This article explains how to remark the traffic class for ptp traffic.
The PTP is configured on IPV6. And we are marking the traffic to class 7 in below example.
set firewall family inet6 filter ptp_gm_ingress term mark_ptp_cs7 from next-header udp
set firewall family inet6 filter ptp_gm_ingress term mark_ptp_cs7 from port 319
set firewall family inet6 filter ptp_gm_ingress term mark_ptp_cs7 from port 320
set firewall family inet6 filter ptp_gm_ingress term mark_ptp_cs7 then count ptp
set firewall family inet6 filter ptp_gm_ingress term mark_ptp_cs7 then traffic-class cs7
set firewall family inet6 filter ptp_gm_ingress term mark_ptp_cs7 then accept
set firewall family inet6 filter ptp_gm_ingress term default then accept
set interfaces <interface> family inet6 filter input ptp_gm_ingress
Configure the filter to remark