21 SolsTiS User Manual v10.0
4.5 Ethernet Control - Installing & Using the Software UI
Background
SolsTiS uses Ethernet control and can be networked, if needed. Every device
on a network (TCP/IP/Internet) needs a unique identifying address. This is
provided in different levels. The lowest level is the Media Access Controller
address (MAC). The MAC address is unique to every individual network-
connected device and is commonly written as six pairs of hexadecimal digits
(0-F). This is set at the hardware level—often coded into memory—and is not
(usually, nor intended to be) changeable by the user. M Squared has pre-
assigned a MAC address to the SolsTiS Wavelength Control Unit that cannot
be changed by the user and, because each MAC is unique, it is also used as
the serial number for the product.
Although unique, the MAC address alone is not convenient for network
administration because in a large network there could be many devices, all of
which will have completely random, but unique, MAC addresses. To make it
easier to manage a network and to provide some structure to it, an IP (Internet
Protocol) address superimposed on top of the MAC address. This is written as
four groups of three decimal numbers (0-9). A network administrator can then
assign different groups of IP addresses to, for example, different floors of an
office or to different groups of users, as needed. An IP address is mapped on
to a MAC address using the user interface of the networked device, be it a
computer, printer, server or M Squared ICE-BLOC module. When two devices
have been assigned IP addresses they can start to talk to each other over a
TCP/IP network, including the Internet. The IP address becomes the
externally visible address of the device on the network, rather than the MAC.
(On top of the IP address there is the possibility of adding a user-friendly
device nickname, such as SolsTiS-SRX. This makes it easier for a user to
identify devices accessible on the network to which he is connected, instead
just viewing a list of IP addresses. This feature is now a feature of all personal
computers, but is not yet implemented in M Squared ICE-BLOC control
modules such as the SolsTiS Wavelength Control Unit.)
When a computer is plugged into a network, it will have a MAC
address, but commonly it will not already have an IP address.
Through a standard process called DHCP (Dynamic Host
Configuration Protocol) the computer requests an IP address from a
DHCP server, which (assuming all security requirements are met)
will within seconds automatically issue an IP address to the
computer, which it will keep until electrically removed from the
network for a period of time. The DHCP server keeps a record of
the MAC address of every device connected, the name of every
device (should it be available), and the IP address assigned to that
device. If no device name is available, a network administrator can
manually assign a name to a device via the DHCP server. The
DHCP server will then remember this name by tying it to the MAC
address of the device, not the IP address, as this can change.
It is possible to set a fixed IP address for a computer or other
network device, although this can result in the assigned name being
the same as another device. This could potentially result in
communications problems if a device with a fixed IP address is
added to an extensive network, but using fixed IP address is not
unusual practice if the device is connected directly to a PC, or is
added to a small, secure and/or safety-critical network.
Note! The laptop and SolsTiS Wavelength Control
Unit ICE-BLOC module that were shipped with your
system were factory pre-configured with fixed IP
addresses. This means that they can be connected
together and powered up without the need for a
network connection.
Even if a PC and a network device are to be connected directly
together the network rules discussed still apply. Because, however,
there is no network or DHCP server between the PC and network
device in this case, the PC will not be automatically assigned an IP
address, so will not be able to communicate with the network device
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