kernrouters

Kernrouters are routing systems whose functionality resides primarily in the kernel, blending a kernel-resident forwarding plane with a user-space or kernel-resident control plane. They aim to minimize kernel-user context switches and to maximize packet processing speed.

The kernel hosts a forwarding information base (FIB) and a basic routing decision mechanism; a control plane configures routes, runs routing protocols, and enforces policies. In many designs, routing protocols run in user space and push updates to the kernel's routing table via netlink or equivalent interfaces; some deployments place more logic in kernel modules to reduce latency.

Applications include high-throughput networks in data centers, edge devices, and virtualized environments such as container networks, where fast path forwarding is critical. Kernel-based routing can reduce latency and improve determinism compared with user-space forwarding paths.

Trade-offs include increased risk from kernel-level bugs, greater development complexity, and portability concerns across different operating systems. Debugging and testing are more challenging, and a failure in the kernel forwarding path can affect the entire system.

Historically, kernel-level forwarding emerged from the need to support line-rate routing in high-performance networks; today many systems use a mixed approach with kernel forwarding for the data plane and user-space control planes for routing protocols.

Related topics include kernel-space networking, forwarding plane, routing protocol, netlink, FIB, and RIB.