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Multicast Network Programming: Understanding Multicast Communication and Applications - Pr, Study notes of Computer Systems Networking and Telecommunications

Jacksonville State University (JSU)Computer Systems Networking and Telecommunications
Prof. Guillermo A. Francia

An overview of multicast network programming, explaining the concepts of unicast, broadcast, and multicast communication. It covers multicast applications such as videoconferencing, usenet news, and computer configuration. The document also discusses multicast addresses and groups, including the ip address range for class d addresses and the process of creating a multicast group. Sending multicast data is covered, including the use of the multicastsocket class in java for multicast communication.

Typology: Study notes

Pre 2010

Uploaded on 08/19/2009

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MULTICAST NETWORK PROGRAMMING
- Unicast is point-to-point communication.
- Broadcast is communication to all connected members.
- Multicast is communication to a selected set of connected members.
Multicast Applications
- Videoconferencing
- Usenet news
- Computer configuration
Multicast Addresses and Groups
- IP address range: 224.0.0.0 to 239.255.255.255 (i.e. first four bits is 1110)
- These are the class D addresses.
- A multicast group is a set of host that shares a multicast address.
- To create a multicast group, select a random address from 225.0.0.0 to
238.255.255.255. After which, create an InetAddress object for that address
and start sending it data.
- Try pinging all-routers.mcast.net to check multicasting capability of the
network.
Common Permanent Multicast Addresses
- 224.0.0.1 ( all-systems.mcast.net ) โ€“ all systems on the local subnet.
- 224.0.0.2 ( all-routers.mcast.net ) โ€“ all routers on the local subnet.
- 224.0.0.11 ( mobile-agents.mcast.net ) โ€“ mobile agents on the local subnet.
- 224.0.1.1 ( ntp.mcast.net ) โ€“ the network time protocol.
- 224.0.1.20 ( experiment.mcast.net ) โ€“ experiments that do not beyond the
local subnet
- 224.2.X.X (Multicast Backbone on the Internet (MBONE)) โ€“ used for audio
and video broadcasts over the Internet.
Sending Multicast Data
- Communication is connectionless. Datagrams are simply UDP datagrams
addressed to a multicast group.
- Need to create a MulticastSocket and put the multicast address in the
Datagram packet that is to be sent.
- Need to set the Time-to-Live (TTL) value properly for the datagram to be
received properly. TTL ( 0 โ€“ 255 ) is approximately the number of routers a
frame goes through before it is discarded.
- Approximate TTL values are:
0 for localhost; 1 for local subnet; 32 for high-bandwidth site in the
USA; 48 for the USA; 64 for North America, 255 for worldwide.
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MULTICAST NETWORK PROGRAMMING

  • Unicast is point-to-point communication.
  • Broadcast is communication to all connected members.
  • Multicast is communication to a selected set of connected members.

Multicast Applications

  • Videoconferencing
  • Usenet news
  • Computer configuration

Multicast Addresses and Groups

  • IP address range: 224.0.0.0 to 239.255.255.255 (i.e. first four bits is 1110)
  • These are the class D addresses.
  • A multicast group is a set of host that shares a multicast address.
  • To create a multicast group, select a random address from 225.0.0.0 to 238.255.255.255. After which, create an InetAddress object for that address and start sending it data.
  • Try pinging all-routers.mcast.net to check multicasting capability of the network.

Common Permanent Multicast Addresses

  • 224.0.0.1 ( all-systems.mcast.net ) โ€“ all systems on the local subnet.
  • 224.0.0.2 ( all-routers.mcast.net ) โ€“ all routers on the local subnet.
  • 224.0.0.11 ( mobile-agents.mcast.net ) โ€“ mobile agents on the local subnet.
  • 224.0.1.1 ( ntp.mcast.net ) โ€“ the network time protocol.
  • 224.0.1.20 ( experiment.mcast.net ) โ€“ experiments that do not beyond the local subnet
  • 224.2.X.X (Multicast Backbone on the Internet (MBONE)) โ€“ used for audio and video broadcasts over the Internet.

Sending Multicast Data

  • Communication is connectionless. Datagrams are simply UDP datagrams addressed to a multicast group.
  • Need to create a MulticastSocket and put the multicast address in the Datagram packet that is to be sent.
  • Need to set the Time-to-Live (TTL) value properly for the datagram to be received properly. TTL ( 0 โ€“ 255 ) is approximately the number of routers a frame goes through before it is discarded.
  • Approximate TTL values are: 0 for localhost; 1 for local subnet; 32 for high-bandwidth site in the USA; 48 for the USA; 64 for North America, 255 for worldwide.
  • When the datagram is sent, it is the responsibility of the multicast routers to duplicate the data and route it to the multicast group members.

Java MulticastSocket Class

  • The MulticastSocket class is a subclass of the DatagramSocket class:

Public class MulticastSocket extends DatagramSocket

  • Constructors:

MulticastSocket ( ) throws SocketException MulticastSocket ( int portNum ) throws SocketException

  • Methods:

public void joinGroup(inetAddress mAddr) throws IOexception

used to join a multicast group using the address, mAddr. Here is an example:

import java.net.; import java.io.; public class MulticastJoin { public static void main(String [ ] args){ try { MulticastSocket mSocket = new MulticastSocket(4001); InetAddress mAddr = InetAddress.getByName("224.0.0.1"); mSocket.joinGroup(mAddr); byte [ ] buffer = new byte[512]; while (true) { DatagramPacket dp = new DatagramPacket(buffer, buffer.length); mSocket.receive(dp); String str = new String(dp.getData(), "8859_1"); System.out.println(str); }//end of while }//end of try catch (SocketException se){ System.out.println("Socket Exception : " + se); } catch (IOException e) { System.out.println("Exception : " + e); } }//end of main }// end of class definition

public void setInterface(InetAddress addr) throws SocketException

used to select the network interface to be used for multicasting in a multihomed system.

public InetAddress getInterface() throws SocketException

used to determine the address of the interface involved in multicasting.

public void setTimeToLive(int TTL) throws IOException

public int getTimeToLive( ) throws IOException sets/gets the time-to-live value of the datagram packet.

Here is one final example of multicasting:

import java.net.; import java.io.; public class MulticastListener { public static void main( String [ ] args) { InetAddress mAddr=null; MulticastSocket mSocket=null; final int PORT_NUM= 4001; try { mAddr = InetAddress.getByName("audionews.mcast.net"); mSocket = new MulticastSocket(PORT_NUM); String hostname = InetAddress.getLocalHost().getHostName(); byte [ ] buffer = new byte[8192]; mSocket.joinGroup(mAddr); System.out.println("Listening from " + hostname + " at " + mAddr.getHostName()); while (true){ DatagramPacket dp = new DatagramPacket(buffer, buffer.length); mSocket.receive(dp); String str = new String(dp.getData(), "8859_1"); System.out.println(str); }//end of while } catch (SocketException se) { System.out.println("Socket Exception : " + se); } catch (IOException e) { System.out.println("Exception : " + e); } finally { if (mSocket != null){ try { mSocket.leaveGroup(mAddr); mSocket.close(); } catch (IOException e){ } }//end of if }//end of finally

}//end of main }