1 RESILIENCY IN LOCAL AREA NETWORKS (LAN’s) By ASAEL OMWAMBA And SINCLAIR GIBORE Dept. of Computer Science Montclair State University CMPT 495-01 - Data Security Instructor: DR. Stefan Robila 2 TABLE OF CONTENTS 1 Introduction……………………………………………………………….. 3 1.1 Introduction………………………………………………………….... 3 1.2 Local Area Networks (LAN)…………………………………………. 3 1.2.1 Design of LAN…………………………………………………. . 3 1.2.2 Peer-to-Peer Architecture……………………………………….3 1.2.3 Client-Server Architecture…………………………………….. 3 2 Types of Failures……………………………………………………….. 5 2.1 Path Failures…………………………………………………………. 5 2.2 Link Failures………………………………………………………….. 5 3 How Failures Are Handled…………………………………………….. 5 3.1 Handling Link Failures………………………………………………. 5 3.2 Handling Path Failures………………………………………………. 6 4 Optimizing Redundancy………………………………………………… 7 4.1 Switching ……………………………………………………………… 7 4.2 Routing ………………………………………………………………… 8 4.2.1 Problems with Routing………………………………………….. 10 4.2.1.1 Looping………………………………………………………… 10 4.2.1.2 How Routing Loops are Handled…………………………….. 11 5 Path Determination……………………………………………………... 12 6 Dead Node Detection…………………………………………………….. 13 7 Conclusion……………………………………………………………….. 133 INTRODUCTION A local-area network (LAN) allows businesses to share resources efficiently and thus makes the internal communications of a business possible. This enables the internal structure of the business to share files, printers and other resources. In this paper we focus on how resiliency is achieved in a LAN. We discuss in depth the causes of path and link failures and how they are handled to attain a highly resilient LAN. The paper also discusses path determination and how dead nodes are detected in a LAN. LOCAL AREA NETWORKS A LAN is described as a high speed, low-error data network covering a relatively small geographic area up to a few thousand meters. LANs connect workstations, peripherals, terminals and other devices in a single building or other geographically limited area. Design of LANs:-LAN’s are designed to achieve the following 1) Operate within a limited geographical area 2) allow multi-access to high bandwidth media 3) Control the network privately under local administration 4) Provide full-time connectivity to local services 5) Connect physically adjacent devices There are two major types of LANS: - These are peer-to-peer and client-server networks. Peer-to-peer In a peer-to-peer network, connected computers or devices act as equal partners as all individual computers perform both the client and server function. Its main advantage is that there is no single point of failure as individual users make there own independent decisions as to whom they can share their resources with. Administration of security is also left to individual users. Figure two in the next page shows a peer-to-peer architecture Client-Server For a client-server environment, resources are located on one computer (server) and all other computers (clients) are connected to the server. The clients send requests to the server and the server responds to these requests. This kind of architecture enhances security, control and ease of access. But on the other hand it introduces a single point of failure. Client-server is the most common type of architecture that is used today. Though this kind of architecture is ideal, there are issues associated to it that needs to be resolved in order to achieve resiliency. These issues are discussed later in this paper. Figure one in the next page shows a peer-to-peer architecture figure 1 and 2 represent a client-server architecture and peer-to-peer4 architecture respectively5 Both client-server and peer-to-peer architectures are prone to failures. These failures might be as a result of a breach of network security by way of denial of service attacks or through a natural disaster that can lead to the distraction of a network node. These failures can lead to the unavailability of the critical services in a network. Types of Failures Failures that occur in a network can be broadly categorized into two. These are link and path failures. Link failures Link failures are a result of a problem that may cause either the device connecting two sub-networks (in this case a router) or a device connecting multiple nodes (in this case a switch) to malfunction. This can also be a failure in the link connecting two routers or switches due to a software error, hardware problem or link disconnection. Path failures Path failures are as