Nest is a secure IP VPN tunnel for FreeBSD. It connects two LANs over an insecure WAN. Nest works on the IP packet level. Its features include packet authentication and integrity checking (with 96-bit SHA1-derived HMAC), packet encryption (with Blowfish and 160-bit key CBC mode), replay protection, adjustable packet queuing, and compression. The VPN traffic appears on the WAN as a bidirectional stream of IP packets or as a unidirectional ICMP request/response stream. The latter case allows the establishment of VPN tunnels through certain firewalls.