1. Protocoles réseaux Sommaire (prévision): Couche liaison de données
Introduction
Rappels programmation réseau (java)
Modèles
Systèmes de transitions, "safety et liveness"
Horloges logiques, ordre causal.
Couche liaison de données
Codes correcteurs d'erreur
Couche réseau
Algorithmes de routage
Couche transport
Communication fiable
Protocole du bit alterné- sliding windows
Compléments:
Algorithmes de diffusion
Algorithmes de vagues
Broadcast et multicast
Réseaux de pairs
ISP= internet service provider
Edge = bord
Introduction

2. Bibliographie
Introduction to Distributed Algorithms. G. Tel. Cambridge University press.
Computer networking J.F. Kurose K.W. Ross Pearson.
Design and analysis of distributed algorithms N. Santoro Wiley-Interscience
TCP-IP Illustrated volume 1: The Protocols R. Stevens Addison-Wesley
Introduction

3. Rappels: Java et internetM1
Internet et java

4. Sommaire Rappels java Rappels tcp-udp Socket tcp et SocketServer
Entrées-sorties
Thread
Rappels tcp-udp
Socket tcp et SocketServer
Socket udp
compléments
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5. Entrées-sorties java Streams Output streams Input streams
Filter streams
Readers et writer
(non blocking I/O)
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6. OuputStream public abstract class OutputStream
public abstract void write(int b) throws IOException
public void write(byte[] data) throws IOException
Public void write(byte[] data, int offset, int length) throws IOException
public void flush( ) throws IOException
public void close( ) throws IOException
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7. InputStream public abstract class InputStream
public abstract int read( ) throws IOException
public int read(byte[] input) throws IOException
public int read(byte[] input, int offset, int length) throws IOException
public long skip(long n) throws IOException
public int available( ) throws IOException
public void close( ) throws IOException
public void mark(int readAheadLimit)
public void reset( ) throws IOException
public boolean markSupported( )
Mark pose une marque et reset remet la stream à cette position
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8. Lecture:
int bytesRead=0; int bytesToRead=1024; byte[] input = new byte[bytesToRead]; while (bytesRead < bytesToRead) { int result = in.read(input, bytesRead, bytesToRead - bytesRead); if (result == -1) break; bytesRead += result; }
Il faut faire attention à ce que le read retourne quand il risque de bloquer, aussi pour tout lire et ne pas bloquer il faut faire quelque chose comme l’exemple
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9. Filtres Chainage des filtres:
DataOutputStream dout = new DataOutputStream(new
BufferedOutputStream(new FileOutputStream("data.txt")));
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10. Filtres Streams avec buffer PrintStream (System.out)
BufferedInputStream
BufferedOutputStream
PrintStream (System.out)
PushbackInputStream
Streams de données (lire et écrire des données java en binaire) le codage est celui de java
DataInputStream
DataOutputStream
Streams avec compression
Streams avec digest
Streams cryptées
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11. Attention Une méthode comme println est dépendante de la plate-forme:
Le séparateur de ligne est soit \n, soit \r, soit \r\n
Le codage par défaut des caractères dépend de la plate-forme
PrintStream capte les exceptions
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12. Compression
public class DeflaterOutputStream extends FilterOutputStream public class InflaterInputStream extends FilterInputStream public class GZIPOutputStream extends DeflaterOutputStream public class GZIPInputStream extends InflaterInputStream public class ZipOutputStream extends DeflaterOutputStream public class ZipInputStream extends InflaterInputStream
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13. décompresser une archive:
FileInputStream fin = new FileInputStream("shareware.zip"); ZipInputStream zin = new ZipInputStream(fin); ZipEntry ze = null; int b = 0; while ((ze = zin.getNextEntry( )) != null) { FileOutputStream fout = new FileOutputStream(ze.getName( )); while ((b = zin.read( )) != -1) fout.write(b); zin.closeEntry( ); fout.flush( ); fout.close( ); } zin.close( );
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14. Décompresser un fichier
FileInputStream fin = new FileInputStream("allnames.gz"); GZIPInputStream gzin = new GZIPInputStream(fin); FileOutputStream fout = new FileOutputStream("allnames"); int b = 0; while ((b = gzin.read( )) != -1) fout.write(b); gzin.close( ); out.flush( ); out.close( );
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15. digest public class DigestOutputStream extends FilterOutputStream
public class DigestInputStream extends FilterInputStream
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16. Digest exemple:
MessageDigest sha = MessageDigest.getInstance("SHA"); DigestOutputStream dout = new DigestOutputStream(out, sha); byte[] buffer = new byte[128]; while (true) { int bytesRead = in.read(buffer); if (bytesRead < 0) break; dout.write(buffer, 0, bytesRead); } dout.flush( ); dout.close( ); byte[] result = dout.getMessageDigest( ).digest( );
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17. Cryptage décryptage public CipherInputStream(InputStream in, Cipher c)
public CipherOutputStream(OutputStream out, Cipher c)
Exemple
byte[] desKeyData =    "Monmotdepasse".getBytes( );
DESKeySpec desKeySpec = new DESKeySpec(desKeyData);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey desKey = keyFactory.generateSecret(desKeySpec);
Cipher des = Cipher.getInstance("DES");
des.init(Cipher.DECRYPT_MODE, desKey);
CipherInputStream cin = new CipherInputStream(fin, des);
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18. Exemple String infile = "secrets.txt"; String outfile = "secrets.des";
String password = "Un mot de passe";
try {
FileInputStream fin = new FileInputStream(infile);
FileOutputStream fout = new FileOutputStream(outfile);
// register the provider that implements the algorithm
Provider sunJce = new com.sun.crypto.provider.SunJCE( );
Security.addProvider(sunJce);
char[] pbeKeyData = password.toCharArray( );
PBEKeySpec pbeKeySpec = new PBEKeySpec(pbeKeyData);
SecretKeyFactory keyFactory =
SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey pbeKey = keyFactory.generateSecret(pbeKeySpec);
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19. Exemple suite
// use Data Encryption Standard Cipher pbe = Cipher.getInstance("PBEWithMD5AndDES"); pbe.init(Cipher.ENCRYPT_MODE, pbeKey); CipherOutputStream cout = new CipherOutputStream(fout, pbe); byte[] input = new byte[64]; while (true) { int bytesRead = fin.read(input); if (bytesRead == -1) break; cout.write(input, 0, bytesRead); } cout.flush( ); cout.close( ); fin.close( ); catch (Exception ex) { System.err.println(ex);
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20. Readers et Writers
Hiérarchie de classe pour les caractères (avec encodage) au lieu d’octets.
Writer et Reader classes abstraites
OutputStreamWriter
InputStreamReader
Filtres
BufferedReader, BufferedWriter
LineNumberReader
PushbackReader
PrintReader
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21. Reader et Writer
OutputStreamWriter reçoit des caractères, les convertit en octets suivant un certain codage
public OutputStreamWriter(OutputStream out, String encoding) throws UnsupportedEncodingException
public OutputStreamWriter(OutputStream out)
Exemple:
OutputStreamWriter w = new OutputStreamWriter(new FileOutputStream(russe.txt,"Cp1251"));
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22. Reader et Writer
InputStreamReader lit des octets et les convertit suivant un certain codage
public InputStreamReader(InputStream in)
public InputStreamReader(InputStream in, String encoding) throws UnsupportedEncodingException
public static String getMacCyrillicString(InputStream in)
throws IOException {
InputStreamReader r = new InputStreamReader(in, "MacCyrillic");
StringBuffer sb = new StringBuffer( );
int c;
while ((c = r.read( )) != -1) sb.append((char) c);
r.close( );
return sb.toString( ); }
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23. Filtres BufferedReader BufferedWriter LineNumberReader PushbackReader
PrintWriter
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24. Threads
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25. Threads
threads: plusieurs activités qui coexistent et partagent des données
exemples:
pendant un chargement long faire autre chose
coopérer
processus versus threads
problème de l'accès aux ressources partagées
verrous
moniteur
synchronisation
thread
POO-L3 H. Fauconnier

