Solution : https://service.sap.com/sap/support/notes/186119 (SAP Service marketplace login required)
Key words : 
data bank host unix, %oracle_home%\net80\admin\protocol, $oracle_home/network/admin/protocol, %oracle_home%\network\admin\protocol, $oracle_home/network/admin/, additional security features, restrict remote access, oracle net8 level, file protocol, access control
Related Notes : 
       
| 586710 | TCP_NODELAY is ignored if protocol.ora is incorrect | 
| 562863 | FAQ: Logon mechanisms | 
| 562403 | FAQ: Oracle Net | 
| 521264 | Hang situations | 
| 198752 | TCP delay problem under Oracle 8.1.x | 
| 194868 | tcp.validnode_checking on Oracle 64-bit | 
| 72638 | Performance problems with SQL*Net | 
| 39267 |