serversocket
DESCRIPTION
ServerSocket. 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) - PowerPoint PPT PresentationTRANSCRIPT
ServerSocket
H. Fauconnier 1-1M2-Internet Java
Principe
1. Création d’un ServerSocket par constructeur
2. Association (bind) de la socket à une adresse et un port ((1) et (2) peuvent être simultanés)
3. Écoute et connexion par accept1. Communication getInputStream et
getOutputStream2. close (par le client ou le serveur ou les
deux)4. Aller en (2)
(en général 3 est dans une thread)
H. Fauconnier M2-Internet Java 2
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
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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 ); } } }
H. Fauconnier M2-Internet Java 4
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
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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); }}
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Connexion accept()
crée et retourne une nouvelle socket pour la connexion associée (IP, port)(IP, port)
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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( );}
H. Fauconnier M2-Internet Java 8
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;
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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 { try { if (connection != null) connection.close(); } catch (IOException ex) {} } } } catch (IOException ex) { System.err.println(ex); } }
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Fermeture
public void close( ) throws IOException
Ferme le ServerSocket et toutes les connexions créées par accept sur la ServerSocket
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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"); } } }
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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); } }
H. Fauconnier M2-Internet Java 13
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); } try { in.close(); out.close(); } catch (IOException ex) { ex.printStackTrace();} } }
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Remarques
utilisation des threads pour traiter le service et éviter de faire attendre les clients
on peut aussi utiliser des entrées/sorties non bloquantes
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Autres méthodes
public InetAddress getInetAddress( ) public int getLocalPort( )
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Options
SO_TIMEOUT SO_REUSEADDR SO_RCVBUF public void setPerformancePreferences(int
connectionTime, int latency, int bandwidth
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Socket UDP
H. Fauconnier 1-18
M2-Internet Java
UDP
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M2-Internet Java 20
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
Running example
Client: 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
Client: Receives line of text Displays
M2-Internet Java 21H. Fauconnier
M2-Internet Java 22
Client/server socket interaction: UDP
Server (running on hostid)
closeclientSocket
read datagram fromclientSocket
create socket,
clientSocket = DatagramSocket()
Client
Create datagram with server IP andport=x; send datagram via clientSocket
create socket,port= x.serverSocket = DatagramSocket()
read datagram fromserverSocket
write reply toserverSocketspecifying client address,port number
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M2-Internet Java 23
Example: Java client (UDP)
sendP
ack
et
to network from network
rece
iveP
ack
et
inF
rom
Use
r
keyboard monitor
Process
clientSocket
UDPpacket
inputstream
UDPpacket
UDPsocket
Output: sends packet (recallthat TCP sent “byte stream”)
Input: receives packet (recall thatTCP received “byte stream”)
Clientprocess
client UDP socket
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M2-Internet Java 24
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();
Createinput stream
Create client socket
Translate hostname to IP
address using DNS
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M2-Internet Java 25
Example: Java client (UDP), cont.
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(); }
}
Create datagram with data-to-send,
length, IP addr, port
Send datagramto server
Read datagramfrom server
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M2-Internet Java 26
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);
Createdatagram socket
at port 9876
Create space forreceived datagram
Receivedatagram
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M2-Internet Java 27
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 addrport #, of
sender
Write out datagramto socket
End of while loop,loop back and wait foranother datagram
Create datagramto send to client
H. Fauconnier
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?
M2-Internet Java 28H. Fauconnier
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)
H. Fauconnier M2-Internet Java 29
Exemple
String s = "On essaie…";byte[] data = s.getBytes("ASCII");
try { InetAddress ia =
InetAddress.getByName("www.liafa.jussieu.fr"); int port = 7;// existe-t-il? DatagramPacket dp = new DatagramPacket(data,
data.length, ia, port);}catch (IOException ex)}
H. Fauconnier M2-Internet Java 30
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)
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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)
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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("www.liafa.jussieu.fr"); 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); } }}
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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)
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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 }}
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Envoyer et recevoir
public void send(DatagramPacket dp) throws IOException
public void receive(DatagramPacket dp) throws IOException
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Un exemple: Echo
UDPServeur UDPEchoServeur
UDPEchoClient• SenderThread• ReceiverThread
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Echo: UDPServeur
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);}
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UDPEchoServeur
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()); try { 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); } }}
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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) { System.err.println(ex); }
} // end lancer}
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ReceiverThread
