Connectivity 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 trac classes while ensuring lossless delivery of
storage trac with best-eort for local area network (LAN) trac and latency-sensitive scheduling of service trac.
• 802.1Qbb — Priority ow control
• 802.1Qaz — Enhanced transmission selection
• Data Center Bridging Exchange (DCBX) protocol
DCB enables the convergence of LAN and storage area network (SAN) trac 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 bre
channel over Ethernet (FCoE) and iSCSI transmission of storage data. DCB is not supported on interfaces with link-level ow control
(LLFC) enabled.
Priority ow control
(PFC)
Use priority-based ow control to ensure lossless transmission of storage trac, while transmitting other trac
classes that perform better without ow control, see Priority ow control.
Enhanced
transmission
selection (ETS)
Assign bandwidth to 802.1p class of service (CoS)-based trac classes. Use ETS to increase preferred trac-class
throughput during network congestion, see Enhanced transmission selection.
Data Center Bridging
Exchange protocol
(DCBX)
Congure the DCBX protocol DCB neighbors use to discover and exchange conguration information for plug-and-
play capability, see Data center bridging eXchange.
Internet small
computer system
interface (iSCSI)
Use iSCSI auto-conguration and detection of storage devices, monitor iSCSI sessions, and apply QoS policies on
iSCSI trac, see Internet small computer system interface.
Priority ow 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-specic trac 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 trac class, it sends a pause frame for the priority trac to the transmitting device. In this way,
PFC ensures that the switch does not drop specied priority trac.
PFC enhances the existing 802.3x pause capability to enable ow control based on 802.1p priorities. Instead of stopping all trac on a link,
as performed by the 802.3x pause mechanism, PFC pauses trac for 802.1p trac types. For example, when LAN trac congestion
occurs on an interface, PFC ensures lossless ows of storage and server trac while allowing for lossy best-eort transmission of other
trac.
PFC handles trac congestion by pausing prioritized dot1p trac on an ingress interface and allowing other dot1p trac best-eort, also
known as lossy data transmission.
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1084 Converged data center services