Zenith At Cogeco in Canada
Cogeco in Canada launched with the 4 Mbit/s, external Rev D cable modem in roughly 1996, and by August 1997 had 2500 subscribers. The network was failing for 3 reasons:
- The Zenith network is a pure bridged CSMA/CD Ethernet. It has no understanding of the Layer 3 ARP protocol. Thus ARP storms through the layer 2 switches used in the first headend designs would clog the network.
- The layer 2 switches and layer 3 routers of the time did perform any QOS or rate limiting, thus a 4 Mbit/s input port on the Channelmizer could be flooded with up to 10 Mbit/s of traffic bursts.
- The Cogeco network contained an unusual reverse path amplifier as part of the retrofit to accommodate return path. This particular amplifier contained a design defect whereby the pad and equalizer plug in modules would literally fall off the circuit board when the device was opened. A thermal incompatibility existed causing the holes for the parts to increase in diameter, while the pins would elongate and become smaller. This fault was documented and proven as a result of Cogeco’s first DOCSIS deployment with the Cisco uBR7246, MC11-FPGA linecard, and IOS 11.3(4)NA, which contained the “flap list.”
Read more about this topic: Zenith Cable Modem
Famous quotes containing the word canada:
“Canadians look down on the United States and consider it Hell. They are right to do so. Canada is to the United States what, in Dantes scheme, Limbo is to Hell.”
—Irving Layton (b. 1912)