multicast tutorial v3

Digital Video Solution for Multiple ViewersDigital Video Solution for Multiple Viewers

iMPathN e t w o r k s

Multicast SolutionMulticast Solution

How does it work ?How does it work ?

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July 2005 version 3


Note to Viewer

• The content of this tutorial provides an overview of IGMP used in Digital Multicast networks to familiarize customers with the technology.

• The information in this document is subject to change without notifice.

• While every precaution was taken in the preparation of this document, iMPath assumes no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information contained herein.

• Should you have any questions, please feel free to contact:

Daniel Brisson

Sr. System Engineer

iMPath Networks Inc

Tel: 613-226-4000 x 297

Email: [email protected]

Gilles Lebel

Sr. System Engineer

iMPath Networks Inc

Tel: 613-226-4000 x 224

Email: [email protected]


Typical Network Requirements

Backbone

Monitor any video from anywhere in the network


Multicast

• Multicast. Allows sending one copy of each packet to the group of computers that want to receive it. Multicast can be implemented at the Ethernet link-layer or at the network layer (layer 3 of the OSI model). Computers join and leave multicast groups by using the IGMP (Internet Group Management Protocol) Each host can register itself as a member of selected multicast groups through use of the Internet Group Management Protocol (IGMP).

• Multicast is commonly used in audio and video streaming applications.

– It allows a single source of traffic to be viewed by multiple destinations simultaneously.

– It is designed to provide an efficient transmission using the least amount of bandwidth on the network to save cost.

• IGMP is a standard IP protocol supported by most LAN/WAN vendors in traditional LAN products, ATM, and gigabit Ethernet solutions.


100 Meg

Typical Network Components

Decoder

Digital Backbone; ATM, SONET, LAN, Gigabit Ethernet...

L3 Switch/Router L3 Switch/Router L3 Switch/Router L3 Switch/Router

L3 Switch/Router L3 Switch/Router

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Decoder

Decoder

Decoder

Virtual Matrix Control Console•Displays video to monitors•Controls camera PTZ

Decoder

L2 Switch

Decoder

Decoder

Decoder


Control Center # 2Control Center # 1Typical field encoder collector network

Typical high speed backbone network consisting of Layer 2 or Layer 3 Ethernet Switches.

High Speed Switches are located at major hub locations to collect or drop off data

traffic from this distribution center.

Field hub locations are distributed where the end devices are located. They are

used to collect and distribute traffic for Cameras, Traffic Controllers, Message

Signs and many more.

Several topologies can be used such as Star and Linear topologies being the

most common.

100 Meg 100 Meg


100 Meg

Typical Network Components

Decoder




L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Decoder

Decoder

Decoder


Decoder

L2 Switch

Decoder

Decoder

Decoder



The Control Centers provide video viewing and control of

the Camera PTZ, Traffic Controllers, or Message signs

to name just a few.

100 Meg 100 Meg

Multiple Control Centers may be deployed with this

architecture.

The Virtual Matrix is commonly used in digital video

networks providing video display and control and to operate complementary integrated applications.


100 Meg

Why use IGMP?

Decoder


L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Decoder

Decoder

Decoder


Decoder

L2 Switch

Decoder

Decoder

Decoder



100 Meg 100 Meg

Without IGMP support, multicast traffic is transmitted to all the ports in each network switch.

This unnecessary traffic floods the interfaces and can quickly bog down the entire network.


100Base-T

Why use IGMP?

Decoder


L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Decoder

Decoder

Decoder


Decoder

L2 Switch

Decoder

Decoder

Decoder



100Base-T

For example:With 25 cameras deployed,

each transmitting at 5 Mbps, you will have over 125 Mbps of

combined traffic on your network

125 Mbps of traffic on each 100Base-X interface !!!!!!

125 Mbps of traffic

125 Mbps of traffic

100Base-T


Why use IGMP?

Decoder


L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Decoder

Decoder

Decoder


Decoder

L2 Switch

Decoder

Decoder

Decoder



On a 100 Mbps interface (optics or electrical) you cannot pass more then 100 Mbps of traffic.

PROBLEMCombined 125 Mbps of traffic

on these interfaces.

