tailieunhanh - The Illustrated Network- P35

The Illustrated Network- P35:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | 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 unauthorized access to privileged modes of operation. According to this position all raw socket restrictions do is hamper legitimate applications and form an impediment to effectiveness 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 interfaces 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 . It was designed at the time to be used with a number of network protocol 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 Interface TLI . The TLI interface was bundled with AT T UNIX System V and also supported other network architectures besides TCP IP. However TLI is also almost always used with TCP IP network interface. Today TLI remains somewhat of a curiosity. WinSock as the socket programming interface for Windows is called is a special case and deserves a section of its own. THE WINDOWS SOCKET INTERFACE One of the most important socket interface implementations today which is not for the Unix environment at all is the Windows Socket interface programming library or WinSock. WinSock is a dynamic link library DLL function that is linked to a Windows TCP IP application program when run. WinSock began with a 16-bit version for .