Disclaimer
This implementation of BGP-4 is constantly improving and evolving, and
examples are not always immediately updated to reflect the most
current version. It is usually (though not always) safe to assume
that an example still runs properly, but the DML files and the output
files may look different than the way there are described in some of
the accompanying documentation.
Compatibility
This example is up-to-date with SSF.OS.BGP4 version 1.1.0.
Conventions
For an explanation of
the debugging output used in this example, refer to BGP Debugging Output Conventions.
Overview
This example does not examine a specific aspect of BGP, but is a more
general one which reveals how BGP is operating from a more macroscopic
perspective. It shows how randomly generated traffic in a network
with 32 autonomous systems is correctly forwarded from source to
destination.
Files
primary source: forwarding1.dml
library source: dictionary.dml
schema source: net.dml
raw output: forwarding1.out
Running
To run this example, SSFNet must be installed and the three source
files, as listed in the previous subsection, must be accessible. As
an example, if the three source files were together in the same
directory, the following command could be used to run the
simulation:
java SSF.Net.Net 150 forwarding1.dml dictionary.dml net.dml
Network Graph
Discussion
In this example, BGP is running at 32 different interconnected ASes,
using a simple shortest path policy for evaluating routes. After
routing information is completely disseminated among the ASes, traffic
is flooded between all pairs of hosts in the network. Each AS has
only one router and one host, so that BGP can be used alone, without
the need for an intra-AS routing protocol to be present. In order to
generate traffic, an application protocol is running at each host.
The applications are set up to send a message every 100 seconds, so
the simulation must be run for at least that long in order for there
to be any interesting results. Output is generated by an application
each time it sends or receives a message, so the results of running
the simulation will contain lines that look like this:
100.0 --- app at 0:4:1 sent msg to 3:6:1 (0.0.1.18/32) 100.0 --- app at 0:4:1 sent msg to 1:7:1 (0.0.0.42/32) 100.0 --- app at 0:4:1 sent msg to 3:4:1 (0.0.1.34/32) 100.000875 +++ app at 3:6:1 rcvd msg from 0:4:1 100.000935 +++ app at 3:4:1 rcvd msg from 0:4:1 100.001365 +++ app at 1:7:1 rcvd msg from 0:4:1 |
The numbers at the far left represent the simulation time in seconds.
Once the example has been run (using make), output
containing additional setup messages--which indicate the progress of
each BGP speaker in setting up the forwarding tables--can be found in
the file example-setup.out. Output without such messages
will be in example.out. The only difference between the
two DML files used to generate these output files is in the values of
the bgpoption attributes.
The numbers at the far left represent the simulation time in seconds.
The example can also be run using an alternative configuration
file--forwarding1-setup.dml--which
prints out additional setup messages indicating the progress of each
BGP speaker in setting up the forwarding tables. The only difference
between this configuration file and the other is in the values of the
bgpoption attributes.