This is the high rate link (1Gb/s) on which the first fragment F1 and the two consecutive high priority packets, P2 and P3, are sent back-to-back by the BB-ISA.
(BB-ISA->carrier IOM->egress IOM-> out-of-the-LNS).
The remaining fragments (F2 and F3) are still waiting in the BB-ISA to be transmitted. They are artificially delayed by 50ms each.
Additional QoS based on the L2TP header can be performed on the egress port in the LNS toward the LAC. This QoS is based on the classification fields inside of the packet or fragment headers (DSCP, dot1.p, EXP).