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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<title>Computer Networks (1)</title>
<meta name="cours-n" content="1">

<meta name="author" content="Rémi Emonet">
<meta name="venue" content="DWA M1 WI/MLDM">
<meta name="date" content="2017">
<meta name="affiliation" content="Université Jean Monnet − Laboratoire Hubert Curien">
<style type="text/css">
.inlineimages img {display: inline !important; }
.slide .above {position:absolute; left: 20px; top: 20px; width: 760px; height: 460px; text-align:center;}
.above {z-index: 100 !important;}
</style>

<!--
<script src="deck.js/extensions/includedeck/load.js"></script>
<script src="extensions/slides-dev.js"></script>
-->
<script src="extensions/deck-packed.js"></script>
<script src="extensions/slides.js"></script>
<script>go()</script>
</head>

<body>

<div class="deck-container">

<div class="deck-loading-splash" style="background: black; color: chartreuse;"><span class="vcenter" style="font-size: 30px; font-family: Arial; ">Please wait, while our marmots are preparing the hot chocolate…</span></div>

<section class="smart">

# @chunk: chunks/title.md


## Disclaimer {image-full bottom-left darkened /black-bg /no-status no-print} // not a very technical course on admin
<div class="img" style="background-image: url('media/part1/cabled-switches.jpg')" data-attribution="https://www.flickr.com/photos/andrewfhart/8106189987/sizes/l" data-attribution-content="CC by andrewfhart (Flickr)" data-scale="">
</div>

## Disclaimer 2 {image-full bottom-right darkened /black-bg /no-status no-print} // shortened version, may evolve
<div class="img" style="background-image: url('media/part1/vader-floppy.jpg')" data-attribution="https://www.flickr.com/photos/nhussein/3583560407/sizes/l" data-attribution-content="CC by nur h (Flickr)" data-scale="">
</div>


# @chunk: chunks/objectives.md

# Before we start {no-print}

## Survey {luckycats libyli no-print}
- Who has internet access?
- What is your internet service provider?
- Who has streaming issues (in the evenings)? // youtube etc
- Preferred programming language(s)?
- Personal laptop for live and practical sessions?
- Which Operating System?

## What happens when we type<br/> <code>wikipedia.com</code> <br/>in our browser address bar?{question}

## Logistics {libyli}
- Lessons and personal work
- 3 hour slots
- courses (and exercises) sessions: ~24h // presence sheet, some live coding
- practical sessions: ~12h // live coding too
- project
- project follow-up: ~4h
- Evaluation {slide}
- theoretical exam: MCQ + open questions and exercises
- practical: attendance, project report, presentation, and demo
- Rules of the game {slide}
- be active, participate, ask questions
- interrupt the lesson if necessary (missing/wrong translation) // english, etc
- Suggest lesson topics and project ideas // we cannot do everything, ...
- Course reference: <a href="http://learn.heeere.com/2017-net-6a42/">http://learn.heeere.com/2017-net-6a42/</a> {slide} // or from claroline

## Learning to Learn (in general) {libyli}
- Work regularly (not a big rush before the deadline)
- repeat exercises
- practice (don't just re-read things)
- Be extremely focused
- limit interruptions
- work for fixed-duration slots (e.g., 25 minutes)
- … but make real and regular breaks
- stretch or have a walk
- practice sport
- sleep well

## Succeeding in this Course {libyli}
- Be pro-active in lessons, as there is a lot of “culture” // general understanding
- Don't wait for the last minute to start your project
- Don't waste practical sessions
- Bring your own objectives and ideas // in a lesser way than in PWA but still
- Look and ask for complement (me, other students, online, ...)

