Design And Implementation Of A Centralized Three-tier Switch Device Software Modules

The layer 3 switch technology which fits for the need of aggregation layer is a combination of the layer 2 switch technologies and routing. The packet processing capacity owned by this technology can reach up to 30Gbps and is as high as that of the layer 2 switch. Layer 3 switch can deal with not only link layer packets but also those in the IP layer. Although the layer 3 switch does not provide profuse kind of physical interfaces and routing protocols when compared with routers running on the backbone, the special needs of the aggregation layer make these two drawbacks not that serious. What is more important is that the provided high switch bandwidth is more likely to fit the requirement of aggregation layer.There are two common switch architectures in layer 3 switches, the integrated architecture and the distributed one. Limited by the layer 3 switch chips and the CPU in the control panel, the original integrated switch architecture has an unsatisfying performance when dealing with switch tasks in the IP layer and between line cards. But this has been largely overcome by the emergence of high performance switch chips and TCAM. These new technologies make this architecture qualified for aggregation layer. On the other hand, compared with distributed architecture, the integrated one has a cheaper line card which makes it competitive in the market.This thesis describes a kind of layer 3 switch based on the integrated architecture which has been developed while I was interning in Harbor Networks in Beijing. In this thesis, the switch chips used in this project are introduced first, which includes switch chips of G750 series, the interfaces between the chips and the CPU, and main routines while dealing with packets. The storage architecture used by this switch is introduced in the following, which includes TCAM, RAM and the corporation between these two parts.This thesis does not discuss how these switch chips process the packets and the related data structures used in the hardware layer in detail. It focuses on the design and implementation of two important software modules in this switch: the interface management module and the memory management module. Concepts in Linux kernel and object oriented programming are adopted here and consequently increase the extension and porting ability of these modules.The interface management module controls all the interfaces in this switch, including the attributes and abilities of the interfaces and the relationship among them. It provides interface management commands in the command line. After processing interface events, it notifies other software modules and also the hardwares to assure the correct behavior of this switch.The memory management module adopts the slab method in Linux kernel. This module manages the user memory in an effectively way. On the other hand, it has reduced the difficulty of locating memory leak by adding the statistics of memory usage information.