Reference: B station computer network Han Ligang teachers and 21 postgraduate courses benevolent review guide
Computer network physical layer Chapter
computer network data link layer Chapter
computer network Chapter network layer
The first chapter outlines a computer network
LAN: Small coverage, their own money to buy equipment, fixed bandwidth, about 100M, own maintenance, covering a range of about 100m
wide area network: distance, to spend money to rent the bandwidth, others give you maintenance services
ADSL: Asymmetric Digital Subscriber Loop, the ordinary telephone lines into a telephone, three independent uplink and downlink channels, i.e., the original dial.
OSI Reference Model
Application Layer: All program can generate network traffic
presentation layer: to encrypt the data prior to transmission or compression processing, converted into ASCII
session layer: can be used to find the Trojan netstat -n
transporting layer: Flow control is not reliable transmission reliable transport
network layer: flow control, error control, congestion control. Routing: determine which way the most appropriate (responsible for planning the best path similar to the high German), planning ip address of
the data link layer: flow control, error control. Defined the beginning and end of the data frame to realize transparent transmission
the physical layer: the device interface standards define the physical, electrical standards
O ( ¯ ▽ to ¯ ) O
physical layer service data link layer, the data link layer, the network layer provides services for the network The transport layer provides services to the layer, transport layer, session layer provides services to the session layer The presentation layer provides services to the presentation layer provides services to the application layer, the application layer provides services for people oh yeah is!
Computer network performance
rate: host digital transmission channel how many bits per second, in units of b / s, kb / s, mb / s, gb / s
Bandwidth: the maximum transmission speed units b / s
Throughput: unit time the amount of data within a network of
transmission delay: data block length (bits) / channel bandwidth (bits per second), transmitted from the host to the desired time on line
time data transfer line: the propagation delay
processing extension: this string of binary router processing time required, if more need to queue
queuing delay: the mouth also sent out to wait in line, which is queuing delay
