Shulou(Shulou.com)06/01 Report--

QOS quality of service is a method to solve network congestion, which allocates the existing network resources reasonably.

QOS technology is divided into four parts: flow classification / identification, speed limit, congestion avoidance and congestion management.

Flow classification / identification:

We can classify the traffic through ACL.

We mark the priority of each flow for classified traffic.

There are two ways to mark the flow priority:

2 IP Precedence: values range from 0 to 7.

0 is best effort data

1 is medium priority data

2 High priority data

3 call signal

4 Video conferencing

5 Voice

6 is reserved

7 is reserved

2 DSCP tag: DiffServ code point. The value ranges from 0 to 63. The higher the value, the higher the priority.

Speed limit:

V traffic regulation: committed rate, discarded if excess traffic is exceeded.

V traffic × ×: adjust the rate and use the traffic of the buffer to forward evenly.

Congestion avoidance:

V WRED: the earliest weighted random detection technique, which consists of three parameters: low threshold, high threshold and discard probability. When the message is less than the low threshold, it is not discarded, and when the message is greater than the high threshold, it is discarded.

V SRED: discards messages randomly according to the discarding probability of the manual adjustment flow. If the drop probability is high, the packet loss rate is high, and if the drop probability is low, the packet loss rate is low.

Congestion management: define who passes the message first and who passes later according to the queue technology.

V FIFO: first-in, first-out queuing technology, which flows on a first-come-first-served basis according to flow priority.

V WFQ: weighted fair queuing technology, which divides different streams into different queues, and allocates the egress bandwidth according to the flow priority. The higher the priority, the greater the bandwidth. WFQ reserves 25% bandwidth by default.

V CBWFQ: class-based weighted fair queuing technology, which consists of three classes: Defalut class, LLQ low latency class and BQ standard class.

(2) the traffic with no flow definition is defined as Defalut traffic, which is scheduled by first-in, first-out or WFQ technology.

(2) when the defined flow is LLQ low-latency traffic, the traffic will be passed first.

(2) when the flow is defined as BQ standard class traffic, WFQ queue technology is used for scheduling.

Understand the idea:

V specifies the direction of the traffic to be controlled, and generally controls the download traffic, so it is the incoming traffic input or inbound.

V-flow classification / identification: classify and manage traffic. Define the flow.

V speed limit: we can understand it as an action to limit the speed of classified traffic and reasonably divide the network bandwidth.

V congestion avoidance: in order to avoid random drop of packets, we manually determine the packet loss probability.

V congestion management: assign priority rules to all defined traffic, who passes first and who passes later.

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