ECE 358: Computer Networks Instructor: Dr. Sagar Naik Introduction 1-1 To give you a thorough understanding of the Internet. Other kinds of emerging/evolving

ECE 358: Computer Networks

Instructor: Dr. Sagar Naik

Introduction 1-1

To give you a thorough understanding of the Internet.

Other kinds of emerging/evolving networks

Mobile ad hoc, delay-tolerant,

sensor, vehicular, body-area,

peer-to-peer, … and cellular

networks

About the instructor

Introduction 1-2

Teaching interest:

Research:

ECE 358, ECE 416, ECE 655(Past: ECE 355, ECE 453)

Energy efficiency of smartphones and tablets

Wireless networks: ad hoc, delay-tolerant, sensor, vehicular, peer-to-peer

Smart grids

Power efficiency of data centres

Teaching Assistants

Introduction 1-3

Greta Cutulenco: [email protected], E5-4111 Yasir Ali: [email protected], EIT-4122

Course website: https://ece.uwaterloo.ca/~ece358/

Class email: [email protected]

Grading scheme

Introduction 1-4

Mini projects (3): 15% (5 + 5 + 5)

Midterm exam: 25%

Final exam: 60% TBA-----------------------------------------------Total: 100%

group size = 2

Introduction 1-5

5-7 Homeworks

(0 marks)

Some exam questions will be based on homeworks.

TAs will solve some of those questions in the tutorials.

Three Objectives of ECE 358Link layer with medium access control: 1-hop comm.

Home network

Institutional network

Mobile network

Global ISP

Regional ISP

router

PC

server

wirelesslaptop

cellular handheld

wiredlinks

access points

Network layer (routing):

multi-hop comm.Transport layer: end-to-end, reliable comm. between apps.

Introduction 1-6Teaching: Bottom-up approach ISP: Internet Service Provider

Physical

Link/MAC (Ch. 5)

Network (Ch. 4)

Transport (Ch. 3)

App

L2 (Layer 2)

L3

L4

L1

Introduction 1-7

For real engineers …

To other LANs on the Internet

LAN1

LAN2

LAN: Local Area NetworkA LAN is a network of computersconnected with a “broadcast” medium,say, an L2 switch.

Introduction 1-8

L2 and L3 switches and connectors

Cisco L3 switch (Catalyst 4948)

48 10/100/1000 BASE-T ports (RJ45)

Mbps (Megabits/sec)

4 1000 BASE-X Small Form-factor Pluggable (SFP) optics ports

Back panel of Catalyst 4948

Dual powersupply

Removablefans

BASE: Baseband Bits are not modulated.T: Twisted pair (copper)

Introduction 1-9


Cisco L2 switch(SF300 24P)

24 10/100 BASE-T PoE (Power over Ethernet) ports 2 Gigabit ports 2 Fiber ports

Introduction 1-10


Category 6 (Cat.6 on cables) cables support

- 10 BASE-T (Ethernet)- 100 BASE-T (Fast Ethernet)- 1000 BASE-T (Giga Ethernet)- 10 GBASE-T (10 Gigabit Ethernet)

Twisted to cancel out electromagnet interference.

Common copper connectors …

Cat 5e

Introduction 1-11


Common fiber connectors …

GBIC: Gigabit Interface Converter (1 Gbps)

SFP: Small Form factor Pluggable trans. (1 Gbps)

CFP: C Form factor Pluggable (C in Latin = 100) (100 Gbps)

SFP+: (10 Gbps)

Cisco CFP-100G-ER4

Introduction 1-12

Lectures, exams, reviews, and office hours

Past exams

Review

Basics of networking

Midterm exam

Network layer (IP protocol)

Final exam

Link layer (Medium access control+)

Transport layer (Trans. Control Protocol)

Past exams

Introduction 1-13

Handle: @SagarNaik101

Hashtag: #ECE358F14

New

Classroom protocol

Introduction 1-14

• All cell phones, including mine, must be turned off.

Interference degrades performance.

• No peer-to-peer communication It causes interference.

A note about the slides

Introduction 1-15

All the slides were originally prepared by Kurose and Ross.

I have added more slides and edited most of the slides.

I will publish ALL slides, but may skip some so that youcontinue to access the full set.

Chapter 1Introduction

Computer Networking: A Top Down Approach ,5th edition. Jim Kurose, Keith RossAddison-Wesley, April 2009.

A note on the use of these ppt slides:We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material.

