There is a huge amount of confusion as to what GSI is.  GSI is an implementation of an entire security infrastructure that incorporates many different services and mechanisms; it is certainly not a spec.  And, in fact, it is several implementations and continues to be a "moving target".  I believe the implementations for GT3 and GT4 of GSIOpenSSH are very different.

 

We should probably refrain from thinking of "GSI" as a target.