DCB Configuration Guide

After network convergence in a data center, three types of traffic exist: LAN traffic, SAN traffic, and IPC traffic, each with distinct QoS requirements:

• SAN traffic is highly sensitive to packet loss and requires in-order delivery of packets during transmission.
• LAN traffic allows packet loss and only requires Best Effort (BE) service from the network.
• IPC traffic (used for server-to-server communication) demands low latency. Data Center Bridging (DCB) is a set of IEEE 802.1 bridging enhancements that meet these QoS requirements by creating a lossless Ethernet infrastructure for converged data center networks.

DCB features primarily include PFC, ETS, and DCBX.

PFC

PFC (Priority-based Flow Control) consists of priority-based flow control and PFCWD (PFC Watchdog). For details, please refer to PFC in QoS configuration guide.

ETS

In a converged data center network, the coexistence of LAN, SAN, and IPC traffic imposes stringent QoS demands. For example:

• SAN traffic is sensitive to packet loss and requires ordered delivery.
• IPC traffic demands ultra-low latency for server communication.
• LAN traffic only requires Best Effort service, where packet loss and reordering can be handled by end hosts, minimizing network intervention. Traditional QoS mechanisms cannot meet these requirements. Enhanced Transmission Selection (ETS) addresses this by enabling flexible traffic scheduling for converged networks. ETS defines a priority-based processing model and bandwidth allocation model for endpoints and bridges in DCB environments. This allows differentiated services and bandwidth allocation for different traffic types.
• For scheduling details, Please configure according to the relevant sections of the configuration guide.
• For priority mapping details, Please configure according to the relevant sections of the configuration guide.

DCBX

Data Center Bridging Exchange Protocol (DCBX) is a component of DCB. It operates in DCB environments to enable devices on both ends of a link to discover and exchange DCB configuration parameters, significantly reducing administrative overhead. Key DCBX Functions:

• Discover the DCB configuration of peer devices.
• Detect DCB configuration errors on peer devices.
• Configure DCB parameters on peer devices. DCBX Exchangeable Parameters:
• ETS scheduling and priority information
• PFC configurations DCBX uses LLDP (Link Layer Discovery Protocol) to exchange information. DCB configuration parameters are encapsulated into TLVs (Type-Length-Value fields) within LLDP frames, enabling automatic DCB parameter negotiation between devices.

Configure DCB

Configure PFC

Please configure according to the relevant sections of the configuration guide.

Configure PFCWD

Please configure according to the relevant sections of the configuration guide.

Configure ETS

Please configure according to the relevant sections of the configuration guide.

Configure DCBX

Note

• Before enabling DCBX, ensure LLDP is enabled.
• Interfaces with ETS configuration synchronization enabled must retain default configurations for scheduling and priority mapping.

Table 1 Configure DCBX

Purpose	Commands	Description
Enter global configuration view	configure terminal	-
Enter interface configuration view.	interface ethernet interface_name	-
Enable DCBX	lldp dcbx enable	-
Enable PFC configuration synchronization	lldp dcbx pfc-willing	-
Enable ETS configuration synchronization	lldp dcbx ets-willing	-

Display and Maintenance

PFC Information

Please configure according to the relevant sections of the configuration guide.

PFCWD Information

Please configure according to the relevant sections of the configuration guide.

ETS Information

Please configure according to the relevant sections of the configuration guide.

DCBX Information

Table 2 DCBX Information

Purpose	Commands	Description
Display DCBX Configuration and Status	show lldp dcbx	-

Typical Configuration Example

1. Networking Requirement In the data center network, two data center switches (Switch A and Switch B) are interconnected, under which servers are running storage traffic, IPC traffic (802.1p priority 7) and general data traffic; it is necessary to achieve no packet loss for storage traffic, low latency for ICP, and best effort forwarding for general traffic.
2. Topology

3. Configuration Roadmap

• Configure DCBX (Data Center Bridging Exchange Protocol) on Switch A to automatically negotiate DCB capabilities with peer devices at both ends of the link.
• Activate Priority-based Flow Control (PFC) on Switch A to ensure lossless transmission for storage traffic (e.g., SAN traffic).
• Set up Enhanced Transmission Selection (ETS) with priority mapping and scheduling policies. Ensure low latency for IPC traffic and guaranteed bandwidth allocation for storage traffic.

4. Procedure

#Configure DCBX

Switch A

sonic# configure
sonic(config)# interface ethernet 0/0
sonic(config-if-0/0)# lldp dcbx enable

Switch B

sonic# configure
sonic(config)# interface ethernet 0/0
sonic(config-if-0/0)# lldp dcbx enable
sonic(config-if-0/0)# lldp dcbx ets-willing
sonic(config-if-0/0)# lldp dcbx pfc-willing

#Configure PFC Enable the PFC function for priority 3 queues. By default, the global PFC function is enabled, and the priority 3 queue has already enabled the PFC function, so this configuration step is omitted.

sonic# configure
sonic(config)# priority-flow-control enable3

#Configure ETS Create priority mapping

sonic# configure
sonic(config)# diffserv-map type 8021p ets
sonic(config-diffservmap-ets)# 8021p 7 cos 7

Create policy-map and bind diffserv-map

sonic# configure
sonic(config)# policy-map ets
sonic(config-pmap-ets)# set cos 8021p diffserv ets

Configure queue-scheduler

sonic(config-pmap-ets)# queue-scheduler queue-limit percent 40 queue 0
sonic(config-pmap-ets)# queue-scheduler priority queue 7

Bind policy-map to interface

sonic# configure
sonic(config)# interface ethernet 0/0
sonic(config-if-0/0)# service-policy ets

5. Verify the Configuration

#PFC configure

sonic# show interface priority-flow-control
Interface    Lossless priorities
-----------  ---------------------
0/0          3,4
0/1          3,4
0/2          3,4
0/3          3,4
0/4          3,4
0/5          3,4
0/6          3,4
0/7          3,4
0/8          3,4
0/12         3,4
0/13         3,4
0/14         3,4
0/15         3,4
0/16         3,4
0/20         3,4
0/24         3,4
0/28         3,4
0/32         3,4
0/33         3,4
0/34         3,4
0/35         3,4
0/36         3,4
0/37         3,4
...

#policy-map configure

sonic# show policy-map ets
！
policy-map ets
queue-scheduler priority queue 7
queue-scheduler queue-limit percent 40 queue 0
set cos dscp diffserv ets

#diffserv-map configure

sonic# show diffserv-map type 8021p ets
Diffserv Map ets:
Type 8021p
    from 7 to 7
#DCBX configure and status
sonic# show lldp dcbx
Interface    ETS Willing    PFC Willing    ETS Accepted    PFC Accepted
-----------  -------------  -------------  --------------  --------------
0/0          True           True           False           False