26. Principes de base extension de la classe Thread
méthode run est le code qui sera exécuté.
la création d'un objet dont la superclasse est Thread crée la thread (mais ne la démarre pas)
la méthode start démarre la thread (et retourne immédiatement)
la méthode join permet d'attendre la fin de la thread
les exécutions des threads sont asynchrones et concurrentes
thread
POO-L3 H. Fauconnier

27. Exemple
class ThreadAffiche extends Thread{ private String mot; private int delay; public ThreadAffiche(String w,int duree){ mot=w; delay=duree; } public void run(){ try{ for(;;){ System.out.println(mot); Thread.sleep(delay); }catch(InterruptedException e){
thread
POO-L3 H. Fauconnier

28. Suite
public static void main(String[] args) { new ThreadAffiche("PING", 10).start(); new ThreadAffiche("PONG", 30).start(); new ThreadAffiche("Splash!",60).start(); }
thread
POO-L3 H. Fauconnier

29. Alternative: Runnable
Une autre solution:
créer une classe qui implémente l'interface Runnable (cette interface contient la méthode run)
créer une Thread à partir du constructeur Thread avec un Runnable comme argument.
thread
POO-L3 H. Fauconnier

30. Exemple class RunnableAffiche implements Runnable{ private String mot;
private int delay;
public RunnableAffiche(String w,int duree){
mot=w;
delay=duree; }
public void run(){
try{
for(;;){
System.out.println(mot);
Thread.sleep(delay);
}catch(InterruptedException e){
thread
POO-L3 H. Fauconnier

31. Suite public static void main(String[] args) {
Runnable ping=new RunnableAffiche("PING", 10);
Runnable pong=new RunnableAffiche("PONG", 50);
new Thread(ping).start();
new Thread(pong).start(); }
thread
POO-L3 H. Fauconnier

32. Synchronisation
les threads s'exécutent concurremment et peuvent accéder concurremment à des objets:
il faut contrôler l'accès:
thread un lit une variable (R1) puis modifie cette variable (W1)
thread deux lit la même variable (R2) puis la modifie (W2)
R1-R2-W2-W1
R1-W1-R2-W2 résultat différent!
thread
POO-L3 H. Fauconnier

33. Exemple class X{ int val; } class Concur extends Thread{ X x; int i;
String nom;
public Concur(String st, X x){
nom=st;
this.x=x;
public void run(){
i=x.val;
System.out.println("thread:"+nom+" valeur x="+i);
try{
Thread.sleep(10);
}catch(Exception e){}
x.val=i+1;
System.out.println("thread:"+nom+" valeur x="+x.val);
thread
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34. Suite public static void main(String[] args) { X x=new X();
Thread un=new Concur("un",x);
Thread deux=new Concur("deux",x);
un.start(); deux.start();
try{
un.join();
deux.join();
}catch (InterruptedException e){}
System.out.println("X="+x.val); }
donnera (par exemple)
thread:un valeur x=0
thread:deux valeur x=0
thread:un valeur x=1
thread:deux valeur x=1
X=1
thread
POO-L3 H. Fauconnier

35. Deuxième exemple
class Y{ int val=0; public int increment(){ int tmp=val; tmp++; try{ Thread.currentThread().sleep(100); }catch(Exception e){} val=tmp; return(tmp); } int getVal(){return val;} class Concur1 extends Thread{ Y y; String nom; public Concur1(String st, Y y){ nom=st; this.y=y; public void run(){ System.out.println("thread:"+nom+" valeur="+y.increment());
thread
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36. Suite thread:un valeur=1 thread:deux valeur=1 Y=1
public static void main(String[] args) {
Y y=new Y();
Thread un=new Concur1("un",y);
Thread deux=new Concur1("deux",y);
un.start(); deux.start();
try{
un.join();
deux.join();
}catch (InterruptedException e){}
System.out.println("Y="+y.getVal()); }
thread:un valeur=1
thread:deux valeur=1
Y=1
thread
POO-L3 H. Fauconnier

37. Verrous à chaque objet est associé un verrou
synchronized(expr) {instructions}
expr doit s'évaluer comme une référence à un objet
verrou sur cet objet pour la durée de l'exécution de instructions
déclarer les méthodes comme synchronized: la thread obtient le verrou et le relâche quand la méthode se termine
thread
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38. synchronised(x)
class Concur extends Thread{ X x; int i; String nom; public Concur(String st, X x){ nom=st; this.x=x; } public void run(){ synchronized(x){ i=x.val; System.out.println("thread:"+nom+" valeur x="+i); try{ Thread.sleep(10); }catch(Exception e){} x.val=i+1; System.out.println("thread:"+nom+" valeur x="+x.val);
thread
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39. Méthode synchronisée thread:un valeur=1 thread:deux valeur=2 Y=2
class Y{
int val=0;
public synchronized int increment(){
int tmp=val;
tmp++;
try{
Thread.currentThread().sleep(100);
}catch(Exception e){}
val=tmp;
return(tmp); }
int getVal(){return val;}
thread:un valeur=1
thread:deux valeur=2
Y=2
thread
POO-L3 H. Fauconnier

