Linux Network Administrator Manual (16)
2000-07-30 20:18
Publisher: NetBull Readings: 1042 Translation: Zhao Wei GoHigh@shtdu.edu.cn Chapter 16 Network News (NetNews) 16.1 USET's Historical Network News (NETWORK News) The concept of NetWork News is produced in 1979, and two graduate students were there. Tom Truscott and Jim Ellis Consider using UUCP between UN * X users to connect each machine for information exchange. They have formed a small network with three machines in North Carolina. Initially, information transmission is processed through many shell scripts (later rewritten with C language), but these scripts have never announced to the outside world. They are quickly replaced by "a" news, which is the first news software released to the outside world. "A" News is only designed to handle very few articles per group per day. When the capacity of the newsgroup continues to increase, the software is overridden by Mark Horton and Matt Glickman, and he is called "B" release (also name BNEWS). BNEWS The first public release is version 2.1 of 1982. It has been continuously expanded, adding several new features. It is currently the version of BNEWS 2.11. Now it has been discarded, and the last official maintainer has also turned to Inn. Another rewrite is done by Geoff Collyer and Henry Spencer in 1987; this is the version "C", or called C News. Many patchs for C News are in the next period of time, the most significant is the C News Performance version. In the site with a large number of newsgroups, the system overhead caused by frequent calling relaynews (which is responsible for inciving the station article to other sites). The Performance version adds an option to RelayNews, which allows it to run in later mode (daemon mode), put yourself into the background. The Performance version is currently included in most Linux version. All News issues that have been basically used for UUCP networks until all the NEWS issuers of "C" are used for UUCP networks. Although they can also be used in other environments. A new solution requires a new solution in terms of TCP / IP, DECN, or other corresponding networks. This is why the "Network News Transfer Protocol" is introduced in 1986, NNTP. It is based on network-connected and specifies a number of commands that interact and collect articles. There are many NNTP-based applications on the Internet. One of them is the NNTPD package of Brian Barber and Phil Lapsley. You can use this software and other software to provide news reading services for many hosts in a local area. NNTPD is a NNTP feature that is designed to make NEWS packages such as BNEWS or C News. Another different NNTP package is Inn, ie Internet news. It is more than just a front-end program, it is a News system. It is a complex News relay background program that can effectively maintain several parallel NNTP links, so many Internet sites select it as a News server. 16.2 In short, what is Usenet? One of the most significant facts about USENET is that it does not belong to any organization, and there is no centralized network management privilege. In fact, this is part of Usenet learning, except for technical instructions, you can't define it, you can only point out what it is not.
If you have the excellent "Zen and Internet Art" of this Brendan Kehoe (online and spentice-havert, see [Kehoe92]), you will find a list of interesting and listing that is not a usenet. Through the risk of feeling stupid, people can define the set of useenet as a collection of separate sites to exchange USENET NEWS. To become a USENET site, you do all what you need is to find another USEnet site and reach an agreement with your owner and maintainer to exchange the NEWS. Providing News for another site is also known as give it to it, which originated from another system of usenet philosophy: "Get a feed and you're on it." USENet News The most basic unit is an article. This is the user writing and "delivery" to the web. In order to allow the News system to be handled, these articles come with management information, the so-called article title (head). It is very similar to the title format of the mail compliant with the Internet mail standard RFC 822. It is also a few lines of text, and each line starts with a field name ending with a colon, and thereafter has a value of fields. [1] The article is submitted to one or more newsgroups. People can regard a newsgroup as a forum related to a common subject article. All newsgroups consist in hierarchical structures, each group name indicates its location in this hierarchy. This makes a group easy to see which aspects. For example, anyone from the name of the newsgroup can see that comp.os.linux.announce is an operating system announcement called Linux. These articles are then exchanged between all the USENET sites that will pass the News from this group. When two sites agree to exchange News exchange News, they can freely exchange any newsgroups that they like, even with their own local NEWS hierarchy. For example, Groucho.edu may have a news link with Branyard.edu (this is a major NEWS feeder), and there is a link to a small site it wants to feed. Now, Barnyard is possible to receive all USENET groups, while GMU only wants to deliver several primary hierarchies such as SCI, Comp, REC, etc. Some downstream sites, such as a UUCP site called Brewhq, even want to deliver less groups because they do not have such a network or hardware resource. On the other hand, BrewHQ may want to receive newsgroups from the FJ hierarchy, and this hierarchical GMU is not transmitted. Therefore, it maintains another link with GargleBlaster.com, but this site transmits all FJ groups and feeds these groups to BrewHQ. The flow of these NEWs is shown in Figure 16.1. Figure 16.1 Usenet News The flow in the University of Groucho Marx Although it is clear, the labels on the arrows issued from BrewHQ may still need to explain. By default, it will have all local News to be sent to Groucho.edu. However, since the Groucho.edu does not transmit the FJ group, there is no arrow to point to these groups. Therefore, the feeding operation from BrewHQ to the GMU is labeled ALL,! FJ, indicating that all groups under FJ are sent to it. 16.3 How does Usenet handle news? Today, UseNet has grown to a huge proportion. Sites for transferring the entire network news usually transmits sixty megabytes per day. [2] Of course, this requires more processing than any setup file. So let's take a look at most UN * X system to handle USENET NEWS. News are released via a variety of transmission channels. Traditional transport media have been UUCP, but the main data traffic now is transmitted by the Internet site.
