Content for slides/images

• campus_smtp
• computer_system
• dns_authoritative_server_view
• dns_client_view
• dns_lookup_server_view
• mail_remote
• master_slave_view
• network_authentication
• physical_memory
• reverse_dns
• s1_comp_components
• s1_model
• s1_semester_diagram
• satellite_smtp
• simple_dns1
• smtp1
• smtp2