The capacity of this network is exceeded with only 25 cameras

In fact a typical recommendation in the industry is not to exceed 70% of the bandwidth

in any segment.

For example:With 25 cameras deployed,

each transmitting at 5 Mbps, you will have over 125 Mbps of traffic

on your network

100Base-T 100Base-T100Base-T


Traffic flow with IGMP

Decoder


L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Decoder

Decoder

Decoder


Decoder

L2 Switch

Decoder

Decoder

Decoder



100Base-T 100 Meg

Only 15 Mbps of multicast traffic flows on this link

Only 5 Mbps of Multicast traffic

Flows on this port

Traffic is only present on the backbone when a decoder requests the specific encoder stream

Video Stream 1

Video Stream 2

Video Stream 3

Video Stream 3

100Base-T


How does it work?




Encoder

Decoder


Control Center # 1Typical field encoder collector network

100 Meg

The Encoder is considered a “server” in the IGMP world. It

generates a video signal that will be made available to any

Decoder (client) on the network.

The Encoder transmits a signal with a distinct destination address.

Between 224.x.x.x to 239.x.x.x.(some addresses are reserved for

specific applications)

The Routers build and share a table of all the “IGMP servers” available on the network. They keep a table of all the available

Multicast Addresses

This Router will not forward any of the multicast traffic until it receives a request from a decoder (client)


Here is how it works - Joining a Group




Encoder

Decoder



100 Meg

The operator makes a request to see a video on a specific monitor

The Virtual Matrix application forwards a message to the decoder to view a specific video stream. (request

to see video from address 224.168.32.55)

The Decoder registers this address in its table and forwards the request (join the multicast group) to the

network

The Router responds and forwards the traffic to this specific port on the Ethernet switch.

224.168.32.55

1

2

3

4





Encoder

Decoder



100 Meg

When the operator makes a request to change the view from video A to

video B…

… the Virtual Matrix application ONLY forwards a single message to the decoder to view video B

stream. (request to see video from address 224.168.32.107)

The Decoder un-registers from the present viewing address (a “leave” message is sent) followed by

a “join” message which is sent with the new multicast stream.

Encoder

Video AVideo B

224.168.32.55224.168.32.107

The Router stops video stream A, adds the new video B to the group, and releases the traffic for video B to

this specific port on the Ethernet switch.

1

2

3

4

Here is how it works - Leaving a Group


Choosing your network elements

• There are several types of digital network technologies to choose from.

– SONET and ATM are still applicable but are now rarely deployed on new installations.

– Ethernet is the most common technology due to the wide range of affordable products available from many manufacturers and the familiarity with Ethernet and IP technology.

– The components more commonly used to build Ethernet networks are Ethernet Switches.

– A high capacity Ethernet network is often referred to as the “backbone” network.


Choosing your network switches

• Choosing Ethernet Switches for your backbone network could depend on several factors…

– Your specific port density requirements

– Network topology

– Temperature hardened requirements (outdoor)

– Support for IGMP protocol

– Your preferred manufacturer

– Specific product functionality

• This tutorial will explore a few topologies and the IGMP functionality of different Ethernet Switches.


Ethernet Switch selection

• There are 3 types of Ethernet Switches

– Layer 2 Switch• Distributes traffic to each destination using MAC addressing table.

• Broadcasts the Multicast traffic across all its ports – There are no Multicast traffic filters with these switches

– Layer 2 Switch with IGMP Snooping• Distributes traffic to each destination using MAC addressing table

• Provides limited control of Multicast traffic to prevent broadcast of the traffic to all ports.

• Layer 3 IGMP master is needed in the network

– Layer 3 Switch/Router with IGMP • Distributes traffic to each destination using MAC addressing table.

• Distributes traffic to each destination using IP subnet addressing table.

• Provides maximum control of Multicast traffic to prevent broadcast of the traffic to all ports and all subnet.


Layer 2 SwitchFunctionality

L2 Switch

Encoder Encoder Encoder

L2 Switch

Decoder DecoderEncoder5

Mbp

s

15 M

bps

5 M

bps

15 M

bps

5 M

bps

15 M

bps

5 M

bps

15 M

bps

0 M

bps

20 M

bps

0 M

bps

20 M

bps

The combined Multicast Traffic is sent to all ports in each Switch

This is a valid network topology for small networksEnsure no more then 70% of the bandwidth of the lowest negotiated Ethernet

port speed is used. Not to be used with 10 Meg Half Duplex devices.

