PLD Upgrade Switchover Using Held Control Signals
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Solution Overview
Problem
Network elements, such as switches and routers, require frequent software and hardware upgrades, which often necessitate downtime due to the need for rebooting or physical hardware replacement, posing challenges in maintaining continuous operation, especially in 24/7 data centers and redundant systems where loss of redundancy is a concern.
Innovation Solution
A method and system for upgrading programmable logic devices (PLDs) in network elements that involves writing configuration data to nonvolatile memory and using a signal control device to hold system control signals at a predefined state, allowing for in-service upgrades without downtime, using various signal control devices like resistors, registers, and shift registers to manage system control signals during the upgrade process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hardware upgrades require physical removal of equipment and replacement of hardware, then the upgrade can be completed, but the network element must be taken out of service causing downtime
Solution Approach 1:
The system is divided into two separate PLD instances: an active PLD handling network traffic and a standby PLD for upgrades. This segmentation allows independent operation of each instance, enabling upgrades without taking the entire system offline. The method involves configuring a first PLD to handle network traffic while a second PLD is upgraded in parallel.
Solution Approach 2:
The upgrade process is prepared in advance by configuring the standby PLD with the new hardware or firmware before it is needed. Configuration data is written to nonvolatile memory beforehand, and the standby PLD is pre-configured so that when switchover occurs, the network element continues operating without interruption.
2Ease of manufacture
If programmable logic parts are upgraded by taking the network element out of service, then the upgrade can be performed, but continuous operation is interrupted
Solution Approach 1:
The system maintains continuous network traffic handling by keeping the first PLD active while the second PLD is upgraded. The useful action of packet switching continues uninterrupted through the active PLD, while the standby PLD undergoes upgrade in the background. After upgrade, roles are swapped seamlessly.
Solution Approach 2:
A signal control device acts as an intermediary between the PLDs and the rest of the system. This mediator manages the switchover process by controlling signal routing, ensuring smooth transition from one PLD to another without interrupting network traffic flow.
3Ease of manufacture
If one component is taken off-line for upgrade in redundant systems, then the upgrade can be performed, but the system suffers from loss-of-redundancy hazard
Solution Approach 1:
The redundant system is segmented into active and standby components. The first PLD remains active handling traffic while the second PLD is upgraded, maintaining system redundancy throughout the upgrade process. This segmentation ensures that one component is always available to handle traffic.
Solution Approach 2:
The system dynamically switches roles between PLDs. The active PLD can be transitioned to standby status while the upgraded PLD becomes active. This dynamic role assignment ensures continuous redundancy and availability, allowing the system to adapt its configuration based on operational needs.
Data Source
AI summary
A method for upgrading a programmable logic device (PLD) in a network element is provided. The method includes writing PLD configuration data to a nonvolatile memory and directing a signal control device external to the PLD to hold system control signals in the network element at a predefined state irrespective of direction by the PLD. The method includes loading the PLD configuration data from the nonvolatile memory into a PLD configuration memory in the PLD, while the signal control device holds the system control signals at the predefined values. The method includes directing the signal control device to release the holding the system control signals, so that the PLD directs the system control signals, responsive to completion of the loading the PLD configuration data into the PLD configuration memory. A network element is also provided.