[j-nsp] JTAC Recommended Junos Software Versions Old?

[Colton Conor]

Why is the JTAC Recommended Junos Software Version for the MX routers
currently Junos 12.3R8.7? There are much newer versions of JUNOS out there.
>From the posts I have read so far, Junos 12.3 in general has flow and nat
issues. I assume some of these bugs have been fixed with the latest .x
versions like R8.7, but still why such an old version?

Is there a guide showing the big changes from 12.3 vs 13.2 vs 13.3 vs 14.1
vs 14.2. I know there a release notes for all of these versions, but is
there an outline showing the reason for the jump in version numbers? Most
of the PR's I have seen show a bug was found and fixed in the current .x of
most all these versions.

I notice that the Juniper JTAC recommends Junos 13.3R4.6 for the MX104 and
PTX series? If Junos 13.3R4.6 is stable enough to run on these platforms,
then I assume its stable enough to run on the other MX platforms, the MX80
to be specific?