Omron SYSMAC CJ1W-EIP21, Operation Manuals

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2-5
2 Installing Ethernet Networks
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
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The following network devices are manufactured by OMRON for EtherNet/IP networks.

Unmanaged Layer 2 (L2) Ethernet Switches
These Ethernet switches use the Ethernet MAC address to switch ports. Ordinary Ethernet switches
have this function. Ethernet switch functions and settings cannot be changed.

Managed Layer 2 (L2) Ethernet Switches
These Ethernet switches use the Ethernet MAC address to switch ports. Ethernet switch functions
and settings can be changed with special software tools for Ethernet switches running on a network
node. You can also collect analytical data. These Ethernet switches provide more-advanced func-
tions than unmanaged layer 2 Ethernet switches.
This section describes the Ethernet switch functions that are important for an EtherNet/IP network. For
an EtherNet/IP Unit, consider whether the Ethernet switch supports these functions when you select
the Ethernet switch.
• Multicast filtering
• QoS (Quality of Service) for TCP/UDP port numbers (L4)

Multicast Filtering
Multicast filtering transfers multicast packets to the specific nodes only. This function is implemented
in the Ethernet switch as IGMP snooping or GMRP. “Specific nodes” are nodes equipped with an
IGMP client that have made transfer requests to the Ethernet switch. (OMRON EtherNet/IP Units
are equipped with an IGMP client.) When the Ethernet switch does not use multicast filtering, multi-
cast packets are sent to all nodes, just like broadcast packets, which increases the traffic in the net-
work. Settings must be made in the Ethernet switch to enable this function. There must be enough
multicast filters for the network.

QoS (Quality of Service) Function for TCP/UDP Port Numbers (L4)
This function controls the priority of packet transmissions so that packets can be sent with higher pri-
ority to a particular IP address or TCP (UDP) port. The TCP and UDP protocols are called transport
layer protocols, leading to the name L4 (layer 4) QoS function. When tag data links and message
communications are executed on the same network, tag data links can be sent at higher priority to
prevent problems such as transmission delays due to message communications traffic and packet
losses due to buffer overflow. Settings must be made in the Ethernet switch to enable this function
and give higher priority to tag data link packets.
2-3-2 Network Devices Manufactured by OMRON
Name
Model num-
ber
Specifications OK: Supported, ---: Not supported.
Description Number of ports
Failure detection
output
Ethernet
Switch W4S1-03B Packet priority control (QoS):
EtherNet/IP control data priority
Failure detection: Broadcast storm,
LSI error detection, 10/100Base-TX,
Auto negotiation
3 ---
W4S1-05B 5 ---
W4S1-05C 5 OK
2-3-3 Ethernet Switch Types
2-3-4 Ethernet Switch Functions