page_title: L4 microkernel family
section_title: L3
hierarchical_section_title: L4 microkernel family / History / L3
caption_attribution_description: English: Family tree of the L4 microkernel with time line
context_page_description: L4 is a family of second-generation microkernels, generally used to implement Unix-like operating systems, but also used in a variety of other systems.
  L4, like its predecessor L3 microkernel, was created by German computer scientist Jochen Liedtke as a response to the poor performance of earlier microkernel-based operating systems. Liedtke felt that a system designed from the start for high performance, rather than other goals, could produce a microkernel of practical use. His original implementation in hand-coded Intel i386-specific assembly language code in 1993 sparked intense interest in the computer industry. Since its introduction, L4 has been developed for platform independence and also in improving security, isolation, and robustness.
  There have been various re-implementations of the original binary L4 kernel interface and its successors, including L4Ka::Pistachio, L4/MIPS, Fiasco. For this reason, the name L4 has been generalized and no longer only refers to Liedtke's original implementation. It now applies to the whole microkernel family including the L4 kernel interface and its different versions.
  L4 is widely deployed.
context_section_description: Jochen Liedtke set out to prove that a well designed thinner IPC layer, with careful attention to performance and machine-specific (as opposed to platform independent) design could yield massive real-world performance improvements. Instead of Mach's complex IPC system, his L3 microkernel simply passed the message without any additional overhead. Defining and implementing the required security policies were considered to be duties of the user space servers. The role of the kernel was only to provide the necessary mechanism to enable the user-level servers to enforce the policies. L3, developed in 1988, proved itself a safe and robust operating system, used for many years for example by TÜV SÜD.
caption: L4 family tree
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