Bandwidth Restriction applies.

Combined 20 Mbps Multicast Video Traffic

5 Mbps Multicast Video per Encoder

20 Mbps


Layer 3 Switch/Router with IGMPFunctionality

L3 Switch


L3 Switch

Decoder DecoderEncoder5

Meg

5 M

eg

5 M

eg

5 M

eg

5 M

eg

Multicast traffic is filtered out at each switch Only the required traffic is transmitted on the network

This is a valid network topology for any network - No topology restrictions

10 Mbps

Deploying a Layer 3 at each collector HUB could be expensive

5 M

bps

0 M

bps

5 M

bps

0 M

bps

5 M

bps

0 M

bps

5 M

bps

0 M

bps

0 M

bps

0 M

bps

Combined 10 Mbps Multicast Video Traffic

5 M

bps

5 M

bps


Layer 2 & 3 SwitchTypical Topology

Decoder Decoder

0 M

bps

5 M

bps

0 M

bps

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

The L3 Switch controls all Multicast traffic. In and out.

It eliminates transmitting the combined multicast traffic unnecessarily to

each port.

0 Mbps

L3 Switch

The use of L2 Switch in this topology is very common. Multicast traffic is repeated on all ports of the switch within the segment but traffic from other segments is not seen. Traffic between the segments is

controlled by the L3 switch. Economical and practical solution that is very easy to deploy.

35 Mbps Combined Multicast Video


5 M

bps


Layer 2 & 3 SwitchTypical Topology – Industry concern

Decoder Decoder

0 M

eg

5 M

eg

0 M

eg

5 M

eg

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

35 Mbps

35 Mbps

0 Mbps L3 Switch

This solution is very effective and greatly simplifies Network Management.

However, it is sometimes necessary to filter IGMP traffic at the edge.Such solutions were previously overlooked for economical reasons.

An economical solution now exist: L2 switch with IGMP Snooping


Overview of OSI Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Layer 7.

Layer 6

Layer 5

Layer 4

Layer 3- This layer defines the addressing and routing structure of the Inter-networkThis layer controls the Multicast traffic on the network.

Layer 2- This layer defines the framing, addressing and error control of Ethernet packets. Port addressing uses MAC address of each device.This layer effectively treats Multicast traffic as broadcast traffic.

Layer 1

Traditionally performed by Routers

Performed by Switches

$$


Overview of OSI Model

Network

Data Link

$

$

New product introduced

$Layer 2 with IGMP Snooping- Layer 2 Switches with IGMP

Snooping functionality are now available. Provide all the functionality of a Layer 2 switch with PARTIAL IGMP support.This layer provides some Multicast traffic control on the network.

This product can be used instead of expensive Routers

Available with different port densities.100Base-Fx to Gigabit trunks.

Temperature HardenedWide choice of manufacturers and products.

Layer 3- This layer defines the addressing and routing structure of the Inter-networkThis layer controls the Multicast traffic on the network.

Layer 2- This layer defines the framing, addressing and error control of Ethernet packets. Port addressing uses MAC address of each device.This layer effectively treats Multicast traffic as broadcast traffic.


Layer 2 Switch with IGMP SnoopingFunctionality

L2 with IGMP Snooping


L3 Switch

Decoder DecoderEncoder

Valid network topology for any networkNo topology restrictions

Local traffic is filtered out at each switch. Eliminates multicasts traffic to all the ports

All the multicast traffic is sent to the central site. The L3 switch still controls the IGMP table of the network.

5 M

bps

0 M

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5 M

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5 M

bps

0 M

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5 M

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0 M

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5 M

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0 M

bps



L2 with Snooping & L3 SwitchTypical Topology

Decoder Decoder

0 M

bps

5 M

bps

0 M

bps

5 M

bps

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

These links contain the combined Multicast traffic

from all the Encoders in their segment i.e. 35 Mbps.

