Simulation and Evaluation for a Network on Chip
Architecture Using Ns-2
Yi-Ran Sun, Shashi Kumar, Axel Jantsch
the Lab of Electronics and Computer Systems (LECS),
the Department of Microelectronics & Information Technology (IMIT),
Royal Institute of Technology (KTH), Stockholm, Sweden
{yiran,shashi,axel}@imit.kth.se
Abstract -- A new chip design paradigm called Network on Chip (NOC) offers a promising
architectural choice for future systems on chips. NOC architectures offer a packet switched
communication among functional cores on the chip. NOC architectures also apply concepts
from computer networks and organize on-chip communication among cores in layers similar
to OSI reference model. We constructed a protomodel using a public domain network simulator
ns-2 and evaluated design options for a specific NOC architecture which has a two-
dimensional mesh of switches. In particular, we analysed the series of simulation results about
the relationship between buffer size in switch, communication load, packet delay and packet
drop probability. All the results are useful for design of an appropriate switch for the NOC.
I. INTRODUCTION
Moore's law predicts that by 2008, it will be possible to integrate over a billion transistors on a
single chip. Current core based on SOC methodologies will not respond to the needs of the
billion transistor era. Network on Chip (NOC), a new chip design paradigm concurrently
proposed by many research groups[1],[2],[3] is expected to be an important architectural
choice for future SOCs. The proposed NOC architectures offer a general but fixed
communication platform which can be reused for a large number of SOC designs. A concept
of computer network in layers based on the classical OSI reference model is used by all of
proposed NOC architectures. We predict that NOC architecture would facilitate reuse at
various levels of system design, thus reducing the time to design and test.
However, NOC research is still in its infancy. A higher-level modelling will give us the
insight of knowing more about its architecture. We would use the tool, Network Simulator ns-
2
1
[4],[5] which has been extensively used in the research for design and evaluation of public
domain computer network, to evaluate various design options for NOC architecture, including
the design of router, communication protocol, routing algorithms.
This paper reports some experimental results based on the simulation of NOC using ns-2.In
the following, we give a brief overview of our NOC architecture and introduction to ns-2.In
section II, we describe how various aspects of our NOC architecture was modelled using ns-2.
Section III gives a description for our simulation experiment, and in section IV some
experimental results and corresponding analyses are presented. Finally, we draw some
conclusions in section V.
A. Overview of Our NOC Architecture
Our NOC is a scalable packet switched communication platform for single chip systems. The
NOC architecture consists of a mesh of switches together with some resources which are
placed on slots formed by the switches. Figure 1 shows a NOC architecture with 16 resources.
Each switch is connected to four neighboring switches and one resource. Resources are
1. Ns is a simulation tool developed by the Network Research Group at the Lawrence Berkeley National Laboratory.
Ns-2, or ns version 2 uses MIT's Object Tcl instead of previous Tcl.
mn×