Netmap is a high-performance packet I/O framework that bypasses the kernel network stack, providing memory-mapped rings for zero-copy packet processing. It consists of a kernel module (character device /dev/netmap), a user-space library (libnetmap), and a suite of applications (pkt-gen, bridge, nmreplay, lb, dedup, etc.). The architecture supports multiple NICs via native driver adapters (Intel, Mellanox, VMware, virtio, etc.) or a generic emulation layer, and includes an in-kernel virtual switch (VALE), inter-process pipes, and traffic monitors. Key entry points are the kernel module's ioctl/poll/mmap operations and the user-space library's port specification parser. Data flows involve memory-mapped rings synchronized via system calls or a lock-free Communication Status Block (CSB). External dependencies include kernel APIs, NIC driver internals, and standard C libraries. The project is cross-platform (FreeBSD, Linux, Windows) and originates from academic research at the University of Pisa.