Reference Guide

Converged data center services
OS10 supports converged data center services, including IEEE 802.1 data center bridging (DCB) extensions to classic Ethernet.
DCB provides I/O consolidation in a data center network. Each network device carries multiple traffic classes while ensuring
lossless delivery of storage traffic with best-effort for LAN traffic and latency-sensitive scheduling of service traffic.
● 802.1Qbb — Priority flow control
● 802.1Qaz — Enhanced transmission selection
● 802.1Qau — Congestion notification
● Data Center Bridging Exchange (DCBX) protocol
DCB enables the convergence of LAN and SAN traffic over a shared physical network in end-to-end links from servers to
storage devices. In a converged network, all server, storage, and networking devices are DCB-enabled. DCB supports fibre
channel over Ethernet (FCoE) and iSCSI transmission of storage data. DCB is not supported on interfaces with link-level flow
control (LLFC) enabled.
Priority flow
control (PFC)
Use priority-based flow control to ensure lossless transmission of storage traffic, while transmitting other
traffic classes that perform better without flow control (see Priority flow control).
Enhanced
transmission
selection (ETS)
Assign bandwidth to 802.1p CoS-based traffic classes. Use ETS to increase preferred traffic-class
throughput during network congestion (see Enhanced transmission selection).
Data Center
Bridging
Exchange
protocol (DCBX)
Configure the DCBX protocol used by DCB neighbors to discover and exchange configuration information
for plug-and-play capability (see Data center bridging eXchange).
Internet small
computer system
interface (iSCSI)
Use iSCSI auto-configuration and detection of storage devices, monitor iSCSI sessions, and apply QoS
policies on iSCSI traffic (see Internet small computer system interface).
Priority flow control
In a converged data-center network, to ensure that no frames are lost due to congestion, use priority flow control (PFC). PFC
uses the 802.1p priority in the Ethernet header to pause priority-specific traffic sent from a transmitting device. The 802.1p
priority is also known as the class of service (CoS) or dot1p priority value.
When PFC detects congestion of a dot1p traffic class, it sends a pause frame for the priority traffic to the transmitting device.
In this way, PFC ensures that specified priority traffic is not dropped by the switch.
PFC enhances the existing 802.3x pause capability to enable flow control based on 802.1p priorities. Instead of stopping all
traffic on a link, as performed by the 802.3x pause mechanism, PFC pauses traffic for 802.1p traffic types. For example, when
LAN traffic congestion occurs on an interface, PFC ensures lossless flows of storage and server traffic while allowing for lossy
best-effort transmission of other traffic.
PFC handles traffic congestion by pausing prioritized dot1p traffic on an ingress interface and allowing other dot1p traffic
best-effort, lossy data transmission.
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