The routing algorithm used is called a diffusion method: each site maintains a lot of links to other sites (News Feeds). Any articles generated by the local News system or received are forwarded to them unless the article is already on that site, in which case the article will be discarded. By observing the PATH: Title field, a site can find all other sites that the article has passed through. This title contains a list of all systems marked by Bang Path markers by it. In order to distinguish various articles and identify duplicate articles, the USENET article must carry a message ID (indicated in the message-id: Title field), which combines the name of the delivery site and a serial number "". "" For each article processed, the News system records this ID into the History log file, accordingly, check all new articles.
Article information flow between any two sites can be restricted by two guidelines: First, the article is assigned a release information (in the Distribution: Title field), which can be used to classify the article into the appropriate group in the site. in. On the other hand, the exchanged newsgroups can be limited by both transmission or receiving systems. The collection of newsgroups and categories that allow for a site transfer is usually saved in the SYS file.
Pure article quantity usually requires improvement of the above scheme. On a UUCP network, it is usually done to collect an article every other period of time and set the collected article into a single file, compress and send it to the remote site. This is called batch processing. [3]
Another technology is the IHAVE / SENDME protocol. This protocol avoids repeated sending articles in the initial place, which saves network bandwidth. Not putting all the articles in a batch file and send them together, but only combines the message ID of the article into a huge "IHAVE" message and sends it to the remote site. Remote site reads this message, compared to its own History file, then returns a list of articles you want in the "SendMe" message. Thereafter, only these articles will be sent.
Of course, IHAVE / SendMe is only meaningful when they involve two large sites, and the two large sites receive NEWS from several separate feeding, and often select each other as a valid NEWS mobile destination.
Site on the Internet usually depends on the software based on TCP / IP, using the network news transfer protocol NNTP [4]. It transmits NEWs between feeders and provides usenet access to separate users on the remote host.
NNTP can deliver News in three ways. One is the real-time version of IHAVE / SendMe, also known as the Pushing News. The second technique is called a pulling news, in which customer requests a list of lists in the specified newsgroup or hierarchy to the server, and selects those articles not in its History file. These articles arrive at the server site after the specified date. The third way is to interactive news reading, allowing you or your news reading readers to extract articles from the specified newsgroup, as well as an incomplete article of the title information.
On each site, News is placed in the directory structure under / var / spool / news, each article is a file, and each newsgroup is in a separate directory. The directory name consists of news group name, and each portion of the news group name makes a path portion. Therefore, the article on Comp.OS.Linux.misc is placed in / var / spool / news / comp / os / linux / misc. The article in a newsgroup is allocated in the order of arrival, this number as the file name. The current online article number is placed in a file called Active, this file is used as a list of newsgroups known as your site. Since the disk space is limited resources, [5] After a while, you need to start discarding some articles. This is called Expiring. Typically, the article from a certain group and the structure has expired after a fixed day after arriving at the site. If the delivery person can override the number of fixed days if you specify an expiration date in the article title field Expires:
Comment
[1] The format of the USENET NEWS message is specified in RFC 1036, the "Standard for Interchange of UseNet Messages).
[2] Wait, transfer 60 megs at 9600 bps, it is 6 million by 1200, that is ... 哝哝, ..., cough! That takes 34 hours!
[3] According to Geoff Collyer, the gold rules of online news are "you need to batch your article."
[4] is discussed in RFC 977.
[5] Some people claim that USENET is the common conspiracy of MODEM and hard disk manufacturers.
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