DCCN First Chapter_1_V6.1

8/20/2019 DCCN First Chapter_1_V6.1

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Introduction 1-1

Mohammad kaleem, PhD

[email protected]

Data Communication andComputer Networks

(DCCN)Course Information

Spring 2016

EEE

-

314


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Introduction 1-2Introduction 1-2

Computer Networking: A

Top Down Approach6th edition Jim Kurose, Keith RossAddison-WesleyMarch 2012

Data

Communicationand Computer

Networks


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Dr. Mohammad kaleem

Asst. Prof. NUST (E&ME) 2002 ---- Feb2014

IT Consultant BT England 1999 ---- 2002

Network Engineer Silicon Software Tech. Ltd. 1998 ---1999

Hard ware Engineer GHS Technology Ltd. 1995---1997 PhD in Nano-photonics

MSEng in Telecommunication and ComputerNetworks England UK

BEng(Hons) in Electrical Electronics andInformation System Engineering England UK

Introduction 2-3


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Introduction

Prerequisites: EEE 343 Computer Organization

EEE Introduction to Communication

Textbook:

Computer Networking, J. Kurose and K. Ross, 6thed. Pearson, 2012

Reference Books:

Data Communications and Networking, Behrouz

A. Forouzan, 4th ed.2003. Data and Computer Communications, William

Stallings,8th ed. Prentice Hall, 2007

Computer Networks, Andrew S. TanenbaumIntroduction 2-4


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Assessment Plan

Introduction 2-5

Theory Quizz

(4)

15%

Homework assignments 10%

2 Sessional exams (in class, 60-80

minutes each, 10%+15%)

25%

Terminal exam (3 hours) 50%

Total (theory) 100%

Lab work Lab

repot

(12)

25%

2 Lab sessionals 25%

Lab project and terminal exam 50%

Total (lab) 100%


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Introduction 1-6

Course Objectives

Focus is on the principles, architectures ,protocols and fundamental techniques related to

computer networks

Goal is to cover core and advanced topics in

depth along with introduction to Network

Modeling, Simulation and Analysis

Lots of interesting topics to cover

Feedback if you would like to discuss some other

technology or any related topic


7/101Introduction 1-7

Course Contents

Introduction: Internet Architecture, End-to-End principle and Internet

design, Physical Layer Technologies Applications and Transport: HTTP, FTP, DNS, SMTP, Overlay Networks

and Peer-to-Peer (P2P) Systems, P2P File Sharing, Transport Services(TCP and UDP)

IP Routing: IP Addressing, Overview of Internet Protocols (e.g. IP, ARP,RARP, ICMP), Distance Vector, Link-State (OSPF), BGP, Multicastrouting.

Congestion Control: Open-loop (Policing and Shaping), Closed-loop(TCP congestion control algorithms - Reno, Tahoe, Vegas); NetworkAssisted – ECN; Active Queue Management (RED).

Internet QoS: QoS Schedulers (WFQ, DRR, PQ), IP QoS

Architectures, IntServ and RSVP, DiffServ, Router Design for IP QoS,Policy-based QoS Management.



Course Contents Traffic Engineering: Principles of IP Traffic Engineering, MPLS, ..

Multimedia Networking: Multimedia Applications, Protocols forMultimedia Support, RTP, RTCP, RTSP, ..

Virtualization: Cloud Computing, SDN, Open Flow, ..

Network Management: Network management framework, SNMP,ASN

Network Security: Cryptography, Symmetric Key Algorithms, PublicKey Algorithms, Digital Signatures, Management of Public Keys,Communication Security, IPSec, Firewalls, VPNs, AuthenticationProtocols

Network Modeling, Simulation and Analysis: System Performance

Evaluation, Traffic Analysis and Optimization, Queuing Theory,Simulation Modeling and Analysis (Network Simulators : ns-3,OMNET, NCTNns)



A Communications Model

Source generates data to be transmitted

Transmitter Converts data into transmittable signals

Transmission System Carries data

Receiver Converts received signal into data

Destination Takes incoming data


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Introduction 1-10

Simplified Communications Model

- Diagram


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Introduction 1-11

Key Communications Tasks

Transmission System Utilization Interfacing

Signal Generation

Synchronization

Exchange Management Error detection and correction

Addressing and routing

Recovery

Message formatting

Security

Network ManagementSuppose we have a digital transmission system

with bandwidth of 4MHz. Let us attempt to transmit

a sequence of alternating 1s and 0s as the square

wave. What data rate can be achieved? Assume f =

1MHz (cycle/sec). Repeat if f = 2MHz (cycle/sec).


