CHAPTER 12 Multiplexing and Sockets 309 Also, in traditional Unix-based operating systems, access to raw sockets is a privileged activity. So, in a sense the issue is not to hamper raw sockets, but to prevent unauthor- ized access to privileged modes of operation. According to this position, all raw socket restrictions do is hamper legitimate applications and form an impediment to effec- tiveness and portability. Restrictions have never prevented a subverted machine from spoofing traffic before Windows XP or since. Socket Libraries Although there is no standard socket programming interface, there are some socket inter- faces that have become very popular for a number of system types. The original socket interface was developed for the 1982 version of the Berkeley Systems Distribution of Unix (BSD 4.1c). It was designed at the time to be used with a number of network pro- tocol architectures, not just TCP/IP alone. But since TCP/IP was bundled with BSD Unix versions, sockets and TCP/IP have been closely related. A number of improvements have been made to the original BSD socket interface since 1982. Some people still call the socket interfaces "Berkeley sockets" to honor the source of the concept. In 1986, AT&T, the original developers of Unix, introduced the Transport Layer