40. Mais… la synchronisation par des verrous peut entraîner un blocage:
la thread un (XA) pose un verrou sur l'objet A et (YB) demande un verrou sur l'objet B
la thread deux (XB) pose un verrou sur l'objet B et (YA) demande un verrou sur l'objet A
si XA –XB : ni YA ni YB ne peuvent être satisfaites -> blocage
(pour une méthode synchronisée, le verrou concerne l'objet globalement et pas seulement la méthode)
thread
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41. Exemple
class Dead{ Dead partenaire; String nom; public Dead(String st){ nom=st; } public synchronized void f(){ try{ Thread.currentThread().sleep(100); }catch(Exception e){} System.out.println(Thread.currentThread().getName()+ " de "+ nom+".f() invoque "+ partenaire.nom+".g()"); partenaire.g(); } public synchronized void g(){ " de "+ nom+".g()"); public void setPartenaire(Dead d){ partenaire=d;
thread
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42. Exemple (suite) T1 de un.f() invoque deux.g()
final Dead un=new Dead("un");
final Dead deux= new Dead("deux");
un.setPartenaire(deux);
deux.setPartenaire(un);
new Thread(new Runnable(){public void run(){un.f();}
},"T1").start();
new Thread(new Runnable(){public void run(){deux.f();}
},"T2").start();
T1 de un.f() invoque deux.g()
T2 de deux.f() invoque un.g()
thread
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43. Synchronisation… wait, notifyAll notify
attendre une condition / notifier le changement de condition:
synchronized void fairesurcondition(){
while(!condition)
wait();
faire ce qu'il faut qaund la condition est vraie }
synchronized void changercondition(){
… changer quelque chose concernant la condition
notifyAll(); // ou notify()
thread
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44. Exemple:
public class Cellule<E>{ private Cellule<E> suivant; private E element; public Cellule(E val) { this.element=val; } public Cellule(E val, Cellule suivant){ this.suivant=suivant; public E getElement(){ return element; public void setElement(E v){ element=v; public Cellule<E> getSuivant(){ return suivant; public void setSuivant(Cellule<E> s){ this.suivant=s;
thread
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45. Files synchronisées
class File<E>{ protected Cellule<E> tete, queue; private int taille=0; public synchronized void enfiler(E item){ Cellule<E> c=new Cellule<E>(item); if (queue==null) tete=c; else{ queue.setSuivant(c); } c.setSuivant(null); queue = c; notifyAll();
thread
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46. File (suite)
public synchronized E defiler() throws InterruptedException{ while (tete == null) wait(); Cellule<E> tmp=tete; tete=tete.getSuivant(); if (tete == null) queue=null; return tmp.getElement(); }
thread
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47. Réseau et Java
Rappels Tcp-udp
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48. I) Introduction
Les couches
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49. Couche Internet
Datagramme IPv4
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50. Couche transport TCP UDP
Mode connecté, flot bidirectionnel, sûr, contrôle de la congestion
Téléphone
UDP
Mode non connecté, messages, sans garantie, déséquencement
Poste
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51. Adresses internet Adresse IP: adresse réseau + site sur le réseau
Exemple:
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52. Classe d’adresses Internet
Classe Bits départ Début Fin Notation CIDR Masque ss-réseau Classe A / Classe B / Classe C / Classe D (mcast) /4 non défini Classe E (réservée) /4 non défini
Classe Nombre de réseaux possibles Nombre d'ordinateurs maxi sur chacun A B C
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53. Connexion Adresse IP +port Ports réservés Ports libres M2 internet
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54. Quelques ports Protocol Port echo 7 TCP/UDP discard 9 daytime 13
FTP data 20
TCP
FTP 21
SSH 22
telnet 23
smtp 25
time 37
Protocol
Port
whois 43
TCP
finger 79
HTTP 80
POP3
110
NNTP
119
IMAP
143
RMI Registry
1099
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55. Proxys
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56. Client-serveur
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57. Classes java.net.InetAddress (implements java.io.Serializable)
java.net.DatagramPacket
java.net.DatagramSocket
java.net.MulticastSocket
java.net.ServerSocket
javax.net.ssl.SSLServerSocket
java.net.Socket
javax.net.ssl.SSLSocket
java.net.SocketAddress (implements java.io.Serializable)
java.net.InetSocketAddress
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58. II) Adresses internet Classe InetAddress: Ontenir une InetAddress:
En utilisant le DNS
public static InetAddress getByName(String hostName) throws UnknownHostException
public static InetAddress[] getAllByName(String hostName) throws UnknownHostException
public static InetAddress getLocalHost( ) throws UnknownHostException
Sans DNS
public static InetAddress getByAddress(byte[] address) throws UnknownHostException
public static InetAddress getByAddress(String hostName, byte[] address) throws UnknownHostException
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59. Exemples
import java.net.*; /... public static void main (String[] args){ try { InetAddress adresse = InetAddress.getByName("liafa.jussieu.fr"); System.out.println(adresse); } catch (UnknownHostException ex) { System.out.println("liafa.jussieu.fr ??"); }
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60. Exemples
public static void main (String[] args){ try { InetAddress ad = InetAddress.getByName(" "); System.out.println(ad); } catch (UnknownHostException ex) { System.out.println(" ??"); }
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61. Toutes les adresses…
public static void AllAdresses(String st) { try { InetAddress[] addresses = InetAddress.getAllByName(st); for (int i = 0; i < addresses.length; i++) { System.out.println(addresses[i]); } } catch (UnknownHostException ex) { System.out.println(st+"est inconnu");
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62. Mon adresse public static String MonAdresse() { try {
InetAddress moi = InetAddress.getLocalHost();
return( moi.getHostAddress());
} catch (UnknownHostException ex) {
return("Mon adresse est inconnue"); }
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63. InetAddress méthodes…
public String getHostName( )
public byte[] getAddress( )
public String getHostAddress( )
Exemple:
public static void main (String[] args) {
try {
InetAddress ia= InetAddress.getByName(" "); System.out.println(ia.getHostName( ));
} catch (Exception ex)
{ System.err.println(ex); } }
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64. Divers… Java 1.5 « wildcard »? IPV4 et IPV6:
public boolean isAnyLocalAddress( )
« wildcard »?
public boolean isLoopbackAddress( )
public boolean isMulticastAddress( )
Java 1.5
public boolean isReachable(int timeout) throws IOException
public boolean isReachable(NetworkInterface interface, int ttl, int timeout) throws IOException
IPV4 et IPV6:
public final class Inet4Address extends InetAddress
public final class Inet6Address extends InetAddress
Wildcard: n'importe quelle adresse ( en IPV4)
Boucle locale
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65. NetworkInterface Exemple: try {
NetworkInterface ni = NetworkInterface.getByName("eth0");
if (ni == null) {
System.err.println(" pas de: eth0" ); }
} catch (SocketException ex) { }
Network interface représente une adresse Ip locale, elle peut être une interface physique (eth0 ici) ou une interface virtuelle.
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66. Exemple
public static String lookup(String host) { InetAddress node; // récupérer l'adresse par getByName try { node = InetAddress.getByName(host); } catch (UnknownHostException ex) { return "hôte inconnu " + host; } if (isHostname(host)) { return node.getHostAddress(); } else { return node.getHostName();
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67. sockets (client)

68. Généralités Une connexion: Serveur: Client:
(IP adresse+port, IP adresse +port)
On peut lire et écrire sur la socket
Serveur:
Associer une socket à une adresse connue (IP+port)
Ecoute sur la socket
Quand une connexion arrive accept : une nouvelle socket est créée
Rendre le service envoyer/recevoir
(en général dans une thread)
Continuer à écouter
Client:
Crée une socket
Demande connexion sur adresse +port du serveur
Connexion
Envoyer/recevoir
Fin de la connexion
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69. Socket en Java Serveur Client Classe ServerSocket Classe Socket
(bind (mais en général par constructeur)
listen)
Accept
getInputStream, getOutputStream
close
Client
Classe Socket
(bind)
connect (mais en général par constructeur)
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70. Attention! L’accès aux ports est souvent restreint
Des firewall peuvent empêcher les connexions
Il faut être root pour utiliser des ports réservés…
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71. Côté client
Création:
public Socket(InetAddress address, int port) throws IOException
Crée une socket + une connexion avec IP adresse et port
En fait:
Création d’une socket locale attachée à un port + une adresse locale
Etablissement de la connexion
IOException en cas d’échec
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72. Exemple
public static void regarderPortBas(String host) { for (int i = 1; i < 1024; i++) { try { Socket s = new Socket(host, i); System.out.println("Il y a un serveur sur " + i + " de "+ host); } catch (UnknownHostException ex) { System.err.println(ex); break; } catch (IOException ex) { // exception s'il n'y a pas de serveur }
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73. Attention Cet exemple peut ne pas bien fonctionner…
Pour des raisons de sécurité la tentative de connexion peut être bloquante
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74. Obtenir des infos… public InetAddress getInetAddress( )
public int getPort( )
public InetAddress getLocalAddress( )
public int getLocalPort( )
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75. Exemple
public static void socketInfo(String ... args) { for (int i = 0; i < args.length; i++) { try { Socket theSocket = new Socket(args[i], 80); System.out.println("Connecté sur " + theSocket.getInetAddress() + " port " + theSocket.getPort() + " depuis port " + theSocket.getLocalPort() + " de " + theSocket.getLocalAddress()); } catch (UnknownHostException ex) { System.err.println("Hôte inconnu " + args[i]); } catch (SocketException ex) { System.err.println("Connection impossible " + args[i]); } catch (IOException ex) { System.err.println(ex);
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76. Communiquer… public InputStream getInputStream( ) throws IOException
public OutputStream getOutputStream( ) throws IOException
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77. Exemple: dayTime public static void time(String ... hlist) {
for (int i=0;i<hlist.length;i++){
try {
Socket theSocket = new Socket(hlist[i], 13);
InputStream timeStream = theSocket.getInputStream();
StringBuffer time = new StringBuffer();
int c;
while ((c = timeStream.read()) != -1) time.append((char) c);
String timeString = time.toString().trim();
System.out.println("Il est " + timeString + " à " + hlist[i]); }
catch (UnknownHostException ex) {
System.err.println(ex);
} catch (IOException ex) {
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78. Exemple: echo M2 internet H. Fauconnier
public static void echo(String hostname, int port) { PrintWriter out = null; BufferedReader networkIn = null; try { Socket theSocket = new Socket(hostname, port); networkIn = new BufferedReader( new InputStreamReader(theSocket.getInputStream())); BufferedReader userIn = new BufferedReader( new InputStreamReader(System.in)); out = new PrintWriter(theSocket.getOutputStream()); System.out.println("Client: Connecté au serveur d'echo "+ theSocket); while (true) { String theLine = userIn.readLine(); out.println(theLine); out.flush(); if (theLine.equals(".")){out.close(); break;} System.out.println(networkIn.readLine()); } catch (IOException ex) {System.err.println(ex); } finally { if (networkIn != null) networkIn.close(); if (out != null) out.close(); } catch (IOException ex) {}
M2 internet
H. Fauconnier