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Introduction 1-12

Simplified Data Communications

Model


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Introduction 1-13

Networking

Point to point communication not usuallypractical

Devices are too far apart

Large set of devices would need impracticalnumber of connections

Solution is a communications network


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Introduction 1-14

Simplified Network Model


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Introduction

Chapter 1: introduction

our goal: get “feel” and

terminology

more depth, detail

later in course approach:

use Internet asexample

overview : what’s the Internet?

what’s a protocol?

network edge; hosts, access net,

physical media network core: packet/circuit

switching, Internet structure

performance: loss, delay,throughput

security protocol layers, service models

history

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Introduction

Chapter 1: roadmap

1.1 Internet1.2 network edge

end systems, access networks, links

1.3 network core

packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security1.7 history

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Introduction

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

millions of connectedcomputing devices:

hosts = end systems

running network apps

communication links fiber, copper, radio,

satellite transmission rate:

bandwidth

Packet switches: forwardpackets (chunks of data)

routers and switches

wiredlinks

wirelesslinks

router

mobile network

global ISP

regional ISP

homenetwork

institutionalnetwork

smartphone

PCserver

wirelesslaptop

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Introduction

“Fun” internet appliances

IP picture frame

http://www.ceiva.com/

Web-enabled toaster +

weather forecaster

Internet phonesInternet

refrigerator

Slingbox: watch,

control cable TV remotely

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Tweet-a-watt:

monitor energy use


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Introduction

Internet: “network of networks” Interconnected ISPs

protocols control sending,receiving of msgs e.g., TCP, IP, HTTP, Skype, 802.11

Internet standards RFC: Request for comments

IETF: Internet Engineering TaskForce

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

mobile network

global ISP

regional ISP

homenetwork


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Q: Given the following information, find the

minimum bandwidth required for the path:

FDM Multiplexing

Five devices, each requiring 4000 Hz.200 Hz guard band for each device.


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What’s the Internet: a service view

Infrastructure that providesservices to applications: Web, VoIP, email, games, e-

commerce, TV/IP, social

nets, … (Distributed bynature..)

provides programminginterface to apps

hooks that allow sendingand receiving app programsto “connect” to Internet

provides service options,analogous to postal service

mobile network

global ISP

regional ISP

homenetwork


Introduction 1-20


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Introduction

What’s a protocol?

human protocols: “what’s the time?”

“I have a question”

introductions

… specific msgs sent

… specific actions takenwhen msgs received, orother events

network protocols: machines rather than

humans

all communication activityin Internet governed by

protocols

protocols define format , order

of msgs sent and received among network entities,

and actions taken on msg

transmission, receipt

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Introduction

a human protocol and a computer network protocol:

Q: other human protocols?

Hi

Hi

Got the

time?

2:00

TCP connectionresponse

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

time

TCP connectionrequest

What’s a protocol?

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Introduction

Chapter 1: roadmap

1.1 what is the Internet?1.2 network edge


1.3 network core





1-23


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Introduction

A closer look at network structure:

network edge: hosts: clients and servers

servers often in datacenters

access networks, physicalmedia: wired, wirelesscommunication links

network core: interconnected routers

network of networks

mobile network

global ISP

regional ISP

home

network


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Introduction

Access networks and physical media

Q: How to connect endsystems to edge router? residential access nets

institutional accessnetworks (school,company)

mobile access networks

keep in mind: bandwidth (bits per second)

of access network?

shared or dedicated?

