Operating instructions

Product properties
3.21 Technical specifications
Industrial Ethernet SCALANCE X-100 and SCALANCE X-200 Product Line
Operating instructions, 09/2006, A5E00349864 Release 7
3-75
Note
The following applies to devices of the SCALANCE X-100 and X-200 product lines that do
not have IRT functionality:
The number of SCALANCE X Industrial Ethernet Switches connected in a line influences the
frame propagation time.
When a frame passes through devices of the SCALANCE X-100 and/or SCALANCE X-200
product lines, it is delayed by the store and forward function of the switch
• with a 64 byte frame length by approx. 10 microseconds (at 100 Mbps)
• with a 1500 byte frame length by approx. 130 microseconds (at 100 Mbps)
This means that the more devices of the SCALANCE X-100 and/or SCALANCE X-200
product lines that a frame passes through, the higher the frame propagation time will be.
Note
The following applies to devices of the SCALANCE X-200 product line with IRT functionality:
The number of SCALANCE X Industrial Ethernet Switches connected in a line influences the
frame propagation time. The more devices of the SCALANCE X-200IRT product line, the
frame passes through, the longer the frame delay.
By using the “cut through” switching mechanism, the SCALANCE X-200IRT switches are
ideal to meet the real-time requirements of PROFINET.
Cut through is not possible
• between a port set to 10 Mbps and a port set to 100 Mbps
• when two packets are to be sent at the same time on one port.
In this case, the switch changes to store and forward and the delay increases.