NNTP Overview and General Operation
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Usenet began as a logical internetwork of cooperating hosts that contacted each other directly. In the early Usenet, a user would post a message to his or her local server. There it would stay until that server either contacted or was contacted by another server. The message would then be transferred to the new server, where it would stay until the second server contacted a third one, and so on.
This transport mechanism was functional, but seriously flawed in a number of ways. Servers were not continually connected to each other; they could only communicate by making a telephone call using an analog modem. Thus, messages would often sit for hours before they could be propagated. Modems in those days were also very slow by today's standards2400 bits per second or even lessso it took a long time to copy a message from one server to another. Worst of all, unless two sites were in the same city, these phone calls were long distance, making them quite expensive.
Why was this system used despite all of these problems? Simple: there was no alternative. In the late 1970s and early 1980s, there was no Internet as we know it, and no other physical infrastructure existed to link Usenet sites together. It was either use UUCP over telephone lines, or nothing.
Everything changed as the fledgling ARPAnet grew into the modern Internet. As the Internet expanded, more and more sites connected to it, including many sites that were participating in Usenet. Once a pair of sites were both on the Internet, it was an easy decision to use the Internet to send Usenet articles rather than slow, expensive telephone calls. Over time, more and more Usenet sites joined the Internet, and it became clear that just as e-mail had moved from UUCP to the TCP/IP Internet, the future of Usenet was on the Internet as well.
The shifting of Usenet from UUCP connections to TCP/IP internetworking meant that some rethinking was required in how Usenet articles were moved from server to server. On the Internet, Usenet was just one of many applications, and the transfer of messages had to be structured using one of the two TCP/IP transport protocols, TCP or UDP.
Thus, like other applications, Usenet required an application-level protocol to describe how to carry Usenet traffic over TCP/IP. Just as Usenet had borrowed its message format from e-mail's RFC 822, it made sense to model its message delivery protocol on the one used by e-mail: the Simple Mail Transfer Protocol (SMTP). The result was the creation of the Network News Transfer Protocol (NNTP), published as RFC 977 in February, 1986.
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