Network Overview and basic concepts

Computer networks function

• Data communications and resource sharing
• Increase system capacity

Network Overview

Peripheral device and a network connection, will be distributed in the same or different regions of a plurality of computers connected together formed

note

• Computer on the network must be independent computer
• The purpose of the network is the exchange of information and resource sharing
• By the network connection \ network connectivity devices and a separate computer system

Network topology

• The apparatus as defined network 结点, the connection between two nodes is referred 链路to see the computer network from said topological view can be formed by the junction and the geometric position of the link is the network of拓扑结构
• There are two types of network nodes:
  • Switching nodes: network connection providing device
  • Access node: computer equipment to provide services

Distributed control

• Bus
  • Each node via one or more communication lines connected to the common bus
• Annulus
  • Each node in the network connected into a ring, the ring network is formed

Centralized control

• Star
  • Star structure central node is the master node, having 中继交换and 数据处理function
• Tree

  • Is actually a 分层结构, a star can be seen as an extension

    The network topology (physical topology)

• The method and form of a network of interconnected nodes of each called network topology.
• Common physical topologies are:
  • Bus topology (Bus)
  • Star topology (Star)
  • Ring topology (Ring)

Bus topology (Bus)

Bus topology uses a single transmission line as the transmission medium, all stations are directly connected to the transmission medium through the corresponding hardware interface.

Features:

• Lower costs
• To both ends terminating resistor
• Smaller number of connected computers ( 一般少于20台)
• Poor stability, primarily for 10M networks

Star topology (Star)

Star topology is made 中央节点and 通过连接到中央节点的各站点constituted

Feature

• Easy access and exit station
• General use twisted-pair connections, in line with current cabling standards
• Meet a variety of bandwidth
  • 10M
  • 100M
  • KM
• Greater dependence on the central node
• The central node can be cascaded, but no more than four

Ring topology (Ring)

Ring topologies are online all the nodes sequentially connected by a cable forming a closed loop physical change =.

Feature

• Each corresponds to a workstation 中继器, a reducing effect signal
• Loop increases the difficulties users
• Poor reliability, difficult to manage

Classification of computer networks

• Geographical coverage of classification
  • Local area network (LAN)
  • Wide Area Network (WAN)
  • Metropolitan Area Network (WAN) a large, LAN
• Classification by transmission technology
  • Broadcast Network broadcast network
  • Point to point network `point-to-point network``

Regional network concept

distance	Computer distribution	Network Type
10 m	The same room	local area network
100 metres	The same building	local area network
1000 meters	The same campus	local area network
10,000 meters	A rural area	local area network
20000-100000	A large enterprise, a city	Wan
1 million or more	A country, a planet	Wan