3
Network AV Infrastructure Prerequisites
C
HOOSING
A
N
E
THERNET
S
WITCH
Switches must support these functions:
•
Jumbo Frames (enabled)
•
IGMP Snooping
•
IGMP Querier
•
IGMP Snooping Fast Leave
If the switches are used for multi-switch networking, they must also support PIM Routing (Sparse, Dense, or Sparse-Dense).
These features may be helpful as well:
•
Dynamic multicast router port
•
Forwarding unknown multicast to multicast router ports only
Any network switch should have a backplane capacity of at least (2 x 1000-Mbps x N) where N is the number of ports on the switch
passing the video traffic. For example, a 24-port switch where all available ports may be used to pass video traffic should have a (2 x
1000 x 24) = 48Gbps backplane. One channel of encoder video can be sent or received from each port in this switch example
although full bandwidth may not be used at any one time.
The maximum distance between devices is 100m (328ft) over CAT 5e (or better) cable. This distance can be extended in increments of
100m (328ft) by using a gigabit switch as a repeater between devices. Copper to fiber adapters can extend the maximum distance
between devices up to 10km through the use of fiber.
Since different brands and models of switches perform differently when handling multicast IP packets, functional verification and
pressure testing are also recommended in any installation. Switches that perform well in smaller installations may not work well in
larger installations. Recommended configuration settings may vary based on your switch.
Visionary Solutions offers sample switch configuration files, optimized for Network AV, for certain switch brands/models for testing
purposes. Contact
to obtain the files.
S
WITCH
G
UIDELINES
1.
Enable IGMP querying and snooping (set IGMP Version to IGMP V2 if the switch is capable)
. To enable the transmission of a
source to multiple destinations, E4200/D4200 devices make use of multicast. The default behavior of a layer-2 switch is to
broadcast those packets, which means that every packet will be transmitted to all possible destinations. IGMP snooping checks
IGMP packets passing through the network, picks out the group registration, and configures multicasting accordingly. A layer-2
switch supporting IGMP Snooping can passively snoop on IGMP Query, Report, and Leave (IGMP version 2) packets transferred
between IP multicast routers/switches and IP multicast hosts to determine the IP multicast group membership. This is why any
network switch used with E4200/D4200 must support IGMP Snooping. Our end points use IGMP protocol to assign the end
points into multicast groups and the router uses IGMP snooping to efficiently route multicast packets only to the receivers that
want to receive them.
IGMP Snooping is used to identify multicast IP packets, assign IP packets into multicast groups so that the router only sends to
devices that want to receive the packets, establish membership in a multicast group, and register a router to receive designated
multicast traffic. Multicast filtering is achieved by dynamic group control management. Many switches have the IGMP Snooping
feature disabled by default and manual configuration is required. Often, checking the
Enable IGMP Snooping
option is the only
setting needed to enable IGMP Snooping. Implementing IGMP Snooping is vendor specific and additional configuration is often
needed.
IGMP Snooping Querier is used to send out group membership queries on a timed interval, retrieve IGMP membership reports
from active members, and update the group membership tables. The Leave Group packet is sent when a device wants to leave a
group.
