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Network Jargon
Doug Fleenor Design strives to make our products reliable and easy to use. Computer
networks, and their complexity, complicate this goal. To help our users de-mystify the
network side of our NODE products, Mr. Fleenor shares some of his insights.
Host
. Mr. Fleenor finds this networking term misleading. To non-networking people, a
host is the person that coordinates an event (or picks up the tab at a hosted bar). There is
often one host, and many guests. In a computer network, the term host is used for any
device connected to the network that generates or uses data; on a computer network
there are many hosts (and no guests).
The term host, in computer networks, stems from the days when computers took up entire
rooms or floors. Remote terminals, similar to mechanical typewriters, allowed multiple
users to access the computer. The computer hosting these dumb terminals, was the host.
Later these host computers were connected together to form a network, and the term
host, for a computer on the network, stuck.
Node.
Every device connected to a computer network is a node: Switches, hubs, routers,
computers, interface devices... Mr. Fleenor likes this term, thus the name of our network
interfaces. Fun fact: All hosts are nodes, but not all nodes are hosts.
Address.
A unique address is required for every device on a lighting control network.
sACN (and Art-Net) use IPv4 addressing which is a 32-bit number, typically written in
"dot-decimal" form (four decimal numbers separated by dots) such as 10.0.1.1. There are
two parts to the Address: the
network-part
and the
host-part
. To talk to each other, all
devices in the network must have the same network-part and a unique host-part. Doug
Fleenor Design recommends users use Network 10 (address 10.X.X.X), which is intended
for private (dedicated) networks that are not connected to the internet. Another private
network number is 192.168 (address 192.168.X.X). (Author's note: sACN sends DMX512
data on network address 239.255.X.X regardless of the Node's address or mask. Thus,
some aspects of a sACN network may work even if the address and/or mask do not
match.)
Subnet mask.
A 32-bit IPv4 address has two parts: the network-part and the host-part.
The number of bits dedicated to each part varies by application and is historically
represented by the subnet mask. The subnet mask is a 32-bit binary number starting with
a series of ones, followed by series of zeros, such as 11111111 00000000 00000000
00000000, with ones representing network-part bits and zeros representing host-part bits.
The subnet mask is typically written in dot-decimal form such as 255.0.0.0. Although the
parts of the IPv4 address can be split in 31 ways, the two most common in lighting are: 8
bits for network, 24 bits for host (subnet mask 255.0.0.0) and 16 bits for each
(255.255.0.0).
DHCP
. The Dynamic Host Configuration Protocol is a tool used to automatically assign
addresses and subnet masks. A device that runs the DHCP is called the DHCP server.
Not all networks have a DHCP server, in which case the addresses and subnet masks
are set manually (DFD products ship with a default address and mask that work in most
applications). Note that DHCP is an app that runs on a computer, router, console, or other