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Introduction

Access net: digital subscriber line (DSL)

central office

ISP

telephonenetwork

DSLAM

voice, data transmitted at different frequencies over

dedicated line to central office

use existing telephone line to central office DSLAM

data over DSL phone line goes to Internet

voice over DSL phone line goes to telephone net

< 2.5 Mbps upstream transmission rate (typically < 1 Mbps)

< 24 Mbps downstream transmission rate (typically < 10 Mbps)

DSLmodem

splitter

DSL accessmultiplexer

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Introduction

Access net: cable network

cablemodem

splitter

…

cable headend

Channels

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

frequency division multiplexing: different channels transmittedin different frequency bands

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Introduction

data, TV transmitted at differentfrequencies over shared cable

distribution network

cablemodem

splitter

…

cable headend

CMTS

ISP

cable modemtermination system

HFC: hybrid fiber coax

asymmetric: up to 30Mbps downstream transmission rate, 2Mbps upstream transmission rate

network of cable, fiber attaches homes to ISP router

homes share access network to cable headend

unlike DSL, which has dedicated access to central office

Access net: cable network

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Introduction

Access net: home network

to/from headend orcentral office

cable or DSL modem

router, firewall, NAT

wired Ethernet (100 Mbps)

wireless accesspoint (54 Mbps)

wireless

devices

often combinedin single box

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Introduction

Enterprise access networks (Ethernet)

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

today, end systems typically connect into Ethernet switch

Ethernetswitch

institutional mail,web servers

institutional router

institutional link toISP (Internet)

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Introduction

Wireless access networks

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

wireless LANs: within building (100 ft)

802.11b/g (WiFi): 11, 54 Mbpstransmission rate

wide-area wireless access provided by telco (cellular)

operator, 10’s km

between 1 and 10 Mbps 3G, 4G: LTE

to Internet

to Internet

1-31

If a periodic signal is decomposed into five sine waves with frequencies of

100, 300, 500, 700,and 900 Hz, what is the bandwidth? Draw the spectrum,assuming all components have a maxi-mum amplitude of 10 V.


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Host: sends packets of data

host sending function:

takes application message

breaks into smallerchunks, known as packets,of length L bits

transmits packet intoaccess network attransmission rate R

link transmission rate,aka link capacity, aka

link bandwidth

R: link transmission ratehost

12

two packets,

L bits each

packettransmission

delay

time needed totransmit L-bit

packet into link

L (bits)

R (bits/sec)= =

1-32

An image is 800x600 pix els with 3 bytes/pixel .

Assume the image is uncompressed. How

long does it take to transmit it:

over a 56-kbps modem channel?

over a 1-Mbps cable modem?over a 10-Mbps Ethernet?


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Introduction

Physical media

bit: propagates betweentransmitter/receiver pairs

physical link: what liesbetween transmitter &receiver

guided media: signals propagate in solid

media: copper, fiber, coax

unguided media:

signals propagate freely,e.g., radio

twisted pair (TP )

two insulated copperwires Category 5: 100 Mbps, 1

Gpbs Ethernet

Category 6: 10Gbps

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Introduction

Physical media: coax, fiber

coaxial cable: two concentric copper

conductors

bidirectional

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’s-100’sGpbs transmission rate)

low error rate: repeaters spaced far apart

immune to electromagnetic

noise

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Introduction 1-35

Optical Fiber


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Introduction 1-36

Optical Fiber Transmission Modes


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Introduction

Physical media: radio

signal carried inelectromagnetic spectrum

no physical “wire”

bidirectional

propagation environment

effects: reflection

obstruction by objects

interference

radio link types: terrestrial microwave

e.g. up to 45 Mbps channels

LAN (e.g., WiFi) 11Mbps, 54 Mbps

wide-area (e.g., cellular) 3G cellular: ~ few Mbps

satellite Kbps to 45Mbps channel (or

multiple smaller channels)

270 msec end-end delay geosynchronous versus low

altitude

1-37

A client-server system uses a satellite network, with the satellite at a height of 15,000 km.

What is the best-case delay in response to a request?


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Introduction

Chapter 1: roadmap



1.3 network core packet switching, circuit switching, network structure




1-38A digital signal has a bit rate of 2000 bps. What is the duration of each bit (bit interval)?


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Introduction

mesh of interconnectedrouters

packet-switching: hostsbreak application-layer

messages into packets forward packets from one

router to the next, acrosslinks on path from sourceto destination

each packet transmitted atfull link capacity

The network core

1-39

A signal has a spectrum with frequencies between 1000 and 2000 Hz (bandwidth of 1000 Hz).

