Moxa VPort 56-2MP-CAM10X-T [35/71] Multicast

VPort 56-2MP System Configuration

4-17

Setting Description Factory Default

Enable ToS Enable ToS for transmitting the video stream with the given

priority

Disable

DSCP Value Set the mapping table with different ToS values 0, 0

NOTE

To configure the ToS values, map to the network environment settings for QoS priority service.

Multicast

The VPort 56-2MP supports the advanced Multicast network protocol IGMP, which can greatly improve the

efficiency of network traffic. In this section, we explain multicasts, multicast filtering, and how multicast can be

implemented on your VPort.

What is Multicast?

A multicast is a packet that is intended for “one-to-many” and “many-to-many” communication. Users

explicitly request to participate in the communication by joining an end-station to a specific multicast group. If

the network is set up correctly, a multicast can only be sent to an end-station or a subset of end-stations on a

LAN or VLAN that belongs to the relevant multicast group. Multicast group members can be distributed across

multiple subnetworks. Therefore, multicast transmissions can occur within a campus LAN or over a WAN. In

addition, networks that support IP multicast send only one copy of the desired information across the network.

The packets are only replicated if they reach a network node that links to two or more members of the multicast

network. Transmitting packets in this way makes more efficient use of network bandwidth. A multicast packet

is identified by the presence of a multicast group address in the destination address field of the packet’s IP

header.

Benefits of Multicast

The benefits of using IP multicast are that it:

• Enables the simultaneous delivery of information to many receivers in the most efficient, logical way.

• Reduces the load on the source (for example, a server) because it does not need to produce multiple copies

of the same data.

• Makes efficient use of network bandwidth and scales well as the number of participants or collaborators

expands.

• Works with other IP protocols and services, such as Quality of Service (QoS).

There are situations where a multicast approach is more logical and efficient than a unicast approach. A typical

use of multicasts is in video-conferencing, in which high volumes of traffic need to be sent to several

end-stations simultaneously, but for which broadcasting that traffic to all end-stations would seriously reduce

network performance. Several industrial automation protocols, such as Allen-Bradley, EtherNet/IP, Siemens

Profibus, and Foundation Fieldbus HSE (High Speed Ethernet), use the multicast approach. These industrial

Ethernet protocols use publisher/subscriber communications models by multicasting packets that could flood a

network with heavy traffic. IGMP provides the ability to prune multicast traffic so that it travels only to those

end destinations that require the traffic, thus reducing the amount of traffic on the Ethernet LAN.