Users 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 local area network (LAN) traffic and latency-sensitive scheduling of
service traffic.
● 802.1Qbb — Priority flow control
● 802.1Qaz — Enhanced transmission selection
● Data Center Bridging Exchange (DCBX) protocol
DCB enables the convergence of LAN and storage area network (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 class of service (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 DCB neighbors use 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.
Configuration notes
All Dell EMC PowerSwitches except MX-Series, S4200-Series, S5200 Series, and Z9332F-ON:
When you do not enable PFC on some of the port channel members between the FIP snooping bridge (FSB) and NPIV proxy
gateway (NPG), FCoE sessions are not established. You should enable all the members of a port channel with PFC, for the FCoE
sessions to establish.
Priority flow control
In a converged data-center network, to ensure that no frames are lost due to congestion, use PFC. PFC uses the 802.1p priority
in the Ethernet header to pause priority-specific traffic that is 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 the switch does not drop specified priority traffic.
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.
NOTE:
Ethernet traffic ingressing from ETS and PFC enabled interfaces will always queue through queue 0, irrespective of
the network type configured on VLAN.
PFC handles traffic congestion by pausing prioritized dot1p traffic on an ingress interface and allowing other dot1p traffic best-
effort, also known as lossy data transmission.
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