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Sunday, July 31, 2011

IP Multicast

IP Multicast

IP multicast is a technique for one-to-many communication over an IP infrastructure in a network. It scales to a larger receiver population by not requiring prior knowledge of whom or how many receivers there are. Multicast uses network infrastructure efficiently by requiring the source to send a packet only once, even if it needs to be delivered to a large number of receivers. The nodes in the network take care of replicating the packet to reach multiple receivers only when necessary. For the addressing each group there is a specific class to assign for multicasting. In the following sub content IP multicast rang will show the reserved multicast addresses. These allocations are done only in the IPV4 but in the new version of IPV6 addressing are mainly base on multicasting, there is no any broadcasting.             

Multicast IP range
In IPV4 there are several classes separated to the usage of the  users. The most famous classes are the Class A, Class B and Class C. From these classes the Class D is reserved  for the multicasting.

Class D Addresses Range                 224 .  0  .  0  .  0      -     239 . 255 . 255 . 255

Within this range also there are some sub categories further separate above mentioned IP range.
Reserved for the IANA    :           224 . 0  .  0  . 1     -   224 .  0  .  0 .  255
Global Range                               :         224 . 0  .  1  . 0     -   238 . 255 . 255 . 255

Supposed To Work On The INTERNET
Originally Designed For The Multicast BACKBONE (MBONE)
Designed To Be Assigned Dynamically

Private Range                  :           239 . 0  .  0  . 0     -   239 . 255 . 255 . 255

Designed For Private Use (Within an Organization)
Can Be Assigned Statically

IP Multicast Protocols
IP (Internet Protocol)

Is the principal communications protocol used for relaying packets across an internet work using the Internet Protocol Suite. Responsible for routing packets across network boundaries, it is the primary protocol that establishes the internet.
IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering packets from the source host to the destination host solely based on their addresses. For this purpose, IP defines addressing methods and structures for packet encapsulation. The first major version of IP, now referred to as Internet Protocol Version 4 (IPv4) is the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6) is in active, growing deployment        worldwide.

UDP (User Datagram Protocol)

One of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths. In multicasting the packet transmission is not base on the TCP/IP, they all in UDP base. Due to this there may be several problems are took place because in UDP there is no error correction mechanism applied in this application.

PIM (Protocol Independent Multicast)
                        PIM is Cisco's protocol for router to router tracking the multicast host client to update the multicast server. This comes in three forms, Dense Mode (DM), Sparse Mode (SM) and Sparse Dense mode. 
Dense Mode:  Is the distribution of media to multiple users within a data network where many or most of the users that are connected to the network are part of the multicast group. In dense mode multicast systems, the network is flooded with multicast messages and group members who are not connected to the network are pruned from the multicast tree. Members of a dense mode multicasting system often request connections to the multicast group after the tree has been created.
Dense mode

Sparse Mode: In this method the media traffic is distributed as the dense mode but the initial setup is different from it. Because there is RP (Rendezvous Point) which route the request to the multicast group and pruning the other multicast client if they are not connected to the multicast group. 
Sparse Mode

Sparse Dense Mode: There may be routers in the network configure as sparse mode and dense mode. When the routers are configure as sparse dense mode it can handle for the both routers configure in dense and sparse mode.
IGMP (Internet Group Management Protocol)
This is the processes and procedures that are used to send control messages and coordinate the multicasting of data through an Internet protocol network. IGMP is used to establish membership into a multicast group that is operating within a network. Using IGMP, users can inform routers within the network that they would like to receive media and control messages from a specific multicast group. There are three versions release by the CISCO for IGMP (1,2, and 3).(Now the CISCO has implement in their routers IGMPV2 as the default)

 (Enhanced Interior  Gateway Routing Protocol)
Is the enhance version of IGRP. It allows to fixed many problems in the entire routing table. Along with rapid convergence discussed above, EIGRP reduces bandwidth usage. It does this by not making scheduled updates but sending updates only when topology changes occur. When EIGRP does send an update, the update contains information only on the change in the topology, which requires a path or metric change. Another plus is the fact that only the routers that need to know about the change receive the update.

Throughout this article I hope you may get something. This provides very basic explanation and future will cover more. Comments are well come. Thank you.

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