Introduction CICS 515 (Part 1) University of British Columbia CICS 515 (Part 1) Internet Computing...

Introduction

University of British Columbia

CICS 515 (Part 1)CICS 515 (Part 1) Internet Computing

Lecture 1 - Overview

Instructor: Dr. Son T. VuongEmail: [email protected]

May 8, 2012

The World Connected

Introduction 1-2

Information and Organization

Instructor: Dr. Son Vuong ► Email: [email protected] ► Office Hours: T, Th: 1:00-2:00pm (CS 329)

TA: ► Jonatan Schroeder [email protected]► Shahed Alam [email protected]

Lectures: T, Th: 11am-1 pm in DMP 110 Lab: Th: 2-4 pm (CS 045/051)

mailto:[email protected]

mailto:[email protected]

Introduction 1-3

Text and Workload Text: Computer Networking: A Top Down Approach

Featuring the Internet, 6th edition. Jim Kurose, Keith Ross. Addison-Wesley, April 2012.

Course Load:► 2 Projects/Asgmts (20%)► 2 Quizzes (10%)► Midterm (25%)► Final exam (45%)► Bonus for class participation, BlueCT + Peerwise (4%)

Late penalty: 5*2i %, 0< i =< 3 (i = # days late)

Website: www.icics.ubc.ca/~cics515 Vista: http://www.vista.ubc.ca/ (id=pwd=CWL)

Introduction 1-4

Revised CISC 515 Outline (Tentative)

1. (T - 08/5) Overview (Chapter 1) P1

2. (Th - 10/5) Application Layer (The Web and HTTP) (Ch 2)

3. (T - 15/5) WebCache and Transport Layer (Ch 3)4. (Th - 17/5) Transport Layer (Ch 3) 5. (T - 22/5) Transport Layer (TCP) (Ch 3) Quiz16. (Th - 24/5) TCP Congestion (P1) P27. (T-29/5) IP (Ch 4) IPv6 (Ch 4) Midterm8. (Th - 31/6) Other Protocols (ICMP, DHCP, DNS),

Routing (RIP, OSPF) (Ch 4)9. (T - 05/6) Routing (RIP, OSPF, BGP) (Ch 4)10. (Th- 07/6) Data Link protocols (Ethernet) (Ch 5) (P2)11. (T- 12/6) Wireless Networks (WiFi) (Ch 6) Quiz212. (Th-14/6) Review 13. (F-15/6) Final Exam

Introduction 1-5

Chapter 1: Introduction

Our goal: get context,

overview, “feel” of networking

more depth, detail later in course

approach:► descriptive► use Internet as

example

Overview: 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 history

Introduction 1-6

Chapter 1: roadmap

1.1 What is the Internet?1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Protocol layers, service models1.7 Delay & loss in packet-switched

networks1.8 History

Introduction 1-7

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

millions of connected computing devices: hosts, end-systems► PCs workstations, servers► PDAs phones, toasters

running network apps communication links

► fiber, copper, radio, satellite

► transmission rate = bandwidth

routers: forward packets (chunks of data)

local ISP

companynetwork

regional ISP

router workstation

servermobile

Introduction 1-8

“Cool” internet appliances

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

IP picture framehttp://www.ceiva.com/

Web-enabled toaster+weather forecaster

Introduction 1-9

What’s the Internet: “nuts and bolts” view protocols control sending,

receiving of msgs► e.g., TCP, IP, HTTP, FTP,

PPP

Internet: “network of networks”► loosely hierarchical► public Internet versus

private intranet

Internet standards► RFC: Request for comments► IETF: Internet Engineering

Task Force

local ISP

companynetwork

regional ISP

router workstation

servermobile

Introduction 1-10

What’s the Internet: a service view communication

infrastructure enables distributed applications:► Web, email, games, e-

commerce, database., voting, file (MP3) sharing

communication services provided to apps:► connectionless► connection-oriented

cyberspace [Gibson]:“a consensual hallucination experienced daily by

billions of operators, in every nation, ...."

Introduction 1-11

Uses of Internet

• Business Applications• Home Applications• Mobile Users• Social Issues

Introduction 1-12

Business Applications of Networks

A network with two clients and one server.

Introduction 1-13

Business Applications of Networks (2)

The client-server model involves requests and replies.

Introduction 1-14

Home Network Applications

Access to remote information Person-to-person

communication Interactive entertainment Electronic commerce

Introduction 1-15

Home Network Applications (2)

In peer-to-peer system there are no fixed clients and servers.

