Release Notes

Data Center Bridging (DCB)
66 Dell PS Series Configuration Guide
13.1 DCB overview
DCB is a collection of Standards designed to improve networking and management in the data center that
enables iSCSI SANs or FCoE SANs or both to converge with regular server LAN traffic on the same physical
infrastructure. DCB aims to increase operational efficiency, constrain costs, and ease network management.
There are primarily three progressive versions of DCB:
• Cisco, Intel, Nuova (CIN) DCBX
• Converged Enhanced Ethernet (CEE) DCBX or baseline DCBX
• Institute of Electrical and Electronic Engineers (IEEE) DCB.
DCB technologies based on standards include:
• PFC – Priority based Flow Control (802.1Qbb)
• ETS – Enhanced Transmission Selection (802.1Qaz)
• CN – Congestion Notification (802.1Qau)
• DCBx – Data Center Bridging Capability eXchange
- Support for iSCSI application protocol priority with DCBX (also known as iSCSI TLV)
Note: DCB uses 10Gb and higher Ethernet only.
I/O convergence using DCB for PS Series iSCSI storage is the direction for “Converged iSCSI” in a lossless
Ethernet environment.
13.2 DCB requirements for PS Series arrays
It is required that all devices in the PS Series SAN support DCB for iSCSI when this functionality is enabled. If
any device in the SAN does not support DCB, then DCB needs to be disabled at the switches for the entire
SAN. Once all devices in the SAN are DCB compliant, then DCB can be re-enabled. Switches and server
CNAs/NICs that are designated as DCB Supported in the Dell Storage Compatibility Matrix have been fully
validated by Dell to ensure compatibility for PS Series SANs.
The minimum requirements for switches and server-based CNA/NICs to support an end-to-end DCB solution
with PS Series arrays are:
• Data Center Bridging Exchange (DCBx): DCB protocol that performs discovery, configuration, and
mismatch resolution using Link Layer Discovery Protocol (LLDP)
• Application Priority (iSCSI TLV): Switches must support configuration of a priority value for iSCSI
protocol and advertisement to peer ports. Server NICs/CNAs: Must support iSCSI protocol in
application priority (learned from the switch) and must support tagging outgoing iSCSI frames with
this priority.
• ETS: Requires a dedicated traffic class (TC) or priority group (PG) for iSCSI priority
• PFC: Requires enabling PFC (no drop or lossless behavior) for iSCSI priority
• Switches: Configure dedicated TC/PG for iSCSI priority with allocated bandwidth and PFC enabled
for iSCSI priority
• Server NICs/CNAs: Adhere to TC/PG mapping for iSCSI priority and PFC for iSCSI priority (learned
from the switch)