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Definition
It was not so long ago that switches were used
in telecommunications primarily for placing telephone calls. Dialing a telephone
number activated a series of switches to set up a voice path that could be as
simple as the next office or as complex as a multinational conference call. Internetworks
and the Internet are beginning to provide similar services for PC workstations,
servers, and mainframes. The primary goal of any data network provider is to eliminate
geographic and media constraints on connectivity while maintaining control over
resources and costs. Embedding Layer 3 Switching into the network is being promoted
as the best way to achieve this. A variety
of switch and router technologies are entering the market and creating confusion
among network professionals. New terms such as Layer 3 switching, multilayer switching,
routing switch, switching router, and Gigabit router are clouding the traditional
distinctions between switches and routers. Furthermore, many wiring closet switches
that traditionally employed simple Layer 2 switching are now offering Layer 3
switching functions or future options for Layer 3 capabilities. These changes
make it difficult for network designers to understand and deploy effective network
solutions. It is clear that a new generation
of Internet and intranet work processes are emerging and that users will benefit
from both increased competition and new services. It is therefore important do
demystify the hype and understand when and where Layer 3 switching is important
by getting back to the basics. Layer 3 switches
are compared to traditional multiprotocol routers. It is demonstrated that Layer
3 Switching is simply a re-invention of the router using new switch based technologies.
This seminar also reviews the basic data forwarding, route processing, and value-added
functions that are required of any intelligent network node.
Network Basics Understanding
the Layers
Internetworking devices
such as bridges, routers, and switches have traditionally been categorized by
the OSI layer they operate at and the role they play in the topology of a network: 1.Bridges
and switches operate at Layer 2: they extend network capabilities by forwarding
traffic among LANs and LAN segments with high throughput. 2.Routers
operate at Layer 3: they perform route calculations based on Layer 3 addresses
and provide multi-protocol support and WAN access, but typically at the cost of
higher latency and much more complex administration requirements. Layer
2 refers to the layer in the communications protocol that contains the physical
address of a client or server station. It is also called the data link layer or
MAC layer.
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