ATM Policing Engine for Dynamic Cell Rate Control
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Solution Overview
Problem
Conventional channel bank expansion architectures face limitations such as potential data transfer termination due to malfunctioning channel bank cards, noise-coupling limitations, and increased expense, which restrict the number of customers that can be serviced by a single channel bank connection.
Innovation Solution
A single switch fabric-based, multi-channel bank architecture with policing engines controlling the rate of ATM cell packets from customer ports to prevent buffer overflow, using peak and sustained cell rate counters to throttle non-conforming cells and ensure efficient data flow conforming to subscription rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bus extension is used to increase the number of line cards, then the number of customers serviced increases, but the risk of data transfer termination due to malfunction increases
Solution Approach 1:
The system divides the channel bank into multiple independent line card slots, each with its own policing engine. This segmentation isolates failures to individual slots rather than affecting the entire bus, allowing other slots to continue operating independently while maintaining the ability to service multiple customers.
Solution Approach 2:
A switch fabric is introduced as an intermediary between line cards and the network, replacing the direct bus extension architecture. The switch fabric provides controlled data paths with policing engines that manage data flow, preventing a single malfunction from terminating all data transfers while still enabling expansion to serve more customers.
2Productivity
If multiple channel banks are daisy chained via bus extension, then capacity increases, but noise-coupling limitations and expense increase
Solution Approach 1:
The harmful bus extension cable is extracted from the architecture and replaced with a switch fabric-based interconnection system. This eliminates the noise-coupling limitations and expense associated with physical bus extensions while preserving the ability to expand system capacity through additional line card slots.
Solution Approach 2:
The mechanical bus extension cable system is replaced with an electronic switch fabric-based interconnection system. This substitution eliminates physical noise-coupling limitations and reduces expense while maintaining or enhancing system capacity for servicing multiple customers.
3Reliability
If policing engines control cell rate dynamically, then buffer overflow is prevented, but system complexity increases
Solution Approach 1:
Policing engines perform preliminary rate control on ATM cells before they enter buffers, using pre-configured peak and sustained cell rate parameters. This preliminary action prevents buffer overflow conditions from developing, simplifying the overall system by avoiding the need for complex real-time buffer management and dynamic rate adjustment mechanisms.
Data Source
AI summary
A policing engine for use in a telecommunication equipment shelf is operative to control the rate at which customer-sourced ATM packets are passed to buffers associated with different classes of service to which customers may subscribe. The policing engine examines the rate at which ATM cells are supplied to it from the line card ports, whether the cells are AAL5 cells, and how full are the buffers into which the cells are to be written. If cells are supplied to the policing engine at a rate faster than prescribed peak or sustained cell rates, or if the cell buffer begins to fill up, the policing engine controllably discards incoming cells, thereby effectively ‘throttling’ the cell flow rate through it.