Ethernet Enhancements in Data Center Bridging
The following section describes DCB.
• The device supports the following DCB features:
– Data center bridging exchange protocol (DCBx)
– Priority-based flow control (PFC)
– Enhanced transmission selection (ETS)
DCB refers to a set of IEEE Ethernet enhancements that provide data centers with a single, robust,
converged network to support multiple traffic types, including local area network (LAN), server, and
storage traffic. Through network consolidation, DCB results in reduced operational cost, simplified
management, and easy scalability by avoiding the need to deploy separate application-specific networks.
For example, instead of deploying an Ethernet network for LAN traffic, include additional storage area
networks (SANs) to ensure lossless Fibre Channel traffic, and a separate InfiniBand network for high-
performance inter-processor computing within server clusters, only one DCB-enabled network is
required in a data center. The Dell Networking switches that support a unified fabric and consolidate
multiple network infrastructures use a single input/output (I/O) device called a converged network
adapter (CNA).
A CNA is a computer input/output device that combines the functionality of a host bus adapter (HBA)
with a network interface controller (NIC). Multiple adapters on different devices for several traffic types
are no longer required.
Data center bridging satisfies the needs of the following types of data center traffic in a unified fabric:
LAN traffic LAN traffic consists of many flows that are insensitive to latency requirements,
while certain applications, such as streaming video, are more sensitive to latency.
Ethernet functions as a best-effort network that may drop packets in the case of
network congestion. IP networks rely on transport protocols (for example, TCP) for
reliable data transmission with the associated cost of greater processing overhead
and performance impact.
Storage traffic Storage traffic based on Fibre Channel media uses the SCSI protocol for data
transfer. This traffic typically consists of large data packets with a payload of 2K
bytes that cannot recover from frame loss. To successfully transport storage traffic,
data center Ethernet must provide no-drop service with lossless links.
InterProcess
Communicatio
n (IPC) traffic
InterProcess Communication (IPC) traffic within high-performance computing
clusters to share information. Server traffic is extremely sensitive to latency
requirements.
To ensure lossless delivery and latency-sensitive scheduling of storage and service traffic and I/O
convergence of LAN, storage, and server traffic over a unified fabric, IEEE data center bridging adds the
following extensions to a classical Ethernet network:
• 802.1Qbb — Priority-based Flow Control (PFC)
• 802.1Qaz — Enhanced Transmission Selection (ETS)
• 802.1Qau — Congestion Notification
1042 FC Flex IO Modules