Introduction 1-16

Home Network Applications (3)

Some forms of e-commerce.

Introduction 1-17

Mobile Network Users

Combinations of wireless networks and mobile computing.

Introduction 1-18

Classification of Networks

Classification of interconnected processors by scale.

Introduction 1-19

Example Networks The Internet

Connection-Oriented Networks: X.25, Frame Relay, and ATM

Ethernet

Wireless LANs: 802:11 (WiFi)

Introduction 1-20

Network Perspective Network users: services that their

applications need, e.g., guarantee that each message it sends will be delivered without error within a certain amount of time

Network designers: cost-effective design e.g., that network resources are efficiently utilized and fairly allocated to different users

Network providers: system that is easy to administer and manage e.g., that faults can be easily isolated and it is easy to account for usage

Introduction 1-21

Connectivity Building Blocks

► links: coax cable, optical fiber...► nodes: general-purpose workstations...

Direct Links► point-to-point

► multiple access

Introduction 1-22

A network can be defined recursively as:

► two or more nodes connected by a physical link,

► or by two or more networks connected by one or more nodes

Internetworks

Internet vs internet

Switched Networks

Introduction 1-23

A closer look at network structure: network edge: applications

and hosts network core:

► routers► network of networks

access networks, physical media: communication links

Introduction 1-24

Chapter 1: roadmap

1.1 What is the Internet?1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs 1.6 Protocol layers, service models1.7 Delay & loss in packet-switched

networks1.8 History

Introduction 1-25

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

Introduction 1-26

Network edge: connection-oriented service

Goal: data transfer between end systems

handshaking: setup (prepare for) data transfer ahead of time► Hello, hello back

human protocol► set up “state” in two

communicating hosts

TCP - Transmission Control Protocol ► Internet’s connection-

oriented service

TCP service [RFC 793] reliable, in-order byte-

stream data transfer► loss: acknowledgements

and retransmissions

flow control: ► sender won’t overwhelm

receiver

congestion control: ► senders “slow down

sending rate” when network congested

Introduction 1-27

Network edge: connectionless service

Goal: data transfer between end systems► same as before!

UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service► unreliable data

transfer► no flow control► no congestion

control

App’s using TCP: HTTP (Web), FTP (file

transfer), Telnet (remote login), SMTP (email)

App’s using UDP: streaming media,

teleconferencing, DNS, Internet telephony

Introduction 1-28

Chapter 1: roadmap


networks1.8 History

Introduction 1-29

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”

Introduction 1-30

Circuit switching: dedicated circuit; send/receive a bit stream► original telephone network

Packet switching: store-and-forward; send/receive messages (packets)► Internet

Switching Strategies

Introduction 1-31

Switching Strategies

(a) Circuit switching (b) Message switching (c) Packet switching

Introduction 1-32

Nodal delay

dproc = processing delay► typically a few microsecs or less

dqueue = queuing delay► depends on congestion

dtrans = transmission delay► = L/R, significant for low-speed links

dprop = propagation delay► a few microsecs to hundreds of msecs

proptransqueueprocnodal ddddd

Introduction 1-33

Packet switching versus circuit switching

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 (chapter 6)

Is packet switching a “slam dunk winner?”

Introduction 1-34

Packet-switching: store-and-forward

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 forward

delay = 3L/R

Example: L = 7.5 Mbits R = 1.5 Mbps delay = 3x 5 sec = 15

sec

R R RL

Introduction 1-35

Packet Switching: Message Segmenting

Now break up the message into 5000 packets

Each packet 1,500 bits

1 msec to transmit packet on one link

pipelining: each link works in parallel

Delay reduced from 15 sec to 5.002 sec

Introduction 1-36

Packet Switching: Message Segmenting

Now assume the message/packets go through 2 additional switches (over the path of 4 switches)

What is the total delay to send the message without breaking into packets (i.e. non-pipelining) ?

What is the total delay to send the message as 5000 packets (i.e. pipelining) ?

R R R

L

R

Introduction 1-37

Q 1.1 Peer Instruction packet switchingNow assume the message/packets go through

2 additional switches (over the path of 4 switches) What is the total delay to send the message as 5000 packets (i.e. pipelining) ?