Thanks and enjoy! JFK/KWR

All material copyright 1996-2010J.F Kurose and K.W. Ross, All Rights Reserved

Introduction 1-16

Chapter 1: roadmap

1.1 What is the Internet?

1.2 Network edge end systems, access networks, links

1.3 Network core: network of nets circuit switching, packet switching, network structure

1.4 Delay, loss, and throughput in packet-switched networks Performance metrics

1.5 Protocol layers, service models

Introduction 1-17

What’s the Internet: component view

Introduction 1-18

CoreAccess net Access net

Access net Access net

server

DHCP

DHCP

DHCPDHCP

DHCP: Dynamic Host

Configuration Protocol

Gives your computer an IP address

DNS

DNS

DNS

DNS

DNS: Domain Name System

Performs mapping:

host name IP address

ecemail.uwaterloo.ca

129.97.x.y

www.amazon.com a.b.c.d


millions of connected computing devices:

running network apps

Home network


Mobile network

Global ISP

Regional ISP

router

PC

server

wirelesslaptop

cellular handheld

wiredlinks

access points communication

links fiber, copper,

radio, satellite

routers: forward packets (chunks of data)

Introduction 1-19

“Fun” internet appliances

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

Web-enabled toaster +weather forecaster

Internet phonesInternet refrigerator

Introduction 1-20


protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, Ethernet

Internet: “network of nets” loosely hierarchical

Internet standards RFC: Request For Comments IETF: Internet Eng. Task Force

Home network


Mobile network

Global ISP

Regional ISP

Introduction 1-21

What’s the Internet: a service view communication infrastructure

enables distributed apps: Web, VoIP, email, games, e-

commerce, file sharing Comm. services provided to

apps: reliable data delivery

from source to destination

“best effort” (unreliable) data delivery

Introduction 1-22

What’s a protocol?

Protocols define Format of messages (Message: Header + Optional data) Order of messages sent and received among network entities Actions taken on msg transmission and reception

Introduction 1-23

A protocol is a set of

communication rules.

Protocols run onhosts, switches, routers...

All comm. activities in Internet are governed by protocols.

An Example

TCP connectionresponse

Get http://www.awl.com/kurose-ross

<file>

time

Introduction 1-24

TCP connectionrequest

Chapter 1: roadmap

1.1 What is the Internet?1.2 Network edge

end systems, access networks, links

1.3 Network core circuit switching, packet switching, network structure

1.4 Delay, loss and throughput in packet-switched networks

1.5 Protocol layers, service models1.6 Networks under attack: security1.7 History

Introduction 1-25

The network edge: end systems (hosts):

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

client/server

peer-peer

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. Skype, BitTorrent

Introduction 1-26

Access networks and physical media

Q: How to connect an end system to an edge router?

residential access nets DSL, Cable

institutional access networks (school, company) Ethernet

mobile access networks WiFi

Introduction 1-27

edge routers

telephonenetwork

DSLmodem

homePC

homephone

Internet

DSLAM

splitter

centraloffice

DSL: Digital Subscriber Line

uses existing telephone infrastructure up to 1 Mbps upstream (today typically < 256

kbps) up to 8 Mbps downstream (today typically < 1

Mbps) Introduction 1-28

DSLAM: DSL Access Multiplexer

To another home

One home

Point-to-Point Protocol (PPP)

::

home

cable headend

cable distributionnetwork

server(s)

Introduction 1-29

Cable Network Architecture: Overview


home

cable headend

cable distributionnetwork (simplified)

Introduction 1-30

home

cable headend

cable distributionnetwork

Channels

VIDEO

VIDEO

VIDEO

VIDEO

VIDEO

VIDEO

DATA

DATA

CONTROL

1 2 3 4 5 6 7 8 9

FDM (more shortly):

Introduction 1-31


100 Mbps

100 Mbps

100 Mbps

1 Gbps

server

Ethernetswitch

institutionalrouter to institution’s

ISP

Ethernet Internet access

typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps Ethernet

Question: How do nodes efficiently share the medium?

Introduction 1-32

Early Ethernet

Wireless access networks

shared wireless access network connects end system to router via base station aka “access

point” wireless LANs:

802.11b/g (WiFi): 11 or 54 Mbps

wider-area wireless access provided by telco operator ~1Mbps over cellular system

