Over the years, the rules of service of process have changed.  Once, long ago, a case was commenced when defendants were served with a summons and complaint and an index number was purchased only when necessary.  Later, in 1992 a commencement by index number rule started, and questions of service then arose.  Under CPLR 306-b a requirement that process be served within a 120 day period was enacted.  Ever since, problems of service and dismissals have abounded.

Bumpus v New York City Tr. Auth. ;2009 NY Slip Op 05737 [66 AD3d 26] ;July 7, 2009 ;Dillon, J., J. is a well written encyclopedia of how to serve a summons when defendant is not easy to find, or, in this case, easy to identify,  Counsel has four choices to identify a "Jane Doe" and serve that party within the statutory period. "The 120-day service provision of CPLR 306-b can be extended by a court, upon motion, "upon good cause shown or in the interest of justice" (CPLR 306-b). "Good cause" and "interest of justice" are two separate and independent statutory standards (see Leader v Maroney, Ponzini & Spencer, 97 NY2d at 104). To establish good cause, a plaintiff must demonstrate reasonable diligence in attempting service (see Leader v Maroney,{**66 AD3d at 32} Ponzini & Spencer, 97 NY2d at 105-106)" 
 

"If good cause for an extension is not established, courts must consider the "interest of justice" standard of CPLR 306-b (see e.g. Busler v Corbett, 259 AD2d at 17). The interest of justice standard does not require reasonably diligent efforts at service, but courts, in making their [*3]determinations, may consider the presence or absence of diligence, along with other factors (see Leader v Maroney, Ponzini & Spencer, 97 NY2d at 105). The interest of justice standard is broader than the good cause standard (see Mead v Singleman, 24 AD3d 1142, 1144 [2005]), "