This document is for information pertaining to the OC3 monitor project used to measure and analyze Internet flows. John Bass (jbass@mcnc.org) at NCSU is currently coordinating the OC3 monitor project for the NC Giganet.

Useful Links

NC Giganet Flows Analysis

The main vBNS OC3Mon/Coral page
the Coral project
details about the OC3Mon implementation
links to published papers from vBNS engineering

How to grab meaningful data from NC Giganet sites

From the initial web page for the "Flows Analysis" ( http://www.vitalnet.org/nc_giganet_flows/), first choose a network (typically nc_giganet). On the next page, choose the actual OC3MON you are interested in getting information from. There are currently (5/14/98) two OC3MON's on each of the points in the NC Giganet mesh (NCSU, UNC, MCNC, Duke) for vBNS. Also, choose the date that you are interested in. For multiple-day time-series data, choose the last day you are interested in.

This brings you to what we refer to as Page 1, which allows you to choose a time interval, and a type of data to examine.

Single-interval Data

Packet Length Histogram

Byte Volume Graphs

Packet Volume Graphs

Flow Volume Graphs Average Packet Size Graphs Aggregate Traffic Graphs (by protocol or application) Fraction of Traffic Graphs (by protocol or application) Average Traffic per Flow Graphs (by protocol or application) Traffic Composition Data (by protocol or application) Monitoring Collection Loss

What we have access to...

We have an account on loopy.ncren.net (, the machine hosting the www.vitalnet.org website for the NC Giganet Flows Analysis. Don Smith knows the username and password.

We can update the currently installed PERL scripts for the Web interface. We can also write new scripts for the Web interface. However, since loopy is not the actual machine that executes the scripts, and the organization of the vitalnet site is a bit of a hack, we must work with John Bass (jbass@mcnc.org) to activate the new scripts.

We hope to soon have an OC3MON (or variant) monitoring the UNC link to the Internet 1.

What it all looks like...

loopy.ncren.net is running SunOS 5.5.1 (System V Unix) and an Apache web server which hosts several virtual domains. Also, loopy runs a cron job to gather information from all eight NC Giganet OC3MONs every five minutes.

This is a list of the important directories:


/dept/flow_stats/bin/ /nc_giganet_data/nc_giganet/ /nc_giganet_data/nc_giganet/{ unc1 | unc2 | ncsu1 | etc }/ /nc_giganet_data/nc_giganet/{oc3mon}/{date}/

Digging throught the PERL code...

First, a disclaimer: The current PERL scripts are basically a hack that evolved from MCI's vBNS project ... they provide the services above, but are not designed in a modular or very extensible fashion.

There are two files which provide all the services: fwsummarize.pl, which handles the collection and display of all single-interval data, and reports.pl, which handles all the collection of intervals data, including time-series plots.

For future work on these scripts, look to reports.pl to see the routines that crunch data for the graphing utilities. In particular, the following routines are especially meaningful:

sub init_and_parse

sub process_options sub get_file_list sub crunch_numbers sub print_report
Other DiRT documents
Author: Jan Borgersen
Last updated: May 14, 1998