Shulou(Shulou.com)11/24 Report--

The highway will be blocked, and so will the information highway of the Internet.

It's been a while since the holidays. I believe everyone has a deep understanding of the painful experience of driving home and staying motionless on the highway all day and night during the holidays. Because the road is narrow and the traffic staff handles the work efficiency is limited, causes the traffic flow to reach the peak in a short time to cause the traffic jam, if compares the network to the highway, the data flow compares the traffic flow, then the network bandwidth and so on resources and the storage, the processing data ability is limited, also can cause the network congestion when the sudden flow occurs.

Network congestion will not only cause resource waste, serious words will also lead to abnormal traffic, network congestion as a common network problem, what mechanism can improve network resource utilization, provide better network quality of service?

To solve this problem, QoS (Quality of Service) was born!

Tip: There are four factors that affect network service quality: bandwidth, delay, jitter and packet loss rate, which are also QoS quality indicators. As for the specific introduction of the four elements of network quality, you can see that the network is not stuck. These four elements are very important.

How does QoS improve network service quality?

How does QoS regulate network traffic to avoid and handle network congestion? QoS is to improve the quality of network service for users through three service models. The following three models will be introduced in detail.

Best-effort service model (best effort) A simple service model implemented through FIFO (Frist in First Out) queues. For example, Xiaoming needs to copy a file from the FTP server to his computer. Xiaoming's computer needs to send a message to the FTP server, and obtain messages from FTP to form the file. The computer can send messages at any time without notifying the network. The messages sent are not classified and marked in the network, and directly enter the FIFO queue for forwarding or discarding. This service model is suitable for FTP, E-Mail and other services with low quality requirements.

2. IntServ service model Integrated Service This model is supported by RSVP (Resource Reservation Protocol) to apply for QoS requirements to work, when watching video with mobile phone, mobile phone sends a message to network video server, and obtains messages from video server to form video picture in mobile phone, mobile phone notifies network of traffic configuration of message to be sent and specific service quality request before sending message to server, All the transmission devices through which the message passes confirm these requests, and then the video server applies for resource reservation to the network. In the network, all the transmission devices through which the message passes are messages sent by mobile phones to the server.

After reserving resources, the mobile phone starts to send messages to the server, and the message traffic sent by the mobile phone should be within the application range. This model is not suitable for backbone networks with large amounts of data, and is currently mainly used with MPLS-TE (Multi-Protocol Label Switching-TE based on traffic engineering).

RSVP works at the transport layer, using Path messages to request resources hop-by-hop from the first node, and using Resv messages to reserve resources hop-by-hop after arriving at the destination.

DiffServ service model (Differentiated Service) This model is generally used to provide QoS for some important applications, mainly including traffic classification and marking, traffic policing, traffic shaping, interface speed limit, congestion management and congestion avoidance technologies. Let me take a convoy of 5 trucks passing on Highway A as an example to illustrate how Device A processes and forwards a 5-bit message under this service model.

Traffic classification and marking There are different convoys on the road, such as transport convoys, parade convoys, donkey convoys, etc. These convoys have different tasks to complete and different needs for transportation services. In order to provide different services to each fleet with different services, the traffic service personnel will classify each incoming fleet according to the service demand, and label the corresponding position of the team leader with different marks after classification to identify the priority level of the fleet handling traffic.

Traffic supervision and traffic shaping placed an automatic card machine at the entrance and exit of Highway A. The card machine kept dropping passes into the card bucket (token bucket) at a certain rate. At this time came a team A with 5 cars, the team leader Xiaoming received 5 passes from the card bucket Xiaoming's team can pass, at this time there are only 3 passes in the bucket, Xiaoming took out the pass from the bucket found that the number is not enough, they are not allowed to pass, Xiaoming had to get frustrated to put the 3 passes back into the bucket to find another way. In order to limit traffic to a certain bandwidth and prevent network congestion, token bucket mechanism is used to evaluate packets, discard packets with excessive traffic, and the processing process of packets not exceeding traffic entering queue scheduling or forwarding is called traffic supervision.

Congestion Management Team A walked on Highway A. Suddenly, traffic congestion occurred on the road ahead. Xiaoming and the others had to enter the dispatching queue to accept the arrangement and coordination of traffic control personnel. The control personnel looked at the signs posted on each leader's car and began to discuss the dispatching plan. Then, they coordinated the order of each team in the team. Congestion management refers to the process of buffering packets in queues and arranging the forwarding order of packets by queue scheduling algorithms such as PQ, CQ, WFQ, WRR, DWRR, etc.

Congestion Avoidance Traffic controller Xiao Wang keeps an eye on the traffic flow. Xiao Wang notices that the traffic is getting heavier and heavier, so he decides to adopt a strategy of strongly banning all or some of the vehicles behind him to ease the traffic congestion. Congestion avoidance is the process of actively adjusting traffic to relieve network overload by adopting drop policy when network is congested.

Traffic shaping team A only received one pass at the exit. After putting back the pass, Xiaoming and his team had a high priority and could queue up for traffic control personnel to arrange and dispatch. After dispatching, Xiaoming got 5 passes from the bucket and finally passed smoothly. Traffic shaping is a traffic control measure that uses token bucket mechanism to evaluate packets at the exit of the device, and the packets exceeding the traffic flow enter the queue buffer for processing.

The interface speed limit does not distinguish between fleets, but adopts a unified flow supervision or flow shaping system for all passing vehicles at the entrance and exit.

QoS upgrade HQoS improves network service quality better?

With the rapid development of the Internet, the scale of network users continues to expand, and the number and types of services continue to increase. Traditional QoS is no longer suitable for deployment on the user access side, and it is impossible to supervise and schedule multiple services of multiple users. To solve this problem, QosHQos (Hierarchical Quality of Service) was born!

HQoS is also used to improve network service quality. The difference between HQoS and traditional QoS is that HQoS can divide scheduling queues into multiple scheduling levels, and each level uses different characteristics for traffic supervision.

HQoS can not only distinguish service traffic more finely, but also supervise and schedule traffic uniformly and hierarchically for transmission objects such as multiple users and multiple services.

Today, we learned the following again!

1. The Internet is an information superhighway that requires QoS to avoid traffic jams.

2. QoS 3 magic weapon, can be used to improve network quality. Best-Effort service model is suitable for FTP, E-Mail and other applications;IntServ service model is suitable for TV conference, video-on-demand and other applications;DiffServ service model is suitable for games/video websites and other applications.

3. HQoS can help operators manage multi-user and multi-service services better by providing more detailed differentiation and multi-layer scheduling.

This article comes from Weixin Official Accounts: ZTE Document (ID: ztedoc), Author: ZTE Document

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