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[ What does it consist of? ] [ How to use it? ] [ Features ] [ More information ]


mcntp - Transport of NetNews over IP-Multicast

What is it?

Mcntp is a (Usenet-)news transport protocol and its implementation. The difference between mcntp and nntp is that with mcntp, articles are transferred over IP-multicast (which uses UDP) and not via TCP. Thus articles that are sent by one sender once can be received by multiple receivers:

multicasting image (983 bytes)

So articles need only be sent once to reach all n receivers as shown in the above graphic. The result in the above example is that on the line from sender to the routers, the bandwidth needed is only one nth relative to sending the article to all receivers separately.

What does mcntp consist of?

The mcntp software consists of three parts: The next figure will show how this might look in practical use.

How to use it

practical use image (3301 bytes)
One sender host has one or more sender processes running that distribute news. In addition, a directory server is running which tells the senders what multicast groups to use and which then distributes this list to a special multicast group. Receivers listen to that group and if they want, they select an appropriate multicast group to receive articles from it. These articles are then fed to a nntp server (which need not be on the same host as the multicast receiver). If the nntp server is not available, articles can be spooled to disk and fed to the server (by an external program such as rnews) when it is available again.


Articles can be compressed by using zlib to reduce bandwidth use further. It has been shown that the packets that are sent to the net are about 60% of the size of the original articles.

In order to prevent injection of forged articles without leaving traces, articles are digitally signed before transport.

At the moment only articles that are smaller than 64kBytes in size can be transmitted via mcntp, as UDP packets can not contain more data. For practical use it is better to reduce the maximum size to about 20 kBytes as many systems can not reserve such large socket buffers or have problems due to bad implementations with packets larger than 32kBytes.
At first this sounds not good, but research has shown that over 90% of all articles are less than 32kBytes in size.

Tests that have been done in cooperation with Loral CyberStar (formerly Orion Network Systems) have shown that mcntp can also be used to distribute NetNews over Satellite. Here are some of the results and config hints.

Sourceforge project page

There is a Project page at [SourceForge Logo].
Everyone is invited in participating. This can be done in various forms:


Where to get it?

Please look at the download page of the mcntp project pages on SourceForge

Mcntp is hosted on SourceForge Logo

Homepage of Heiko W. Rupp (pilhuhn)

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