Cisco's interest in data center networking has continued to grow, and a facet of its approach to data center networking involves "unified I/O," the idea that all the I/O connections going into or out of a server can be condensed into a single connection.

The larger vision is something Cisco calls "Data Center 3.0," and the company recently advanced many of its products toward that vision with software updates. The idea is to virtualize data-center resources - servers, storage and so forth - to make them more flexible and efficient.

Unified I/O is part of this vision. If everything has a single connection to a network cloud, it can access all the other resources in that cloud. The idea of having separate connections for separate I/O functions or separate networks goes away.

The unifying network connection, in Cisco's view, is 10 Gigabit Ethernet. It can carry multiprotocol traffic, it can carry Fibre Channel (using Fibre Channel over Ethernet technology) and it can do RDMA.

Cisco argues that new standards are making this transition easier. The PCI-Express server bus standard means that the I/O bottleneck at the bus level has been cleared away, according to Cisco. Servers can take full advantage of a 10 Gigabit Ethernet link.

Cisco further argues that the move toward multiple processors, processor cores and virtual machines existing on single servers will mean that there will be a higher demand for network traffic. In other words, that 10 Gigabit pipe will fill up.

The company notes that to converge traffic onto a single Ethernet connection, the Ethernet fabric has to become lossless for certain types of transmissions. So, Cisco describes a pause mechanism for Ethernet that doesn't halt all traffic - just a certain type. With different traffic types getting their own pause mechanisms, the traffic can coexist on the same link.

Jeff Caruso is site editor at Network World.