The first line cards for the MX router platform were called DPC's. These are now End of Life in favor of MPC line cards.

The interfaces associated with DPC, and services associated with MS-DPC will fail to operate as expected. MS-DPC will give an error like:

May 20 22:14:52 mx480-lab fpc4 Channel 0 for the ifl 340 deletion failed for the service ifl table 945

May 20 22:14:52 mx480-lab fpc4 Iif iif_single_delete: chip(0) Deleting unknown channel 0(len 2), stream 0

MS-DPC should not be used after JUNOS 18.2, and after 20.4, the router will fail to initialize the DPC properly. Refer to TSB17796 [juniper.net] and TSB16812 [juniper.net].

MS-DPC removed from software list on 2021-04-02, so 20.4 make sense as the last working release:

https://supportportal.juniper.net/s/article/Junos-Software-Versions-Suggested-Releases-to-Consider-and-Evaluate?language=en_US