A medium can pass frequencies from 3000 to 4000 Hz (a bandwidth of 1000 Hz). Can this

signal faithfully pass through this medium?


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Introduction

Packet-switching: store-and-forward

takes L/R seconds totransmit (push out) L-bitpacket into link at R bps

store and forward: entirepacket must arrive at routerbefore it can be transmittedon next link

one-hop numerical example:

L = 7.5 Mbits

R = 1.5 Mbps

one-hop transmissiondelay = 5 sec

more on delay shortly …

1-40

sourceR bps

destination123

L bitsper packet

R bps

end-end delay = 2L/R (assumingzero propagation delay)


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Introduction

Packet Switching: queueing delay, loss

A

B

CR = 100 Mb/s

R = 1.5 Mb/sD

Equeue of packetswaiting for output link

1-41

queuing and loss: If arrival rate (in bits) to link exceeds transmission rate of

link for a period of time: packets will queue, wait to be transmitted on link

packets can be dropped (lost) if memory (buffer) fills up


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Network Layer 4-42

Two key network-core functions

forwarding : move packets fromrouter’s input to appropriaterouter output

routing: determines source-destination route taken bypackets routing algorithms

routing algorithm

local forwarding table

header value output link

0100

01010111

1001

3

22

1

1

23

dest address in arriving

packet’s header


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Introduction

Alternative core: circuit switching

end-end resources allocatedto, reserved for “call”between source & dest:

In diagram, each link has fourcircuits.

call gets 2nd circuit in toplink and 1st circuit in rightlink.

dedicated resources: no sharing

circuit-like (guaranteed)performance

circuit segment idle if not usedby call (no sharing)

Commonly used in traditional

telephone networks 1-43


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Introduction

Circuit switching: FDM versus TDM

FDM

frequency

timeTDM

frequency

time

4 users

Example:

1-44


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Introduction

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 lessthan .0004 *

packet switching allows more users to use network!

Nusers

1 Mbps link

Q: how did we get value 0.0004?

Q: what happens if > 35 users ?

1-45* Check out the online interactive exercises for more examples


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Introduction

great for bursty data

resource sharing

simpler, no call setup

excessive congestion possible: packet delay and loss

protocols needed for reliable data transfer, congestioncontrol

Q: How to provide circuit-like behavior?

bandwidth guarantees needed for audio/video apps

still an unsolved problem (chapter 7)

is packet switching a “slam dunk winner?”

Q: human analogies of reserved resources (circuit switching)

versus on-demand allocation (packet-switching)?

Packet switching versus circuit switching

1-46

I k f k


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Internet structure: network of networks

End systems connect to Internet via access ISPs (Internet

Service Providers) Residential, company and university ISPs

Access ISPs in turn must be interconnected.

So that any two hosts can send packets to each other

Resulting network of networks is very complex Evolution was driven by economics and national policies

Let’s take a stepwise approach to describe current Internetstructure

I k f k


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Question: given millions of access ISPs, how to connect them

together?

accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

I k f k


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Option: connect each access ISP to every other access ISP?

accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

connecting each access ISP

to each other directly

I t t t t t k f t k


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accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

Option: connect each access ISP to a global transit ISP? Customer

and provider ISPs have economic agreement.

global

ISP

I t t t t t k f t k


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accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

But if one global ISP is viable business, there will be competitors

….

ISP B

ISP A

ISP C

I t t t t t k f t k


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accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

But if one global ISP is viable business, there will be competitors

…. which must be interconnected

ISP B

ISP A

ISP C

IXP

IXP

peering link

Internet exchange point

I t t t t t k f t k


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accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

… and regional networks may arise to connect access nets to

ISPS

ISP B

ISP A

ISP C

IXP

IXP

regional net

I t t t t t k f t k


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accessnet

access

net

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

… and content provider networks (e.g., Google, Microsoft,Akamai ) may run their own network, to bring services, contentclose to end users

ISP B

ISP A

ISP B

IXP

IXP

regional net

Content provider network



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Introduction


at center: small # of well-connected large networks “tier-1” commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national &

international coverage

content provider network (e.g, Google): private network that connects

it data centers to Internet, often bypassing tier-1, regional ISPs 1-55

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

Regional ISP Regional ISP

IXP IXP

Tier 1 ISP Tier 1 ISP Google

IXP


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Introduction 1-56

COMSATS Institute of Information Technology, Islamabad CampusAssignment – 1 Spring 2016

Class: Marks:

Write a short report which shows the Internet layout plan of

COMSATS, Institute of Information technology.The Layout plan should also discuss the bandwidth distribution

to different departments and the back bone Internet provider

(ISPs).

