Appendix 1
Link Initiation
1. Client Mode with Fixed IP Address
At start up an ARP (Address Resolution Protocol) request is issued. If the request is resolved
Netiom-UDP will know the MAC address of the target device and will know that it is present
on the network. A network packet will then be transmitted with the current status of the inputs.
This should then result in the return of a packet from the target end thus establishing the link.
If the ARP request is not resolved then Netiom-UDP will wait for the Timeout period and then
re-issue the request. This will continue until a response is returned.
If there is a break in the receipt of packets from the remote end of the link for the Timeout
period then the link is reset and a new ARP request is issued. Again this is repeated until the
link is re-established.
2. Client Mode with Broadcast IP Address
At start up a network packet is transmitted with the current input status. The IP address will be
255.255.255.255 and the MAC address will be 0xFFFFFFFF both defined as broadcast
values. The target will recognise that this is a packet from a Netiom-UDP and will respond
using the originating IP and MAC addresses as their target addresses. The originating device
will receive the packet, recognise that it a Netiom-UDP package and will now deduce the IP
and MAC addresses of the remote end. The next packet transmitted by the originating end
will use this new information thus establishing the link.
3. Non-Client Mode
At start up the Netiom-UDP will listen for packets on the assigned Port Number. It will not
transmit and data at this time. When a packet is received it is inspected to determine if it is a
Netiom-UDP packet. If it is then it will respond to the packet with the current status of its
inputs using the originating IP and MAC addresses as the target address thus establishing the
link.
If there is a break in the receipt of packets from the remote end of the link for the Timeout
period then the Netiom-UDP will stop transmitting and revert to listening mode again.
