Kantronics KPC-9612, Getting Started And Reference Manual

Page: 77 / 81

KPC-9612 Version 6.0 October 25, 1995
77
Firmware for the KAM Plus, KPC-3, KPC-9612 and KAM Enhancement Board now includes
support for the DAMA protocol (slave mode) as used by many amateur radio operators in
Germany, Belgium, Luxembourg, the Netherlands, France, Switzerland and other parts of
Europe. To the best of our knowledge there are
no DAMA nodes in the US or any-
where else outside of Europe.
What is DAMA?
Anyone who has used packet radio has, from time to time, experienced problems in communicat-
ing through the packet network. Problems vary from place to place and tend to be related to the
types of nodes being used, the amount of traffic in a given area, and other factors.
DAMA (Demand Assigned Multiple Access) is a network protocol for regulating packet traffic to
eliminate or dramatically reduce collisions among users on the crowded channels available to ama-
teurs in densely-populated northern Europe. It was developed in Germany by NORDxLINK. (Refer-
ences to more information on DAMA are provided in the bibliography section of this addendum.)
In the DAMA system, a "master" node is set up in each local area to control transmissions from all
stations connected to the node. By local agreement, users do not connect directly to each other;
they connect only through the master.
What does a DAMA system look like?
The DAMA master node requires a computer running specialized DAMA software. TheNetNode
(TNN) software, developed by NORD><LINK, is one such specialized program which is used in the
computer of a DAMA master along with one TNC with a special EPROM for each radio frequency
used on the system. RMNC/FlexNet software is another program which is very popular in Germany.
Within each Local Area Network (LAN), end users set themselves up as DAMA "slaves," using spe-
cially equipped TNCs which contain firmware (EPROM) that can operate in a DAMA "slave" mode
(such as the Kantronics TNCs with DAMA slave mode support). The slaves may use a standard ter-
minal or host mode program or any of a variety of specially written European programs, such as
SP, Grafik Packet and ESKAY, some of which make use of the KISS Mode feature of the TNC.
To use the DAMA system, the user connects to the DAMA master with a normal connect frame.
When the master responds to the connect frame, the TNC is automatically placed into DAMA slave
mode. The DAMA master polls each slave within the LAN in a "round-robin" fashion (somewhat like
the token passing method) and the slave TNCs transmit packets when the master has granted per-
mission to do so.
The slave TNCs continue to he polled with priority among the slaves assigned according to the
number of times each responds with information frames (as opposed to IT frames - i.e., no data to
send). Priority is dynamically assigned so that those stations that are sending information are pol-
led more frequently than idle stations. However, once an "idle" station responds with information,
its priority is upgraded.
Communication over the wider area is handled between the DAMA master nodes which are con-
nected to each other using the standard NET/ROM™ type protocol. For the DAMA system to work
effectively, each slave associates with only one master node and connects only to that master. If
an end user is connected to more than one master, each master will poll the slave TNC according
to its polling schedule. When polled, the slave TNC will transmit all frames it has available to
whichever master polls it. This would increase the probability of collisions with other users, thus
defeating the purpose of the DAMA system.