20-04-2011, 04:12 PM
Presented By
Mukesh kumar
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Abstract
Computer Networks have greatly evolved in the last decade. These changes included improvement in network speed, latency and also related issues in physical media and computer architecture. All this was motivated by the requirements for new services and the introduction of new technologies. This change accumulated until they reached a point in which the nature of networks itself was transformed. The basic concerns and design principles will suffer a metamorphosis that will affect how gigabit networks will be handled.
The focus of this Report is the recent development of gigabit networking. The basic concepts of gigabit networking, issues on high-speed switching and routing, congestion control, various routing protocols and current gigabit technologies are discussed in this report.
Chapter 1
Introduction
Technology advancement in the fields of fiber optics, computing systems, computer applications, data communications and internetworking has been linked closely to the development of networks that have the capability of operating at gigabit speeds. The capability of today's fiber optic signaling equipment to transmit several gigabits per second over long distances with very low error rates through optical fiber has convinced the researchers that gigabit networks are technologically feasible.
Further, technology has realized a tremendous increase in the power and bandwidth of many parts of computing systems today at an affordable price. This is demonstrated by the existence of fast CPUs (for acronyms, please refer to the list of acronyms), fast memory, and high-speed buses in desktop computers, workstations, and servers. According to Moore’s Law, processor speeds double every 18 months, while it is commonly agreed that network capacity is increasing even faster at the factor of 1.78 per year. High-bandwidth storage systems have also been improved in performance. It is now possible to have gigabit-bandwidth file systems with a technology known as RAID.
As computing power and storage systems become increasingly powerful, it is easier now to support new and existing network and computer applications with high-bandwidth data, high-resolution graphics, and other complex and rich multimedia data. Real-time video conferencing, 3D animation modeling, Internet telephony, medical imaging, CAD/CAM applications, and Mbone transmissions just to name a few were unthinkable in a few years ago, but are being used extensively today. Table 1, gives a good summary of the new and existing applications that drive network growth.
Most existing networks today are slower than most current computers and servers. Many current computers and servers using an industry-standard PCI (Peripheral Component Interconnect) bus architecture are capable of processing raw I/O with throughput of 132 MBps, or 1.05 Gbps. When these computers or servers are connected to the network through FDDI (Fiber Distributed Data Interface) or Fast Ethernet, the most widely implemented networks today, the maximum transfer rate is just 12.5 MBps. As a result, a bottleneck occurs between the computers or servers and the network, or a relatively high number of CPU interrupts per transfer happens as the computer adapts itself to the slower networks.
Further, the explosive growth of the Internet, the WWW (World Wide Web) and enterprise intranets is radically changing the pattern of network traffic by introducing more and more different subnets. Network users are constantly accessing servers from many subnets and geographies rather than local servers to serve internal organizational needs. As a result, the traditional "80/20" rule is no longer true. In the past, the network traffic was 80% locally based in the subnet and 20% leaving the subnet, or running over the corporate backbone and across WAN (wide area network). The reverse trend is happening today. Today's network must be able to handle anywhere-to-anywhere traffic with 80% of the traffic crossing subnet boundaries.
With today's data-intensive applications, increasing number of network users, enterprise intranets, LANs (Local Area Networks), and new methods of information delivery, pressure for higher bandwidth is growing rapidly at desktops, servers, hubs, and switches. The concern is how to achieve a high-performance network with a bandwidth that matches the capabilities of its processing power and memory capacity. Therefore, the primary goal of data communications today is not only to facilitate data exchange between computing systems, but to do it fast as well. This drives a widespread interest in the technologies for gigabit networking.
Further, achieving true gigabit networks is not only the matter of raw bandwidth increases. Other aspects of networking should be considered. Such aspects are the existing legacy infrastructure networks in the existing switches, the software and network interface cards (NICs), and the ability of the protocol stacks to move data in and out of the computer, fast routing and switching. Other issues are increasing traffic demands, unpredictable traffic flows, and the priority of critical applications. Therefore, all of these aspects of the networking system should be taken into account in order to achieve true high-bandwidth networking.
This Report discusses the basic concepts of gigabit networking and the issues on switching and routing. It also presents the recent development of gigabit technologies, various techniques for congestion control, gigabit protocols and also various technologies supporting gigabit networks. Finally, current gigabit technologies available for high-speed LAN are discussed.
Chapter 2
Basic Concepts of Gigabit Networking
What is the speed for true gigabit networks? From the ATM (Asynchronous Transfer Mode) world, it could be 622,000,000 bps (OC-12), 1,244,000,000 bps (OC-24), or/and 2,488,000,000 bps (OC-48). With 100 MBps Fiber Channel, it would be 800,000,000 bps. In Ethernet, it is 1,000,000,000 bps. It also could be 1,073,741,800 bps (which is equal to 2 30 bps, where 2 10 equals 1,024 or 1 k). Standardized by IEEE 802.3z, a true gigabit network will provide connections between two nodes at a rate of at least 1,000 Mbps. By comparison, it is approximately ten times that of both FDDI and Fast Ethernet.
The networks with at least 1 Gbps are feasible today basically due to the technology advancement in fiber optics, and cell networking (cell switching, or cell relay).
2.1. Fiber Optics
Light has the properties of reflection and refraction. When light passes from one medium to another, some part of it gets reflected and the rest gets refracted (Figure 1). Fiber optics use the properties of light refraction to send signals over long distances across a thin strand glass (core), which is surrounded by a thicker outer layer (cladding). The structure of a fiber is shown in Figure 2. In fiber optics, bits are sent by transmitting pulses of light through the core of fiber.
