay of link: ‰ R=link bandwidth (bps) ‰ L=packet length (bits) ‰ time to send bits into link = L/R

4. Propagation delay of medium: ‰ d = length of physical link ‰ s = propagation speed in medium (~2x108 m/sec) ‰ propagation delay = d/s Note: s and R are very different quantities!

transmission

A

propagation

B

nodal processing

queueing

Overview

1-50

25

Total End-End Delay

homogeneous links

dend-end = N(dnodal) = N(dproc + dqueue+ dtrans + dprop) ‰ N

= #links between source and destination = #routers + 1

‰ dproc = processing delay at router (task 1) ™

typically a few microsecs or less

‰ dqueue = queuing delay at router (task 2)

depends on congestion (neglect if light traffic) ‰ dtrans = transmission delay for router to put data on medium (task 3) ™ = L/R, significant for low-speed links ‰ dprop = propagation delay at medium (task 4) ™ a few microsecs to hundreds of msecs ™

d

N q q = ∑ ⎡⎢d qproc + dqueue + dtrans + d qprop ⎤⎥ heterogeneous links end − end q = 1⎣ ⎦ Overview

1-51

Overview

1-52

The cause of Queueing delay R=link bandwidth (bps) ‰ L=packet length (bits) ‰ a=average packet arrival rate (requests/sec) ‰

traffic intensity (link utilization) = La/R

La/R ~ 0: average queueing delay small ‰ La/R -> 1: delays become large ‰ La/R > 1: more “work” arriving than can be serviced, average delay infinite! ‰

26

“Real” Internet delays and routes What do “real” Internet delay & loss look like? ‰ Traceroute program (in Unix) or Tracert (MSDOS): provides delay measurement from source to router along end-end Internet path towards destination. For all i: ‰

™ ™ ™

sends three packets that will reach router i on path towards destination router i will return packets to sender sender times interval between transmission and reply. 3 probes

3 probes

3 probes

Overview

1-53

“Real” Internet delays and routes traceroute: gaia.cs.umass.edu to www.eurecom.fr Three delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu 1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms 2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms 3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms 4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 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 22 ms 22 ms trans-oceanic 8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms link 9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms 10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms 11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms 12 nio-n2.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 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms 15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms 16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms 17 * * * * means no response (probe lost, router not replying at any one of the 3 msgs) 18 * * * 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms Overview

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27

“Real” Internet delays and routes tracert www.yahoo.com

Tracing route to www.yahoo.akadns.net [216.109.118.67] over a maximum of 30 hops: 1 2 3 4 5 6 7 8 9 10 11 12 13 14

1 ms 11 ms 7 ms 7 ms 12 ms 13 ms 12 ms 13 ms 31 ms 36 ms 37 ms 36 ms 35 ms 36 ms

3 delay (end-end) measurements for each of the 3 msgs

1 ms 1 ms 192.168.0.1 9 ms 8 ms 64.230.197.241 7 ms 7 ms 64.230.235.85 7 ms 7 ms 64.230.235.97 12 ms 12 ms rtp627197rts [64.230.220.254] 13 ms 12 ms 64.230.242.205 12 ms 12 ms bx3-toronto12-pos5-0.in.bellnexxia.net [206.108.107.234] 13 ms 13 ms if-7-0.core1.TTT-Scarborough.teleglobe.net [209.58.25.69] 32 ms 31 ms if-3-3.mcore3.NJY-Newark.teleglobe.net [216.6.57.33] 36 ms 36 ms if-13-0.core1.AEQ-Ashburn.teleglobe.net [216.6.57.42] 36 ms 36 ms ix-14-2.core1.AEQ-Ashburn.teleglobe.net [63.243.149.110] 36 ms 36 ms vlan200-msr1.dcn.yahoo.com [216.115.96.161] 36 ms 36 ms ge3-1.bas2-m.dcn.yahoo.com [216.109.120.146] 36 ms 37 ms p4.www.dcn.yahoo.com [216.109.118.67]

Note: an * in one of the routers result means no response (probe lost, router did not Trace complete. reply for at least one of the 3 msgs) It took 13 routers to get from my house to www.yahoo.com

Overview

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“Real” Internet delays and routes ‰

