University: University of Maryland, College Park
Name of Sponsoring Professor: John S. Baras
Department: Center for Satellite and Hybrid Communication Networks, Institute for Systems Research, Department of Electrical and Computer Engineering

We are using OPNET for:

1. Hybrid Internet Simulation Test-bed

Internet technology as a widely accepted modern telecommunication standard has been widely extended to combine with numerous other technologies, e.g., satellite, ATM, wireless. This is what we term as Hybrid Internet. Along with this technology emerging, various enhancements and alterations of standard TCP/IP for different purposes have been proposed and studied intensively. More and more frequently we are facing the question of how to choose from these different schemes to design a system for a particular purpose, which would inevitably involve the interaction and trade-off study. We believe that simulation is a powerful tool for this type of work.

In this project, we implemented a series of traffic models and TCP/IP enhancements. The goal of our work is to make a set of reusable modules upon which we can build complex systems to study the standard protocols and their variations.

Our traffic models includes:

Auto-Regression

Pareto

Weibull

Log-normal

Markov Modulated Possion Process

Aggregated On-Off Sources

Fractional Brownian Motion

Our protocol models includes:

TCP splitting/spoofing

Fast Retransmit Fast Recovery (also available with OPNET6)

Window scaling and fine resolution time stamp (also available with OPNET6)

Selected Acknowledgment (SACK) and Forward Acknowledgment (FACK)

IP flow classification for per-flow queuing

First Come First Serve

Round Robin

Start-time Fair Queuing

Tail Drop

Drop From Front

Longest Queue Drop

Random Longest Queue Drop

Random Early Discard

Probabilistic Fair Drop

Protocol Booster -- Forward Erasure Correction (FZC) protocol booster

2. Enhanced TCP/IP Gateways

The demand for Internet bandwidth has been growing rapidly over the years and the use of high bandwidth satellites has been proposed as one possible solution to meet the increasing demand. However, there are certain performance problems with providing Internet over satellite due to the nature of TCP/IP protocol suite and the satellite link characteristics. This project is a simulation study of an architecture for improving the performance of TCP/IP over satellite links. On each end of the satellite link, there are gateways that split the TCP connection so that the satellite link is transparent to the end hosts. The split TCP connection over the satellite segment is then optimized. TCP congestion control is maintained on each segment of the split connection.