(EVDO, HSDPA) LTE (Long Term Evolution)

basestation

mobilehosts

router

Introduction 1-33

Home networks

Typical home network components: DSL or cable modem router/NAT (Network Address Translation) Ethernet wireless access point

wirelessaccess point

wirelesslaptops

routercablemodem

to/fromcable

headend

Ethernet

Introduction 1-34

Chapter 1: roadmap






Introduction 1-35

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 1-36

Network Core: Circuit Switching

End-end resources are reserved for “call”

link bandwidth, switch capacity

dedicated resources: no sharing

circuit-like (guaranteed) performance

call setup required

Introduction 1-37

Network Core: Circuit Switching

Network resources (e.g., bandwidth) divided into “pieces”

pieces allocated to calls

resource piece remains idle if not used by owning call

dividing link bandwidth into “pieces” frequency division time division

Introduction 1-38

Circuit Switching: FDM and TDM

FDM

frequency

time

TDM

frequency

time

4 users

Example:

Introduction 1-39

Numerical example (Fall 2012 Final Exam)

How long does it take to send a file of 640,000 bits from host A to host B over a circuit-switched network? Assume that:

• all link speeds: 1.536 Mbps (Megabits per second)• each link uses TDM with 24 slots/sec• a user receives one slot every 8 slots in the TDM

scheme• it takes 500 msec to establish an end-to-end circuit

Show the details of your calculations.

Introduction 1-40

3/60 marks

7 minutes

Numerical example (Contd.: Answer)

The number of bits transmitted by a user in 1 slot = (1/24)* 1.536 Mbps = 64000 bits.

A user gets to transmit in 3 ( = 24/8) slots in each second. So, the amount of data transmitted by a user in 1 second =

3 * 64000 bits. To be able to transmit 640,000 bits, time needed =

640,000/(3*64,000) = 10/3 second. = 3.33 seconds. You need 0.5 seconds to establish a connection.

Therefore, total time needed = 3.33 s + 0.5 s = 3.83 seconds

Introduction 1-41

Network Core: Packet Switching

each end-end data stream is divided into packets

user A, B packets share network resources

each packet uses full link bandwidth

resources used as needed

resource contention: aggregate resource

demand can exceed amount available

congestion: packets queue, wait for link use

store and forward: packets move one hop at a time node receives complete

packet before forwarding

Bandwidth division into “pieces”Dedicated allocationResource reservation

Introduction 1-42

Packet Switching: Statistical Multiplexing

sequence of A & B packets has no fixed timing pattern bandwidth shared on demand: statistical multiplexing.

TDM: each host gets same slot in revolving TDM frame.

A

B

C100 Mb/sEthernet

1.5 Mb/s

D E

statistical multiplexing

queue of packetswaiting for output link

Introduction 1-43

Packet-switching: store-and-forward

takes L/R seconds to transmit (push out) packet of L bits on to link at R bps

store and forward: entire packet must arrive at router before it can be transmitted on next link

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

Example: L = 7.5 Mbits (Note: packets are not that

long! ~1.5KB is very common)

R = 1.5 Mbps transmission delay = 15

sec

R R RL

more on delay shortly …

Introduction 1-44

Packet-switching: store-and-forward

Introduction 1-45

Fall 2012 mid-term exam question #1

Introduction 1-46

Figure 1.

BRouter 2Router 1

Link 1R1

Link 2R2

Link 3R3

• Suppose that host A wants to send a 1 Gigabit file to host B.• The network between A and B has three links (See Fig. 1.) of rates R1 = 4Mbps, R2 = 2Mbps, and R3 = 1Mbps.

“Giga” means 109, “Mega” means 106, and “Kilo” means 103.

•If A sends the file as 1000-byte packets, how long does it take to movethe file from A to B? Show the details of your calculation.

•Assume that the propagation delays on the three links are zero seconds. •Make other assumptions as necessary and appropriate.

A

Numerical example: Fall 2012 mid-term exam

Introduction 1-47

Numerical example: Fall 2012 mid-term examFile size, F = 1 Gigabit = 10^9 bits Packet size, P = 8 x 10^3 bitsPacket count, N = F/P = 125 x 10^3 Ti = Time to transmit 1 packet over link i.T1 = P/R1 = 8 x 10^3 bits / (4 x 10^6 bps) = 2 x 10^(-3) sec = 2 ms.T2 = P/R2 = 8 x 10^3 bits / (2 x 10^6 bps) = 4 x 10^(-3) sec = 4 ms.T3 = P/R3 = 8 x 10^3 bits / (1 x 10^6 bps) = 8 x 10^(-3) sec = 8 ms. Host A will take N x T1 = 125 x 10^3 x 2 x 10^(-3) sec = 250 secRouter 1 will take N x T2 = 125 x 10^3 x 4 x 10^(-3) sec = 500 secRouter 2 will take N x T3 = 125 x 10^3 x 8 x 10^(-3) sec = 1000 sec

File transfer time (exact solution: see next page) = 1000.006 s. Approximate solution Bottleneck link is link 3 so the throughput of the network between A and B is R3.Therefore, file transfer time= F / R3

= 1 x 10^9 bits/ 1 x 10^6 bps= 1 x 10^3 sec = 1000 sec.