# Project Ideas?








<!-- global -->
# @chunk: chunks/global.md






## Part 1: General Introduction {#plan overview}
- Goal
- have a tour of the main concepts
- that will be seen in details later
- Overview
- what is internet {it1}
- what is a protocol {it2}
- the network edge {it3}
- layers and encapsulation {it6}
- security {it7}
- some history {it8}
- the network core {it4}
- performance: latency, bandwidth, throughput, etc. {it5}
# @copy:#plan




<!-- what is internet -->
# @copy:#plan: %+class:inred: .it1

## How do you use internet? <br/> (list your use cases){question}
// usages, applications (after will come : important properties)

## What are the important properties of the network for each use case?{question}

# Internet

## Internet: hardware aspects

@SVG: media/part1/internet.svg 400px 500px {floatright no}

- Millions or billions of interconnected hosts, executing applications
- workstations, laptops, servers{s1}
- phones, tablets, …{s1}
- fridges, scales, toasters, …{s2}
- host == machine == end system{s3}
- Communication links{s4}
- wires, optical fibers, satellites, …
- Routing nodes{s5}
- routers and switches
- @anim: .s1 | .s2 | .s3 | .s4 | .s5

## Internet: some hosts and appliances {inlineimages}
- Machines/Hosts
- {no}
<img style="height: 200px" src="media/part1/toaster.jpg"/>
<img class="floatright" src="media/part1/fridge.jpg"/>
<img style="height: 200px" src="media/part1/scale.jpg"/>
<img style="height: 200px" src="media/part1/domotic.jpg"/>
<img src="media/part1/telephones.jpg"/>
<img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/><img src="media/part1/iphone.png"/>
- Applications{slide}
// reuse what they said ( + reverse Q : what app is not connected today?) {above}



## Internet: fundamentals {illustrations-left}
@SVG: media/part1/internet.svg 400px 500px {illustrations}

- A network of networks
- interconnection of networks
// private sub-networks
- multi-level hierarchy
- A set of protocols{slide}
- communication rules
- ex: HTTP, FTP, TCP, IP, PPP
- A set of standards{slide}
- « RFC » (<i>Request For Comments</i>)
- « IETF » (<i>Internet Engineering Task Force</i>)


# “The Internet” <br/> youtube://iDbyYGrswtg <br/> youtube://UTBsm0LzSP0

## {fsvideo no-print}
<video src=",,videos/iDbyYGrswtg.webm" onclick="this.paused ? this.play() : this.pause();" controls ></video>

- @anim: %play:video | %pause:video

## {fsvideo no-print}
<video src=",,videos/UTBsm0LzSP0.webm" onclick="this.paused ? this.play() : this.pause();" controls ></video>

- @anim: %play:video | %pause:video




<!-- Protocol? -->
# @copy:#plan: %+class:inred: .it2

## Meaning of the Word “Protocol”? Examples?{question}

## Protocol: Examples

@SVG: media/part1/protocols.svg 800px 400px {svg}

- @anim: #temps | #protohum | #hello | #gettime
- @anim: #protoweb | #pc | #server | #rcvfile | #openconn | #sendget


## Protocols
- Human examples{col1 hum}
- asking the current time
- ask a question in class
- introduce someone to someone else
- …
- Computer protocols{col2 inf}
- between machines // machines: less flexible than humans
- all communications on Internet follow some protocols
- different levels (HTTP, TCP, ...)
- Elements of (human) protocols {col1 prohum}
- etiquette, politeness, [etc](http://www.ehow.com/how_4780527_write-proper-email.html)
- communication rules
- messages sent <br/> (content and sequence)
- expected reactions
- Definition of computer protocols {col2 proinf}
- formats definition, and sequence (ordering)
- … of all messages<br/> (sent and received)
- … exchanged by connected hosts
- \+ the actions taken after these messages
- @anim: .hum | .prohum | .inf | .proinf



<!-- network edge-->
# @copy:#plan: %+class:inred: .it3

# The Network Edge <br/><br/> Internet access

## Internet Network Structure {anim-continue}
@SVG: media/part1/internet-border.svg 400px 500px {floatright}

- Network core{core}
- interconnections of routers
- network of networks
- Physical links{links}
- wires, cables
- wireless transmissions
- Network edge, network border {border}
- hosts (clients, servers)
- access points (routers)
- @anim: %dur:1 | -#mask-core | %dur:
- @anim: #mask-border + -#mask-core + .core | .links | .border + -#mask-border + #mask-core


