by John Wobus  Upgrading Your Network Backbone The network backbone at many large sites -where networks can span multiple buildings-usually undergoes many minor upgrades in its lifetime. Most often, the upgrades are simple : You add parts to the backbone, such as additional interface cards in routers or switches. This chapter of the Network Design Manual deals with major upgrades: when all the backbone equipment is replaced. The issues discussed here will pertain any time a hardware upgrade is considered. Chapter 2 of the Network Design Manual, "Local Area Network Design," addresses similar topics, including some basics in backbone topology, and provides much useful material. Other chapters on relevant topics include Chapter 1, "Designing Your Network for Internet Access," Chapter 3, "Fault Tolerant Network Design," Chapter 9, "Web-Based Networking Resources," Chapter 10, "TCP/IP Firewalls," Chapter 11, "Building Virtual LANs," a nd Chapter 12, "Managing Your Network." This chapter will deal with the issues above and beyond those covered by the other chapters , detailing the long-range planning a large upgrade requires. Some of these issues are not specific to networking. This chapter will apprise you of a many of the issues applicable to the process. It may be that you find it raises more questions than it answers, but it should give you some sense of the breadth of problems that need to be addressed in the process. The simplest upgrade is to add "more of the same." A more radical upgrade has you replacing the router or switch with newer devices of the same general type, perhaps replacing some smaller devices with fewer larger ones. Or you might change the technology of a backbone network, retaining the same backbone routers or switches. In these cases, everything outside the backbone remains the same, and with planning, the disturbance to users and system administrators is minimized. The most radical upgrade would be to replace routers with switches (or vice versa), to deploy ATM as the primary backbone or to deploy virtual LANs (VLANs) widely, for example. These types of changes require modifications to the configuration of every computer on the network. The network and system changes must be coordinated, requiring extensive work with system administrators. With luck, you might find some lengthy down time and enlist all the system administrators in order to accomplish the necessary changes at once. But, more likely, you'll make the changes over time, moving the network and systems to the new scheme LAN by LAN. Because of the many factors and options involved in a major upgrade-the variations in the type of institutions, the myriad ways backbones are constructed, the number of vendors and proprietary technologies and the decisions regarding outsouring-this chapter cannot give you step-by-step procedures likely to fit your situation. However, we can provide some universal guidelines. Next Is It Time To Upgrade? What Do You Need To Know? What Sort Of Upgrade? Evaluating Proposals Additional Issues John Wobus manages Syracuse University's Network Design and Development group. He can be reached at jmwobus@syr.edu Updated March 14, 1997 Print This Page E-mail this URL