Netmap is available on both Linux and FreeBSD. However, Netmap brings some additional benefits that are not found elsewhere: it does not force applications to resort to busy-polling, it protects devices from uncontrolled user-space access, and it introduces a common API which can also be used for fast VM networking and Inter-Process Communication. Exploring Netmap is a good introduction to these topics, common to all frameworks. When combined together, these techniques allow user-space applications to send/receive tens of millions of packets per second, saturating the NIC capacity even with short packets. They also use simple packet representation structures optimized for raw packet I/O rather than for full-fledged protocol stack. The bypass solutions overcome these limitations by pre-allocating packet buffers, mapping those buffers in the application address space and allowing applications to send and receive multiple packets using a single operation (e.g. Moreover, moving networking to userspace facilitates experimentation and improves portability.
sk_buff on Linux), NIC register access and interrupts. These limitations are largely due to per-packet size-independent costs: system call, packet copy across user/kernel boundary, VFS layer overheads, dynamic (de)allocation of packet metadata (e.g. Using a traditional socket API a single processor core is not able to send or receive more than 1-2 million packets per second (Mpps) at minimum packet size (60 bytes), despite of much faster modern NICs which support 10-100 Mpps. implementation) in terms of maximum packet rate. bypass projects (DPDK, PF RING), and comes from the performance limitations of the traditional socket API (and the associated O.S. The need for an alternative mechanism and APIs for network I/O has been recognized by several O.S.
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