[Case Study Analysis and Simulation-Based Comparative Study of IS-IS and OSPF in any Enterprise Environment]

By

ACKNOWLEDGEMENT

I would take this opportunity to thank my research supervisor, family and friends for their support and guidance without which this research would not have been possible.

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

Signed __________________ Date _________________

ABSTRACT

OSPF and IS-IS are two main standard link state routing protocols designed to operate in various complex network topologies. One aspect that both protocols handle is the reliable dissemination of routing information over broadcast networks such as Ethernet and FDDI. Both protocols suggest different schemes for this purpose, and in this research we compare the two. The performance criteria being checked are: the longest arrival time of a routing update packet at all the routers; the average arrival time of routing update packets at all the routers; the total required bandwidth; and the number of memory accesses a router performs, which is evidence of the amount of internal work it performs. It was found that in the model of broadcast networks the scheme suggested in IS-IS is more efficient than that of OSPF in terms of the arrival times of routing update packets. In particular, the average arrival time of routing update packets in OSPF is 2-10 times longer than in IS-IS. In terms of the bandwidth each scheme consumes, there are scenarios where OSPF outperforms IS-IS and vice versa. In terms of the number of memory accesses routers perform in each scheme, IS-IS outperforms OSPF.

TABLE OF CONTENTS

ACKNOWLEDGEMENT2

DECLARATION3

ABSTRACT4

CHAPTER 1: INTRODUCTION6

CHAPTER 2: DISTANCE VECTOR AND LINK STATE ROUTING PROTOCOLS8

Distance Vector Protocols8

Link State Protocols9

Comparison9

An Overview of the OSPF and IS-IS Routing Protocols11

Routing Protocols: OSPF and IS-IS12

Common Characteristics14

Packet Encoding Issues15

Multiplexing Layer15

Avoiding Large Control Packets15

The Routing Domain16

Routing Packets19

CHAPTER 3: METHODOLOGY AND MODEL DEVELOPMENT23

LSA Packet Dissemination over Broadcast Networks in IS-IS and OSPF25

The Broadcast Network Model25

Transmission and Encapsulation of Routing Packets27

The Dissemination of LSA Packets in IS-IS28

The Dissemination of LSA Packets in OSPF29

CHAPTER 4: SIMULATION AND COMPARISON34

The System Model35

Simulation and Comparison37

CHAPTER 5: CONCLUSION42

REFERENCES43

CHAPTER 1: INTRODUCTION

Routing protocols are divided into two classes: distance vector protocols and link state protocols. In distance vector protocols a router maintains a vector of its distances to all destinations and periodically transmits this vector to its neighbors. Also, a router uses the distance vectors it receives from its neighbors to update its own distance vector. This process is guaranteed to converge at each router to the correct distances to all destinations. On the other hand, in link state protocols a router maintains a topology map of the routing domain in which it is located (Cidon & Ofek, 1993: 110).

A routing protocol operates within a routing domain, which contains interconnected routers and networks. There are two types of networks point-to-point and multi-access. A pointto- point network is a serial transmission line ...