79. Echo suite catch (IOException ex) { System.err.println(ex);
} finally {
try {
if (networkIn != null) networkIn.close();
if (out != null) out.close();
} catch (IOException ex) {} }
M2 internet
H. Fauconnier

80. Fermeture public void close( ) throws IOException
Fermeture de la socket:
Automatique si une des parties fait un close
garbage collector
(le réseau utilise des ressources systèmes qui sont par définition partagées et limitées)
(a priori à mettre dans une clause finally )
M2 internet
H. Fauconnier

81. En plus public boolean isClosed( ) public boolean isConnected( )
public boolean isBound( )
public void shutdownInput( ) throws IOException
public void shutdownOutput( ) throws IOException
Attention isConnected précise seulement si la socket a été connectée.
M2 internet
H. Fauconnier

82. ServerSocket

83. Principe Création d’un ServerSocket par constructeur
Association (bind) de la socket à une adresse et un port ((1) et (2) peuvent être simultanés)
Écoute et connexion par accept
Communication getInputStream et getOutputStream
close (par le client ou le serveur ou les deux)
Aller en (2) (en général 3 est dans une thread)
M2 internet
H. Fauconnier

84. Constructeurs
public ServerSocket(int port) throws BindException, IOException
public ServerSocket(int port, int queueLength) throws BindException, IOException
public ServerSocket(int port, int queueLength, InetAddress bindAddress) throws IOException
Ces constructeurs associent un port et une adresse au ServerSocket l’usage du port est exclusif et si le port est déjà occupé une exception est lancée
public ServerSocket( ) throws IOException
M2 internet
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85. Exemple
public static void portsLibres() { for (int port = 1; port <= 65535; port++) { try { // exception si le port est utilisé ServerSocket server = new ServerSocket(port); } catch (IOException ex) { System.out.println("serveur sur port" + port ); }
M2 internet
H. Fauconnier

86. Remarques port 0: choisi par le système
on peut donner une taille sur la file des connexions en attente
on peut choisir une adresse particulière sur la machine locale
En java >1.4 on peut faire un "bind" explicite:
public void bind(SocketAddress endpoint) throws IOException
public void bind(SocketAddress endpoint, int queueLength) throws IOException
M2 internet
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87. Exemple
public static void portQuelconque() { try { ServerSocket server = new ServerSocket(0); System.out.println("Le port obtenu est " + server.getLocalPort()); } catch (IOException ex) { System.err.println(ex); }
M2 internet
H. Fauconnier

88. Connexion accept()
crée et retourne une nouvelle socket pour la connexion associée (IP, port)(IP, port)
M2 internet
H. Fauconnier

89. Exemple ServerSocket server = new ServerSocket(5776); while (true) {
Socket connection = server.accept( );
OutputStreamWriter out = new OutputStreamWriter( connection.getOutputStream( ));
out.write("Connecté:" +connection+"\r\n");
connection.close( ); }
M2 internet
H. Fauconnier

90. Exemple plus complet
public final static int DEFAULT_PORT = 13; public static void dayTime(){ dayTime(DEFAULT_PORT); } public static void dayTime(int port) { if (port < 0 || port >= 65536) { System.out.println("Erreur port:"); return; try { ServerSocket server = new ServerSocket(port); Socket connection = null;
M2 internet
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91. Exemple suite while (true) { try { connection = server.accept();
Writer out = new OutputStreamWriter( connection.getOutputStream());
Date now = new Date();
out.write(now.toString() +"\r\n");
out.flush();
connection.close();
} catch (IOException ex) {} finally {
if (connection != null) connection.close();
} catch (IOException ex) {} }
} catch (IOException ex) {
System.err.println(ex);
M2 internet
H. Fauconnier

92. Fermeture
public void close( ) throws IOException
Ferme le ServerSocket et toutes les connexions créées par accept sur la ServerSocket
M2 internet
H. Fauconnier

93. Serveur echo
public static void serveurEcho(int port) { try { ServerSocket server = new ServerSocket(port,100); System.out.println("Serveur:"+server+" en écoute sur le port: " + server.getLocalPort()+" est lancé"); while (true) { Socket connection = server.accept(); System.out.println("Serveur connexion avec: " + connection); Thread echo=new EchoThread(connection); echo.start(); } catch (IOException ex) { System.out.println("le port" + port + " est occupé"); System.out.println("On suppose donc que le service estlancé"); }
M2 internet
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94. serveur echo: EchoThread
class EchoThread extends Thread { BufferedReader in; PrintWriter out; Socket connection; public EchoThread(Socket connection) { try{ this.connection=connection; InputStream in=connection.getInputStream(); OutputStream out=connection.getOutputStream(); this.in = new BufferedReader(new InputStreamReader(in)); this.out = new PrintWriter(out); } catch (IOException ex) { System.err.println(ex); }
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95. run
public void run() { try { while (true) { String st; st = in.readLine(); if (st.equals(".")) in.close(); out.close(); break; } System.out.println("Serveur a reçu:"+st+" de "+connection); out.println(st); out.flush(); } catch (SocketException ex) { ex.printStackTrace(); } catch (IOException ex) { System.err.println(ex); } catch (IOException ex) { ex.printStackTrace();}
M2 internet
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96. Remarques
utilisation des threads pour traiter le service et éviter de faire attendre les clients
on peut aussi utiliser des entrées/sorties non bloquantes
M2 internet
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97. Autres méthodes public InetAddress getInetAddress( )
public int getLocalPort( )
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98. Socket UDP
H. Fauconnier
M2-Internet Java

99. UDP
H. Fauconnier
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100. Socket programming with UDP
UDP: no “connection” between client and server
no handshaking
sender explicitly attaches IP address and port of destination to each segment
OS attaches IP address and port of sending socket to each segment
Server can extract IP address, port of sender from received segment
application viewpoint
UDP provides unreliable transfer
of groups of bytes (“datagrams”)
between client and server
Note: the official terminology
for a UDP packet is “datagram”. In this class, we instead use “UDP segment”.
H. Fauconnier
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101. Running example Client: Server: User types line of text
Client program sends line to server
Server:
Server receives line of text
Capitalizes all the letters
Sends modified line to client
Receives line of text
Displays
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102. Client/server socket interaction: UDP
Server (running on hostid)
create socket,
clientSocket =
DatagramSocket()
Client
Create datagram with server IP and
port=x; send datagram via clientSocket
create socket,
port= x.
serverSocket =
DatagramSocket()
read datagram from
serverSocket
close
clientSocket
read datagram from
write reply to
serverSocket
specifying client address,
port number
H. Fauconnier
M2-Internet Java

