A TCP / IP four-layer model
TCP / IP is a set of communication protocols used to implement a network interconnection. Internet network architecture with TCP / IP as the core. TCP / IP is the protocol reference model is divided into four levels, they are: the network access layer, internetworking layer, a transport layer (host to host), and application layers.
1. Application Layer
The application layer corresponds to the level of the OSI reference model, to provide users with various services required, such as:. FTP, Telnet, DNS, SMTP , etc.
2. transport layer
transporting layer corresponding to the transport layer of the OSI reference model, to-end application layer entity to the communication function, and ensure the integrity of the data-sequence delivery of packets. This layer defines two main protocols: transmission control protocol (TCP) and User Datagram Protocol (UDP)
is the TCP protocol provides a reliable data transmission service through the "three-way handshake" to connection; UDP, is not guaranteed to provide reliable (not reliable), data transmission services. connectionless
3. Internetworking layer
internetworking layer corresponds to the network layer of the OSI reference model, the main problem to solve a host-to-host communications. Design protocol packets it contains logical transmission across the network. Pay attention to reassign IP addresses to host a complete route to the address of the host, it is also responsible for a variety of data packets in the network. The agreement has three main layers: the Internet Protocol (IP), Internet Group Management Protocol (IGMP) and Internet Control Message Protocol (ICMP).
IP protocol is the most important protocol Internetworking layer, is that it provides a reliable, connectionless datagram delivery service.
4. The network access layer (i.e., host - network layer)
network access layer of the OSI reference model physical layer and the data link layer, respectively. It is responsible for monitoring the exchange of data between the host and the network. In fact, TCP / IP layer itself does not define the protocol, and the participation interconnected network using their respective physical layer and data link layer protocol, and then connect to the TCP / IP network access layer. Address Resolution Protocol (ARP) working in this layer, the data link layer of the OSI reference model.
Two TCP IP and OSI similarities and differences /
Common
(1) OSI reference model and TCP / IP reference models have adopted the concept of hierarchy.
(2) can provide connection-oriented and connectionless services two communication mechanisms.
Different from
(1) using the OSI seven-layer model, while TCP / IP is a four-layer structure.
(2) TCP / IP network interface layer reference model does not actually defined, but some conceptual description. The OSI reference model is not only divided the two layers, and each layer functions are very detailed, even in the data link layer gave off a media access sublayer, specifically address the problem of shared media LAN.
(3) OSI model protocol development prior design, having versatility. TCP / IP is the first set of protocols and model, does not apply to non-TCP / IP networks.
(4) OSI reference model and the transport layer functions TCP / IP reference model is substantially similar, the user is responsible for providing a communication service truly end to end, also shields the top of the implementation details of the underlying network. Except that the transport layer TCP / IP reference model is built on the basis of network interconnection layer, and the network interconnection layers only provide connectionless network service, the connection-oriented TCP protocol implemented in a fully functional, of course, TCP / IP transport layer also provides a connectionless service, such as the UDP; the contrary OSI transport layer reference model is built on the basis of the network layer, the network layer provides both a connection-oriented service, and connectionless service, the transport layer only provide connection-oriented services.
High abstraction (5) OSI reference model for the description of the various networks; and TCP / IP is the first with the agreement in order to develop TCP / IP model.
Concept (6) OSI reference model clearly divided, but are rather complex; the TCP / IP reference model clear distinction in service, interfaces and protocols, and implementation details of the functions described mix.
(7) TCP / IP network interface layer reference model is not a real one; shortcomings of the OSI reference model are too many levels, meaning not divide but adds complexity.
Although (8) OSI reference model to be optimistic, because they did not grasp the opportunity, immature technology, it is difficult to achieve; the contrary, TCP / IP reference model, although there are many places unsatisfactory, but it is quite successful.