User manual

TD990200-0ME
12
• Excessive traffic or Ethernet failures may cause Metasys offline
reports. An offline report is generated if a Metasys message
response is not received within 12 seconds.
• Customer equipment attached to the Ethernet network could
cause Ethernet network down time.
In order to minimize the impact of these problems, consider the
following:
• Avoid using Ethernet networks running at more than 20% of
capacity.
• Avoid networks using slower speed links for routing
(< 56 kbps).
• Do not use control algorithms that cross the Ethernet network.
In particular: do not share an object between the two networks;
do not initiate closed loop control; and do not program
interlocks between NCMs across the Ethernet network.
Also, due to the unknown operation of customer devices on the
Ethernet network, the Metasys Network may not be as reliable as
before.
Ethernet Network May Be Affected
The Metasys Ethernet Router may affect the Ethernet network.
Three points can be made here:
• Metasys Ethernet Routers look like standard PCs to the Ethernet
network. Metasys Ethernet Routers use the UDP/IP protocol for
data transmission.
• Typical Metasys loading will be less than 0.1% of the Ethernet
bandwidth per Metasys node. During large data transfers, such
as during downloads, loading is no higher than 1%. The base
traffic level generated by Metasys is calculated as follows:
(Number of Metasys Nodes)*(Number of Ethernet Routers-1) =
Packets/Minute
• Each packet is about 150 bytes long. Sharing data between
NCMs or accessing data causes additional traffic.
• Maximum data packet size is 512 bytes plus the UDP header.
Typically, the packet size is much smaller.