## Access Network: ADSL <i>Asymmetric Digital Subscriber Line</i> // and VDSL VDSL2
@SVG: media/part1/adsl.svg 800px 400px {floatright}

- Using existing phone telephone lines
- Asymmetric: download (&lt;25Mbps) vs upload (&lt;2.5Mbps)
// VDSL2 free: 50-100Mb/s both ways
- A dedicated line per habitation
// Explain Mbps

## Access Network: Cable (and fiber)
@SVG: media/part1/cable.svg 800px 400px {floatright}

- Using television network, shared line
- Frequency channels
- Original cable: download (&lt;30Mbps), upload (&lt;2Mbps)
- Fiber: same principle but faster
// Fiber at Free.fr: 1Gb/s and 200Mb

## Residential Network
@SVG: media/part1/residential-network.svg 800px 400px {floatright}

## Institutional Networks: companies, university, …
@SVG: media/part1/institutional-network.svg 800px 400px {floatright}

- Dedicated routers and switches
- Mostly wired connections at 10Gbps

## Wireless Access
- Wifi
- residential
- institutional
- public spaces
- limited range // 70m for n
- bandwidth: 802.11n norm, &lt;300Mbps // actual 74Mbs
- Mobile networks: 2G, 3G, 4G, ...
- mobile phone antennas
- long range // 30km
- bandwidth: 4G, 100Mbps // 1Gbps when non-moving

## Sending Information from Host to Host {libyli}
- Application level abstraction
- messages can be big
- ex: an audio or video file
- Work to be done by the host
- splitting the message in “packets”
- sending each packet on the network
- sending data via a network link
- Network link properties
- a given “binary bitrate” (or rate), e.g., 1Gbps
- time/delay for transferring a packet of size $L$
<br/> as a function of the bandwidth $R$
<br/> $t = \frac{L}{R}{}$

## Types of Physical Links
<img class="above twisted"src="media/part1/twisted-cable.jpg">
<img class="above fib1" src="media/part1/fiber-lamp.jpg">
<img class="above fib2" src="media/part1/optical-fiber-cable.jpg">

- Cables etc
- coaxial cables: multiple frequency channel
- RJ45 cables (twisted pair), 10Gbps
- <a href="https://www.youtube.com/watch?v=0MwMkBET_5I">optical fiber</a> {fibre}
- glass fiber, light pulses
- low error rates, 100Gbps
// low attenuation
- Radio waves, etc{radio}
- electromagnetic waves, multiple frequency channels
- interference, occlusions, …
- different technologies
- wifi: 54Mbps {wifi}
// karl's example
- 3G: 0.3 à 2Mbps{ggg}
- satellites: 45Mbps, latency (250ms){sat}
// geostationary vs low altitude
- @anim: .twisted | -.twisted + .fibre | .fib1 | -.fib1 + .fib2 | -.fib2 | .radio | .wifi | .ggg | .sat



## Given a 5MB message (e.g., image). <br/><span style="font-size: 75%">when sent from host&rarr;host</span> what happens ? <br/> How long does it take? {question}










<!-- layered architecture -->
# @copy:#plan: %+class:inred: .it6

## Layered Architecture
- Complexity of the network architecture
- hosts, routers, links (cables, …)
- applications, protocols
- mixing hardware and software
- Layered architectures general advantages {slide}
- advantages for complex systems
- specification of services/roles of each layer
- isolation of abstraction levels
- easier maintenance
// replacing an implementation for a service, etc
- drawbacks?
// perf, hidden information, leaky abstractions, etc



## The Network Stack: the 5 layer model
@SVG: media/part1/stack.svg 200px 500px {floatright}

- 5-layer model
- application{slide}
- ex: HTTP, FTP, SMTP (mails), DNS
- transport{slide}
- ex: TCP, UDP
- network{slide}
- ex: IP, ICMP
- link{slide}
- ex: Ethernet, 802.11 (wifi)
- physical{slide}
- ex: telephone, ADSL, satellite
- Other well known model: OSI (7 layers){slide}


