02-CCNA 200-120 (Lecture 2 – OSI Layers (open system interconnection)) By Eng-Ahmed Nazmy | Arabic https://www.facebook.com/free4arab http://www.free4arab.com https://twitter.com/free4arab1 https://plus.google.com/113503705132872627915 نور الهدى لتكنولوجيا المعلومات