I would like to connect 4 (perhaps more) RS232 devices to one PC using PortServer TS devices.
Currently the PC has a Digi Neo multiport serial card that these 4 devices connect to.
The devices are polled every 10ms by the PC. The device then responds after being polled, so communication is constant.
The RS232 parameters are 9600 8N1 full-duplex
I am thinking of the following configuration:
PC–Ethernet cable–Network Switch–50 meters fibre optics – Network Switch–4xEthernet cable–PortServer TS–serial cable–device (Ie. from the switch I will have 4 separate devices connected)
My question is how many of these devices could I connect across the Ethernet link before I use up all of the bandwidth, the link becomes clogged and communication begins to stall?
I will be using a dedicated Ethernet link for all of this (Ie. It will not be used for any other purpose than to connect these devices)
Calculating the network utilization requires you to find out how many bytes of network traffic are being handled by the network over a set period. This value depends on the type of network interface that is being monitored.
Half-duplex devices can only carry data in one direction at a time, and therefore calculating their network utilization involves totaling the input and output byte counts for a set period, and dividing by the total capacity of the device interface for that period. To determine the total number of bits received on the interfaces, each of the packet byte rates is multiplied by 8. This value is divided by the total interface capacity multiplied by the time interval of the
sample (in seconds):
%utilization = ((datasent + datarecv) * 8) / (intspeed * sampletime) * 100
For example, a 10-MB half-duplex network interface that over a 5-second period sends 700,000 bytes of data and receives 175,000 bytes would have a network utilization of:
%utilization = (((700,000 + 175,000) * 8) / (10,000,000 * 5) * 100 = 14%
The 14-percent utilization represents the network utilization only for that 5-second period. It is not uncommon to see high network utilization for a short period of time, given that Ethernet traffic is often bursty in nature. You have a problem when you take the same calculation for a longer period of time, such as a 5- or 30-minute interval, and still get high network utilization.