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 and not via TCP. Thus articles that are sent by one sender 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.

What does it 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 bandwithd 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 Orion Network Systems have shown that mcntp can also be used to distribute NetNews over Satelite. Here are some of the results and config hints.


The librsa from RSA DSI and Euro-RSA lib from Reaper Technologies have different ideas what data type one item in the key structure should have.

Therefore keys produced by rsaeuro can not be exchanged with rsaref at the moment!!


October 98 issue of German iX magazine has an article about Mcntp on page 90ff

There exist two mailing lists about mcntp.

Mcntp runs already on the listed platforms.

Some further reading including my thesis as HTML version.

Some of the manual pages that come with mcntp are translated to html and online available.

Here is a little How To to show the steps that are needed to send and/or receive News with mcntp.

Look at this page if you have problems compiling RSAEuro.

At 40. IETF meeting in Washington a BOF took place to find out weather a IETF working group should be founded to standardize a Multicast NetNews Protocol (mnnp).

Where to get it?

Please look at the download page of the mcntp project pages on SourceForge
2001/07/27 hwr