MesoNetHS: A Mesoscopic Simulation Model of a Router-Level 

Internet-like Network with High Speed TCP Replacements 

MesoNetHS is a mesoscopic (medium scale) simulation model of a router-level Internetlike network with support for high speed TCP replacements. The model, written in SLX1

, 

facilitates investigation of global behavior through simulation of a network representing a 

single Internet Service Provider. MesoNetHS is uniquely positioned between microscopic 

models, which require hundreds of parameters to fully specify detailed behavior of 

individual network elements, and macroscopic models, which aggregate behavior of 

many network elements into abstract representations that may lose key interactions on 

fine spatiotemporal scales. 

MesoNetHS assumes a three-tier hierarchy of routers (backbone, point-of-presence 

and access), while also supporting some heterogeneity, including: variations in speed 

among access routers and traffic sources, ability to connect access routers directly to 

backbone routers, and six classes of transport flow. Network links are simulated in detail 

only on the backbone, where propagation delays become important. The current model 

routes network traffic on static, shortest-path routes. Network traffic in MesoNetHS is 

supplied through simulated sources and receivers, which operate under connectionestablishment and congestion-control procedures representing the Reno version of the 

transmission control protocol (TCP). MesoNetHS can also use congestion-control 

procedures representing high-speed TCP replacements (C-TCP, HS-TCP, FAST-TCP, STCP, or H-TCP). Each source cycles continuously among three steps: (1) think for some 

exponentially distributed time, (2) connect to a receiver with probabilities reflecting the 

network topology, and (3) transfer a web page of some Pareto distributed size. Size is 

increased for selected transfers to simulate users who decide to download a paper, image 

or music file from a web site. 

Given a specified topology, MesoNetHS can be parameterized with a multiplier on 

propagation delays, queue limits and speeds for routers in each tier, average think period 

and file size (plus distribution shape), probability of a larger transfer and associated 

multiplier on file size. During simulation, model state is captured at each user-specified 

measurement interval, leading to time series for response variables. The current model 

records response variables at several levels, including: network wide, each router, and 

each flow class. Recorded responses include utilizations, queue sizes, losses, active and 

completed flows, retransmission rates, connection failures, throughputs, and rate of 

window increases, timeouts, and negative acknowledgments. MesoNetHS is also capable 

of logging detailed state changes and packet transfers for randomly sampled flows. 

MesoNetHS is implemented as an agent-automata model, where every active element 

is updated at each time step. For a topology of 171 routers, 28 backbone links, 27,600 

sources and 12,000 simultaneously active flows, MesoNetHS must update around 40,000 

elements per time step, where some elements are updated multiple times to reflect speed 

differences. For such a topology, MesoNetHS executes about 10 times slower than real 

time, depending on the processor used. To date, MesoNetHS has been used to simulate 

network evolution over periods from 20 minutes to 17 hours. 

 

1

 SLX is a commercial simulation system available from Wolverine Software, see: 

http://www.wolverinesoftware.com.