VXLAN Tunnel DSCP Operations
Cumulus Linux provides configuration options to control DSCP operations during VXLAN encapsulation and decapsulation, specifically for solutions that require end-to-end quality of service, such as RDMA over Converged Ethernet.
The configuration options propagate ECN between the underlay and overlay according to RFC 6040, which describes how to construct the IP header of an ECN field on both ingress to and egress from an IP-in-IP tunnel.
Configure DSCP Operations
You can set the following DSCP operations:
- The VXLAN encapsulation DSCP action. The action can be
copyif the inner packet is IP,setto configure a specific value, orderiveto derive the value from the switch priority. The default setting isderive. - The VXLAN decapsulation DSCP or COS action. The action can be
copyto copy the DSCP value from the outer packet (underlay),preserveto keep the values configured in the inner packet (overlay), orderiveto derive the value from the switch priority. The default setting isderive.
The following example sets the VXLAN encapsulation DSCP action to copy.
cumulus@switch:~$ nv set nve vxlan encapsulation dscp action copy
cumulus@switch:~$ nv config apply
The following example sets the VXLAN encapsulation DSCP value to 16.
cumulus@switch:~$ nv set nve vxlan encapsulation dscp action set
cumulus@switch:~$ nv set nve vxlan encapsulation dscp value 16
cumulus@switch:~$ nv config apply
The following example sets the VXLAN decapsulation DSCP value to preserve.
cumulus@switch:~$ nv set nve vxlan decapsulation dscp action preserve
cumulus@switch:~$ nv config apply
Edit the /etc/cumulus/switchd.conf file, then reload switchd.
The following example sets the VXLAN encapsulation DSCP action to copy.
cumulus@switch:~$ sudo nano /etc/cumulus/switchd.conf
...
# vxlan encapsulation update
vxlan.def_encap_dscp_action = copy
# default vxlan encap dscp value, only applicable if action is 'set'
#vxlan.def_encap_dscp_value =
# vxlan decapsulation update
#vxlan.def_decap_dscp_action = derive
The following example sets the VXLAN encapsulation DSCP value to 16.
cumulus@switch:~$ sudo nano /etc/cumulus/switchd.conf
...
# vxlan encapsulation update
vxlan.def_encap_dscp_action = set
# default vxlan encap dscp value, only applicable if action is 'set'
vxlan.def_encap_dscp_value = 16
# vxlan decapsulation update
#vxlan.def_decap_dscp_action = derive
The following example sets the VXLAN decapsulation DSCP value to preserve.
cumulus@switch:~$ sudo nano /etc/cumulus/switchd.conf
...
# vxlan encapsulation update
#vxlan.def_encap_dscp_action = derive
# default vxlan encap dscp value, only applicable if action is 'set'
#vxlan.def_encap_dscp_value =
# vxlan decapsulation update
vxlan.def_decap_dscp_action = preserve
...
After you modify /etc/cumulus/switchd.conf file, you must reload switchd with the sudo systemctl reload switchd.service command.
Show the DSCP Setting
To show the VXLAN encapsulation DSCP setting, run the nv show nve vxlan encapsulation dscp command:
cumulus@switch:~$ nv show nve vxlan encapsulation dscp
operational applied
------ ----------- -------
action copy copy
To show the VXLAN decapsulation DSCP setting, run the nv show nve vxlan decapsulation dscp command.
cumulus@switch:~$ nv show nve vxlan decapsulation dscp
operational applied
------ ----------- --------
action preserve preserve
Considerations
You can only set the VXLAN encapsulation and decapsulation DSCP actions globally. Cumulus Linux does not support per-VXLAN or per-tunnel settings.