Code Point,Description,Reference
0,Reserved,[RFC9830]
1,"Push an IPv4 Explicit NULL label on an unlabeled IPv4 packet
      but do not push an IPv6 Explicit NULL label on an unlabeled IPv6 packet",[RFC9830]
2,"Push an IPv6 Explicit NULL label on an unlabeled IPv6 packet
      but do not push an IPv4 Explicit NULL label on an unlabeled IPv4 packet",[RFC9830]
3,"Push an IPv6 Explicit NULL label on an unlabeled IPv6 packet
      and push an IPv4 Explicit NULL label on an unlabeled IPv4 packet",[RFC9830]
4,Do not push an Explicit NULL label,[RFC9830]
5-255,Unassigned,