103. Example: Java client (UDP)
process
Input: receives packet (recall thatTCP received “byte stream”)
Output: sends packet (recall
that TCP sent “byte stream”)
client UDP socket
H. Fauconnier
M2-Internet Java

104. Example: Java client (UDP)
import java.io.*;
import java.net.*;
class UDPClient {
public static void main(String args[]) throws Exception {
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("hostname");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
Create
input stream
Create
client socket
Translate
hostname to IP
address using DNS
H. Fauconnier
M2-Internet Java

105. Example: Java client (UDP), cont.
Create datagram with data-to-send,
length, IP addr, port
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modifiedSentence =
new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close(); }
Send datagram
to server
Read datagram
from server
H. Fauconnier
M2-Internet Java

106. Example: Java server (UDP)
import java.io.*;
import java.net.*;
class UDPServer {
public static void main(String args[]) throws Exception {
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while(true)
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
Create
datagram socket
at port 9876
Create space for
received datagram
Receive
datagram
H. Fauconnier
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107. Example: Java server (UDP), cont
String sentence = new String(receivePacket.getData());
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress,
port);
serverSocket.send(sendPacket); }
Get IP addr
port #, of
sender
Create datagram
to send to client
Write out
datagram
to socket
End of while loop,
loop back and wait for
another datagram
H. Fauconnier
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108. UDP observations & questions
Both client server use DatagramSocket
Dest IP and port are explicitly attached to segment.
What would happen if change both clientSocket and serverSocket to “mySocket”?
Can the client send a segment to server without knowing the server’s IP address and/or port number?
Can multiple clients use the server?
H. Fauconnier
M2-Internet Java

109. DatagramPacket Un paquet contient au plus 65,507 bytes
Pour construire les paquet
public DatagramPacket(byte[] buffer, int length)
public DatagramPacket(byte[] buffer, int offset, int length)
Pour construire et envoyer
public DatagramPacket(byte[] data, int length, InetAddress destination, int port)
public DatagramPacket(byte[] data, int offset, int length, InetAddress destination, int port)
public DatagramPacket(byte[] data, int length, SocketAddress destination, int port)
public DatagramPacket(byte[] data, int offset, int length, SocketAddress destination, int port)
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110. Exemple
String s = "On essaie…"; byte[] data = s.getBytes("ASCII"); try { InetAddress ia = InetAddress.getByName(" int port = 7;// existe-t-il? DatagramPacket dp = new DatagramPacket(data, data.length, ia, port); } catch (IOException ex)
H. Fauconnier
M2-Internet Java

111. Méthodes Adresses public InetAddress getAddress( )
public int getPort( )
public SocketAddress getSocketAddress( )
public void setAddress(InetAddress remote)
public void setPort(int port)
public void setAddress(SocketAddress remote)
H. Fauconnier
M2-Internet Java

112. Méthodes (suite) Manipulation des données: public byte[] getData( )
public int getLength( )
public int getOffset( )
public void setData(byte[] data)
public void setData(byte[] data, int offset, int length )
public void setLength(int length)
H. Fauconnier
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113. Exemple
import java.net.*; public class DatagramExample { public static void main(String[] args) { String s = "Essayons."; byte[] data = s.getBytes( ); try { InetAddress ia = InetAddress.getByName(" int port =7; DatagramPacket dp = new DatagramPacket(data, data.length, ia, port); System.out.println(" Un packet pour" + dp.getAddress( ) + " port " + dp.getPort( )); System.out.println("il y a " + dp.getLength( ) + " bytes dans le packet"); System.out.println( new String(dp.getData( ), dp.getOffset( ), dp.getLength( ))); } catch (UnknownHostException e) { System.err.println(e);
H. Fauconnier
M2-Internet Java

114. DatagramSocket Constructeurs
public DatagramSocket( ) throws SocketException
public DatagramSocket(int port) throws SocketException
public DatagramSocket(int port, InetAddress interface) throws SocketException
public DatagramSocket(SocketAddress interface) throws SocketException
(protected DatagramSocket(DatagramSocketImpl impl) throws SocketException)
H. Fauconnier
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115. Exemple
java.net.*; public class UDPPortScanner { public static void main(String[] args) { for (int port = 1024; port <= 65535; port++) { try { // exception si utilisé DatagramSocket server = new DatagramSocket(port); server.close( ); } catch (SocketException ex) { System.out.println("Port occupé" + port + "."); } // end try } // end for
H. Fauconnier
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116. Envoyer et recevoir
public void send(DatagramPacket dp) throws IOException
public void receive(DatagramPacket dp) throws IOException
H. Fauconnier
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117. Un exemple: Echo UDPServeur UDPEchoClient UDPEchoServeur SenderThread
ReceiverThread
H. Fauconnier
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118. Echo: UDPServeur H. Fauconnier M2-Internet Java
import java.net.*; import java.io.*; public abstract class UDPServeur extends Thread { private int bufferSize; protected DatagramSocket sock; public UDPServeur(int port, int bufferSize) throws SocketException { this.bufferSize = bufferSize; this.sock = new DatagramSocket(port); } public UDPServeur(int port) throws SocketException { this(port, 8192); public void run() { byte[] buffer = new byte[bufferSize]; while (true) { DatagramPacket incoming = new DatagramPacket(buffer, buffer.length); try { sock.receive(incoming); this.respond(incoming); catch (IOException e) { System.err.println(e); } // end while public abstract void respond(DatagramPacket request);
H. Fauconnier
M2-Internet Java

119. UDPEchoServeur H. Fauconnier M2-Internet Java
public class UDPEchoServeur extends UDPServeur { public final static int DEFAULT_PORT = 2222; public UDPEchoServeur() throws SocketException { super(DEFAULT_PORT); } public void respond(DatagramPacket packet) { try { byte[] data = new byte[packet.getLength()]; System.arraycopy(packet.getData(), 0, data, 0, packet.getLength()); String s = new String(data, "8859_1"); System.out.println(packet.getAddress() + " port " + packet.getPort() + " reçu " + s); } catch (java.io.UnsupportedEncodingException ex) {} DatagramPacket outgoing = new DatagramPacket(packet.getData(), packet.getLength(), packet.getAddress(), packet.getPort()); sock.send(outgoing); } catch (IOException ex) { System.err.println(ex);
H. Fauconnier
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120. Client: UDPEchoClient
public class UDPEchoClient { public static void lancer(String hostname, int port) { try { InetAddress ia = InetAddress.getByName(hostname); SenderThread sender = new SenderThread(ia, port); sender.start(); Thread receiver = new ReceiverThread(sender.getSocket()); receiver.start(); } catch (UnknownHostException ex) { System.err.println(ex); catch (SocketException ex) { } // end lancer
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121. ReceiverThread H. Fauconnier M2-Internet Java
class ReceiverThread extends Thread { DatagramSocket socket; private boolean stopped = false; public ReceiverThread(DatagramSocket ds) throws SocketException { this.socket = ds; } public void halt() { this.stopped = true; public DatagramSocket getSocket(){ return socket; public void run() { byte[] buffer = new byte[65507]; while (true) { if (stopped) return; DatagramPacket dp = new DatagramPacket(buffer, buffer.length); try { socket.receive(dp); String s = new String(dp.getData(), 0, dp.getLength()); System.out.println(s); Thread.yield(); } catch (IOException ex) {System.err.println(ex); }
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122. SenderThread
public class SenderThread extends Thread { private InetAddress server; private DatagramSocket socket; private boolean stopped = false; private int port; public SenderThread(InetAddress address, int port) throws SocketException { this.server = address; this.port = port; this.socket = new DatagramSocket(); this.socket.connect(server, port); } public void halt() { this.stopped = true; //…
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123. SenderThread H. Fauconnier M2-Internet Java
//… public DatagramSocket getSocket() { return this.socket; } public void run() { try { BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in)); while (true) { if (stopped) return; String theLine = userInput.readLine(); if (theLine.equals(".")) break; byte[] data = theLine.getBytes(); DatagramPacket output = new DatagramPacket(data, data.length, server, port); socket.send(output); Thread.yield(); } // end try catch (IOException ex) {System.err.println(ex); } } // end run
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124. Autres méthodes public void close( ) public int getLocalPort( )
public InetAddress getLocalAddress( )
public SocketAddress getLocalSocketAddress( )
public void connect(InetAddress host, int port)
public void disconnect( )
public int getPort( )
public InetAddress getInetAddress( )
public InetAddress getRemoteSocketAddress( )
H. Fauconnier
M2-Internet Java

