Hi everyone, my name is Nick Russo,
and welcome to Pluralsight's Deep Dive course on IGMP and MLD.
This first module introduces one of my favorite topics, IP multicast.
Let's dive in.
This course assumes that viewers have little to no multicast experience,
so we'll start at the beginning.
I begin with a general overview of IP multicast and the
main protocols upon which it relies.
One of those protocols is IGMP, and I'll demonstrate how it works.
This includes a detailed packet analysis of the entire exchange.
Though PIM is a beast of a protocol and is outside the scope of this course,
I must explain how it works at a high level; otherwise,
testing IGMP and MLD will be pretty boring.
Last,
I'll demonstrate multicast flow across the network to help solidify your
confidence in IGMP and PIM before moving onto more advanced topics.
The best way to explain the value of IP multicast
is by using a pair of examples.
The first example depicts the traffic flows when unicast,
or one-to-one communication, is used to stream a fitness video stream.
The first user begins to stream the live video,
setting up a dedicated delivery flow from the live studio to their living room.
The second user does the exact same thing,
except to a slightly different location.
The third user follows suit, except in a faraway location.
Towards the right side of the diagram,
notice how many additional streams are being pushed onto the network.
These redundant flows consume bandwidth,
which can be costly for companies, especially for high volume flows like video.
Let's redraw the diagram using multicast,
or one-to-many, as a transport mechanism.
The live video begins streaming and unconditionally
sends traffic to the first top router.
Assuming there are interested receivers downstream,
multicast is pulled downwards towards them.
At the final hop, multicast is delivered to the clients,
all of which are viewing the same live video feed.
Do you see how this delivery technique reduces the bandwidth demand?
No matter how many clients tune into this video,
the amount of bandwidth is limited to one video stream.
This can reduce transport costs for enterprises and
service providers in many environments.
A quick note that in IPv4, multicast uses the range 224.0 .0 .0 /4,
also called Class D addressing.
IP multicast is primarily built on three protocols.
IGMP stands for Internet Group Management Protocol.
The word group refers to multicast groups,
and IGMP governs communication between hosts and routers.
IGMP works with IPv4 only.
MLD stands for Multicast Listener Discovery and
performs a function identical to IGMP, except supports IPv6.
PIM stands for Protocol Independent Multicast and is special because
it is the de facto multicast routing protocol.
It enables multicast transport between routers,
but is quite complex and is beyond the scope of this course.
Let's add some business context.
You and I work as network engineers at Globomantics,
a large corporation currently growing through acquisition.
All the blue objects are devices in our existing network.
The Globomantics client is our multicast receiver.
We recent acquired Wired Brain Coffee Company to expand our
product portfolio through diversification.
Their servers are the multicast sources in the network.
Their equipment is shown in orange.
For the time being, the network is IPv4 only,
and I've added simple device names to the devices shown.
Because this is a course on IGMP and MLD as protocols and not a course
on specific operating systems or their command-lines,
all devices in this network are running Cisco iOS.
That just simplifies the demonstrations and keeps the focus on multicast where it belongs.