Answer:

(A) 25 s (B) 15 s (C) 5.002 s (D) 5.004 s (E) None of the above

Introduction 1-38

Q 1.1 Peer Instruction packet switchingNow assume the message/packets go through

2 additional switches (over the path of 4 switches) What is the total delay to send the message as 5000 packets (i.e. pipelining) ?

Answer:

(A) 25 s (B) 15 s (C) 5.002 s (D) 5.004 s (E) None of the above

Introduction 1-39

Packet-switched networks: forwarding Goal: move packets through routers from source to

destination► we’ll study several path selection (i.e. routing)algorithms

(chapter 4)

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

virtual circuit network: ► each packet carries tag (virtual circuit ID), tag determines

next hop► fixed path determined at call setup time, remains fixed thru

call► routers maintain per-call state

Introduction 1-40

Addressing and Routing Address: byte-string that identifies a node

► usually unique

Routing: how to forward messages towards the destination node based on its address

Types of addresses► unicast: node-specific► broadcast: all nodes on the network► multicast: some subset of nodes on the

network

Introduction 1-41

Multiplexing Time-Division Multiplexing (TDM)

Frequency-Division Multiplexing (FDM)

L1

L2

L3

R1

R2

R3Switch 1 Switch 2

Introduction 1-42

Circuit Switching: FDMA and TDMA

FDMA

frequency

time

TDMA

frequency

time

4 users

Example:

Introduction 1-43

Time Division Multiplexing (T1 Carrier)

The T1 carrier (1.544 Mbps).

(1 bit + 24 slots * 8 bits/slot) * 8000 frames/s

= 193 bits/frame * 8000 frames/s = 1.544 Mbps

Introduction 1-44

Peer Instruction 1.1 – T1 TDM Question How long does it take to send a file of 640,000 bits

from host A to host B over a (sub)channel (a circuit) in a T1 TDM based circuit-switched network?

► Overall T1 TDM carrier capacity is 1.536 Mbps► Data transmission uses one of the 24 slots of the T1 carrier► 500 msec to establish end-to-end circuit

Work it out!

(A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s(E) None of the above

Introduction 1-45

1.1 Peer Instruction – T1 TDM Answer How long does it take to send a file of 640,000 bits

from host A to host B over a (sub)channel (a circuit) in a T1 TDM based circuit-switched network?

► Overall TDM channel capacity is 1.536 Mbps (T1: 1.544 Mbps with 8Kbps framing)

► Data transmission uses one of the 24 slots of the TDM channel► 500 msec = 0.5s to establish end-to-end circuit

Answer: Each circuit= 1.536Mbps/24 = 64Kbps

Tx(file) = 640Kb/64Kbps = 10s plus Tsetup


Introduction 1-46

Peer Instruction 1.1 – T1 TDM Question How long does it take to send a file of 640,000 bits

from host A to host B over 5 (sub)channels (circuits) in a T1 TDM based circuit-switched network?

► Overall T1 TDM carrier capacity is 1.536 Mbps► Data transmission uses one of the 24 slots of the T1 carrier► 500 msec to establish end-to-end circuit

Work it out!


Introduction 1-47

1.1 Peer Instruction – T1 TDM Answer How long does it take to send a file of 640,000 bits from

host A to host B over 5 (sub)channel (circuits) in a T1 TDM based circuit-switched network?

► Overall TDM channel capacity is 1.536 Mbps (T1: 1.544 Mbps with 8Kbps framing)

► Data transmission uses one of the 24 slots of the TDM channel► 500 msec = 0.5s to establish end-to-end circuit

Answer: Each circuit= 1.536Mbps/24 = 64Kbps

Tx(file) = 640Kb/(5x64Kbps) = 2s plus Tsetup


Introduction 1-48

Statistical Multiplexing (ATDM) On-demand time-division, rather than fixed

(STDM) Schedule link on a per-packet basis Packets from different sources interleaved on link Buffer packets that are contending for the link Packet queue may be processed FIFO Buffer (queue) overflow is called congestion

…

ATDM or Concentrator

Introduction 1-49

Chapter 1: roadmap


networks1.8 History

Introduction 1-50

Protocols Building blocks of a network

architecture Each protocol object has two

different interfaces:► service: operations on this protocol► peer-to-peer (protocol): messages

exchanged with peer Term “protocol” is overloaded

► specification of peer-to-peer interface► module that implements this interface

Introduction 1-51

Host 1

Protocol

Host 2

Protocol

High-levelobject

High-levelobject

SERVICEinterface

Peer-to-peer

interface

Interfaces (Protocol and Service)

PROTOCOL

Introduction 1-52

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

… specific msgs sent… specific actions

taken when msgs received, or other events

network protocols: machines rather than

humans all communication

activity in Internet governed by protocols

protocols define format, order of msgs sent and

received among network entities, and actions taken on msg transmission, receipt

Introduction 1-53

What’s a protocol?a human protocol and a computer network protocol:

Q: Other human protocols?

