Network Traffic Policing with Cyclic Queuing Synchronization
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Solution Overview
Problem
Conventional credit-based policing in networks implementing Cyclic Queuing and Forwarding (CQF) is inadequate in preventing data loss due to its inability to accurately manage short-term throughput variations, leading to potential overflow and packet loss.
Innovation Solution
Implementing a policer policy synchronized with the queuing schedule that enforces a predetermined bandwidth by computing bit-times-on-the-wire per cycle and using credit-based counters to ensure that traffic flows do not exceed allocated bandwidth, thereby preventing data loss and ensuring contracted bandwidth for non-offending flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional credit-based policing is used to limit bandwidth, then the network can prevent congestion, but it cannot accurately prevent data loss on short timescales due to jitter in transmissions
Solution Approach 1:
The patent changes the measurement parameter from average throughput to instantaneous bit-rate per cycle. By measuring the actual number of bits transmitted in each discrete time cycle rather than averaging over longer periods, the system achieves precise short-term throughput control that accounts for transmission jitter, enabling accurate policing decisions on fast timescales
Solution Approach 2:
The patent implements periodic policing by enforcing bandwidth limits on a per-cycle basis using discrete time clocks that synchronize with the CQF buffer swapping rhythm. This periodic measurement and enforcement mechanism ensures that each transmission cycle is independently controlled, preventing accumulation of excess bits that would cause buffer overflow
2Productivity
If multiple input ports place extra packets into output buffers, then the network can handle variable traffic loads, but the network device becomes unable to transmit the extra packets in one cycle
Solution Approach 1:
The patent applies preliminary action by having policers at input ports pre-limit the number of packets that can be placed into output buffers before the actual transmission occurs. By enforcing bandwidth constraints in advance on each input port's transmissions, the system prevents buffer overflow conditions from arising in the first place, ensuring that cumulative packet counts remain within acceptable limits
Data Source
AI summary
Devices and methods for policing traffic flows in a network are described herein. For example, a network device can include a processing unit and a memory operably coupled to the processing unit. The network device can be configured to provide an input port and an output port, the input and output ports being configured to process a traffic flow received at the network device. The network device can also be configured to queue the traffic flow using a plurality of buffers associated with the output port, cyclically direct the traffic flow from the input port to each of the plurality of buffers according to a queuing schedule, and enforce a policer policy synchronized to the queuing schedule. The policer policy can ensure that the traffic flow does not exceed a predetermined bandwidth.