Introduction 1-48

Numerical example: Fall 2012 mid-term exam

1000.006 s

Packet switching versus circuit switching

Example: 1 Mb/s link each user:

• 100 kb/s when “active”• active 10% of time

circuit-switching: 10 users

packet switching: with 35 users,

probability > 10 active at same time is less than .0004

Packet switching allows more users to use network!

N users

1 Mbps link

Introduction 1-49

…..

Packet switching versus circuit switching

great for bursty data: you can support more users 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 7)

Introduction 1-50

Introduction 1-51

Fall 2012 final exam question (6/60 marks)Compare circuit switching with packet switching by identifying five attributes of communication systems. For full credit, state the most important attributes.

Attributes Circuit switching Packet switching

Introduction 1-52

Fall 2012 final exam question (6/60 marks)

Attributes Circuit switching Packet switching

Conn. Estm. Yes No

Resource Res Yes No

Multiplexing Time Division MultiplexingFrequency Division Multiplexing

Statistical Multiplexing

PerformanceGuarantee

Yes No

Number of users

Upper bounded, for a given multiplexing scheme

Not bounded

Resource utilization

Slots can go unused if users do not have traffic

A smaller number of users meansthat they get more share of thebandwidth

Internet structure: network of networks roughly hierarchical at center: small # of well-connected large networks

“tier-1” commercial ISPs (e.g., Verizon, Sprint, AT&T, Qwest, Level3), national & international coverage

large content distributors (Google, Akamai (Netflix: Open Connect), Microsoft)

treat each other as equals (no charges)

Tier 1 ISP Tier 1 ISP

Introduction 1-53

Large Content Distributor

(e.g., Google)


(e.g., Akamai)

IXP IXP

Tier 1 ISP

Tier-1 ISPs &Content

Distributors, interconnect

(peer) privately

… or at Internet Exchange Points (IXPs)

Canadian Tier-1: MTS Allstream (MTS: Manitoba Telco Service)

Tier-1 ISP: e.g., Sprint

…

to/from customers

peering

to/from backbone

….

………POP: point-of-presence

Introduction 1-54

Tier 2ISP

Internet structure: network of networks

Introduction 1-55



(e.g., Google)


(e.g., Akamai)

IXP IXP

Tier 1 ISP

“tier-2” ISPs: smaller (often regional) ISPsconnect to one or more tier-1 (provider) ISPs

each tier-1 has many tier-2 customer nets tier 2 pays tier 1 provider

tier-2 nets sometimes peer directly with each other (bypassing tier 1) , or at IXP

Tier 2ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP Tier 2

ISPTier 2

ISPTier 2

ISP

Tier 2ISP

Tier 2ISP


Introduction 1-56



(e.g., Google)


(e.g., Akamai)

IXP IXP

Tier 1 ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP Tier 2

ISPTier 2

ISPTier 2

ISP

Tier 2ISP

“Tier-3” ISPs, local ISPs customer of tier 1 or tier 2 network

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

Tier 2ISP


Introduction 1-57



(e.g., Google)


(e.g., Akamai)

IXP IXP

Tier 1 ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP Tier 2

ISPTier 2

ISPTier 2

ISP

Tier 2ISP

a packet passes through many networks from source host to destination hostIn near future…end-end data

transfer is likely to be like this:

First segment: statistical multiplexing..Middle segment: Light path (i.e. circuit with WDM)Final segment: statistical multiplexing..

Chapter 1: roadmap






Introduction 1-58

How do loss and delay occur?

packets queue in router buffers (i.e. memory) 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 1-59

1.5 Mbps

Corrupted packets are dropped.

Four sources of packet delay

dproc: nodal processing check bit errors determine output link typically < msec

A

B

propagation

transmission

nodalprocessing queueing

dqueue: queueing delay time waiting at output

link for transmission depends on congestion

level of router

Introduction 1-60

dnodal = dproc + dqueue + dtrans + dprop

Four sources of packet delay

A

B

propagation

transmission

nodalprocessing queueing

Introduction 1-61

dnodal = dproc + dqueue + dtrans + dprop

dtrans: transmission delay:

L: packet length (bits) R: link bandwidth (bps) dtrans = L/R

dprop: propagation delay: d: length of physical link s: propagation speed in

medium (~2x108 m/sec) dprop = d/sdtrans and dprop

very different

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

rate (#packets/s)

traffic intensity = La/R

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

Introduction 1-62

avera

ge

queu

ein

g

dela

y

La/R ~ 0

Queueing delay (revisited)

La/R -> 1

“Real” Internet delays

What do real Internet delay look like? Traceroute program: provides delay

measurement from source to router along end-end Internet path towards destination.

