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Users Manual
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.
To better understand what takes place when RHAON tells a loudspeaker “Set Gain to -10dB”, think of Russian nested dolls. Your com-
puter will send out the whole doll, which contains an IP doll, which contains a UDP doll, which contains an SNMP doll, which contains
the message “Set Gain to -10dB”. When a device sends out a piece of CobraNet audio, it sends out a whole doll, which contains a
CobraNet doll, which contains the piece of audio.
With CobraNet, since both devices have a ‘burnt-in’ MAC address, communication can happen right away. For SNMP communication
between the computer and RHAON loudspeaker to happen, both devices must have a valid IP address. In most home or office net-
works, there is a device called a ‘router’ that not only contains a network switch, but can also handle the assignment of IP addresses
within its network through a protocol called DHCP. CobraNet (and, by extension, RHAON) uses a different protocol for requesting /
assigning IP addresses, but the end result is still the same. Your router has a static IP address assigned to it, devices ask it for an IP,
and the router obliges. For this same reason you must assign a static IP address to your computer.
Troubleshooting Tips
Since RHAON relies on standard networking communications and hardware along with CobraNet, general networking and CobraNet
troubleshooting documents can also be of assistance in solving problems. Don’t throw away any documentation related to the network
switches or CobraNet source devices.
You may also want to install and use the CobraNet Discovery program as a supplement to the RHAON Network Manager. CobraNet
Discovery is a network management program similar to the RHAON Network Manager, but more extensive. Both are invaluable in
identifying and solving network problems.
If you don’t have CobraNet Discovery, you can download it at no cost from our ftp site, Go to;
hftp://ftp.renkus-heinz.com/Software/CNDisco345.exe
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SERVICING and TROUBLE SHOOTING (cont)
