Designing Switched LAN Internetworks.

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Designing Switched LAN Internetworks

design switched LAN internetworks:

  • LAN switching
  • Virtual LANs (VLANs)
  • ATM switching

Evolution from Shared to Switched Networks

In the past, network designers had only a limited number of hardware options when purchasing a technology for their campus networks. Hubs were for wiring closets and routers were for the data center or main telecommunications operations. The increasing power of desktop processors and the requirements of client-server and multimedia applications, however, have driven the need for greater bandwidth in traditional shared-media environments. These requirements are prompting network designers to replace hubs in their wiring closets with switches, as shown in Figure 12-1.


Figure 12-1: Evolution from shared to switched internetworks. 


This strategy allows network managers to protect their existing wiring investments and boost network performance with dedicated bandwidth to the desktop for each user. Coinciding with the wiring closet evolution is a similar trend in the network backbone. Here, the role of Asynchronous Transfer Mode (ATM) is increasing as a result of standardizing protocols, such as LAN emulation (LANE), that enable ATM devices to coexist with existing LAN technologies. Network designers are collapsing their router backbones with ATM switches, which offer the greater backbone bandwidth required by high-throughput data services.

Technologies for Building Switched LAN Internetworks

With the advent of such technologies as Layer 3 switching, LAN switching, and VLANs, building campus LANs is becoming more complex than in the past. Today, the following three technologies are required to build successful campus networks:

  • LAN switching technologies
  • Ethernet switching—Provides Layer 2 switching and offers broadcast domain segmentation using VLANs. This is the base fabric of the network.
  • Token Ring switchingOffers the same functionality as Ethernet switching but uses Token Ring technology. You can use a Token Ring switch as either a transparent bridge or source-route bridge.
  • Copper Data Distributed Interface (CDDI)Provides a single-attachment station (SAS) or dual-attachment station (DAS) to two Category 5 unshielded twisted-pair (UTP), 100 Mbps RJ-45 connectors.
  • Fiber Distributed Data Interface (FDDI)Provides an SAS or DAS connection to the FDDI backbone network using two multimode, media interface connector (MIC) fiber- optic connections.
  • ATM switching technologies

ATM switching offers high-speed switching technology for voice, video, and data. Its operation is similar to LAN switching technologies for data operations. ATM, however, offers superior voice, video, and data integration today.

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  • Routing technologies

Routing is a key technology for connecting LANs in a campus network. It can be either Layer 3 switching or more traditional routing with Layer 3 switching features and enhanced Layer 3 software features.

Note Switched LAN internetworks are also referred to as campus LANs.

Role of LAN Switching Technology in Campus Networks

Most network designers are beginning to integrate switching devices into their existing shared- media networks to achieve the following goals:

  • Increase the bandwidth that is available to each user, thereby alleviating congestion in their shared-media networks.
  • Employ the manageability of ...

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