Technical FAQs

Ask a Question

TwidoPort Sensitivity to Broadcast Packets

Release Notice

note to modify that exposure to this type of packets over a period of time will have this effect

Goals and Symptoms

TwidoPort modules that are subjected to high Broadcast traffic found in an office network or PC network protocol may suffer from lockup as a result it will require a manual or automatic reboot.

  • TwidoPort firmware version 2.7 or lower will require manual reboot
  • TwidoPort firmware version 2.9.9 or higher will perform an automatic reboot

Please be aware that during lockup communications will be lost and will not resume until the module is either manual or automatically rebooted. This duration may range from 10s to 60s.

Facts and Changes

Although broadcast activity is a normal part of Ethernet and TCP/IP operation, excessive or unnecessary broadcast traffic should be avoided on PLC/Control network environment.

Causes and Fixes

Below is a list of common protocols that can cause problems:

  • ARP – Address Resolution Protocol - excessive ARP traffic created due to missing device that are being polled by I/O Scanner
  • NetBIOS Broadcast – NetBIOS protocol is an OSI Layer 5 (Session), protocol which manages the machine names, sessions and data delivery between them.
  • IPX/SPX – Internetwork Packet Exchange/Sequenced Packet Exchange developed by Novel and is a 7 layer routable protocol.
  • NetBEUI – NetBIOS Extended User Interface protocol – Broadcast based peer-to-peer network protocol uses a sliding window, (adaptive send/receive message sizes), and is optimized for small LAN’s.

Some of the ways that you can prevent such situation is by:
  • Connecting the TwidoPort to the network via a switch instead of using a hub. Although this may not protect the module from broadcast data it will reduce the amount of packets that the module will have to evaluate.
  • Turning on broadcast limiting on the switch. This will limit the amount of broadcast packets to which TwidoPort is exposed to. Schneider switches such as TCSESM switches support broadcast limiting feature.
  • Physically separating the control network from the office network will eliminate the office network traffic from the plant network. If physically separating the two networks is not an option then by using VLAN you can logically separate the two networks. The TCSESM switches also support VLAN configurations.

Was this helpful?
What can we do to improve the information ?