NNTP has commands which provide a straightforward method of exchanging articles between cooperating hosts. Hosts which are well connected on a local area or other fast network and who wish to actually obtain copies of news articles for local storage might well find NNTP to be a more efficient way to distribute news than more traditional transfer methods (such as UUCP).
In the traditional method of distributing news articles, news is propagated from host to host by flooding - that is, each host will send all its new news articles on to each host that it feeds. These hosts will then in turn send these new articles on to other hosts that they feed. Clearly, sending articles that a host already has obtained a copy of from another feed (many hosts that receive news are redundantly fed) again is a waste of time and communications resources, but for transport mechanisms that are single-transaction based rather than interactive (such as UUCP in the UNIX-world <1>), distribution time is diminished by sending all articles and having the receiving host simply discard the duplicates. This is an especially true when communications sessions are limited to once a day.
Using NNTP, hosts exchanging news articles have an interactive mechanism for deciding which articles are to be transmitted. A host desiring new news, or which has new news to send, will typically contact one or more of its neighbors using NNTP. First it will inquire if any new news groups have been created on the serving host by means of the NEWGROUPS command. If so, and those are appropriate or desired (as established by local site-dependent rules), those new newsgroups can be created.
The client host will then inquire as to which new articles have arrived in all or some of the newsgroups that it desires to receive, using the NEWNEWS command. It will receive a list of new articles from the server, and can request transmission of those articles that it desires and does not already have.
Finally, the client can advise the server of those new articles which the client has recently received. The server will indicate those articles that it has already obtained copies of, and which articles should be sent to add to its collection.
In this manner, only those articles which are not duplicates and which are desired are transferred.