L3 Switch

Very practical implementationManagement of the Ethernet Switches is required.

Switches with IGMP Snooping eliminate flooding local interfaces

with Multicast traffic.

Bandwidth Restriction applies. No more “70% of link capacity”

35 Mbps

35 Mbps


How does it work?From the Encoder to the L3 Switch

Decoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

The L3 Switch forwards the IGMP Query on all its ports to determine if there are any devices that wish

to subscribe to a Multicast Group.

0 Mbps L3 Switch

Each Encoder forwards a constant Multicast stream

to the Ethernet Switch(224-239.x.x.x)

The L2 Switch detects/identifies the

Multicast stream source and logs internally what

port this stream came from.

The L2 Switch with IGMP Snooping detects the

Query message from the L3 Switch and logs

internally the ports that pass traffic to the L3

Switch

L2 Switch eliminates flooding of the local

interfaces and passes the Multicast traffic to the L3

Switch for processing.

0 M

bps

5 M

bps

35 Mbps


How does it work?From the Encoder to the L3 Switch

Decoder

0 M

bps

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

The L3 Switch detects the Multicast traffic arriving on this interface and logs internally all

the Multicast address for distribution.

0 Mbps

L3 Switch

At this point, the Multicast traffic from all Encoders is

combined on this link towards the L3 Switch.

35 Mbps Combined Multicast Traffic

5 M

bps


How does it work?From the L3 Switch to the Decoder

Decoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

0 Meg L3 Switch


Control Center # 1The operator makes a request to see

a video on a specific monitor

The Virtual Matrix application forwards a message to the decoder to view a specific

video stream on a specific monitor. (request to see video from address 224.168.32.55)

The Decoder registers this address in its table and forwards the request (“join” the multicast group) to

the network

The L3 Switch responds and releases the traffic to this specific port on the Ethernet switch.

35 Mbps Combined Multicast Traffic

0 M

bps

5 M

bps


How does it work?From the L3 Switch to the Decoder

Decoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

35 Mbps

0 Meg L3 Switch


Control Center # 1

The operator makes a NEW request to see a video on a specific monitor

The Virtual Matrix application forwards a message to the decoder to view a specific video stream.

(224.168.32.140)

The Decoder registers this address in its table and forwards two messages to the switch

The L3 Switch responds by stopping the stream 224.168.32.55

The Decoder sends an IGMP “leave” message.No longer need to receive the Multicast steam

(224.168.32.55)

The Decoder sends an IGMP request to join

(224.168.32.140)

The L3 Switch responds by forwarding the stream 224.168.32.140

0 M

bps

5 M

bps


How does it work?Typical Star Topology

Decoders

L3 Switch

Multicast traffic flows from all Encoders to the

L3 Switch

L3 Switch controls the distribution of all Multicast traffic to Decoders

Encoder

L2 Switch with IGMP Snooping


Watch for…Limitations of IGMP Snooping

Decoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L3 Switch

L2 Switches with IGMP Snooping have limitations.

In the event of a communication break between the L2 and L3

switches, the L2 IGMP Snooping switch will behave like a L2 switch

A few minutes after loss of signal, the switches may* flood all Multicast signals

to the ports of every switch * Behavior may differ depending on switch manufacturer.

If this is a Gig E link and you have more then 70 Meg of Video traffic, no

other application will run on this network until the link is re-established.

Maximum port traffic will be exceeded.


Watch for…Distributed Control Centers

L2 Snooping

Encoder

L3 Switch


L2 Snooping

Control Center # 2

Decoder Decoder

Control Center # 1

Multicast traffic flows to the L3 Switch

Multicast “join” request sent to the L3

Switch

This switch will allow traffic from network A to flow to the Decoder when

a “join” request is received.

Video Source A

NetworkA



L2 Snooping

Encoder

L3 Switch


L2 Snooping

Control Center # 2

Decoder Decoder

Control Center # 1

This switch requires connectivity to the L3 switch to provide local “join”

It will not be possible to view any video. Not even local video.

Communication break

This limitation can be eliminated by installing an L3 Switch at all Control Centers.

