The OSI (Open Systems Interconnect) Model
		○ 7 layers
		○ ISO (International Standards Organization) OSI Model
			§ Physical
			§ Data Link Layer
			§ Network Layer
			§ Transport Layer
			§ Session Layer - example is SIP (Session Initiation Protocol)
			§ Presentation Layer - example ASCII, EBCDIC, encryption (presentation of data)
			§ Application Layer - example Desktop Service queried by agents on other machines

	The TCP/IP Model - DoD Model(Department of Defense)
		○ Network Access (Network Interface) (Link) Layer
			§ Physical
			§ Data Link (Network Interface)
		○ Internet Layer
		○ Transport Layer
		○ Application Layer


	IP, ICMP, UDP, TCP

	DNS

	Ports and Protocols
		client port > 1023
		FTP : 20,21
		SSH : 22
		SFTP : 22
		SCP : 22
		Telnet : 23
		SMTP : 25
		DNS : 53 (UDP)
		TFTP : 69 (UDP)
		DHCP : 67 (UDP)
		HTTP : 80
		POP3 : 110
		NNTP : 119 (Network News Transport Protocol)
		NTP : 123 (UDP)
		SNTP : 123 (UDP)
		IMAP4 : 143
		LDAP : 389
		HTTPS : 443
		rsh : 514 (Remote shell)
		RTSP : 554 (Remote Time Streaming Protocol)
		RDP : 3389

	PDU (Protocol Data Unit)
		Application	
		Presentation	
		Session	
		Transport	Segments
		Network	Packets (Datagrams)
		Data Link	Frames
		Physical 	Bits