ECE 358: Computer Networks Instructor: Dr. Sagar Naik Introduction 1-1 ece358

ECE 358: Computer Networks Instructor: Dr. Sagar Naik

Introduction 1-1

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

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

Performance testing of software, including mobile apps

Teaching Assistants

Introduction 1-3

Atulan Zaman [email protected]

Adel Ghanbari [email protected]

Shilpa [email protected]

Class email: [email protected]

Grading scheme

Introduction 1-4

Mini projects (3): 15% (5 + 5 + 5) group size = 2

Midterm exam: 25%

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

Classroom protocol

Introduction 1-5

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

Interference degrades performance.

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

Introduction 1-6

Connected Society

App

App

App

Online Services

Body Area Network

Smart Grid Internet of Things (IoT)to monitor traffic, environment,water, infrastructure, people….

for smart living

Introduction 1-7

App

App

App

Online Services

LAN: Local Area Network; WLAN: Wireless LAN

LAN

WLAN

Layer-2 (L2) switch

Layer-3 (L3) switch (Router)

Accees Point (AP)

Ethernet/Fibre connectors

Free space

A LAN is a network of computersconnected by means of a wired “broadcast” medium.

A WLAN is a network of computersconnected by means of a wireless “broadcast” medium.

Introduction 1-8

3 Objectives of ECE 358

App

App

App

Online Services

App

1. 1-hop comm to reach the first router

2. Multi-hop comm among routers3. App-App (End-to-End) reliable comm

App

Comp.—Comp. comm

Introduction 1-9

3 Objectives of ECE 358

App

App

App

Online Services

App

1. 1-hop comm to reach first router (Link/MAC)

2. Multi-hop comm among routers (Network)3. App-App (End-to-End) reliable comm (Transport)

App

Comp.—Comp. comm

PhysicalLink/MAC (Ch. 5)

Network (Ch. 4)

Transport (Ch. 3)

App

L2 (Layer 2)L3L4

L1

MAC: Medium Access Control

Home network

Institutional network

Mobile network

Global ISP

Regional ISP

Introduction 1-10

(ISP: Internet Service Provider)

A hierarchical view of the Internet

Introduction 1-11

New

Time

Intro.(5 Hrs)

Link Layer(13 Hrs)

Network(12 Hrs)

Transport(6 Hrs)

App1 App2

45points

101points

53points

45points

StudyPoints

Introduction 1-12

New

Frequently, I will pause to ask: Do you have questions?

More exam-kind questions on homeworks

Note

There are too many acronyms in the field ofcomputer networks.

The course has too much details.

Introduction 1-13

For real engineers …

To other LANs on the Internet

LAN1

LAN2

Introduction 1-14

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 1-15


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

Cisco L2 switch(SF300 24P)

Introduction 1-16


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 electromagnetic interference.

Common copper connectors …

Cat 5e

Introduction 1-17


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

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 1-18

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 1-19

What’s the Internet: component view of an ISP

Introduction 1-20

DHCP: Dynamic Host Configuration ProtocolGives your computer an IP address

DNS: Domain Name SystemPerforms mapping:

host name IP addressecemail.uwaterloo.ca 129.97.x.ywww.amazon.com a.b.c.d

Access Network

DHCP

DNS

server

Distribution Network

UW core

Eng.

EIT 4

UW ISP

Regional ISP

Global ISP

coverage,load balancing,reliability

security +connectivity policies

Core Network

Connected to other ISPs

What’s the Internet: component view

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

Introduction 1-21

DHCP

DNS

server

Distribution Network

Reg. ISP

Global ISP

Core Network

Connected to other ISPs

Access Network

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” 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 on 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



1.3 Network core circuit switching, packet switching, network structure

1.4 Delay, loss and throughput in packet-switched networks


1.6 Networks under attack: security

1.7 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?

