[Bier] Possible conflict between nibble value in RFC 8296 and IANA registry of IP version number

[Greg Mirsky <[e-mail]>]

Dear All,
RFC 8296 explains the nibble field on BIER header as:
   Nibble:

      This field is set to the binary value 0101; this ensures that the
      MPLS ECMP logic will not confuse the remainder of the BIER header
      with an IP header or with the header of a pseudowire packet.  In
      an MPLS network, if a BFR receives a BIER packet with any other
      value in the first nibble after the label stack, it SHOULD discard
      the packet and log an error.

But IANA registry for IP version numbers
<https://www.iana.org/assignments/version-numbers/version-numbers.xhtml>
reflects allocation of 5 for ST RFC 1819 (thanks to Loa for pointing me to
the registry):

Decimal Keyword Version Reference
0-1 Reserved [Jon_Postel][RFC4928]
2-3 Unassigned [Jon_Postel]
4 IP Internet Protocol [RFC791][Jon_Postel]
5 ST ST Datagram Mode [RFC1819][Jim_Forgie]
6 IPv6 Internet Protocol version 6 [RFC8200]
7 TP/IX TP/IX: The Next Internet [RFC6814]
8 PIP The P Internet Protocol [RFC1621]
9 TUBA TUBA [RFC1347]
10-14 Unassigned [Jon_Postel]
15 Reserved [Jon_Postel]

Perhaps ST Datagram never saw the light of deployment but, as it looks, we
may have formal conflict at hand. The way to remedy the situation may be to
re-assign value 5 to BIER or, at the minimum, make it reserved.
What do you think?

Regards,
Greg