125. Options SO_TIMEOUT SO_RCVBUF SO_SNDBUF
public synchronized void setSoTimeout(int timeout) throws SocketException
public synchronized int getSoTimeout( ) throws IOException
SO_RCVBUF
public void setReceiveBufferSize(int size) throws SocketException
public int getReceiveBufferSize( ) throws SocketException
SO_SNDBUF
public void setSendBufferSize(int size) throws SocketException
int getSendBufferSize( ) throws SocketException
SO_REUSEADDR (plusieurs sockets sur la même adresse)
public void setReuseAddress(boolean on) throws SocketException
boolean getReuseAddress( ) throws SocketException
SO_BROADCAST
public void setBroadcast(boolean on) throws SocketException
public boolean getBroadcast( ) throws SocketException
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126. Chapitre 1 Introduction
Les transparents sont adaptés de (et en anglais):
Computer Networking: A Top Down Approach Featuring the Internet
J.F Kurose and K.W. Ross
Introduction

127. Chapter 1: Introduction
Our goal:
get “feel” and terminology
more depth, detail later in course
approach:
use Internet as example
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
Introduction

128. Chapitre 1: sommaire 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 models
1.6 Networks under attack: security
1.7 History
Introduction

129. What’s the Internet: PC
server
wireless
laptop
cellular
handheld
millions of connected computing devices: hosts = end systems
running network apps
Home network
Institutional network
Mobile network
Global ISP
Regional ISP
communication links
fiber, copper, radio, satellite
transmission rate = bandwidth
wired
links
access
points
Nuts and bolts
routers: forward packets (chunks of data)
router
Introduction

130. “Cool” internet appliances
Web-enabled toaster +
weather forecaster
IP picture frame
World’s smallest web server
Internet phones
Introduction

131. What’s the Internet: protocols control sending, receiving of msgs
e.g., TCP, IP, HTTP, Skype, Ethernet
Internet: “network of networks”
loosely hierarchical
public Internet versus private intranet
Internet standards
RFC: Request for comments
IETF: Internet Engineering Task Force
Home network
Institutional network
Mobile network
Global ISP
Regional ISP
Introduction

132. What’s the Internet: a service view
communication infrastructure enables distributed applications:
Web, VoIP, , games, e-commerce, file sharing
communication services provided to apps:
reliable data delivery from source to destination
“best effort” (unreliable) data delivery
Introduction

133. What’s a protocol? human protocols: “what’s the time?”
“I have a question”
introductions
… specific msgs sent
… specific actions taken when msgs received, or other events
network protocols:
machines rather than humans
all communication activity in Internet governed by protocols
protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt
Introduction

134. What’s a protocol? a human protocol and a computer network protocol:Hi
TCP connection
request Hi
TCP connection
response
Got the
time?
Get
2:00
<file>
time
Q: Other human protocols?
Introduction

135. 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 models
1.6 Networks under attack: security
1.7 History
Introduction

136. A closer look at network structure:
network edge: applications and hosts
access networks, physical media: wired, wireless communication links
network core:
interconnected routers
network of networks
Introduction

137. The network edge: end systems (hosts): client/server model
run application programs
e.g. Web,
at “edge of network”
peer-peer
client/server
client/server model
client host requests, receives service from always-on server
e.g. Web browser/server; client/server
peer-peer model:
minimal (or no) use of dedicated servers
e.g. Skype, BitTorrent
Introduction

138. Access networks and physical media
Q: How to connect end systems to edge router?
residential access nets
institutional access networks (school, company)
mobile access networks
Keep in mind:
bandwidth (bits per second) of access network?
shared or dedicated?
Introduction

139. Dial-up Modem Uses existing telephony infrastructure
telephone
network
Internet
home dial-up
modem
ISP modem
(e.g., AOL)
home PC
central office
Uses existing telephony infrastructure
Home is connected to central office
up to 56Kbps direct access to router (often less)
Can’t surf and phone at same time: not “always on”

140. Digital Subscriber Line (DSL)
telephone
network
DSL
modem
home PC
phone
Internet
DSLAM
Existing phone line: 0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream data
splitter
central
office
Also uses existing telephone infrastruture
up to 1 Mbps upstream (today typically < 256 kbps)
up to 8 Mbps downstream (today typically < 1 Mbps)
dedicated physical line to telephone central office
DSLAM= digital subscriber line access multiplexer

141. Residential access: cable modems
Does not use telephone infrastructure
Instead uses cable TV infrastructure
HFC: hybrid fiber coax
asymmetric: up to 30Mbps downstream, 2 Mbps upstream
network of cable and fiber attaches homes to ISP router
homes share access to router
unlike DSL, which has dedicated access
ISP= internet service provider
Introduction

142. Residential access: cable modems
Diagram:
Introduction

143. Cable Network Architecture: Overview
Typically 500 to 5,000 homes
cable headend
home
cable distribution
network (simplified)
Introduction

144. Cable Network Architecture: Overview
server(s)
cable headend
home
cable distribution
network
Introduction

145. Cable Network Architecture: Overview
cable headend
home
cable distribution
network (simplified)
Introduction

146. Cable Network Architecture: Overview
FDM (more shortly):
Channels V I D E O A T C N R L 1 2 3 4 5 6 7 8 9
FDM: frequency division mulitplexing
cable headend
home
cable distribution
network
Introduction

147. Fiber to the Home OLT Optical links from central office to the home
ONT
OLT
central office
optical
splitter
optical fiber
optical fibers
Internet
Optical links from central office to the home
Two competing optical technologies:
Passive Optical network (PON)
Active Optical Network (PAN)
Much higher Internet rates; fiber also carries television and phone services
ONT optical network terminal
OLT optical line terminator (conversion otpique electrique)
Avec PON tous les packets de l'OLT vers le splitter sont répliqués sur le splitter
Avec PAN = switched internet

148. Ethernet Internet access
100 Mbps
1 Gbps
server
Ethernet
switch
Institutional
router
To Institution’s ISP
Typically used in companies, universities, etc
10 Mbs, 100Mbps, 1Gbps, 10Gbps Ethernet
Today, end systems typically connect into Ethernet switch

149. 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)
next up (?): WiMAX (10’s Mbps) over wide area
router
base
station
EV-DO - Evolution data optimized reéseau sans fil haut débit
HSDPA= high speed downlink packet access (3G+)
WiMax worldwide Interoperability for Microwave Access
mobile
hosts
Introduction

