Summary OSI7 layer model:
7-layer model, each layer provides a special network functions. From the functional point of view the network: the following four layers (physical layer, data link layer, network layer and transport layer) mainly provides data transmission and switching functions, i.e., to the node-based communication between the nodes; the fourth layer as an upper and lower two bridge portions, the whole network architecture is the most critical part; 3 and the upper layer (session layer, presentation layer and application layer) appear to provide information processing capabilities and data between the user and application based. Briefly, the lower layer mainly 4 completion subnetworks, the main layer 3 subnet completion resources. The following is a TCP / IP hierarchical model
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│ ││D│F│W│F│H│G│T│I│S│U│E | |
│ ││N│I│H│T│T│O│E│R│M│S│ | | |
│ fourth layer, application layer ││S│N│O│P│T│P│L│C│T│E│M | |
│ ││ │G│I│ │P│H│N│ │P│N│A│ other |
│ │ │E│E│ ││ │E│S│ │ │E│I | |
│ │ │ │R│T│ ││ │R│ │ │T│L | |
└─────── - ─┘└─┴─┴─-┴─┴─-┴─┴─-┴─┴─-┴─┴ ----------
┌── ───── - ─┐┌───────── --- --- ─────────┐ ┬──
│ third layer, transport layer │ | TCP | UDP |
└─────── - ─┘└──────── --- ─┴──────────- -─┘
┌─────── - ─┐┌─── - ──┬───-─┬──────── --- ──┐
│ │ | │ICMP│ IGMP |
| A second layer, network layer │ | └──-──┘ |
│ │ | the IP |
└──────── - ┘└─────────────── ------┘ ─ ─────
┌──────── - ┐┌───────── --- --- - the ┬────── ───┐
│ a first layer, a network interface ││ARP / RARP | other |
└──────── - ┘└───────── - ┴─────- --──────┘
the TCP / the IP four-layer reference model
TCP / IP protocol concepts are organized into four layers, which correspond to respective three layers of the ISO reference model. ICP / IP protocol suite does not contain the data link layer and the physical layer, so it can not complete the entire computer network system independent function, it is necessary to work with many other protocols.
Layer four protocol TCP / IP layer model respectively, to complete the following functions:
The first layer: a network interface layer is the physical layer
comprises a cooperative protocol IP data transmitted over the existing network media for. Indeed TCP / IP with the ISO standard does not define the physical layer and the data link layer function corresponding. Instead, it defines such as ARP (Address Resolution Protocol, ARP) protocol, provides an interface between the actual physical data structures and hardware TCP / IP protocol.
Second layer: The network layer
corresponds to the network layer of the OSI reference model. This includes an IP layer protocol, the protocol the RIP (Routing Information Protocol, Routing Information Protocol), is responsible for data packing, addressing and routing. It also includes Internet Control Message Protocol (Internet Control Message Protocol, ICMP) is used to provide network diagnostics information.
The third layer: the transport layer
corresponding to the transport layer of the OSI reference model, which provides two-end communication services. In which the TCP protocol (Transmission Control Protocol) provides reliable stream transport service, UDP protocol (Use Datagram Protocol) provides unreliable datagram service user.
Fourth layer: Application Layer
The application layer and the layer of the OSI reference model expression corresponds. Internet application layer protocol comprises Finger, Whois, FTP (File Transfer Protocol), Gopher, HTTP (hypertext transfer protocol), Telent (Remote Terminal Protocol), the SMTP (Simple Mail Transfer Protocol), the IRC (Internet relay session), NNTP (network News transfer protocol) and so on.