For completeness:
```
<x:ref>PUSH_PROMISE</x:ref>
```

If this is an HTTP application layer restriction, does that mean that frames like GOAWAY, ALTSVC, & SETTINGS are not constrained to 16K? Should they be?

If so, perhaps instead:
```
The application payload portion of any frame type, which is the payload of the frame exclusive of padding, MUST NOT exceed 2<x:sup>14</x:sup>-1 (16,383) octets in length.
```