layers of TCP/IP

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TCP/IP协议分层

提到协议分层，我们很容易联想到ISO-OSI的七层协议经典架构，但是TCP/IP协议族的结构则稍有不同。如图所示 

Layer names and number of layers in the literature

The following table shows the layer names and the number of layers of networking models presented in RFCs and textbooks in widespread use in today's university computer networking courses.

RFC 1122 [7]	Tanenbaum	Cisco Academy[8]	Kurose[9] Forouzan [10]	Comer[11] Kozierok[12]	Stallings[13]	Arpanet Reference Model 1982 (RFC 871)
Four layers [14]	Four layers [15]	Four layers	Five layers	Four+one layers	Five layers	Three layers
"Internet model"[citation needed]	"TCP/IP reference model"[16]	"Internet model"	"Five-layer Internet model" or "TCP/IP protocol suite"	"TCP/IP 5-layer reference model"	"TCP/IP model"	"Arpanet reference model"
Application [14][17]	Application	Application	Application	Application	Application	Application/Process
Transport [14]	Transport	Transport	Transport	Transport	Host-to-host or transport	Host-to-host
Internet [14]	Internet	Internetwork	Network	Internet	Internet
Link [14]	Host-to-network	Network interface	Data link	Data link (Network interface)	Network access	Network interface
			Physical	(Hardware)	Physical

OSI Model
	Data unit	Layer	Function
Host layers	Data	7. Application	Network process to application
		6. Presentation	Data representation, encryption and decryption, convert machine dependent data to machine independent data
		5. Session	Interhost communication
	Segments	4. Transport	End-to-end connections, reliability and flow control
Media layers	Packet/Datagram	3. Network	Path determination and logical addressing
	Frame	2. Data Link	Physical addressing
	Bit	1. Physical	Media, signal and binary transmission