Note:

Copied or plagiarized assignments will result in a zero grade.

Submission Date: 10-03-2016


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Introduction

Tier-1 ISP: e.g., Sprint

…

to/from customers

peering

to/from backbone

…

… … …

POP: point-of-presence

1-57


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Introduction

Chapter 1: roadmap



1.3 network core





1-58

H d l d d l ?


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Introduction

How do loss and delay occur?

packets queue in router buffers packet arrival rate to link (temporarily) 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

1-59

F f k d l


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Introduction

Four sources of packet delay

d proc

: nodal processing check bit errors

determine output link

typically < msec

A

B

propagation

transmission

nodal

processing queueing

d queue

: queueing delay time waiting at output link

for transmission

depends on congestionlevel of router

d nodal = d proc + d queue + d trans + d prop

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Introduction 1-61

Subject Projects

Software Define NetworksSystem on Chip

Network on Chip

Lab on Chip

OFDM based Supper Channel for DWDMLink performance Analysis of an Optical DWDM (QAM/QPSK).

Investigation of Foure Wave Mixing in Ultra Dense WDM Networks

Birefringence Effects in Multimode Fiber Transmission Systems

Implementation of Multimedia over IPV6

F f k t d l


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Introduction

d trans: transmission delay:

L: packet length (bits) R: link bandwidth (bps)

d trans = L/R

d prop: propagation delay:

d : length of physical link s: propagation speed in medium

(~2x108 m/sec)

d prop = d /sd trans and d propvery different

Four sources of packet delay

propagation

nodal

processing queueing

d nodal = d proc + d queue + d trans + d prop

1-62

A

B

transmission

* Check out the Java applet for an interactive animation on trans vs. prop delay

Caravan analogy


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Introduction

Caravan analogy

cars “propagate” at100 km/hr

toll booth takes 12 sec toservice car (bit transmissiontime)

car~bit; caravan ~ packet Q: How long until caravan is

lined up before 2nd tollbooth?

time to “push” entirecaravan through tollbooth onto highway =12*10 = 120 sec

time for last car topropagate from 1st to2nd toll both:100km/(100km/hr)= 1hr

A: 62 minutes

toll

booth

toll

booth

ten-car

caravan

100 km 100 km

1-63

Caravan analogy (more)


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Introduction

Caravan analogy (more)

suppose cars now “propagate” at 1000 km/hr

and suppose toll booth now takes one min to service a car Q: Will cars arrive to 2nd booth before all cars serviced at first

booth?

A: Yes! after 7 min, 1st car arrives at second booth; threecars still at 1st booth.

toll

booth

toll

booth

ten-car

caravan

100 km 100 km

1-64

Q d l ( d)


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Introduction

R: link bandwidth (bps)

L: packet length (bits)

a: average packet arrivalrate

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!

a v

e r a g e

q u e u e i n g

d e l a y

La/R ~ 0

Queueing delay (revisited)

La/R -> 1

1-65

* Check out the Java applet for an interactive animation on queuing and loss

“R l” I d l d


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Introduction

“Real” Internet delays and routes

what do “real” Internet delay & loss look like?

traceroute program: provides delaymeasurement 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

1-66

“R l” I t t d l t


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Introduction

Real Internet delays, 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 ms6 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.fr

3 delay measurements from

gaia.cs.umass.edu to cs-gw.cs.umass.edu

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

trans-oceanic

link

1-67* Do some traceroutes from exotic countries at www.traceroute.org

P k l


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Introduction

Packet loss

queue (aka buffer) preceding link in buffer has finitecapacity

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 to

full buffer is lost

buffer

(waiting area)

1-68* Check out the Java applet for an interactive animation on queuing and loss

Th h


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Introduction

Throughput

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

average: rate over longer period of time

server, withfile of F bits

to send to client

link capacityRs bits/sec

link capacityRc bits/sec

server sends bits(fluid) into pipe

pipe that can carryfluid at rateRs bits/sec)

pipe that can carryfluid at rateRc bits/sec)

1-69

Th h tSuppose a MP3 file = 32Million bits, the

Server has the transmission rate of Rs= 2Mbp


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Introduction

Throughput

Rs < Rc What is average end-end throughput?