## Encapsulation and Routing
@SVG: media/part1/encapsulation-and-routing.svg 800px 500px {floatright}

- @anim: #srcstack | #msg | #segment | #datagram | #frame | #p1
- @anim: #routerstack | #routercontent + #p2 | #p3
- @anim: #switchstack | #switchcontent + #p4
- @anim: #deststack + #p5 | #p6



<!-- security -->
# @copy:#plan: %+class:inred: .it7

# Security {no-print}

## Network Security
- Security area
- identify possible means of attack
- find ways to protect from these
- conceive architectures that are immune to attacks{slide}
- Internet{slide}
- original vision
- a network of trusted users
- transparent communications
- need to add security at every layer{slide}

## What security problems <br/> can you imagine on internet? <br/>(list possible attacks){question no-print}

## Malware: malicious software
@SVG: media/part1/malware.svg 800px 375px {svg}

- propagated via users over the internet
- remote control of machines
- spying on user (keyboard, etc)

## Denial of Service (DoS) // github has it often
- @anim: .svg | #zombs | #attack

@SVG: media/part1/dos.svg 800px 380px {svg}


## Packet Sniffing and Spoofing
@SVG: media/part1/sniffing-et-spoofing.svg 800px 225px {svg}

- @anim: .svg | #packet | #badguy | #snif + .snif | -#snif + -#packet | #spoof + .spoof | #tob
- Sniffing{snif}
- spying of transmitted packets
- sensitive data, passwords, ...
- Spoofing {spoof}
- sending new packets
- falsifying the packet source
- pass for someone else



<!-- history -->
# @copy:#plan: %+class:inred: .it8

## Internet: a few key dates
- 1961: packet switching (Kleinrock)
- 1967: conception of ARPAnet
- 1969: ARPAnet is operational
- 1972
- public demonstration of ARPAnet
- 15 nodes
- first emails
- 1976: Ethernet at Xerox
- 1979: ARPAnet has 200 nodes
- 1970's: many other networks than ARPAnet{slide}

## Internet: a few key dates
- 1969: ARPAnet is operational <br/> 
- 1982: SMTP
- 1983: TCP/IP, DNS
- 1985: FTP
- 1988: congestion control for TCP
- 1980's: even more networks{slide}
- including the Minitel
- 100k hosts
// 100k over the whole federation of networks

## Internet: last decade
- early 1990's: public internet, web, HTTP, HTML
- late 1990's{slide}
- instant messaging, peer to peer file sharing
- importance of security
- 50M hosts
- network core uses Gbps links
- 2000+{slide}
- high-speed internet: democratization of internet access
- ubiquity: mobile access on smart-phones, tablets
- more and more online services (google, facebook, ...)
- dedicated network in parallel to internet
- created by content provides (Google, Microsoft, ...)
- online education
- Iaas, PaaS, SaaS
- many companies externalize their services
- in the cloud





<!-- network core -->
# @copy:#plan: %+class:inred: .it4

## Given a 5MB message (e.g., image). <br/><span style="font-size: 75%">when sent from host&rarr;host</span> what happens ? <br/> How long does it take? {question}

## The Network Core {no-print}
@SVG: media/part1/internet-core.svg 800px 400px {svg}


## Sending Messages from Host to Host
- Applications
- splitting of the message in « packets », sent on the network
- Network link capacity
- capacity == binary rate == <i>bitrate</i> == <i>rate</i> <br/> (language shortcut) == bandwidth
- transmission delay (1 packet): $t = \frac{\text{packet size}}{\text{bitrate}} = \frac{L}{R}{}$
// 3x more for the example below
- @anim: .svg | #packetstosend

