Computer network principle One

1.1 Computer networks provide users with two of the most important features:

(1) Connectivity: Computer networks enable users to exchange information between the Internet;

(2) Sharing: Sharing of resources, namely: information sharing, software sharing, hardware sharing.

1.2 The network consists of several nodes (computers, hubs, switches, routers, etc.) and links that connect these nodes

The three stages of Internet development: (1) from a single network arpanet to the Internet; the Internet (Internet or interconnection) is a generic term that refers to a network interconnected by multiple computer networks, and the communication protocol can be arbitrary. Internet (Internet) is a proper noun, it values the world's largest, open, there are many networks connected to the specific computer network, using the TCP/IP protocol family as a communication rule, the predecessor ARPANET.

(2) The Internet of level three structure: backbone network, regional network, campus network or Enterprise network.

(3) Multi-level ISP structure of the Internet: Internet Exchange point: IXP: Allow two groups to directly connect and exchange packets, improve the efficiency of packet forwarding and network resources utilization. WWW World Wide Web promotes the development of computer network.

The Internet Architecture Committee, IAB: (1) Internet Engineering IETF: Protocol Development and Standardization; (2) Internet Research Department IRTF: Theoretical research to explore some long-term issues to be considered.

The internet is the standard four stages: (1) Internet draft (2) proposed standard (3) Draft standard (4) Internet standards

1.3 The composition of the Internet:

The edge part: consists of all the hosts connected to the Internet, the core part: a large number of networks and the routers that make up these networks, providing services (connectivity and switching) to the edge portion.

Edge part: Communication between computers is actually inter-process communication: Client server Mode C/s: Describes the relationship between inter-process services and services, (clients, servers are processes in the application layer)

Customer: Service requester, server: service provider. The client program is called by the user to run, (know the server IP), the initiative to the remote server to initiate the request.

Server: A service provider that specializes in providing a specific service that can handle multiple requests at the same time, without knowing the client IP, running continuously, passively waiting for communication requests, and requiring strong hardware and advanced operating system support.

Peer Mode peers: The user does not distinguish between a service provider and a service requester when communicating.

Core: Routers implement packet switching, forwarding received groupings.

(1) Circuit Exchange: Establish a connection-call-release connection; features: End-to-end channel resources, channel exclusive, transfer of computer data efficiency is low;

(2) Message exchange: The entire message first to the adjacent nodes, all storage after the search for forwarding, forwarded to the next node; Features: Extended

(3) A single packet (the whole part of the message) is transmitted to the neighboring node, and the post is stored for forwarding to the next node. Specifically: efficient, fast, flexible, reliable.

1.4 Types of computer networks:

(1) by scope of Action: Wan Wan, man, Lan LAN, personal area network pan

(2) According to network users: Public network, private network

(3) A network used to connect users to the Internet: Access networks, which are neither core nor part of the edge.