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ConfDB is a common term for complex of measures for high-level device configuration processing within NOC. Vendors tend to invent own configuration formats, often mimicking each other, and to introduce incompatibilities between releases and platforms. Besides simple change tracking and regular expression search, the multi-vendor configuration processing may be very challenging task.
NOC addresses the challenge with following approach:
- Decomposition - complex task may be split to simple steps
- Reusability - all tools may be reused whenever possible
- Pipelining - each steps combined together into configuration processing pipelines
- Clean contract between steps - each step performs own task. Steps accept predictable result from previous steps and pass predictable result to following steps
- Clean API - each step must be understandable and easy to implement
- Quick result - First result must be reached easily and quickly. Then you can became to implement more complex things
To better understand the concept of ConfDB one should refer to widely-used concept in programming languages - Virtual Machines. Virtual Machine (VM) is the fictional computer with own native assembly language (or machine codes). Its sometimes easier to break the task of compiling the program from programming language to target processor to two steps: to compile to fictional machine codes and to compile from fictional codes to target ones. The benefits in clear separation of common functions, suitable for all target platforms, and of specific functions, addressed for single platform. Common functions moved to the left (Code -> VM translation), while specific moved to the right (VM -> Target platform translation). Hence VM represents clean contract between hardware-dependent and hardware independent functions.
Device configuration is the programming language of target platform. So we can split the task of configuration analysis by applying clean barrier between hardware-dependent and hardware-independent parts. Just like Virtual Machine NOC introduces fictional configuration language for non-existing (yet?) network equipment. All hardware-dependent parts are moved to the left. All hardware-independent parts are moved to the right and may be reused.
ConfDB pipeline stages¶
Config processing pipeline and stages are repesented on chart below