Before the explosion of routing tables and of forwarded traffic, the classic routing paradigm constituted routing table lookups in increasingly complex routing tables. These tables were populated by more or less scalable and fast-converging dynamic routing protocols together with connected routes and static routes.
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Showing posts with label Article. Show all posts
Cisco IOS Software
Cisco IOS Software has been around for quite some time. The original intention of the developers was to provide a small embedded system for limited-memory and speed-critical packet-switching routing appliances. Speed requirements within embedded systems are usually met by design simplicity and removal of unnecessary features. Cisco IOS Software has a cooperative multitasking kernel architecture featuring several processes and "resembles a loose collection of components and functions linked with the rest of IOS. Everything including the kernel runs in user mode on the CPU and has full access to systems resources."[1]
Linux
This UNIX-like operating system is based on the work of Linus Torvalds and was inspired to some extent by Andrew Tanenbaum's Minix operating system. However, Torvalds also had in mind to overcome the limitations of Minix and abandon its microkernel concept for the sake of a modular kernel. Over the recent years, it has grown to a huge collaborative effort with thousands of developers.
Chapter 2. User-Space Routing Software
As described in Chapter 1, "Operating System Issues and Features—The Big Picture," user-space routing tools run as one single process (monolithic architectures) or as a set of daemons external to the kernel routines, either single-threaded or multithreaded. As long as these daemons are alive, routing information—signaling information to be more precise—can be exchanged or withdrawn and eventually populate the gateway's routing table.
The GNU Zebra Routing Software
GNU Zebra is a free and mature software package that manages TCP/IP-based routing protocols. Zebra's unique architectural foundation is based on the concept of one single process for each signaling routing protocol. Each module can run, be restarted, or be upgraded independently of the others, which greatly increases the stability of the entire system. In addition, the protocol daemons can be run just to exchange signaling information or populate the system's forwarding table via the Zebra master daemon (zebra). Particularly popular applications that use signaling information are route servers and route reflectors that distribute Border Gateway Protocol (BGP) reachability information. Chapter 10, "ISP Connectivity with BGP4: An Exterior Gateway Path-Vector Routing Protocol for Interdomain Routing," discusses these applications in depth. GNU Zebra does not support or make use of threads yet—it has its own internal cooperative user-space thread model (not really multithreaded). Zebra code constitutes the development foundation for IP Infusion's commercial ZebOS. The following list presents some useful details about the software:
MRT (Multithreaded Routing Toolkit)
The MRT Project is a monolithic multithreaded routing engine (MRTd) that was developed under a research grant at the University of Michigan. It contains multiprotocol IPv4/IPv6 routing daemons and accompanying analysis and simulation tools. The following list presents some useful details about the software:
Chapter 3. Kernel Requirements for a Full-Featured Lab
This chapter discusses various important aspects of networking-related kernel configurations on which we will rely heavily as we advance throughout this book. Some of these features need to be enabled at kernel compile time, some utilize loadable kernel modules, and others require user-space configuration tools and utilities such as the firewall or virtual local-area network (VLAN) configuration tasks. In the context of kernel parameters, the sysctl utility is introduced and thoroughly discussed.
