ATM scales well and is compatible with most other types of networks. And many of the compatibility problems among manufacturers' ATM products have been solved by evolving ATM standards. Some say that ATM, once seen as the future of networking, will be relegated to a subsidiary role as a transport mechanism for IP traffic. These users seem uninterested in making a changeover to unfamiliar ATM territory. FDDI, at 100 Mbps, was designed from the outset to be fast and reliable.
FDDI traffic is carried over two rings, one primary and one secondary.
The secondary ring is inactive, going into play only when a fault occurs in the primary ring. Devices or LANs can be attached to one or both rings. When both are used it creates a fault-tolerant system that can heal itself in case the primary ring, or cable, fails. CDDI results from adopting new standards for use of UTP-5 copper cable. Proponents of Gigabit Ethernet say it provides 1 Gbps of bandwidth for campus networks with the simplicity of Ethernet for a lower cost than competing high-bandwidth network technologies.