Owner`s manual

54 | Data Center Bridging (DCB)
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Different traffic types have different service needs. Using ETS, you can create groups within an 802.1p
priority class to configure different treatment for traffic with different bandwidth, latency, and best-effort
needs.
For example, storage traffic is sensitive to frame loss; interprocess communication (IPC) traffic is
latency-sensitive. ETS allows different traffic types to coexist without interruption in the same converged
link by:•
• Allocating a guaranteed share of bandwidth to each priority group.
• Allowing each group to exceed its minimum guaranteed bandwidth if another group is not fully
using its allotted bandwidth.
To configure ETS and apply an ETS output policy to an interface, you must:
1. Create a QoS output policy with ETS scheduling and bandwidth allocation settings.
2. Create a priority group of 802.1p traffic classes.
3. Configure a DCB output policy in which you associate a priority group with a QoS ETS output policy.
Apply the DCB output policy to an interface.
Data Center Bridging Exchange Protocol (DCBx)
The data center bridging exchange (DCBx) protocol is enabled by default on any switch on which PFC or
ETS are enabled. DCBx allows a switch to automatically discover DCB-enabled peers and exchange
configuration information. PFC and ETS use DCBx to exchange and negotiate parameters with peer
devices. DCBx capabilities include:
• Discovery of DCB capabilities on peer-device connections
• Determination of possible mismatch in DCB configuration on a peer link
• Configuration of a peer device over a DCB link
DCBx requires the link layer discovery protocol (LLDP) to provide the path to exchange DCB parameters
with peer devices. Exchanged parameters are sent in organizationally specific type, length, values (TLVs)
in LLDP data units. For more information, refer to the Link Layer Discovery Protocol (LLDP) chapter.
The following LLDP TLVs are supported for DCB parameter exchange:
• PFC parameters: PFC Configuration TLV and Application Priority Configuration TLV.
• ETS parameters: ETS Configuration TLV and ETS Recommendation TLV.
Data Center Bridging in a Traffic Flow
Figure 5-3 shows how DCB handles a traffic flow on an interface.