The QoS mechanism
1.classification Category: dividing the data into different categories
2.marking marker: the data set to a different priority
3.congestion management congestion management: Each interface has a queue mechanism, when the network congestion occurs, a predetermined in what order the data transmission
4.congestion avoidance congestion avoidance: when network congestion (queue) occurs, how to drop packets to prevent network congestion
5.policing and shaping and shaping control: when the user than the nominal bandwidth of more than bandwidth can not be transferred, processed in other ways.
Control discard the extra bandwidth
shaping cache bandwidth exceeds
6.link efficiency link efficiency: the link segment through the header compression or improve the bandwidth efficiency.
Category
classification is to identify and isolate the flow of different classes of
traffic can be classified in various ways, including the DSCP
Modular the CLI allows the QoS policy classified by performing
Marker
tag, also referred to as coloring colored
according to different categories of traffic marking each packet, so that the transmission of traffic classification, can be quickly identified in the network.
Congestion management
congestion management is the tag on each packet, to determine the place in the queue the data packet, congestion management queues using advanced techniques, such as WFQ how the LLQ, to ensure time-sensitive traffic can be preferentially transmitted, for example, voice traffic is transmitted first.
Congestion avoidance
when the threshold of the queue reaches a predefined limit, to avoid congestion may randomly discarding packets in the "earlier time" Start packet loss, congestion avoidance facilitate downstream bottleneck of the network.
Congestion avoidance techniques include random early detection and weighted random early detection mechanism detects random weight-based random detection mechanism.
Control
when the predefined limit is reached, the packet is discarded
Shaping
when reaches a predefined limit, the excess bandwidth of the buffer.
Compression
Header compression can significantly reduce the overhead associated with voice transmission.
In an IP data stream, the data header is a lot of information remains the same, which provide the basis for header compression, the sender only needs to start when transmission of a complete header, followed by the same part can not pass.
Link Fragmentation and interactive transmission
in the absence of fragmentation and interactive transmission link used for the time delay sensitive voice packets being spaced a large packet, the default delay is relatively large, With the above technique, the intermediate large data packets into a plurality of smaller packets, and then transmits the interactive, thus reducing the delay of voice data.
Network Application letter
