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

QOS service model:

1) Do your best.

All data is equal, tail dropping is implemented when congestion occurs; forwarding--FIFO

2. RSVP (Resource Reservation Protocol) is adopted in the integrated service model.

Advantages: (1) Management control of network resources

(2) Different policies can be used to allocate traffic for each transmission.

(3) is based on each type of traffic definition

(4) QOS on a per-flow basis rather than a per-packet basis

(5) The established session is dynamic

3. Differentiated service models EF, AF, CS, EB

Traffic classification can be implemented on a per-packet basis without session maintenance for end-to-end traffic;

DSCP Differentiated Services Coding Points are used to define packet priority; they are usually classified according to per hop behavior; DSCP values: 0---63;

EF---Fast forwarding----voice traffic, maximum one-way delay not exceeding 150ms; one-way jitter not exceeding 30ms;---guaranteed forwarding; corresponding DSCP value is 46;

AF--safeguard forwarding;AF1, AF2, AF3, AF4;

CS class selector---is consistent with IP priority;

Do your best;

DSCP value and PHB value are not one-to-one correspondence; AF---DD discard priority bit in PHB, 01 discard quantity is less than 10;

AF4 takes precedence over AF3--AF2--AF1;

II. Queue: FIFO, PQ, CQ, WFQ, CBWFQ, LLQ

FIFO: First in, first out

PQ: strict priority mechanism, high priority, medium priority, ordinary priority, low priority. High-priority queues must be processed first, and other queues are processed only when high-priority queues are free

(3) CQ: custom queue, using circular processing queue mode, regardless of priority, average processing of each queue, each queue processing 1500 bytes, if a data size exceeds 1500 bytes, must be processed completely before processing the next queue.

(4) WFQ: Weighted fair queue, different data packets have different priorities, the priority is high priority forwarding, the priority is high weight value is small, the weight value determines the service time, the default in the low speed link has been enabled

(5) CBWFQ: Different bandwidth guarantees are given based on different categories, WFQ queue design is carried out for different categories, and the bandwidth of all non-system categories does not exceed 75% of the total bandwidth.

LLQ Low Delay Queue: Mainly used when there is voice traffic, in order to ensure low delay and low jitter of voice traffic, it is a PQ+CBWFQ method, that is, according to priority queues, bandwidth is allocated proportionally according to priority, and exists as a guarantee. At this time, the allocated bandwidth is strict (even in the case of non-congestion, the guaranteed bandwidth is also non-shared).

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