Timestamping of Port-Mirrored Packets

Overview

You can specify that the software provide a 64-bit nanosecond EPOCH timestamp over port-mirrored packets.

The feature applies to port-mirrored packets that are configured for family any, and it applies to packets that are mirrored in an incoming or outgoing direction.

• In ingress, the timestamp approximates the mainline packet arrival time on the interface.

• In egress, the timestamp approximates the mainline packet departure time on the interface.

The port-mirroring destination can be a next-hop group, which is a collection of multiple interfaces. For these destinations, every mirrored packet carries the same timestamp for each member of the group.

Location – overwrite 2-bytes LSB of DMAC + 6-bytes SMAC

Guidelines and Limitations

• Before you apply the timestamping feature, configure port mirroring as you usually would do under the [edit forwarding-options port-mirroring] hierarchy, and also configure the firewall filters for port mirroring.

• The timestamp on a mirrored packet is extracted during port-mirror post processing, which executes after the mainline packet is processed. Thus there is a microseconds' worth delay between the mainline packet's entering or exiting on the corresponding interface and the actual timestamping.

• Any L2 or L3 feature that depends on the MAC address for forwarding of the mirrored packet might not function as expected, because the MAC header fields are overwritten with the timestamp.

• The timestamp feature is available only for the port-mirroring family any. For other families, the packet-timestamp configuration has no effect, and port mirroring for those other families follows default behavior.