UDP tuning

User Datagram Protocol (UDP) is a datagram protocol that is used by Network File System (NFS), name server (named), Trivial File Transfer Protocol (TFTP), and other special purpose protocols.

Since UDP is a datagram protocol, the entire message (datagram) must be copied into the kernel on a send operation as one atomic operation. The datagram is also received as one complete message on the recv or recvfrom system call. You must set the udp_sendspace and udp_recvspace parameters to handle the buffering requirements on a per-socket basis.

The largest UDP datagram that can be sent is 64 KB, minus the UDP header size (8 bytes) and the IP header size (20 bytes for IPv4 or 40 bytes for IPv6 headers).