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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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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SenderThread
//… 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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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 void disconnect( ) public int getPort( ) public InetAddress getInetAddress( ) public InetAddress getRemoteSocketAddress( )
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Options
SO_TIMEOUT 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
H. Fauconnier M2-Internet Java 45
Multicast
46H. Fauconnier
M2-Internet Java
M2-Internet Java 4-47
R1
R2
R3 R4
sourceduplication
R1
R2
R3 R4
in-networkduplication
duplicatecreation/transmissionduplicate
duplicate
Broadcast Routing Deliver packets from srce to all other nodes Source duplication is inefficient:
Source duplication: how does source determine recipient addresses
H. Fauconnier
M2-Internet Java 4-48
In-network duplication
Flooding: when node receives brdcst pckt, sends copy to all neighbors Problems: cycles & broadcast storm
Controlled flooding: node only brdcsts pkt if it hasn’t brdcst same packet before Node keeps track of pckt ids already brdcsted Or reverse path forwarding (RPF): only forward
pckt if it arrived on shortest path between node and source
Spanning tree No redundant packets received by any node
H. Fauconnier
M2-Internet Java 4-49
A
B
G
DE
c
F
A
B
G
DE
c
F
(a) Broadcast initiated at A (b) Broadcast initiated at D
Spanning Tree
First construct a spanning tree Nodes forward copies only along
spanning tree
H. Fauconnier
M2-Internet Java 4-50
A
B
G
DE
c
F1
2
3
4
5
(a)Stepwise construction of spanning tree
A
B
G
DE
c
F
(b) Constructed spanning tree
Spanning Tree: Creation Center node Each node sends unicast join message to
center node Message forwarded until it arrives at a node already
belonging to spanning tree
H. Fauconnier
Multicast
Groupe: adresse IP de classe D Un hôte peut joindre un groupe
Protocole pour établir les groupes (IGMP)
Protocole et algorithme pour le routage
M2-Internet Java 4-51
H. Fauconnier
IGMP
IGMP (internet Group Management Protocol Entre un hôte et son routeur (multicast)
• Membership_query: du routeur vers tous les hôtes pour déterminer quels hôtes appartiennent à quels groupes
• Membership_report: des hôtes vers le routeur• Membership_leave: pour quitter un groupe
(optionnel)
M2-Internet Java 4-52
H. Fauconnier
Multicast Routing: Problem Statement Goal: find a tree (or trees) connecting
routers having local mcast group members tree: not all paths between routers used source-based: different tree from each sender to rcvrs shared-tree: same tree used by all group members
Shared tree Source-based treesH. Fauconnier 1-
53M2-Internet Java
Approaches for building mcast treesApproaches: source-based tree: one tree per source
shortest path trees reverse path forwarding
group-shared tree: group uses one tree minimal spanning (Steiner) center-based trees
…we first look at basic approaches, then specific protocols adopting these approaches
H. Fauconnier 1-54
M2-Internet Java
Shortest Path Tree
mcast forwarding tree: tree of shortest path routes from source to all receivers Dijkstra’s algorithm
R1
R2
R3
R4
R5
R6 R7
21
6
3 45
i
router with attachedgroup member
router with no attachedgroup memberlink used for forwarding,i indicates order linkadded by algorithm
LEGENDS: source
H. Fauconnier 1-55
M2-Internet Java
Reverse Path Forwarding
if (mcast datagram received on incoming link on shortest path back to center)
then flood datagram onto all outgoing links else ignore datagram
rely on router’s knowledge of unicast shortest path from it to sender
each router has simple forwarding behavior:
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M2-Internet Java
Reverse Path Forwarding: example
• result is a source-specific reverse SPT– may be a bad choice with asymmetric links
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R2
R3
R4
R5
R6 R7
router with attachedgroup member
router with no attachedgroup memberdatagram will be forwarded
LEGENDS: source
datagram will not be forwarded
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M2-Internet Java
Reverse Path Forwarding: pruning forwarding tree contains subtrees with no mcast
group members no need to forward datagrams down subtree “prune” msgs sent upstream by router with no
downstream group members
R1
R2
R3
R4
R5
R6 R7
router with attachedgroup memberrouter with no attachedgroup member
prune message
LEGENDS: source
links with multicastforwarding
P
P
P
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M2-Internet Java
Shared-Tree: Steiner Tree
Steiner Tree: minimum cost tree connecting all routers with attached group members
problem is NP-complete excellent heuristics exists not used in practice:
computational complexity information about entire network needed monolithic: rerun whenever a router needs
to join/leave
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M2-Internet Java
Center-based trees
single delivery tree shared by all one router identified as “center” of tree to join:
edge router sends unicast join-msg addressed to center router
join-msg “processed” by intermediate routers and forwarded towards center
join-msg either hits existing tree branch for this center, or arrives at center
path taken by join-msg becomes new branch of tree for this router
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M2-Internet Java
Center-based trees: an example
Suppose R6 chosen as center:
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R3
R4
R5
R6 R7
router with attachedgroup member
router with no attachedgroup member
path order in which join messages generated
LEGEND
21
3
1
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M2-Internet Java
Internet Multicasting Routing: DVMRP
DVMRP: distance vector multicast routing protocol, RFC1075
flood and prune: reverse path forwarding, source-based tree RPF tree based on DVMRP’s own routing tables
constructed by communicating DVMRP routers no assumptions about underlying unicast initial datagram to mcast group flooded
everywhere via RPF routers not wanting group: send upstream
prune msgs
H. Fauconnier 1-62
M2-Internet Java
DVMRP: continued…
soft state: DVMRP router periodically (1 min.) “forgets” branches are pruned: mcast data again flows down unpruned branch downstream router: reprune or else continue to
receive data routers can quickly regraft to tree
following IGMP join at leaf odds and ends
commonly implemented in commercial routers Mbone routing done using DVMRP
H. Fauconnier 1-63
M2-Internet Java
Tunneling
Q: How to connect “islands” of multicast routers in a “sea” of unicast routers?
