
				TIERS
				-----
	
	   		   Matthew B. Doar		


1) Purpose


TIERS is a freely available model, algorithm and source code for the generation
of random networks. The user specifies a number of parameters to describe the 
number of nodes and their interconnectivity and the algorithm generates a list 
of nodes and a list of edges. These randomly generated networks are intended to
resemble real data communication networks more closely than some models which 
have been used in the past.


2) Compilation

The code is written in C++ and the Makefile which is distributed with the code
assumes that g++ is available on your UNIX system. If this is the case, just 
type

cd src
make

Some warning of unused variables may appear if the -Wall flag is used (they 
are for future use). TIERS has been successfully compiled and tested under 
SunOS 4.1.4 on a Sparc20.


3) Running the Model

The executable is named `tiers' by default and can be run from the command 
line. Output appears on the standard output, so can be redirected to a file.

There are 6 major parameters and five parameters to control the redundancy 
in the generated network. What each parameter represents can be found by 
typing `tiers' with no arguments or by reading the accompanying paper.

Example parameter settings
--------------------------

To see just a WAN with some redundancy, try

tiers 1 0 0 30 0 0 3 1 1 1 1

To see a WAN with some MANs, try

tiers 1 3 0 20 10 0 3 2 1 1 1

To see a three tier network with redundancy, try

tiers 1 10 5 10 10 5 2 1 1 2 1

If the output format is set for gnuplot (in tiers_config), and gnuplot 3.6 or 
higher is found in the execution path, the following will pop a network up in 
a gnuplot window:

tiers 1 8 3 10 20 3 3 2 1 1 1 > myfile.gnu ; gnuplot "myfile.gnu"

If gnuplot 3.5 or lower is available, the .gnu output can be converted to a 
file suitable for plotting by using the strip4gnuplot3.5 command in the bin 
directory in this distribution.

cd ../bin
strip4gnuplot3.5 ../src/myfile.gnu
gnuplot "../src/myfile.gnu.gnu3.5"

To change the output format, edit the file 'tiers_config', from where 
configuration details are read at run time.

4) PNNI 

New with tiers version 1.2 is the ability to generate models of PNNI
networks, with multiple peer groups and two levels of peer groups. The
number of nodes in a WAN (SW) and the number of MANs (NM) have to be
the equal. To create a PNNI model, add an extra non-zero parameter to
the command line arguments at the beginning:

tiers 1 1 8 3 8 20 3 3 2 1 1 1 > myfile.gnu ; gnuplot "myfile.gnu"
      a   b   c

note:
a. 	Non-zero first parameter to enable PNNI 
b,c. 	Equal
      
5) More Information

See the PostScript file 'Tiers_Manual.ps' for further information.

End of file.
