Cisco 12000 Gigabit Switch Routers (GSRs) are currently the only Cisco IP Routing products that have an IP OC-48 interface. Modified Deficit Round Robin (MDRR) extends Deficit Round Robin (DRR) to provide priority for real-time traffic such as VoIP. Within MDRR, IP packets are mapped to different CoS queues based on precedence bits.
All the queues are serviced in round-robin fashion except for one: the priority queue used to handle voice traffic.
DRR provides queuing similar to WFQ but for higher-speed interfaces from OC-3 to OC-48. MDRR extends the DRR protocol to include a high-priority queue that is treated differently from the other queues associated with service classes.
For each set of CoS queues supported, MDRR includes a low-latency, high-priority (LLHP) queue for VoIP or other real-time traffic. Except for the LLHP queue, MDRR services all queues in round-robin fashion.
This enables service providers or others with a need for high-speed queuing to ensure that VoIP is prioritized above all other traffic.
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