
KSwitch D10 MMT Managed Time Sensitive Ethernet Switch - Preliminary User Guide, Rev. 0.99
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5.4.
Frame Preemption
Frame Preemption is defined in the IEEE 802.1Qbu and IEEE 802.3br standards.
Frame Preemption is the ability to suspend the transmission of a non time-critical frame, and allow for one or more
time-critical frames to be transmitted. When the time-critical frames have been transmitted, the transmission of the
non time-critical frame is resumed. A non time-critical frame could be preempted multiple times.
The use of Frame Preemption with Time Aware Shaping reduces the guard band needed from the size of the largest
possible interfering frame to the size of the largest possible interfering fragment.
Frame Preemption must be enabled on both egress port level and on egress port/ queue level.
Frame Preemption is disabled by default on port level and disabled by default on port/queue level.
5.4.1.
Configuration Examples
CLI commands example:
! Enable frame-preemption on port level for port 1.
# configure terminal
(config)# interface GigabitEthernet 1/1
! Enable frame-preemption on port (disabled by default)
(config-if)# tsn frame-preemption
! Enable frame-preemption on queue level for port 1, queue 0 and 1.
# configure terminal
(config)# interface GigabitEthernet 1/1
! Enable frame-preemption on queue 0 and 1
(config-if)# tsn frame-preemption queue 0-1
! Disable verification of preemption capability of link partner.
# configure terminal
(config)# interface GigabitEthernet 1/1
! Disable verification of preemption capability of link partner.
(config-if)# tsn frame-preemption verify-disable
! Do not wait to receive lldp message before enabling frame-preemption in transmit
direction.
# configure terminal
(config)# interface GigabitEthernet 1/1
! Do not wait to receive lldp message before enabling frame-preemption in transmit
direction.
(config-if)# tsn frame-preemption ignore-lldp
! Disable frame-preemption on port level for port 1
# configure terminal
(config)# interface GigabitEthernet 1/1
! Disable frame-preemption on port
(config-if)# no tsn frame-preemption
! Disable frame-preemption on on queue level for port 1, queue 0 and 1.
# configure terminal
(config)# interface GigabitEthernet 1/1
! Disable frame-preemption on queue 0 and 1
(config-if)# no tsn frame-preemption queue 0-1
! Show configuration using 'show running-config'.
! Note that frame-preemption on port level is disabled by default
! and not shown unless the 'all-defaults' option is used.
# show running-config
[...]
tsn frame-preemption queue 0
tsn frame-preemption queue 1