@SVG: media/part1/link-capacity.svg 800px 200px {svg no}

## Host to Host Messages: routing
@SVG: media/part1/link-capacity-2.svg 800px 200px {svg}

- Router: transfers/routes packets {dirige}
- forwarding table (routing table)
// hardcoded + learned + default
- Router: stores and forward packets {forward}
- unit of transfer: packet
- receives a whole packet
- then forwards it
// then, delay for 1 packet?
- Delay for 1 packet: sum of delays{delai}
- @anim: #direct + #packetstosend | #routed + -#direct + .dirige
- @anim: -#routed + #routetableetc + #table | #routepacket | #routepacketheader | #arrow
- @anim: .forward | .delai


## Routing: buffers and packet loss
@SVG: media/part1/link-capacity-3.svg 800px 200px {svg}

- Buffering of packets {buffering}
- too many received packets
- not enough output capacity
- queuing/buffering
// cas aussi avec 1 machine si elle ne se limite pas à l'envoi et que Rout \lt Rin
- Packet loss {loss}
- memory full / buffer overflow
- cannot store, packets are dropped
- @anim: #second | #secondpackets | -#p3red + -#p3blue + #bufferandnext + #wave1 + .buffering | -#wave1 + #wave2 | #loss + .loss

## Host to host communication? <br/> Case with 3 packets: rate? delay? {question bottom anim-continue}
@SVG: media/part1/link-capacity-2.svg 800px 200px {svg}

- @anim: %dur:1 + -#direct + -#routetableetc | %dur:
- {notes}
- Ici, on peut s'intéresser à quand part (fini de partir) le premier paquet.
- Puis quand est-ce qu'il arrive à la fin...
- Puis le second et le troisième.

## Principle of Multiplexing
- Multiple channels on a single link
// example of the radio, really suited to the case
- in the frequency domain, FDM: frequency-division multiplexing
- in the time domain, TDM: time-division multiplexing
- @anim: .svg

@SVG: media/part1/time-frequency-multiplexing.svg 800px 380px {svg}


## Alternative to packet switching
- Idea: dedicated virtual lines using multiplexing
- Circuit switching {slide}
- dedicated connection through the whole interaction
- guaranteed performances (throughput, latency)
// no loss, no latency, constant bitrate
- used for telephone communications
// constant rate, need for a latency guarantee
- @anim: .svg | #addedchannels | #blueconn | #redconn

@SVG: media/part1/circuit-switching.svg 800px 220px {svg}


## Why doesn't internet use circuit switching?<br/>(no loss, guaranteed throughput and latency){question dense}

<div class="notes">
Here we look for limitations of circuit switching
</div>


## Why Doesn't Internet Use Circuit Switch.?
- Packet switching allows for more simultaneous users {slide}
- Example{slide}
- a link at 1Mbps
- a typical user behavior
- active only 10% of the time
- using 100kbps when active
- Circuit switching{col1 slide}
- max 10 users
- Packet switching {col2 ps2}
- ex: 11 users
- $p(n_{\text{actifs}} > 10) = 10^{-11}{}$
// R: n=35 ; sum(dbinom(11:n, n, 0.1))
- ex: 35 users
- $p(n_{\text{active}} > 10) < 0.0004$
// how? que se passe-t-il à 36 ?
- ex: 50 users
- $p(n_{\text{active}} > 10) \approx 0.01$
- Packet switching{col1 ps1}
- how often do we queue?
- probability of congestion
- ex: 10 users (or less) {ps11}
- $p(n_{\text{active}} > 10) = 0{}$
- @anim: .ps1 | .ps11 | .ps2

## Internet Structure: a network of networks
// we saw how it gets routed locally, let's get to a broader view

@SVG: media/part1/internet-tiers.svg 1px 400px {svg}

- Tiers{col1}
- Tier1 (~12)
// or quasi-tier1 (cogent)
- the network core
- free data exchange // between them
- Tier2 (numerous)
- buys bandwidth to Tier1 actors
- sells bandwidth
- Tier3 (numerous)
- buy only
- Interconnections and agreements{col2}
- PoP: Point of Presence
- IXP: Internet Exchange Point
// saintétix, lyonix
- peering agreements
// cogent, free-etc
- @anim: %attr:.hasSVG: width: 800px
- @anim: %attr:.hasSVG: height: 200px
- @anim: .col1 | .col2



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