For all i: (ith router) 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 1-63C:xyz>tracert u-aizu.ac.jp

“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 measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu

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

trans-oceaniclink

Introduction 1-64

Packet loss

queue (i.e. buffer) preceding link has finite capacity

packet arriving to full queue dropped (aka lost)

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

A

B

packet being transmitted

packet arriving tofull buffer is lost

buffer (waiting area)

Introduction 1-65

Throughput (the output rate of an input/output system)

throughput: rate (bits/time unit) at which bits transferred between sender/receiver instantaneous: rate at given point in time (=max

rate) average: rate over longer period of time

server, withfile of F bits

to send to client

link capacity

Rs bits/sec

link capacity

Rc bits/secserver sends bits (fluid) into pipe

Introduction 1-66

pipe that can carryfluid at rate

Rs bits/sec)

pipe that can carryfluid at rate

Rc bits/sec)

Throughput (more)

Rs < Rc What is average end-end throughput?

Rs bits/sec Rc bits/sec

Rs > Rc What is average end-end throughput?

Rs bits/sec Rc bits/sec

link on end-end path that constrains end-end throughput

bottleneck link

Introduction 1-67

Throughput: Internet scenario

10 connections (fairly) share backbone bottleneck link R

bits/sec

Rs

Rs

Rs

Rc

Rc

Rc

R

per-connection end-end throughput: min(Rc,Rs,R/10)

in practice: Rc or Rs is often bottleneck

Introduction 1-68

Chapter 1: roadmap






Introduction 1-69

Protocol “Layers”

Networks are complex,with many “pieces”:

hosts routers links of various

media applications protocols hardware, software

Introduction 1-70

Physical

Link/MAC (Ch. 5)

Network (Ch. 4)

Transport (Ch. 3)

App

Why layering? Very different functionalities are addressed in

different layers. Ex.: medium access is very different from routing

Modularization eases maintenance and system evolution Ex.: change in network interface does not require

TCP to be modified.

Introduction 1-71

Physical

Link/MAC (Ch. 5)

Network (Ch. 4)

Transport (Ch. 3)

App

Internet protocol stack (on end devices) application: supporting network

applications FTP, SMTP, HTTP

Introduction 1-72

physical: bits “on the wire”: Ethernet, 802.11 (WiFi)

transport: process-process data transfer TCP, UDP

network: routing of datagrams from source to destination IP, routing protocols

link: data transfer between neighboring network elements (MAC/Link)

Physical

Link

Network

Transport

App

ISO/OSI reference model

presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventions

session: synchronization, checkpointing, recovery of data exchange

Internet stack “missing” these layers! these services, if needed, must

be implemented in application needed?

application

presentation

session

transport

network

link

physical

Introduction 1-73

International Standards Organization/ Open System Interconnection

ITU Ex.: X.400: E-mail envelope

sourceapplicatio

ntransportnetwork

linkphysical

HtHn M

segment Ht

datagram

destination

application

transportnetwork

linkphysical

HtHnHl M

HtHn M

Ht M

M

networklink

physical

linkphysical

HtHnHl M

HtHn M

HtHn M

HtHnHl M

router

switch

Encapsulation using headersmessage M

Ht M

Hn

frame

Introduction 1-74

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 public

demonstration NCP (Network Control

Protocol) first host-host protocol

first e-mail program ARPAnet has 15 nodes

1961-1972: Early packet-switching principles

Introduction 1-75

Internet History

1970: ALOHAnet satellite network in Hawaii

1974: Cerf and Kahn - architecture for interconnecting networks

1976: Ethernet at Xerox PARC

late70’s: proprietary architectures: DECnet, SNA

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 1-76

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 1-77

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, P2P file sharing

network security to forefront

est. 50 million host, 100 million+ users

backbone links running at Gbps

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

Introduction 1-78

Internet History

2010: ~750 million hosts voice, video over IP P2P applications: BitTorrent

(file sharing) Skype (VoIP), PPLive (video)

more applications: YouTube, gaming, Twitter

wireless, mobility

Introduction 1-79

Next….. 1-hop communication

Multi-hop communication

End-to-end reliable comm. with TCP

Introduction 1-80

Documents

ECE 358: Computer Networks Instructor: Dr. Sagar Naik Introduction 1-1 To give you a thorough understanding of the Internet. Other kinds of emerging/evolving