Hub and router falls to switched internetworking.
Until now, the accepted internetworking paradigm has been to utilize hubs and routers to construct enterprise-wide internetworks.
In this scheme, the hubs interconnect the physical links and serve as monitoring and control points for internetwork management, while the routers are used to segment local area backbones into multiple subnetworks. The routers provide multiprotocol network-to-network connectivity across the enterprise and supply the primary means for enforcing security and access control.
Now, it seems, the hub-router configuration is giving way to a new paradigm: switched internetworking.
With the hub-router approach, companies can be constrained in how they organize themselves by the physical structure of their network. Further, as businesses reorganize, moving and adding users means regularly reconfiguring the network, which is time consuming and costly with today's technology.
Switching simplifies the administration of user moves, adds and changes by creating "virtual" LANs, structured logically, with changes done via software.
Switched internetworks also address the changing needs of the workplace, where computers are delivering more power to the desktop, fueling new applications that place increasing demands on the network. Switching eases the traffic bottleneck by providing dedicated rather than shared bandwidth to the desktop.
Switching also provides scalable backbone bandwidth for client/server computing along with support for new bandwidth-intensive and delay-sensitive applications. Despite these benefits, many industry analysts have a caveat: proceed with caution.
For one thing, standards for switched internetworking are incomplete, so network managers risk locking themselves into a single vendor if they deploy the equipment widely. Also, with uncertainties still surrounding interoperability between the switches and asynchronous transfer mode (ATM) backbones, managers could jeopardize their long-term internetworking options.
Another problem is the dearth of network management and diagnostic tools for switched internetworks. Managers have grown used to a high level of network management functionality for their hub-router networks. However, the switched environment raises a new set of network management issues and calls for new network management tools, especially for enterprise-wide coverage.
In particular, large-scale deployments will require RMON (remote monitoring) capability to allow remote network devices to be managed from a central site. Remote monitoring defines a set of statistics and functions that can be exchanged between RMON-compliant management consoles and network probes using the Simple Network Management Protocol (SNMP). It lets network managers track alarms, events and other historical data and keep tabs on such things as network utilization.
Implementing RMON can be expensive, though, because it requires its own dedicated hardware and robs the switch of some of its processing power to handle the data generated. Vendors are addressing the problem by integrating RMON into their switches, either at the silicon level or via software.
Vendors also are embracing RMON2, the next-generation monitoring capability, which provides information on the transport layer of the OSI reference model to supplement the physical- and data-link level data supplied by RMON.
Recognizing that the shift to switched internetworking will be evolutionary, vendors are also combining the benefits of switching technology with hub-router capabilities.
One example is Bay Networks, which incorporates both functions in its new BaySIS architecture for switched internetworking. The idea behind the architecture is to use switches for what they do best, which is supplying bandwidth, and routers for what they do best-supporting logical connectivity between networks.
"Switching technology promises to revolutionize network computing today in much the same way that LAN technology changed mainframe and minicomputer-based computing over ten years ago," says Dick Eyestone, vice president of Bay Networks.
Data communications consultant Morris Edwards is program chairman of the Network Computing Solutions Conference and Expo, or Netcom, to be held Feb. 28-29 in Fort Lauderdale and March 20-21 in Atlanta.