mcast datagram encapsulated inside “normal” (non-multicast-addressed) datagram
normal IP datagram sent thru “tunnel” via regular IP unicast to receiving mcast router
receiving mcast router unencapsulates to get mcast datagram
physical topology logical topology
H. Fauconnier 1-64
M2-Internet Java
PIM: Protocol Independent Multicast
not dependent on any specific underlying unicast routing algorithm (works with all)
two different multicast distribution scenarios :
Dense: group members densely
packed, in “close” proximity.
bandwidth more plentiful
Sparse: # networks with group members
small wrt # interconnected networks
group members “widely dispersed”
bandwidth not plentiful
H. Fauconnier 1-65
M2-Internet Java
Consequences of Sparse-Dense Dichotomy: Dense group membership by
routers assumed until routers explicitly prune
data-driven construction on mcast tree (e.g., RPF)
bandwidth and non-group-router processing profligate
Sparse: no membership until
routers explicitly join receiver- driven
construction of mcast tree (e.g., center-based)
bandwidth and non-group-router processing conservative
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M2-Internet Java
PIM- Dense Mode
flood-and-prune RPF, similar to DVMRP but underlying unicast protocol provides RPF info for
incoming datagram less complicated (less efficient) downstream flood than
DVMRP reduces reliance on underlying routing algorithm
has protocol mechanism for router to detect it is a leaf-node router
H. Fauconnier 1-67
M2-Internet Java
PIM - Sparse Mode
center-based approach router sends join msg
to rendezvous point (RP) intermediate routers
update state and forward join
after joining via RP, router can switch to source-specific tree increased performance:
less concentration, shorter paths
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R6R7
join
join
join
all data multicastfrom rendezvouspoint
rendezvouspoint
H. Fauconnier 1-68
M2-Internet Java
PIM - Sparse Mode
sender(s): unicast data to RP,
which distributes down RP-rooted tree
RP can extend mcast tree upstream to source
RP can send stop msg if no attached receivers “no one is listening!”
R1
R2
R3
R4
R5
R6R7
join
join
join
all data multicastfrom rendezvouspoint
rendezvouspoint
H. Fauconnier 1-69
M2-Internet Java
Multicast
Géré par les routeurs Pas de garantie…
Importance du ttl• (Évaluation)
– Local:0
– Sous-réseau local:1
– Pays:48
– Continent:64
– Le monde:255
M2-Internet Java 4-70
H. Fauconnier
Multicast
Un groupe est identifié par une adresse IP (classe D) entre 224.0.0.0 et 239.255.255.255
Une adresse multicast peut avoir un nom Exemple ntp.mcast.net 224.0.1.1
M2-Internet Java 4-71
H. Fauconnier
Sockets multicast
Extension de DatagramSocket public class MulticastSocket extends
DatagramSocket
Principe: Créer une MulticastSocket Rejoindre un group: joinGroup()
• Créer DatagramPacket – Receive()
• leaveGroup() Close()
H. Fauconnier M2-Internet Java 72
Création
try { MulticastSocket ms = new MulticastSocket( ); // send datagrams...}catch (SocketException se){System.err.println(se);}-------try { SocketAddress address = new
InetSocketAddress("192.168.254.32", 4000); MulticastSocket ms = new MulticastSocket(address);
// receive datagrams...}catch (SocketException ex) {System.err.println(ex);}
H. Fauconnier M2-Internet Java 73
Création
try { MulticastSocket ms = new MulticastSocket(null);ms.setReuseAddress(false); SocketAddress address = new InetSocketAddress(4000); ms.bind(address); // receive datagrams...
}catch (SocketException ex) { System.err.println(ex);}
H. Fauconnier M2-Internet Java 74
Rejoindre…
try { MulticastSocket ms = new MulticastSocket(4000);InetAddress ia = InetAddress.getByName("224.2.2.2"); ms.joinGroup(ia); byte[] buffer = new byte[8192]; while (true) {
DatagramPacket dp = new DatagramPacket(buffer, buffer.length); ms.receive(dp);
String s = new String(dp.getData( ), "8859_1");System.out.println(s);
}}catch (IOException ex) { System.err.println(ex);}
H. Fauconnier M2-Internet Java 75
send
try { InetAddress ia = InetAddress.getByName("experiment.mcast.net");byte[] data = "un packet…\r\n".getBytes( ); int port = 4000;DatagramPacket dp = new DatagramPacket(data,
data.length, ia, port); MulticastSocket ms = new MulticastSocket( );ms.send(dp,64);
}catch (IOException ex) {System.err.println(ex);}
H. Fauconnier M2-Internet Java 76