Ping program: checks if a host is live or not and provides RTT delay measurement from source to destination along end-end Internet path. ™ ™ ™

sends n requests of size 32 bytes and calculates avg RTT sender times interval between transmission and reply. ping -n

n probes

Overview

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28

“Real” Internet delays and routes ping www.yahoo.com

Pinging www.yahoo.akadns.net [68.142.226.34] with 32 bytes of data: Reply from 68.142.226.34: bytes=32 time=38ms TTL=51 Reply from 68.142.226.34: bytes=32 time=39ms TTL=51 Reply from 68.142.226.34: bytes=32 time=38ms TTL=51 Reply from 68.142.226.34: bytes=32 time=39ms TTL=51 RTTs Ping statistics for 68.142.226.34: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 38ms, Maximum = 39ms, Average = 38ms

Overview

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Outline 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Overview

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29

Protocol “Layers” Networks are complex! ‰ many “pieces”: ™ hosts ™ routers ™ links of various media ™ applications ™ protocols ™ hardware, software

Overview

1-59

Why layering? Dealing with complex systems: explicit structure allows identification, relationship of complex system’s pieces ™ layered reference model for discussion ‰ modularization eases maintenance, updating of system ™ change of implementation of layer’s service transparent to rest of system ™ e.g., change in gate procedure doesn’t affect rest of system ‰ Layering negatives: duplicate functionality and inter-dependency. ‰

Overview

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30

Internet protocol stack ‰

application: supporting network applications ™

‰

transport: process-process data transfer ™

‰

network

TCP, UDP

link

IP

link: data transfer between neighboring network elements ™

‰

transport

network: host-host data transfer ™

‰

application

FTP, SMTP, HTTP

physical

PPP, Ethernet

physical: bits “on the wire” Overview

source message segment Ht

datagram Hn Ht

frame

Hl Hn Ht

M M M M

1-61

Encapsulation

application transport network link physical

Hl Hn Ht

M

link physical

Hl Hn Ht

M

switch

destination M Ht

M

Hn Ht

M

Hl Hn Ht

M

application transport network link physical

Hn Ht

M

Hl Hn Ht

M

network link physical

Hn Ht

M

Hl Hn Ht

M

router

Overview

1-62

31

Overview

1-63

Internet History 1961-1972: Early packet-switching principles ‰ 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

‰ 1972: ™ ™

™ ™

ARPAnet demonstrated publicly NCP (Network Control Protocol) first hosthost protocol first e-mail program ARPAnet has 15 nodes

Overview

1-64

32

Internet History 1972-1980: Internetworking, new and proprietary nets ‰ 1970: ALOHAnet satellite ‰ ‰

‰

‰ ‰

network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn architecture for interconnecting networks late70’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: ™ minimalism, autonomy - no internal changes required to interconnect networks ™ best effort service model ™ stateless routers ™ decentralized control define today’s Internet architecture 2005 ACM Turing Award “A protocol for packet network interconnection”, IEEE Trans. on Communications Technology, vol.22(5), 627-641 Overview

1-65

Internet History 1980-1990: new protocols, a proliferation of networks ‰ ‰ ‰

‰ ‰

1983: deployment of TCP/IP 1982: SMTP e-mail protocol defined 1983: DNS defined for name-to-IPaddress translation 1985: FTP protocol defined 1988: TCP congestion control

new national networks: Csnet, BITnet, NSFnet, Minitel ‰ 100,000 hosts connected to confederation of networks ‰

Overview

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33

Internet History 1990, 2000’s: commercialization, the Web, new apps ‰ Early 1990’s: ARPAnet

decommissioned ‰ 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) ‰ early 1990s: Web ™ hypertext [Bush 1945, Nelson 1960’s] ™ HTML, HTTP: Berners-Lee ™ 1994: Mosaic, later Netscape ™ late 1990’s: commercialization of the Web

Late 1990’s – 2000’s:

more killer apps: instant messaging, peer2peer file sharing (e.g., Naptser) ‰ network security to forefront ‰ est. 50 million host, 100 million+ users ‰ backbone links running at Gbps ‰

Overview

1-67

Part II Summary ‰

Internet Access from Home: ™

Dialup via modem, ADSL, HFC

‰

Physical medium:

‰

Internet Structure:

™

™

‰

Guided media(TP, optical), Unguided media (Wi-Fi, Radio) tier-1,2,3 ISPs connected via NAPs and POPs

Total end-end delay in homogeneous packet networks:

d = N (d ) = N (d + d +d +d ) Traceroute/Tracert and Ping programs measure delays ‰ layering and service models:

‰

end -end

™

‰

nodal

proc

queue

trans

prop

Internet Protocol Stack (application, transport, network, link, physical)

Four decades history

Overview

1-68

34