Video Source A

NetworkA



L2 Snooping

Encoder

L3 Switch


L2 Snooping

Control Center # 2

Decoder Decoder

Control Center # 1

L2 Snooping

EncoderEncoder

All Multicast traffic will flow to the L3 SwitchMulticast traffic flows to the L3 Switch

This switch will only forward traffic from video source B when the

Decoder requests to join a video from source B

Multicast “join” requests are sent to the L3 Switch

Video Source A Video Source B


Configuration TipsL2 Switch with IGMP Snooping

L2 Snooping

Encoder

L3 Switch


L2 Snooping

Control Center # 2

Decoder Decoder

Control Center # 1

L2 Snooping

EncoderEncoder

Two IGMP configuration modes can be set in the switches.

Passive Passive Passive

This switch generates IGMP Queries. It is considered as the

“Master” or the “Active” device

In this topology, there can only be one Master unit.


Configuration TipsL2 Switch with IGMP Snooping

L2 Snooping

Encoder Decoder DecoderEncoder

L2 Snooping

Control Center # 2

Decoder Decoder

Control Center # 1

L2 Snooping

EncoderEncoder

Some L2 Switches with IGMP Snooping can be configured as Passive or Active


This switch generates IGMP Queries. It is considered as the

“Master” or the “Active” device

In this topology, there can only be one Master unit.

L2 Snooping

This topology should only be considered for small networks. Most L2 IGMP Snooping Switches do not have the capacity to handle

a large table of IGMP Multicast traffic.


Multi-Vendor SupportAvoid…Mixing IGMP Snooping Switches

L2 Snooping

Encoder Decoder DecoderEncoder

L2 Snooping

Control Center # 2

Decoder Decoder

Control Center # 1

L2 Snooping

EncoderEncoder


L2 Snooping

Although some L2 IGMP Snooping Switch manufacturers may imply that they can integrate into a multi-vendor solution, this is not recommended since

IGMP Snooping is not an RFC standard. Implementation differs between manufacturers. (Proven to fail in our labs)

Active

Manufacturer A Manufacturer A Manufacturer B Manufacturer B


Multi-Vendor SupportRecommendation …

Decoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L3 Switch

High end products should be used for L3 Switch to control all your Multicast traffic. Products from Foundry, Extreme, Nortel and

Cisco (to name just a few) should be used.

These are typically non-hardened products

Use L2 with IGMP Snooping

“Hardened” products are available

Keep it simple.A single manufacturer

solution is recommended

Several vendors offer a wide range of products for this application. Several

(including Magnum 6Ks from GarrettCom) were tested at iMPath with

positive results.


Multi-Vendor SupportAvoid…

Decoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L2 Switch

Encoder

L3 Switch

Do not MIX different vendors IGMP Snooping switches in this topology. It will most-likely not

work

Manufacturer A

Manufacturer A

Manufacturer A

Manufacturer A

Manufacturer A

Manufacturer B

Manufacturer B

Although some L2 IGMP Snooping Switch vendors may suggest they can integrate into a multi-vendor

solution, this is not recommended since IGMP Snooping is not a RFC standard. Implementation differs between manufacturers. (Proven to fail in

our labs)


Manufacturer B

Manufacturer C

Manufacturer A

Manufacturer A

Manufacturer B

Manufacturer C

Multi-Vendor SupportRecommendation…

Decoder

L3 Switch

When multi-vendor solutions are used, it is recommended to use a single manufacturer solution on each link. Use the L3 Switch to separate each group (manufacturer) of L2 IGMP switches.

This is the most reliable topology to support multi-vendor solutions.


Credits

• The information shared in this document was obtained by performing numerous IGMP related tests at iMPath facilities between January and June 2005.

– Tests were performed using L2, L2 IGMP Snooping, and L3 switches.

– Over 30 MPEG-2 iMPath Encoders were used during these tests to validate the proper function and performance of the switches under stress.

• iMPath would like to thank its business partners for their participations and providing equipment and support during the research phase.

– L2 IGMP Snooping switch manufacturers• GarrettCom, as well as Etherwan, IFS, Ruggedcom

– L3 switch manufacturer• Foundry Networks

• Test Coordinator

– iMPath Networks, Daniel Brisson, Sr. System Engineer

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