Hi

Hi

Got thetime?

2:00

TCP connection req

TCP connectionresponseGet http://www.awl.com/kurose-ross

<file>time

Introduction 1-54

Internet Architecture

Defined by Internet Engineering Task Force (IETF)

Hourglass Design Application vs Application Protocol (FTP,

HTTP)

…

FTP HTTP NV TFTP

TCP UDP

IP

NET1 NET2 NETn

TCP UDP

IP

Network

Application

Introduction 1-55

ISO Architecture

Application

Presentation

Session

Transport

End host

One or more nodes

within the network

Network

Data link

Physical

Network

Data link

Physical

Network

Data link

Physical

Application

Presentation

Session

Transport

End host

Network

Data link

Physical

Introduction 1-56

Reference Models

The TCP/IP reference model.

Introduction 1-57

Layering Use abstractions to hide complexity Abstraction naturally lead to layering Alternative abstractions at each layer

Request/replychannel

Message streamchannel

Application programs

Hardware

Host-to-host connectivity

Application programs

Process-to-process

Hardware

Host-to-host connectivity

Introduction 1-58

Layering: logical communication

applicationtransportnetwork

linkphysical


linkphysical


linkphysical


linkphysical

networklink

physical

Each layer: distributed “entities”

implement layer functions at each node

entities perform actions, exchange messages with peers

Introduction 1-59

Layering: logical communication


linkphysical


linkphysical


linkphysical


linkphysical

networklink

physical

data

data

E.g.: transport take data from

app add addressing,

reliability check info to form “datagram”

send datagram to peer

wait for peer to ack receipt

analogy: post office

data

transport

transport

ack

Introduction 1-60

Layering: physical communication


linkphysical


linkphysical


linkphysical


linkphysical

networklink

physical

data

data

Introduction 1-61

Protocol layering and data

Each layer takes data from above adds header information to create new data unit passes new data unit to layer below


linkphysical


linkphysical

source destination

M

M

M

M

Ht

HtHn

HtHnHl

M

M

M

M

Ht

HtHn

HtHnHl

message

segment

datagram

frame

Introduction 1-62

Chapter 1: roadmap


networks1.8 History

Introduction 1-63

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

A

B

packet being transmitted (delay)

packets queueing (delay)

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

Introduction 1-64

1.2 Peer Instruction - Packet Error Prob Question

Let p be the bit error probability. Assume packet of length L bits. What's the packet error probability in terms of p and L?

(A) (1- p) **L(B) 1- p**L(C) 1- p * L(D) 1- (1-p)**L(E) None of the above

Introduction 1-65

1.2 Peer Instruction - Packet Error Prob AnswerLet p be the bit error probability. Assume packet of

length L bits. What's the packet error probability in terms of p and L?

(A) (1- p) **L(B) 1- p**L prob (not all bits in error) (C) 1- p * L(D) 1- (1-p)**L(E) None of the above

Answer: (D) prob(a bit not in error) = 1-pprob (L bits not in error) = (1-p)**L

prob(packet error) = prob (not all bits not in error)

= 1- (1-p)**L

Introduction 1-66

What Goes Wrong in the Network? Bit-level errors (electrical interference) prob=p Packet-level errors (congestion) = 1-(1-p)f

Link and node failures

Messages are delayed Messages are delivered out-of-order Third parties eavesdrop

The key problem is to fill in the gap between whatapplications expect and what the underlying technology provides.

Introduction 1-67

Four sources of packet delay

1. nodal processing: ► check bit errors► determine output link

A

B

propagation

transmission

nodalprocessing queueing

2. queueing► time waiting at output

link for transmission ► depends on

congestion level of router

Introduction 1-68

Delay in packet-switched networks3. Transmission delay: R=link bandwidth

(bps) L=packet length (bits) time to send bits into

link = L/R

4. Propagation delay: d = length of physical

link s = propagation speed in

medium (~2x108 m/sec) propagation delay = d/s

A

B

propagation

transmission

nodalprocessing queueing

Note: s and R are very different quantities!