Rs bits/sec Rc bits/sec

Rs > Rc What is average end-end throughput?

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

bottleneck link

Rs bits/sec Rc bits/sec

1-70

You have an access link of Rc=1Mbps.

The time needed to transmit the file =

Throughput: Internet scenario


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Introduction

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 Rsis often bottleneck

1-71


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Introduction

Chapter 1: roadmap



1.3 network core





1-72

P t l “l ”


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Introduction

Protocol layers

Networks are complex,with many “ pieces” :

hosts

routers

links of variousmedia

applications

protocols

hardware,software

Question:is there any hope of

organizing structure ofnetwork?

…. or at least our

discussion of networks?

1-73

O i i f i l


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Introduction

Organization of air travel

a series of steps

ticket (purchase)

baggage (check)

gates (load)

runway takeoff

airplane routing

ticket (complain)

baggage (claim)

gates (unload)

runway landing

airplane routing

airplane routing

1-74

Layering of airline functionality


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Introduction

ticket (purchase)

baggage (check)

gates (load)

runway (takeoff)

airplane routing

departure

airportarrival

airport

intermediate air-traffic

control centers

airplane routing airplane routing

ticket (complain)

baggage (claim

gates (unload)

runway (land)

airplane routing

ticket

baggage

gate

takeoff/landing

airplane routing

Layering of airline functionality

layers: each layer implements a service

via its own internal-layer actions

relying on services provided by layer below

1-75

Wh l ?


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Introduction

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 ofsystem change of implementation of layer’s service

transparent to rest of system

e.g., change in gate procedure doesn

’t affect rest ofsystem

layering considered harmful?

1-76

TCP/IP Protocol Architecture


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Introduction 1-77


Developed by the US Defense Advanced ResearchProject Agency (DARPA) for its packet switchednetwork (ARPANET)

Used by the global Internet

No official model but a working one. Application layer Host to host or transport layer

Internet layer

Network access layer

Physical layer

Physical Layer


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Introduction 1-78

Physical Layer

Physical interface between data transmission device(e.g. computer) and transmission medium ornetwork

Characteristics of transmission medium

Signal levels Data rates

etc.

Network Access Layer


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Introduction 1-79

Network Access Layer

Exchange of data between end system and network Destination address provision

Invoking services like priority

Internet Layer (IP)


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Introduction 1-80

Internet Layer (IP)

Systems may be attached to different networks Routing functions across multiple networks

Implemented in end systems and routers

Transport Layer (TCP)


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Introduction 1-81

Transport Layer (TCP)

Reliable delivery of data Ordering of delivery

Application Layer


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Introduction 1-82

Application Layer

Support for user applications

e.g. http, SMTP



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Introduction 1-83


Model

OSI Model


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Introduction 1-84

OSI Model

Open Systems Interconnection Developed by the International Organization

for Standardization (ISO)

Seven layers

A theoretical system delivered too late! TCP/IP is the de facto standard

Internet protocol stack


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Introduction

Internet protocol stack

application: supporting networkapplications FTP, SMTP, HTTP

transport: process-process datatransfer

TCP, UDP network: routing of datagrams

from source to destination IP, routing protocols

link: data transfer betweenneighboring network elements Ethernet, 802.111 (WiFi), PPP

physical: bits “on the wire”

application

transport

network

link

physical

1-85

ISO/OSI reference model


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Introduction

ISO/OSI reference model

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

session: synchronization,checkpointing, recovery of dataexchange

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

implemented in application

needed?

application

presentation

session

transport

network

link

physical

1-86

OSI v TCP/IP


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Introduction 1-87

OSI v TCP/IP

source

Encapsulation


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Introduction

application

transport

network

linkphysical

HtHn M

segment Ht

datagram

destination

application

transport

network

link

physical

HtHnHl M

HtHn M

Ht M

M

network

link

physical

link

physical

HtHnHl M

HtHn M

HtHn M

HtHnHl M

router

switch

Encapsulationmessage M

Ht M

Hn

frame

1-88

Cha ter 1: r adma


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Introduction

Chapter 1: roadmap



1.3 network core





1-89

Network security


90/101

Introduction

Network security

field of network security: how bad guys can attack computer networks

how we can defend networks against attacks

how to design architectures that are immune toattacks

Internet not originally designed with (much)security in mind original vision: “a group of mutually trusting users

attached to a transparent network ”

Internet protocol designers playing“catch-up

”

security considerations in all layers!

