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Virtual Networking The migration to switched networks is a step on the footpath to virtual networking. Switches can be incorporated into existing LANs and provide immediate benefits without altering the network infrastructure. Virtual networks free corporations from the bounds of the physical technologies they use by collapsing them into a single logical network structure. In other words, the network manager is no longer constrained by different network architectures. The network, as businesses know it today (e.g., FDDI, Token Ring, or Ethernet) becomes an interface to the new network structure rather than a separate network. For more aggressive organizations that are certain that ATM network is in their future, ATM to the desktop, for workgroups or workstation users with networked multimedia requirements, is worth considering. In particular, 25M-bps ATM over UTP3 cable for client applications can solve todays applications problems and position customers for the future as well. The ATM Forum has already approved a LAN emulation standard that allows organizations to run existing LAN applications over an ATM network. The LAN emulation standard provides organizations co-existence with existing LAN technology as well as a migration path to ATM. ADDITIONAL PERFORMANCE CONSIDERATIONS Optimizing the LAN for client/server-based multimedia applications is only part of the story for improving overall system performance. System bottlenecks can come from several sources: network I/O, CPU I/O, or disk I/O. Not only must the network manager reconfigure the network to accommodate multimedia applications, but IS departments must install desktop devices and servers powerful enough and architected with data-intensive applications in mind. The performance requirements for tomorrows multimedia applications will require high-capacity systems where symmetrical multiprocessing (SMP) allows multiple microprocessors to share the processing load; disk I/O architectures that segregate disk I/O processing from the main CPU, so that access to the system does not contend with disk I/O traffic; and, of course, lots of memory. In addition, network managers must have a sophisticated network management environment to analyze performance. Network management products and network utilities that measure throughput, such as utilization of the CPU, bandwidth on the system bus, and subsystem performance, can help the network manager identify bottlenecks and reconfigure the system accordingly, to achieve the desired system balance and performance. The good news is that more vendors offer tools to help manage multimedia over the LAN, giving network managers options for management. There are tools to help throttle bandwidth allocation and set parameters, and others that allow graceful network degradation. Intranet Considerations Intranets will require communication between desktops and servers or legacy systems. They will impact the network and change the functionality and service users can expect from their applications. Network considerations loom large in an intranet environment because of the nature of the traffic. The goal of an intranet is to broaden the scope of communications. The reality is less predictable traffic patterns. Additionally, Internet protocol HTTP, the protocol between the desktop browser and the Web server, is inefficient on network bandwidth. A lot of short-lived connections that never become optimized to the network they are running on, which in turn increases the difficulty of tuning the network. There are steps an organization can take to rein in on network performance and bandwidth issues in an intranet environment, including:
SUMMARY The types of information users expect to transmit over a LAN are changing, and the LAN infrastructure must change with them. Videoconferencing, for example, is one of the most common new traffic types. The quantities of traffic are also increasing. Adapting existing LANs for multimedia traffic is an imperative for any business interested in new desktop applications such as videoconferencing. The solutions discussed in this chapter include the use of switched hub technology and the implementation of a high-speed LAN backbone employing Fast Ethernet, FDDI, or ATM technology.
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