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Luminous E200: Enlightened Transport for Ethernet: Page 3 of 5

One troubling aspect of LMS is that there is no way to edit an existing circuit. If a user wants to change the bandwidth or QoS, the circuit has to be deleted and re-added. This is cumbersome, and the circuit must be down while changes are being made. Newer LMS versions should correct this.

All this sounds much like other Ethernet switching products until you add the "resilient" part of RPR. Ethernet traffic can be marked as protected or unprotected. Protected circuits are automatically rerouted in the opposite direction the moment the devices realize a ring break has occurred.

I tested this by creating a circuit around the ring with protected Ethernet traffic. I used an Ixia 400 traffic generator with its four-port 10/100 Ethernet blade. With one Ethernet port connected to the E200 and the other connected to one C-Series device, I began blasting traffic. A few seconds later I disconnected the primary pair of Gigabit Ethernet fibers and watched the network go into alarm. By measuring the number of packets received and sent by the Ixia, and the packet size, I was able to deduce that I lost 11 ms's worth of packets on my 10 feet of fiber. In comparison, Sonet systems have a failover rate of less than 50 ms. Luminous cites a sub-50-ms failover for the longest fiber runs.

TDM Traffic

Luminous' implementation of RPR--which it calls Resilient Packet Transport, or RPT--allows the transport of not only Ethernet traffic but TDM (Time-Division Multiplex) traffic as well. So any TDM service (voice, frame relay, private line and so on) can be transported over the ring. The four TDM ports on the E200 can be configured as T1 or E1 circuits. Each port can have different line codings, but they all need to be T1 or E1 ports.