150. Home networks Typical home network components: DSL or cable modem
router/firewall/NAT
Ethernet
wireless access
point
wireless
laptops
to/from
cable
headend
cable
modem
router/
firewall
NAT= network access translation
wireless
access
point
Ethernet
Introduction

151. Physical Media Twisted Pair (TP) two insulated copper wires
Category 3: traditional phone wires, 10 Mbps Ethernet
Category 5: 100Mbps Ethernet
Bit: propagates between transmitter/rcvr pairs
physical link: what lies between transmitter & receiver
guided media:
signals propagate in solid media: copper, fiber, coax
unguided media:
signals propagate freely, e.g., radio
Introduction

152. Physical Media: coax, fiber
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’s Gps)
low error rate: repeaters spaced far apart ; immune to electromagnetic noise
Coaxial cable:
two concentric copper conductors
bidirectional
baseband:
single channel on cable
legacy Ethernet
broadband:
multiple channels on cable
HFC
HFC
Introduction

153. Physical media: radio 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: ~ 1 Mbps
satellite
Kbps to 45Mbps channel (or multiple smaller channels)
270 msec end-end delay
geosynchronous versus low altitude
signal carried in electromagnetic spectrum
no physical “wire”
bidirectional
propagation environment effects:
reflection
obstruction by objects
interference
Introduction

154. 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 models
1.6 Networks under attack: security
1.7 History
Introduction

155. 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

156. Network Core: Circuit Switching
End-end resources reserved for “call”
link bandwidth, switch capacity
dedicated resources: no sharing
circuit-like (guaranteed) performance
call setup required
Introduction

157. Network Core: Circuit Switching
network resources (e.g., bandwidth) divided into “pieces”
pieces allocated to calls
resource piece idle if not used by owning call (no sharing)
dividing link bandwidth into “pieces”
frequency division
time division
Introduction

158. Circuit Switching: FDM and TDM
4 users
Example:
FDM
frequency
time
TDM
frequency
time
Two simple multiple access control techniques.
Each mobile’s share of the bandwidth is divided into portions for the uplink and the downlink. Also, possibly, out of band signaling.
As we will see, used in AMPS, GSM, IS-54/136
FDM frequency division modulation
TDM time
Introduction

159. Numerical example
How long does it take to send a file of 640,000 bits from host A to host B over a circuit-switched network?
All links are Mbps
Each link uses TDM with 24 slots/sec
500 msec to establish end-to-end circuit
Let’s work it out!
1 slot tous les 1/24 secondes ->0,6* 1,536/ ms => 0,1*1/4 +500ms => 0,9ms
Introduction

160. Network Core: Packet Switching
each end-end data stream 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 allocation
Resource reservation
Introduction

161. Packet Switching: Statistical Multiplexing
100 Mb/s
Ethernet C A
statistical multiplexing
1.5 Mb/s B
queue of packets
waiting for output
link D E
Sequence of A & B packets does not have fixed pattern, bandwidth shared on demand  statistical multiplexing.
TDM: each host gets same slot in revolving TDM frame.
Introduction

162. Packet-switching: store-and-forwardL R R R
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
R = 1.5 Mbps
transmission delay = 15 sec
more on delay shortly …
Introduction

163. Packet switching versus circuit switching
Packet switching allows more users to use network!
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
N users
1 Mbps link
Q: how did we get value ?
Introduction

164. Packet switching versus circuit switching
Is packet switching the definitive winner?
great for bursty data
resource sharing
simpler, no call setup
excessive congestion: packet delay and loss
protocols needed for reliable data transfer, congestion control
Q: How to provide circuit-like behavior?
bandwidth guarantees needed for audio/video apps
Slam dunk = smash (slam dunk winner vainqueur par ko)
Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)?
Introduction

165. Internet structure: network of networks
roughly hierarchical
at center: “tier-1” ISPs (e.g., Verizon, Sprint, AT&T, Cable and Wireless), national/international coverage
treat each other as equals
Tier 1 ISP
Tier-1 providers interconnect (peer) privately
ISP internet system provider
Tier= gradin (niveau)
Tier 1 ISP
Tier 1 ISP
Introduction

166. Tier-1 ISP: e.g., Sprint … …. to/from backbone peering
to/from customers
peering
to/from backbone ….
POP: point-of-presence
Introduction

167. Internet structure: network of networks
“Tier-2” ISPs: smaller (often regional) ISPs
Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
Tier-2 ISPs also peer privately with each other.
Tier-2 ISP
Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet
tier-2 ISP is customer of
tier-1 provider
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Introduction

168. Internet structure: network of networks
“Tier-3” ISPs and local ISPs
last hop (“access”) network (closest to end systems)
local
ISP
Tier 3
Local and tier- 3 ISPs are customers of
higher tier ISPs
connecting them to rest of Internet
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Introduction

169. Internet structure: network of networks
a packet passes through many networks!
local
ISP
Tier 3
ISP
local
ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
local
ISP
local
ISP
local
ISP
local
ISP
Introduction

170. 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 models
1.6 Networks under attack: security
1.7 History
Introduction

171. How do loss and delay occur?
packets queue in router buffers
packet arrival rate to link exceeds output link capacity
packets queue, wait for turn
packet being transmitted (delay) A
free (available) buffers: arriving packets
dropped (loss) if no free buffers
packets queueing (delay) B
Introduction

172. Four sources of packet delay
1. nodal processing:
check bit errors
determine output link
2. queueing
time waiting at output link for transmission
depends on congestion level of router A B
propagation
transmission
nodal
processing
queueing
Introduction

173. Delay in packet-switched networks
3. Transmission delay:
R=link bandwidth (bps)
L=packet length (bits)
time to send bits into link = L/R
4. Propagation delay:
d = length of physical link
s = propagation speed in medium (~2x108 m/sec)
propagation delay = d/s
Note: s and R are very different quantities! A B
propagation
transmission
nodal
processing
queueing
Introduction

174. Caravan analogy
toll
booth
ten-car
caravan
100 km
cars “propagate” at 100 km/hr
toll booth takes 12 sec to service car (transmission time)
car~bit; caravan ~ packet
Q: How long until caravan is lined up before 2nd toll booth?
Time to “push” entire caravan through toll booth onto highway = 12*10 = 120 sec
Time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hr
A: 62 minutes
Introduction

175. Caravan analogy (more)
toll
booth
ten-car
caravan
100 km
Yes! After 7 min, 1st car at 2nd booth and 3 cars still at 1st booth.
1st bit of packet can arrive at 2nd router before packet is fully transmitted at 1st router!
Cars now “propagate” at km/hr
Toll booth now takes 1 min to service a car
Q: Will cars arrive to 2nd booth before all cars serviced at 1st booth?
See Ethernet applet at AWL Web site
Introduction

176. Nodal delay dproc = processing delay dqueue = queuing delay
typically a few microsecs or less
dqueue = queuing delay
depends on congestion
dtrans = transmission delay
= L/R, significant for low-speed links
dprop = propagation delay
a few microsecs to hundreds of msecs
Introduction

177. Queueing delay (revisited)
R=link bandwidth (bps)
L=packet length (bits)
a=average packet arrival rate
traffic intensity = La/R
La/R ~ 0: average queueing delay small
La/R -> 1: delays become large
La/R > 1: more “work” arriving than can be serviced, average delay infinite!
Introduction

178. “Real” Internet delays and routes
What do “real” Internet delay & loss look like?
Traceroute program: provides delay measurement from source to router along end-end Internet path towards destination. For all i:
sends three packets that will reach router i on path towards destination
router i will return packets to sender
sender times interval between transmission and reply.
3 probes
3 probes
3 probes
Introduction

