Siemens Industrial Ethernet Switches SCALANCE X-200 - Manual (Page 283)

Technical specifications
SCALANCE X-200
Operating Instructions, 12/2011, A5E00349864-19
283
Note
Note the mounting position of the SCALANCE XF-200 and X204-2TS
If a SCALANCE XF-200 or X204-2TS are mounted on a vertical rail, an ambient temperature
of maximum +40 °C is permitted.
Note
The following applies to IE Switches X-200 that do not have IRT functionality:
The number of IE Switches X-200 connected in a line influences the frame delay.
When a frame passes through X-200 IE switches, it is delayed by the Store&Forward
function of the X-200 IE 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 IE Switch X-200 devices the frame passes through, the longer the
frame delay.
Note
The following applies to X-200 IE switches that have IRT functionality:
The number of IE Switches X-200 connected in a line influences the frame delay. The more
X-200IRT IE switches a frame runs through, the higher the frame delay.
By using the "cut through" switching mechanism, the X-200IRT IE 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, an IE Switch X-200 changes to Store&Forward and the delay increases.