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
over ip-multicast and not via TCP. Thus articles that are sent by one
sender can be received by multiple receivers:
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.
- A directory server: This one coordinates the relationship between
news- and multicast groups
- A multicast sender: This one gets its articles from the file
system and sends them over ip-multicast.
- A multicast receiver: This one receives articles that have been
sent over ip-multicast and feeds them to a nntp server.
How to use it
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
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
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
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
Therefore keys produced by rsaeuro can not be exchanged with rsaref at
October 98 issue of German iX magazine
has an article about Mcntp on page 90ff
There exist two mailing lists about
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
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