Introduction 1-27

edge routers

mobile access networks

WiFi

residential access nets DSL (Digital Subscriber Line),

Cable

institutional access networks (school, company)Ethernet

telephonenetwork

homePC

homephone

Internet

DSLAM

centraloffice

DSL: Digital Subscriber Line

Uses existing telephone infrastructure

Introduction 1-28

DSLAM: DSL Access Multiplexer

One home

Point-to-Point Protocol (PPP)

To another home ::

voice

data

DSL modem

splitter

Upstream: up to 1 Mbps (today typically < 256 kbps) Downstream: up to 8 Mbps (today typically < 1 Mbps)

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


Ethernet Internet access

100 Mbps

100 Mbps

100 Mbps

1 Gbps

typically used in companies, universities, etc

Introduction 1-32

institutionalrouter to institution’s

ISP

server

Early Ethernet

Ethernetswitch

Question: How do nodes efficiently share the medium?

10 Mbps, 100Mbps, 1Gbps, 10Gbps Ethernet

Wireless access networks

shared wireless access network connects end systems to router via base station aka “access point” (AP)

Introduction 1-33

basestation

router

wireless LANs: 802.11b/g (WiFi): 11 or 54 Mbps 802.11ac: 1 Gbps WLAN;

0.5Gbps/host

wider-area wireless access provided by telco operators ~1Mbps over cellular system (EVDO,

HSDPA) LTE (Long Term Evolution)

(On the wired net.)

To Internet

Mobile hosts

EVDO: Evolutionary -- Data Only; HSDPA: High Speed Data Packet Access

Outside ECE 358

Home networksTypical home network components: DSL or cable modem router/NAT (Network Address Translation) In IP layer Ethernet wireless access point

wirelessaccess

point

wirelesslaptops

routerCable modemto/fromcable

headend

Ethernet

Introduction 1-34

Chapter 1: roadmap







1.7 History

Introduction 1-35

The Network Core

mesh of interconnected routers

Introduction 1-36

the fundamental question: how is data transferred through a net?

circuit switching: dedicated circuit per call: telephone net

packet-switching: data sent thru the net in discrete “chunks”

Network Core: Circuit Switching (not yet there…)

End-end resources are reserved for “call” (aka a session)

Introduction 1-37

call setup required

link bandwidth, switch capacity

dedicated resources: no sharing

circuit-like (guaranteed) performance

Network Core: Circuit Switching

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

frequency division multiplexing (FDM) time division multiplexing (TDM)

Introduction 1-38

resource piece remains idle if not used by owning call

pieces allocated to calls

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.

Introduction 1-41

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

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 transmit 640,000 bits, time needed = Total data / Rate = 640,000/(3*64,000) = 10/3 sec. = 3.33 seconds.

You need 0.5 seconds to establish a connection.

Network Core: Packet Switching

each end-end data stream is divided into packets

resource contention:

Bandwidth division into “pieces”

Dedicated allocation

Resource reservation

Introduction 1-42

resources are used as needed

user A, B packets share network resources

each packet uses full link bandwidth

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

forwarding

aggregate resource demand can exceed amount available

congestion: packets queue, wait for link use

Routers ….

Packet Switching: Statistical Multiplexing

sequence of A & B packets has no fixed timing pattern

A

B

C100 MbpsEthernet

1.5 Mbps

D E

statistical multiplexing

queue of packetswaiting for output link

Introduction 1-43

bandwidth is shared on demand: statistical multiplexing.

R1 R2

R3

Packet-switching: store-and-forward

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

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

~1.5KB is very common) R = 1.5 Mbps transmission delay = 3*5 =

15sec

R R RL

more on delay shortly …

Introduction 1-44

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

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

Packet-switching: store-and-forward

Introduction 1-45

Fall 2012 mid-term exam question #1

Introduction 1-46

• Suppose that host A wants to send a 1 Gigabit file to host B.

Link 3R3

Figure 1.

BRouter 2Router 1

Link 1R1

Link 2R2

A

Numerical example: Fall 2012 mid-term exam

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

•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.

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

Approximate solution

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.

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.

Link 3R3

BRouter 2Router 1

Link 1R1

Link 2R2

A

Introduction 1-48

Numerical example: Fall 2012 mid-term exam

1000.006 s

This is how all the packetsare moved.

Time

Packet switching versus circuit switching

Example: 1 Mb/s link each user:

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

Packet switching allows more users to use network!

N users

1 Mbps link

Introduction 1-49

…..

circuit-switching: 10 users (= 1Mb/s / 100Kb/s)

packet switching: with 35 users, probability of more than 10 active at same time is less

than .0004.