Introduction 1-69

Nodal delay

dproc = processing delay► typically a few microsecs or less

dqueue = queuing delay► depends on congestion

dtrans = transmission delay► = L/R, significant for low-speed links

dprop = propagation delay► a few microsecs to hundreds of msecs

proptransqueueprocnodal ddddd

Introduction 1-70

Queueing delay (revisited)

R=link bandwidth (bps) L=packet length (bits) a=average packet

arrival rate

traffic intensity = 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!

Introduction 1-71

Digression- Simple Queuing ModelQueuing system – general properties: Arrival rate: λ = a msg/s Service rate: μ = R/L msg/s Service time: Ts = L/R = ρ / a

s/msgTraffic intensity = Utilization factor = ρ = λ / μ = aL / RLittle Formula: N = λ T = a T or T = N/aN = Nw + Ns and T = Tw + Ts

M/M/1 Queue Model (M/M/1 is Kendall’ notation):Can derive:# in system: N = ρ / (1- ρ) # waiting in queue: Nw = ρ2 / (1-

ρ) => Time in system: T = N/a = Ts / (1- ρ) (using Little formula) = Tw + Ts = N Ts + Ts = (N+1) TsWaiting time: Tw = T – Ts = Ts / (1- ρ) - Ts = (1/ (1- ρ) - 1 )Ts = ρ Ts / (1- ρ) = N Ts

Introduction 1-72

“Real” Internet delays and routes What do “real” Internet delay & loss look like? Traceroute program: 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

Introduction 1-73

“Real” Internet delays and routes

1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 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 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 * * *18 * * *19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms

traceroute: gaia.cs.umass.edu to www.eurecom.frThree delay measements from gaia.cs.umass.edu to cs-gw.cs.umass.edu

* means no reponse (probe lost, router not replying)

trans-oceaniclink

Introduction 1-74

Packet loss

queue (aka buffer) preceding link in buffer has finite capacity

when packet arrives to full queue, packet is dropped (aka lost)

lost packet may be retransmitted by previous node, by source end system, or not retransmitted at all

Introduction 1-75

Performance Metrics

Bandwidth (throughput)► data transmitted per time unit► link versus end-to-end► notation

KB = 210 bytesMbps = 106 bits per second

Latency (delay)► time to send message from point A to point B► one-way versus round-trip time (RTT)► components

Latency = Propagation + Transmit + QueuePropagation = Distance / c (c=3, 2.3, 2x10**8 m/s)Transmit = Size / Bandwidth

1 second

(a)

1 second

(b)

Introduction 1-76

Bandwidth versus Latency Relative importance

► 1-byte: 1ms vs 100ms dominates 1Mbps vs 100Mbps

► 25MB: 1Mbps vs 100Mbps dominates 1ms vs 100ms

Infinite bandwidth► RTT dominates

Throughput = TransferSize / TransferTimeTransferTime = RTT + TransferSize / Bandwidth

► 1-GB file to 1-Gbps link as 1-MB packet to 1-Mbps link

Introduction 1-77

Delay x Bandwidth Product

Amount of data “in flight” or “in the pipe”

Example: 100ms x 45Mbps = 560KB

Bandwidth

Delay

Introduction 1-78

ITU Main sectors

• Radiocommunications• Telecommunications Standardization• Development

Classes of Members• National governments• Sector members• Associate members• Regulatory agencies

Introduction 1-79

IEEE 802 Standards

The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with † gave up.

Introduction 1-80

Bad Timing

The apocalypse of the two elephants.

Introduction 1-81

Chapter 1: roadmap


networks1.8 History

Introduction 1-82

Internet History

1961: Kleinrock - queueing theory shows effectiveness of packet-switching

1964: Baran - packet-switching 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 host-host protocol

► first e-mail program► ARPAnet has 15 nodes

1961-1972: Early packet-switching principles

Introduction 1-83

Internet History

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

1972-1980: Internetworking, new and proprietary nets

Introduction 1-84

Internet History

1983: deployment of 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

new national networks: Csnet, BITnet, NSFnet, Minitel

100,000 hosts connected to confederation of networks

1980-1990: new protocols, a proliferation of networks

Introduction 1-85

Internet History

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. 100 million host, 500 million+ users

backbone links running at Gbps

1990, 2000’s: commercialization, the Web, new apps

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