1-90

Bad guys: put malware into hosts via Internet


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Introduction

Bad guys: put malware into hosts via Internet

malware can get in host from: virus: self-replicating infection by receiving/executing

object (e.g., e-mail attachment)

worm: self-replicating infection by passively receiving

object that gets itself executed spyware malware can record keystrokes, web

sites visited, upload info to collection site

infected host can be enrolled in botnet, used forspam. DoS attacks

1-91

Bad guys: attack server, network infrastructure


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Introduction

target

Denial of Service (DoS): attackers make resources

(server, bandwidth) unavailable to legitimate trafficby overwhelming resource with bogus traffic

1. select target

2. break into hosts aroundthe network (see botnet)

3. send packets to target from

compromised hosts

g y ,

1-92

Bad guys can sniff packets


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Introduction

Bad guys can sniff packets

packet“ sniffing

” : broadcast media (shared ethernet, wireless)

promiscuous network interface reads/records all packets(e.g., including passwords!) passing by

A

B

C

src:B dest:A payload

wireshark software used for end-of-chapter labs is a

(free) packet-sniffer

1-93

Bad guys can use fake addresses


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Introduction

Bad guys can use fake addresses

IP spoofing: send packet with false source address

A

B

C

src:B dest:A payload

1-94

… lots more on security (throughout, Chapter 8)

Chapter 1: roadmap


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Introduction

Chapter 1: roadmap



1.3 network core





1-95

Internet history


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Introduction

y

1961: Kleinrock -queueing theory showseffectiveness of packet-switching

1964: Baran - packet-switching in military nets

1967: ARPAnetconceived by AdvancedResearch Projects

Agency 1969: first ARPAnet

node operational

1972:

ARPAnet public demo

NCP (Network ControlProtocol) first host-host

protocol first e-mail program

ARPAnet has 15 nodes

1961-1972: Early packet-switching principles

1-96

Internet history


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Introduction

1970: ALOHAnet satellitenetwork in Hawaii

1974: Cerf and Kahn -architecture for interconnecting

networks 1976: Ethernet at Xerox PARC

late70’s: proprietaryarchitectures: DECnet, SNA,XNA

late 70’s: switching fixed lengthpackets (ATM precursor)

1979: ARPAnet has 200 nodes

Cerf and Kahn’sinternetworking principles: minimalism, autonomy - no

internal changes required tointerconnect networks

best effort service model

stateless routers

decentralized control

define today’s Internetarchitecture

1972-1980: Internetworking, new and proprietary nets

y

1-97


98/101

Internet history


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Introduction

early 1990’s: ARPAnetdecommissioned

1991: NSF lifts restrictions oncommercial 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: instantmessaging, P2P file sharing

network security to

forefront est. 50 million host, 100

million+ users

backbone links running atGbps

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

y

1-99

Internet history


100/101

Introduction

2005-present

~750 million hosts Smartphones and tablets

Aggressive deployment of broadband access

Increasing ubiquity of high-speed wireless access

Emergence of online social networks: Facebook: soon one billion users

Service providers (Google, Microsoft) create their ownnetworks

Bypass Internet, providing “instantaneous” access

to search, emai, etc. E-commerce, universities, enterprises running their

services in “cloud” (eg, Amazon EC2)

y

1-100

Introduction: summary


101/101

y

covered a“ ton

” of material!

Internet overview

what’s a protocol? network edge, core, access

network

packet-switching versuscircuit-switching

Internet structure

performance: loss, delay,throughput

layering, service models

security

history

you now have: context, overview, “feel”

of networking

more depth, detail tofollow!

DCCN First Chapter_1_V6.1

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