Congestion management mechanism on an S series switch


On S series switches (except S1700), each physical port has eight sending queues numbered from 7 to 0 in descending order of priority. Queue 7 has the highest priority and queue 0 has the lowest priority. Sending ports support the following queue scheduling modes: PQ, WRR, DRR, PQ+WRR, and PQ+DRR.
When PQ+WRR or PQ+DRR is used, packets in PQ queues are scheduled first. The PQ queue with the highest priority is scheduled preferentially and then PQ queues with lower priorities are scheduled in succession. After all PQ queues are scheduled, WRR or DRR queues are then scheduled.
For WRR and DRR queues, the queues are scheduled to ensure bandwidth first and then scheduled based on weights.
The S5720HI fixed switch and X series cards of S series modular switches do not support WRR and PQ+WRR scheduling.

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Method used to configure congestion avoidance and congestion management on S series switches
For S series switches (except the S1700), congestion avoidance prevents a network from being overloaded using a packet discarding policy. Congestion management ensures that high-priority services are preferentially processed based on the specified packet scheduling sequence. On a traditional network, quality of services (QoS) is affected by network congestion. Congestion means the low data forwarding rate and delay resulting from insufficient network resources. Congestion results in delay of packet transmission, low throughput rate, and high resource consumption. Congestion often occurs in a complex networking environment where packet transmission and provision of various services are both required. Congestion avoidance and congestion management are two flow control mechanisms for resolving congestion on a network. For the configuration of congestion management on S series fixed switches, see "Example for Configuring Congestion Management (Schedule Template Mode)" in the Typical QoS Configuration. For the comprehensive configuration example of S series fixed and modular switches, see "Example for Configuring Congestion Avoidance and Congestion Management (Using WRR Scheduling and an SRED Policy)" or "Example for Configuring Congestion Avoidance and Congestion Management (Using PQ+DRR Scheduling and a WERD Profile)" in the Typical QoS Configuration.

PoE mechanism of an S series switch
PoE mechanism of S series switches: Power over Ethernet (PoE) is a remote power supply function. With this function, a device can provide power to powered devices (PDs) connected to its Ethernet electrical interfaces over twisted pair cables. PoE is reliable and standard and requires simple connections. Note: A PC connected to a PoE-enabled interface will not be affected or burned because the following PoE detection process is performed: 1. Detect PDs. A power sourcing equipment (PSE) periodically transmits a low voltage with limited current through its ports to detect PDs. If the PSE detects a resistance with a specified value, PDs that comply with IEEE 802.3af or IEEE 802.3at are connected to the other ends of cables. 2. Negotiate power supply. A PSE classifies PDs and negotiates the power with PDs. Power supply capabilities can be negotiated by resolving detected resistances or the LLDP protocol. 3. Start to provide power. During the startup period (less than 15 ?s generally), the PSE starts to provide power to PDs from a low voltage and increases the voltage until the voltage reaches 48 V DC. 4. Provide power normally. Finally, the output voltage provided to PDs is stabilized at 48 V DC, and the power consumption of each PD does not exceed 30 W. 5. Stop providing power. The PSE keeps detecting the input current of PDs while supplying power. When detecting that the current of a PD falls below the minimum value or increases sharply, the PSE stops supplying power to the PD and repeats PD detection. This situation occurs when a PD is disconnected from the PSE or encounters a power overload or short circuit, or its power consumption exceeds the power supply capacity of the PSE. For details, see Tell You About PoE.

ACL configuration on S series switch
An ACL filters packets based on rules. A switch with an ACL configured matches packets based on the rules to obtain the packets of a certain type, and then decides to forward or discard these packets according to the policies used by the service module to which the ACL is applied. The S series switch supports basic ACL (2000-2999), advanced ACL (3000-3999), Layer 2 ACL (4000-4999), user-defined ACL (5000-5999), USER acl (6000-9999), basic ACL6 (2000-2999), and advanced ACL6 (3000-3999). For more information about the ACL feature supported by S series switches, except S1700, click S1720&S2700&S3700&S5700&S6700&S7700&S9700 Common Operation Guide or S1720&S2700&S3700&S5700&S6700&S7700&S9700 Typical Configuration Examples.

NQA association mechanism of S series switches
NQA of S series switches (except S1700 switches) in V200R001C00SPC300 and later versions can be associated with static routes and VRRP. The following is an example of associating NQA with a static route. Network connectivity and routes between devices have been configured. 1. Configure an NQA test instance. # On Switch A, configure an NQA test instance, and set the NQA test type to icmp, and the destination IP address to [HUAWEI] nqa test-instance user test //Configure the administrator of the NQA test instance as user and the test instance name as test. [HUAWEI-nqa-user-test] test-type icmp //Set the NQA test type to icmp. [HUAWEI-nqa-user-test] destination-address ipv4 //Set the destination address to [HUAWEI-nqa-user-test] frequency 10 //Set the interval at which the NQA test instance automatically runs to 10, in seconds. [HUAWEI-nqa-user-test] probe-count 2 //Set the number of probes to be sent each time to 2. [HUAWEI-nqa-user-test] interval seconds 5 //Set the interval at which probe packets are sent to 5, in seconds. [HUAWEI-nqa-user-test] timeout 4 //Set the timeout period of a probe to 4, in seconds. [HUAWEI-nqa-user-test] start now end delay seconds 10000 //Start the test instance and configure the test instance to end after 10,000 seconds. [HUAWEI-nqa-user-test] quit 2. Associate a static route with the NQA test instance. [HUAWEI] ip route-static Vlanif 10 track nqa user test

Configuration examples of congestion management and congestion avoidance on an AR
For details about the comprehensive examples for configuring congestion avoidance and congestion management on an AR, see "4.7.1 Example for Configuring Congestion Management and Congestion Avoidance" on "CLI-based Configuration Guide - QoS", link for ""

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