Packet switching versus circuit switching

great for bursty data: you can support more users resource sharing simpler, no call setup

Introduction 1-50

Q: How to provide circuit-like behavior?bandwidth guarantees needed for audio/video appsstill an unsolved problem (chapter 7)

excessive congestion: packet delay and loss protocols needed for reliable data transfer,

congestion control

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

Introduction 1-53

IXP IXP

Large Content Distributor

(e.g., Google)


(e.g., Akamai)

Tier 1 ISP Tier 1 ISP

Tier 1 ISP

Tier-1 ISPs &Content

Distributors, interconnect

(peer) privately

… or at Internet Exchange Points (IXPs)

at center: small # of well-connected large networks “tier-1” commercial ISPs (e.g., Verizon, Sprint, AT&T, Qwest, Level3),

national & international coverage

treat each other as equals (no charges)

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

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) ISPs

Tier 2ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP Tier 2

ISPTier 2ISP

Tier 2ISP

Tier 2ISP

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

connect to one or more tier-1 (provider) ISPs each tier-1 has many tier-2 customer nets tier 2 pays tier-1 provider

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 2ISP

Tier 2ISP

Tier 2ISP

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

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







1.7 History

Introduction 1-58

How do loss and delay occur?

packets queue in router buffers (i.e. memory)

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 MbpsCorrupted packets are dropped loss

packets queue, wait for turn

packet arrival rate to link exceeds output link capacity

Four sources of packet delay

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

A

Bnodal

processing queueing

dqueue: queueing delay time waiting at output link for

transmission depends on congestion level

of router

Introduction 1-60

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 Queuing delay vs. 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

traffic intensity = La/R

aver

age

que

uein

g de

lay

La/R ~ 0

Queueing delay (revisited)

La/R -> 1

“Real” Internet delays What do real Internet delay look like?

3 probes

3 probes

3 probes

Introduction 1-63

C:xyz>tracert u-aizu.ac.jp

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.

Traceroute program: provides delay measurement from source to router along end-end Internet path towards destination.

C:xyz>tracert swin.edu.au

“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

A

B

packet being transmitted

packet arriving tofull buffer is lost

buffer (waiting area)

Introduction 1-65

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

packet arriving to full queue dropped (aka lost)

……

……

……

Throughput

throughput: the rate (bits/time unit) at which bits are transferred between sender/receiver

server 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)

instantaneous: rate at given point in time (=max rate)

(the output rate of an input/output system)

average: rate over a long period of time

I/OSysteminput

output

Interface capabilities and link quality determine Rs

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

bottleneck link

Introduction 1-67

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

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)

Introduction 1-68

in practice:

Rc or Rs is often the

bottleneck

Chapter 1: roadmap







1.7 History

Introduction 1-69

Why layering?

Very different functionalities are addressed in different layers. Ex.: medium access is very different than routing

Introduction 1-70

Physical

Link/MAC (Ch. 5)

Network (Ch. 4)

Transport (Ch. 3)

App

Modularization facilitates better maintenance and system evolution Ex.: change in network interface does not require TCP

to be modified.

Internet protocol stack (on end devices)

application: supporting network applications FTP, SMTP, HTTP

Introduction 1-71

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

transport: process-process data transfer TCP, UDP

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

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

Physical

Link

Network

Transport

App

ISO/OSI reference model with 7 layers

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

7. application

6. presentation

5. session

4. transport

3. network

2. link

1. physical

Introduction 1-72

International Standards Organization/ Open System Interconnection

X.400: E-mail envelope

session: synchronization, checkpointing, recovery of data exchange (Ex.: Skype call session)

Internet stack “missing” these layers!

these services, if needed, must be implemented in application

Internetstack

source

applicationtransportnetwork

linkphysical

HtHn M

segment Htpacket(datagram)

destination

applicationtransportnetwork

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 1-73

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 1-74

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 1-75

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 1-76

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 1-77

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 1-78

Next…..

1-hop communication

Introduction 1-79

Multi-hop communication

End-to-end reliable comm. with TCP

Review what you

learned

in 2 weeks.

Documents

ECE 358: Computer Networks Instructor: Dr. Sagar Naik Introduction 1-1 ece358