Hello John,
I haven't done it but NW SSO system provides SSO with Cloud Apps like Success Factors using SAML. NW Secure Login Server is must.
You can check below links.
Configuring SAML 2.0 Authentication for your Secure Login Server
Single Sign-On to SuccessFactors from SAP HCM
Single Sign-On between SAP Portal and SuccessFactors
Regards,
Yuksel AKCINAR