In the past, Ethernet used relatively simple mechanisms to transport data in enterprise networks, supporting only a single traffic priority and dropping frames during periods of congestion. As Ethernet is migrating to support converged fabrics in the data center, it is borrowing many techniques that have been previously used in carrier class networks.
The IEEE has defined several data center bridging (DCB) standards that may look very familiar to telecom switch-fabric designers. For example, Priority Flow Control (PFC) operates similarly to link level flow control techniques used in SPI4.2 telecom interfaces. It’s also used to provide lossless operation for traffic such as storage.
Enhanced Transmission Selection (ETS) provides the type of traffic scheduling found in many previous-generation telecom switch-fabric chips. It’s used to provide minimum-bandwidth guarantees for traffic such as storage. Quantized Congestion Notification (QCN) is very similar to the backward congestion notification mechanisms popular in telecom backplanes, and it’s used to minimize hot spots in multistage data-center fabrics.
To maximize the overall data-center network bandwidth, vendors such as Cisco and Brocade are adopting TRILL, which is very similar to Shortest Path Bridging (SPB) in carrier networks and uses a frame encapsulation technique that looks a lot like MAC-in-MAC. Emerging server virtualization networking standards such as VEPA and VN-Tag use technologies that are very similar to Q-in-Q.
Finally, cloud data-center managers are looking at ways to support high availability and provide service-level monitoring for their customers. To do this, they are adopting EOAM techniques from the carrier networks such as connectivity checking, performance monitoring, and fast failover mechanisms.
Although the data center doesn’t need to support hundreds of thousands of end users that are found in a carrier network, it will soon need to support tens of thousands of virtual machines using converged fabrics while providing service level guarantees. To support this, many carrier-grade technologies are now emerging in the data center.
