IP MULTICAST ROUTING Part -3 E-Book

Ummed Singh

• Herausgeber: BookRix
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2023

Beschreibung

 IP multicast routing is a technique used in computer networks to efficiently deliver data packets from a single sender to multiple recipients. It is specifically designed for applications where data needs to be distributed simultaneously to a group of interested receivers. In traditional unicast communication, a sender sends packets to individual receivers using their unique IP addresses. This creates a point-to-point connection between the sender and each receiver, resulting in duplicate transmissions if multiple receivers are interested in the same data. Unicast is inefficient for one-to-many or many-to-many communication scenarios. Multicast routing, on the other hand, allows a sender to transmit a single copy of a packet, and network routers replicate and forward it to all interested receivers. This saves network bandwidth and processing resources, as the data is distributed only once. Multicast routing uses special IP multicast addresses, typically in the range of 224.0.0.0 to 239.255.255.255, to identify multicast groups. To enable IP multicast routing, routers in the network need to support multicast routing protocols such as Protocol Independent Multicast (PIM). These protocols enable routers to exchange information about multicast groups and determine the optimal path for forwarding multicast traffic. Routers maintain multicast routing tables that specify the outgoing interfaces and next-hop routers for forwarding multicast packets. When a sender wants to send data to a multicast group, it encapsulates the data in a multicast packet and sets the appropriate multicast IP destination address. The routers along the path use the multicast routing tables to determine how to forward the packet to all interested receivers. Receivers interested in receiving multicast data join the multicast group by sending a membership request to the nearest router. The router adds the receiver to the multicast distribution tree, and subsequent multicast packets are forwarded. 

Leseprobe

Ummed Singh

IP MULTICAST ROUTING Part -3

Use of multicast routing.

BookRix GmbH & Co. KG81371 Munich

Table of content

What is Multicast Routing?Routing protocols of MulticastDense Mode:What is Multicast PIM Dense Mode?Reverse Path Forwarding (RPF)Sparse Mode:Scoping in MulticastTTL ScopingAdministrative ScopingPIM Dense Neighbors:Prune Message for PIM Dense:PIM Graft Message:What is Multicast PIM Sparse Mode?RP Discovery ProtocolsPIM Sparse ModePIM Sparse NeighborsRendezvous Point (RP)PIM RegisterJoining the RPT (Root Path Tree)What is Multicast PIM Sparse-Dense Mode?

This eBook is based on IP MULTICAST ROUTING that has been collected from different sources and people. For more information about this ebook. Kindly write to [email protected]. I will happy to help you.

Copyright 2023 by Ummed Singh This eBook is a guide and serves as a next part of first & second guides. Previous Parts IP MULTICAST ROUTING Part-1 & 2 have already been published. In addition, please get expert advice or you can write to [email protected] for any query, we will be happy to help you. This book has been written on the advice of many experts and sources who have good command over Networking and routing. They are listed at the end of this book. All images used in this book are taken from the LAB which is created by experts. All rights reserved, including the right to reproduce this book or portions thereof in any form whatsoever. For any query reach out to the author through email.

What is Multicast Routing?

The primary purpose of a router is to efficiently direct packets to their intended destinations. When the router receives an IP packet, it analyzes the destination address and consults its routing table to determine the appropriate next hop for forwarding the packet. To accomplish this, various routing protocols are employed, enabling the router to learn about different networks and populate its routing table accordingly.

Let's use an analogy to explain this process:

Imagine a router as a diligent mail carrier whose job is to deliver letters to specific addresses. Each letter (IP packet) has a destination address written on it. The router looks at the address on the letter and checks its "delivery instructions" stored in the routing table. For unicast traffic (regular one-to-one communication), the router follows the standard delivery process. Suppose Router R1 wants to send a letter to Destination 2.2.2.2. It consults its routing table and finds an entry for the path to 2.2.2.2, indicating that it should send the letter to the next hop, Router R2 (identified by the address 192.168.12.2). By doing so, R1 efficiently forwards the letter towards the destination.

However, when it comes to multicast traffic (one-to-many communication), the routing table is like a directory that only contains instructions for delivering regular letters (unicast addresses). The router lacks information about how to handle multicast addresses, such as 239.1.1.1, as they are not listed in the routing table. Consequently, the router is clueless about the proper destination for multicast traffic. In summary, a router's fundamental role is to route packets based on their destination addresses, utilizing routing protocols to acquire knowledge about various networks and populate its routing table accordingly. For unicast traffic, this process works seamlessly, but for multicast traffic, the router requires additional mechanisms to handle the one-to-many communication effectively.

Routing protocols of Multicast

To effectively route multicast traffic, we rely on multicast routing protocols, which come in two types: Dense Mode and Sparse Mode. Let's delve into Dense Mode multicast routing protocols first.

1.Dense Mode:

Dense Mode multicast routing protocols are best suited for networks where the majority of subnets need to receive the multicast traffic. When a router receives multicast traffic, it floods it out on all of its interfaces, except for the one it received the multicast traffic on. Here's a practical illustration to clarify:

Consider the scenario above, where a video server sends multicast traffic to Router R1. As R1 receives these packets, it floods them on all its interfaces. Routers R2 and R3, in turn, repeat the same process, allowing hosts H2 and H3 to receive the multicast traffic. In this particular example, both hosts are interested in the multicast traffic. However, what if there are hosts that do not wish to receive it? In such cases, a multicast router can inform its neighboring routers that it no longer wants to receive the multicast traffic. This occurs when:

The router has no downstream neighbors that require the multicast traffic.

The router has no hosts on its directly connected interface that require the multicast traffic.

To illustrate this, let's look at the following example: