The Ricochet network back-end consists of 4 major components:

external image poletop-web.jpg
Poletops, which are shoebox-sized radio repeaters usually mounted on streetlights. A poletop is the center of a "Microcell". They communicate in the 900MHz band with a whip antenna that sticks down from the center of the housing, and in the 2.4GHz band with small panel antennae mounted on the corners underneath plastic covers. (Controlled by the OctantSwitcher) They suckle power from the streetlight photocell socket with a nifty piggyback cord. There are approximately 5 poletops per square mile in covered areas. These radios should not be confused with the Wireless Oakland project's poletop radios, which look quite similar and draw their power the same way.



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Ethernet Radios, which are in the same housing as poletops but without the corner antennae. Each E-radio brings out the 900MHz and 2.4GHz signals to N connectors, which are cabled to large panel antennae, behind which the E-radio physically sits. Twelve or sixteen E-radios will be mounted at a WAP (wired access point) site, usually located on a cell tower. At the base of the tower is a cabinet containing a router which connects the E-radios to the wired infrastructure.



The nameserver should not be confused with DNS but it did similar things.

The Ricochet nameserver is a database that remembers where every device in the network is. Devices could be classified as to types of service that they offered (such as IP or PSTN interfaces) and queried either as to the specific device or the type of service. In the case of services, multiple devices could provide that service and the nameserver attempted to provide a round-robin group of like devices (changing the order of the group in order to spread out utilization). For example, a client requesting internet access might get a list of eight IP gateways and the client would cycle through that list until it found a gateway that responded to it. Another client, in the same area, would get the same list but in a different order so that it would not tend to select the same gateway as the prior client.

The name server performed path construction for any device/service that was looked up. Ricochet used geographic source routing and it was the nameserver that figured each path out. The general algorithm was to route a client to a requested service that was as close as possible, geographically, to that client. Paths could be constructed that were RF only (i.e. never went into a wired network), a combination of RF and wired routes, or all wired. All of this allows the RoutingProtocol to work, by telling the endpoints where to find each other.

The nameserver also enforced access control such that a client device could only query other devices that it was authorized to access. This implemented a "security by obscurity" mechanism; clients could not get addresses to services or devices unless they were authorized to do so. The nameserver also maintained, and provisioned, various connection parameters the most notable of which related to "hog control" (i.e. making sure that some devices did not "hog" all network resources in an area).

When the network was operational, there was only one nameserver visible to clients but this was actually a group of name servers behind the scene. The nameserver was implemented using recursive geographic replication. There were two sites (one in Texas and one in California) that had name server instances. Each instance could in fact be multiple redundant servers but the actual implemenation proved so robust that it was decided to have just one copy at each site. The nameservers were linked together using Oracle symmetric replication.

The only remaining nameserer is in Denver and it runs the Denver and San Diego networks. But the rest of the service areas aren't connected to it any longer. In addition to the nameserver, there was a test platform made called the "garage gateway". This gateway pretended to be a name server and was able to give some limited capability to small networks when no nameserver was available.



The gateway, which managed the network headers and wrappers, and terminated tunnels from the modems, enabling subscriber data to reach the internet.