MS-DPC is considered EoL(end of life) module and is no longer supported from JUNOS 15.1 onwards for "JUNOS Subscriber Managment / BNG" use case. You should upgrade to MS-MPC unit for Junos Subscriber Managment service.
For BNG+GCNAT use, would suggest JUNOS 16.1R6-S2 & upcoming JUNOS 16.1R7.
The Next Gen, Subscriber Management (on MX) is supported from JUNOS 15.1R4 onwards (meaning 15.1R5, 15.1R6 and so on) and its subsequent services release (SR).
MX Services on MS-DPC from Junos 15.1R6 as per KB may traditionally fuction but its NOT recommened for B-RAS/CGNAT use. Basically we've not qaulified its use for B-RAS/CGNAT.
Other than CGNAT, Service such as Static HTTP Redirect may work but at limited extend. As mentioned in my previous post, its considered EoL since late 2015 & it old h/w module that it lacks the S/w enhancement introduced in JUNOS 15.1 onwards hence suggested you MS-MPC.
I do know that you seek advice; i've no doubt in that. Unfortunately no JunOS S/w tweak (on 15 onwards) can tune your requirement on MS-DPC. Even if it goes through a workaround (sort of hope), it would have its negative impact in terms of performance and that in the end, it not really worth hence suggest you the advice for switching MS-MPC.
Karan has pretty much explained that BNG+DPC will not work in next-generation-release. Problem is that DPC is based on I-Chip and doesn't understand NG VBF flow. Traffic will be dropped with VBF lookup fail.
Workaround: Till you migrate to TRIO based chipset MS-MPC.
To overcome MS-DPC sending traffic to subscriber interface. Please use following workaround.
1. Subscriber traffic will match filter and redirected to CGNAT VRF. 2. Route in VRF point the traffic to SP interface. 3. Subscriber IP will be translated to Public IP and traffic will go to internet via inet.0. 4. Traffic from Internet comes back go to inet.0, then via MS-DPC goes back to CGNAT VRF. 5. CGNAT mapping convert the Public IP to Subscriber IP. Rather than pointing the traffic back to inet.0 you need route to move the traffic back to core. 6. Traffic will again sent back to core. From there it should be looped back to BNG device. This time traffic will come to uplink with destination as subscriber IP rather than NATTED IP. This will resolve the MS-DPC limitation.