Lesson 1: Switched Networks
The Ethernet protocol is a frame-based computer networking technology for local area networks (LANs). This means it is a system for
sending uniquely addressed packets of information from a source to a destination, similar to how one sends a letter through the postal
service. When you mail a letter to Aunt Gertrude across town, the letter doesn’t just go straight from your mailbox to your Aunt’s. It
goes to the post office, where it is sorted and sent along with Gertie’s local mailman. The same holds true for networks, only replace
“post office” with “network switch”.
Switched networks are laid out in a “star” configuration, in that the topology has the switch at the center with links fanning out to all
devices and/or other stars. Typical transport media are CAT5e cable (up to 100m) or optical fiber (up to more than 2km).
Communication is handled in a “Point-to-Point” fashion, in that each node communicates solely with the next node attached to it. Using
our previous example, the letter starts in your mailbox and is picked up by your mailman, who then transports your letter to the post
office, where it is sorted and given to Gertrude’s mailman, who then drops it off in her mailbox. How do the switches know where to
send the packets? By remembering, of course! Just as the letter to Aunt Gertrude includes a “To” and “From” address, so does a pack-
et. The switch remembers which “From” addresses come from which port in order to speed up future traffic.
Two of the main distinguishing characteristics between switches are speed and management. The two main speed standards that com-
prise the majority of RHAON installations are 100Base-T (Fast Ethernet) and 1000Base-T (Gigabit Ethernet). While RHAON device
connections are Fast Ethernet, either speed may be used as higher speed switches are backwards compatible with those of lower
speeds. The advantage to using Gigabit switches with a RHAON network is that while the individual connections are 100Base-T, the
switching times (the time it takes between packet ingress and egress) are much shorter. This becomes especially important from both a
hop and total nodes standpoint as the size of a network grows. We recommend Gigabit switches for large networks.
Aside from speed, switches come in two flavors: Managed and Unmanaged. An unmanaged switch is essentially a “dumb” black box
that takes packets in and sends them where they need to go. A managed switch, however, allows you much more control. With a man-
aged switch, one can designate subsets of ports as separate networks, control which types of packets are allowed in or out of certain
ports, monitor current network traffic conditions, port status, etc. For a great number of installations, an unmanaged switch will suffice.
However, for larger or more complex setups, a managed switch becomes critical, though a decent level of networking expertise is
required for proper setup.
Lesson 2: Packet Addressing
On a Local Area Network (LAN), packets are addressed by the Media Access Control (MAC) address of the network device. MAC
addresses are “burnt-in” by the manufacturer of your network device (computer network card, RHAON loudspeaker, etc.) and are glob-
ally unique. This is like the VIN on your car. No matter where you register your car, the VIN stays the same and is unlike that for any
other vehicle worldwide.
Not all communication happens on a LAN, however. In order to address different devices on different networks, Internet Protocol (IP)
addresses were introduced. They allow for easier routing for a vast array of interconnected networks. Similar to this is the license plate
on a car. Rather than attempting to search for the car by going through the VINs for every car in the world, one could narrow things
down by first selecting the country in which it was registered and then by license plate number within that country. RHAON acts as the
license plate authority, if a CobraNet device (RHAON speaker, mixer, etc.) doesn’t yet have a “license plate”, it asks RHAON for one
and the software kindly obliges.
Packets addressed by MAC address are known as “Ethernet packets”. In addition to information about the source and destination and
the payload, there is a marker for what type of Ethernet packet is being sent. IP packets (ones that can be sent within or out of the
LAN) have one identifier and CobraNet packets have another. Because CobraNet packets don’t contain IP information in their payload,
CobraNet is limited to being LAN-only. The structure of an IP packet is very similar, in that it contains - among other information - a
source address, a destination address, and protocol type. For RHAON, the protocol types of UDP and TCP are the ones in heavy use.
Building upon the UDP protocol is the Simple Network Management Protocol (SNMP), which is what RHAON uses to monitor or manip-
ulate exposed variables (EQ, Bundle Assignments, etc.) on a RHAON loudspeaker or other CobraNet device. At each stage in the
process of handling a packet, the previous layer is left behind. Once a payload type is determined, just that payload is handed off to the
appropriate handler.
Networking and RHAON Systems
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Users Manual
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