179. “Real” Internet delays and routes
traceroute: gaia.cs.umass.edu to
Three delay measurements from
gaia.cs.umass.edu to cs-gw.cs.umass.edu
1 cs-gw ( ) 1 ms 1 ms 2 ms
2 border1-rt-fa5-1-0.gw.umass.edu ( ) 1 ms 1 ms 2 ms
3 cht-vbns.gw.umass.edu ( ) 6 ms 5 ms 5 ms
4 jn1-at wor.vbns.net ( ) 16 ms 11 ms 13 ms
5 jn1-so wae.vbns.net ( ) 21 ms 18 ms 18 ms
6 abilene-vbns.abilene.ucaid.edu ( ) 22 ms 18 ms 22 ms
7 nycm-wash.abilene.ucaid.edu ( ) 22 ms 22 ms 22 ms
( ) 104 ms 109 ms 106 ms
9 de2-1.de1.de.geant.net ( ) 109 ms 102 ms 104 ms
10 de.fr1.fr.geant.net ( ) 113 ms 121 ms 114 ms
11 renater-gw.fr1.fr.geant.net ( ) 112 ms 114 ms 112 ms
12 nio-n2.cssi.renater.fr ( ) 111 ms 114 ms 116 ms
13 nice.cssi.renater.fr ( ) 123 ms 125 ms 124 ms
14 r3t2-nice.cssi.renater.fr ( ) 126 ms 126 ms 124 ms
15 eurecom-valbonne.r3t2.ft.net ( ) 135 ms 128 ms 133 ms
( ) 126 ms 128 ms 126 ms
17 * * *
18 * * *
19 fantasia.eurecom.fr ( ) 132 ms 128 ms 136 ms
trans-oceanic
link
* means no response (probe lost, router not replying)
Introduction

180. Packet loss
queue (aka buffer) preceding link in buffer 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
buffer
(waiting area)
packet being transmitted A B
packet arriving to
full buffer is lost
Introduction

181. Throughput
throughput: rate (bits/time unit) at which bits transferred between sender/receiver
instantaneous: rate at given point in time
average: rate over longer period of time
pipe that can carry
fluid at rate
Rc bits/sec)
pipe that can carry
fluid at rate
Rs bits/sec)
Troughput=débit
link capacity
Rs bits/sec
link capacity
Rc bits/sec
server sends bits
(fluid) into pipe
server, with
file of F bits
to send to client
Introduction

182. Throughput (more) Rs < Rc What is average end-end throughput?
Rc bits/sec
Rs bits/sec
Rs > Rc What is average end-end throughput?
Rs bits/sec
Rc bits/sec
Throughput= débit
link on end-end path that constrains end-end throughput
bottleneck link
Introduction

183. Throughput: Internet scenarioRs
per-connection end-end throughput: min(Rc,Rs,R/10)
in practice: Rc or Rs is often bottleneck Rs Rs R Rc Rc Rc
10 connections (fairly) share backbone bottleneck link R bits/sec
Introduction

184. 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 models
1.6 Networks under attack: security
1.7 History
Introduction

185. Protocol “Layers” Question: Networks are complex! many “pieces”: hosts
routers
links of various media
applications
protocols
hardware, software
Question:
Is there any hope of organizing structure of network?
Or at least our discussion of networks?
Introduction

186. Organization of air travel
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticket (complain)
baggage (claim)
gates (unload)
runway landing
a series of steps
Introduction

187. Layering of airline functionality
ticket (purchase)
baggage (check)
gates (load)
runway (takeoff)
airplane routing
departure
airport
arrival
intermediate air-traffic
control centers
ticket (complain)
baggage (claim
gates (unload)
runway (land)
ticket
baggage
gate
takeoff/landing
Layers: each layer implements a service
via its own internal-layer actions
relying on services provided by layer below
Introduction

188. 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 of system
change of implementation of layer’s service transparent to rest of system
e.g., change in gate procedure doesn’t affect rest of system
layering considered harmful?
Introduction

189. Internet protocol stack
application: supporting network applications
FTP, SMTP, HTTP
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
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
Introduction

190. 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

191. Encapsulation source destination application transport network link
message M
application
transport
network
link
physical
segment Ht M Ht
datagram Ht Hn M Hn
frame Ht Hn Hl M
link
physical
switch
destination
network
link
physical Ht Hn M Ht Hn Hl M M
application
transport
network
link
physical Ht Hn M Ht M Ht Hn M
router Ht Hn Hl M
Introduction

192. 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 models
1.6 Networks under attack: security
1.7 History
Introduction

193. Network Security The field of network security is about:
how bad guys can attack computer networks
how we can defend networks against attacks
how to design architectures that are immune to attacks
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!
Introduction

194. Bad guys can put malware into hosts via Internet
Malware can get in host from a virus, worm, or trojan horse.
Spyware malware can record keystrokes, web sites visited, upload info to collection site.
Infected host can be enrolled in a botnet, used for spam and DDoS attacks.
Malware is often self-replicating: from an infected host, seeks entry into other hosts
Keystroke : frappe au clavier
Botnets= machines zombies (machines contrôlées par des pirates)
Introduction

195. Bad guys can put malware into hosts via Internet
Trojan horse
Hidden part of some otherwise useful software
Today often on a Web page (Active-X, plugin)
Virus
infection by receiving object (e.g., attachment), actively executing
self-replicating: propagate itself to other hosts, users
Worm:
infection by passively receiving object that gets itself executed
self- replicating: propagates to other hosts, users
Sapphire Worm: aggregate scans/sec
in first 5 minutes of outbreak (CAIDA, UWisc data)
Introduction

196. Bad guys can attack servers and network infrastructure
Denial of service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic
select target
target
break into hosts around the network (see botnet)
send packets toward target from compromised hosts
Introduction

197. The 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 C
src:B dest:A payload B
Wireshark software is a (free) packet-sniffer
Introduction

198. The bad guys can use false source addresses
IP spoofing: send packet with false source address A C
src:B dest:A payload B
Introduction

199. The bad guys can record and playback
record-and-playback: sniff sensitive info (e.g., password), and use later
password holder is that user from system point of view C A
src:B dest:A user: B; password: foo B
Introduction

200. Network Security more throughout this course
chapter 8: focus on security
crypographic techniques: obvious uses and not so obvious uses
Introduction

201. 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 models
1.6 Networks under attack: security
1.7 History
Introduction

202. Internet History 1961-1972: Early packet-switching principles
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 program
ARPAnet has 15 nodes
Introduction

203. Internet History 1972-1980: Internetworking, new and proprietary nets
1970: ALOHAnet satellite network in Hawaii
1974: Cerf and Kahn - architecture for interconnecting networks
1976: Ethernet at Xerox PARC
ate70’s: proprietary architectures: DECnet, SNA, XNA
late 70’s: switching fixed length packets (ATM precursor)
1979: ARPAnet has 200 nodes
Cerf and Kahn’s internetworking principles:
minimalism, autonomy - no internal changes required to interconnect networks
best effort service model
stateless routers
decentralized control
define today’s Internet architecture
Introduction

204. Internet History 1980-1990: new protocols, a proliferation of networks
1983: deployment of TCP/IP
1982: smtp 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
Introduction

205. Internet History 1990, 2000’s: commercialization, the Web, new apps
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
Introduction

206. Internet History 2007: ~500 million hosts Voice, Video over IP
P2P applications: BitTorrent (file sharing) Skype (VoIP), PPLive (video)
more applications: YouTube, gaming
wireless, mobility
Introduction

207. Internet 2010
Introduction

208. Internet 2010
Introduction

209. Facebook
Introduction