Indicates whether this link station will be used
for connections to down-level or migration partners.
1 Indicates that this is a back-level node supporting XID0
protocols.
2 Indicates that this is an up-level node supporting XID3
protocols including the Network Name CV
3 Indicates that this is a back-level node supporting XID3
protocols (but does not include the Network Name CV)
4 Indicates that this is a back-level node which does not
support XID protocols. (This is valid on NONSWITCHED
ports, and is not valid on negotiable ports.