Self review information on the Internet and its applications
Internet Overview
1, the Internet is a collection of a computer network to TCP / IP data communication, computer networks around the world joined together to achieve information exchange and sharing of resources.
The Internet is a collection of network equipment and established a physical line on a common set of protocols, a set of set of resources that can be shared. It includes inter-network based on TCP / IP protocols; the user groups and the development of these networks; set of resources available from the network. Narrow the set of all the Internet using the IP protocol is a network of interconnected packet TCP / IP routing protocol implemented by each transmission, it may also be referred to as IP Internet. Generalized Internet IP means Internet plus all routing through the network to the destination station, including the use of a set of e-mail network application layer gateway, a variety of store and forward network and non-IP protocol network interconnection.
2, the Internet originated in the ARPA network. NSFnet has become an important backbone of the Internet.
1969 to 1983 was the formative period of the Internet, mainly for research and testing of network technology.
1983 to 1994 is the practical stage of the Internet.
1989, CERN developed by the World Wide Web, the Internet began to enter the fast development period.
The original purpose of the Internet is used to support education and research activities.
Three gold projects: the Golden Bridge; Kim Guan; Gold. Primary network access providers: CHINANET;, CSTNET; of CERNET;
. 3, Internet: refers to a collection of a plurality of computers connected to each other. Typically include two interconnect and interconnect levels. Interconnections are physical, realized by hardware. Internet is logical, implemented by software. At the lowest level of the network structure, the information embodied transmitted bit stream exchange between the two machines directly connected. Information exchange network of low-level implemented in hardware, and to the high level by the software.
Computer Network: is another shared resource connected together, each provided with a set of independent functions of the computer system. (Autonomous and independent, a collection of computers connected to each other)
Computer Network: all different geographical locations, and having a function independent computer systems connected by a plurality of communication devices and lines, to improve the function of the network resource sharing network software system. (2012.10.41)
4, the material basis is the network hardware of a computer network system. Common network hardware: computers, network interface cards, concentrator node computers, modems, routers, and other transmission media.
Computers on the network can be divided into two categories
① client: a common computer network access functions that provide network services to customers, also known as workstations.
② server: a strong high-end computer computing capabilities and rich information resources that provide services for network clients, and is responsible for management of network resources.
Network software is an indispensable function for network soft environment. Generally it includes: network protocols and protocol software, network communications software and network operating systems.
5, the network architecture: the hierarchy is a collection of computer networks and protocols proposed by hierarchical design method.
In the network hierarchy: Each layer is logically independent; each layer has specific functions; between the functional layers have clear boundaries; an interface standard between adjacent layers, excuse It defines the underlying operating services provided to senior; communication between computers is based on the same level between.
Features of the layered architecture
independence of layer ①
② suitable flexibility
divisibility of the structure ③
④ easy to implement and maintain
⑤ promoting standardization
6, the Internet uses packet switching and packet switching as a means of communication.
7, the bus structure
advantages: high channel utilization, the structure is simple, relatively cheap.
Disadvantages: the same time, only two network nodes communicate with each other, extending a limited distance network, a limited number of nodes in the network to accommodate.
Ring structure
Advantages: maximum transmission time information is transmitted in the communication network delay is fixed; each line node physical link only two directly interconnected with other nodes, the transmission control mechanism is simple and practical.
Disadvantages: a node failure may terminate the operation of the whole network, and therefore less reliable. Star structure advantages: simple structure, easy to build networks, control is relatively simple. Disadvantages: Due to centralized control, the host overload, low reliability, communication line utilization rate.
This tree structure reduces the cost compared with the communication line star structure, but increases the network complexity.
Classification mesh structure:
① fully connected mesh: each node and the other network nodes are connected to the link.
② incomplete connection net: there is not necessarily a direct link connection between two nodes, communications between them, rely on other switching nodes.
Advantages: multi-path between nodes, collisions and congestion can be greatly reduced, local area network failure will not affect the normal operation of the entire network, high reliability; network expansion and network hosts more flexible and simple.
Disadvantages: complex relationship network, network construction difficult, complex network control mechanism.
Tree and mesh structure is relatively common in the wide area network.
8, connected to the Internet network is implemented by means of an intermediate computer. Network connection comprises two contents:
① To implement two physical networks connected by a intermediate computer, i.e., to solve first network interconnect
② intermediate computer implemented between the two networks to packet switching and protocol conversion involves finding a path problems , that is, to solve networking.
Intermediate computer called the Internet gateway.
9, Internet performance metrics: Bandwidth (Bandwidth), time delay (Delay), throughput, quality of service (Qos).
Bandwidth: This means a bandwidth of a signal having a. Equivalent to the actual frequency (the field of communications and network) and data transmission rates (for digital channels) both. K is 1024, k is 1000.
Delay: the propagation delay, transmission delay, queuing delay composition. Transmission delay and a channel length of the data block to bandwidth.
Throughput: measures on data transfer rates. Mainly used in parallel processing, the unit is bit / s.
Quality of Service: Solution to network latency and congestion.
It has a function: the classification (protocol, TCP, and UDP port number, source IP address, a physical port number);
label; priority.
10, Intranet is an Internet-based TCP \ IP protocol to build the internal network, including pure LAN, not interconnected with the external network; and limited external network interconnection.
Intranet features:
①Intranet is based on the needs within the enterprise and the construction of its size and function is based on demand management and development of enterprises identified.
②Intranet should facilitate contact with the outside world and, in particular, and Internet connection.
③Intranet using TCP \ IP protocol and the appropriate technology and tools, it is an open system.
④Intranet set up a firewall, and other security agents in accordance with corporate security requirements to protect the information within the enterprise, to prevent outside intrusion.
⑤Intranet widely used WWW tool that enables employees and users can easily view and share information within the enterprise as well as a wealth of information resources on the Internet.
11, Internet applications: Telnet, e-mail, file transfer, WWW browser, Internet news groups, online communities, blog, multimedia applications, Internet telephony, network fax, video conferencing, video on demand and broadcast, online games, Internet instant messaging , e-commerce.
12, Next Generation Internet (NGI) Features: bigger, faster, safer and more convenient.
United States: internet 2.
China Next Generation Internet (CNGI), the core network CERNET 2.
exercise:
1, and illustrate the concept of the difference between the Internet and Intranet.
A: Internet to establish a physical collection of routers and circuits on a common set of protocols. It applied to the WAN.
Intranet intranet, use the Internet as a tool, protocol, lines.
2. What is a computer network?
Answer: to share resources (hardware, software, databases, etc.) are connected to each other and the way each has a set of independent functions of the computer system.
3, IP address and brief function.
A: According to TCP / IP protocol, the computer connected to the Internet has a unique address identifier, this identifier is called an IP address.
Function: IP address is unique, that is, all computers connected to the Internet has a unique IP address.
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