4
Network AV Infrastructure Prerequisites
Because multicasting video traffic can flood a network and significantly reduce the flow of traffic, it is important to ensure that
your network infrastructure and backbone switches support IGMP Snooping so that your core network is able to ignore the traffic
streams multicasting can generate. By default, all multicast traffic should be blocked until requested by a multicast group
member. Without IGMP Querying/Snooping, multicast traffic is treated in the same manner as a broadcast transmission, which
forwards packets to all ports on the network. With IGMP Querying/Snooping, multicast traffic is only forwarded to ports that
are members of that multicast group. IGMP Snooping generates no additional network traffic, which significantly reduces the
multicast traffic passing through your switch.
Note
: Some switches require that the routing table be pre-loaded so that the switch does not have to interrogate each IP packet to
determine its destination. Static routing can be used to route multicast traffic. Protocols similar to Generic Routing Encapsulation
(GRE) can be used to encapsulate multicast packets in unicast wrappers for point-to-point transmission between switches, and
when the packets arrive at the destination IP address, the unicast wrapper is removed.
2.
Enable Fast Leave
. The switch may also support IGMP Snooping Fast Leave, which shortens the time takes for a device to leave a
group and be made available to join to a different group. A switch can be informed that a device wants to leave a multicast
channel by sending it a IGMP Leave Group packet. Once received, the time it takes for the switch to apply the new configuration
may vary from one switch to another. Most switches have a Fastleave configuration option. When enabled, Fastleave speeds up
the time needed for a port assigned to one multicast group to leave the group and join a different multicast group. This
significantly reduces the video switching time. Always enable the Fastleave option when it is available.
3.
Allow multicast traffic on all network ports through which video streams pass
.
4.
Ensure current Access Control Lists (ACLs) are not filtering multicast or control traffic
.
5.
Remove Flow Control and/or Storm Control on any network port passing the video stream
.
6.
Enable VLANs to separate video traffic from data and voice
.
7.
Enable Jumbo Frames
.
8.
Disable Green Ethernet (or efficiency mode)
. Some switches have the ability to lower the power consumption on the ports as a
“Green” feature. This can cause issues with bandwidth intensive devices (like our encoders and decoders).
I
MPLEMENTATION
C
ONSIDERATIONS
E4200/D4200 devices can be installed on a physically separate network or converged onto an existing GbE network. When
implementing, it is important to decide at the earliest stages of planning if the system will be integrated into the rest of the network
or if it will reside on a dedicated AV network. Each has its own advantages and disadvantages, but wherever possible we recommend
the use of a dedicated AV switch. Using the existing network is of course possible–but it adds extra complexity to the installation and
often removes control of the networking equipment from the site’s AV staff or installer.
The first thing to consider is how much control the install and site teams have over the network configuration. Do they have access
and clearance to change the managed switch configurations on the fly? Is the network administrator willing to make the necessary
changes to support multicast and IGMP traffic on their network? Will they allow the creation of a VLAN or change their existing
VLAN configuration to support the required configuration? If the answer to these questions is no, then it is highly recommended that
the system be installed on a separate dedicated network switch. If this is not an option, then a conversation needs to take place with
the network admin staff to ensure they are aware of the requirements.
I
NSTALLING
O
N
A
C
ONVERGED
N
ETWORK
Figure 1 illustrates how E4200/D4200 endpoints can be installed on an existing (converged) network. When using an existing
infrastructure, dedicated VLANs are recommended to separate the video traffic from other network data. All switches that will
handle AV traffic must be 1 GbE capable per the specifications in
Network Requirements
.
Visionary Solutions recommends that all encoders be turned off before connecting to an existing network. Once connected,
encoders can be turned on one at a time to determine network impact.
