Table of Contents 1 QoS Overview 1-1 Introduction to QoS 1-1 Introduction to QoS Service Models 1-1 Best-Effort Service Model 1-1 IntServ Service Model 1-2 DiffServ Service Model 1-2 QoS Techniques Overview 1-2 Applying QoS Techniques in a Network 1-3 QoS Processing Flow in an AP 1-4 2 QoS Policy Configuration 2-1 QoS Configuration Approach Overview 2-1 Non-Policy Approach 2-1 Policy Approach 2-1 Configuring a QoS Policy 2-1 Defining a Class 2-2 Defining a Traffic Behavior 2-2 Defining a QoS Policy and Applying the QoS Policy to an Interface 2-3 Displaying and Maintaining QoS Policies 2-3 3 Priority Mapping Configuration 3-1 Introduction to Packet Precedences 3-1 IP Precedence and DSCP Values 3-1 802.1p Priority 3-2 802.11e Priority 3-3 Priority Mapping Overview 3-3 Introduction to Priority Mapping 3-3 Introduction to Priority Mapping Tables 3-4 Priority Mapping Configuration Task List 3-5 Configuring Priority Mapping 3-6 Configuring a Priority Mapping Table 3-6 Configuring a Port to Trust Packet Priority for Priority Mapping 3-6 Changing the Port Priority of an Interface 3-7 Displaying and Maintaining Priority Mapping 3-7 Priority Mapping Configuration Example 3-7 i
The models listed in this document are not applicable to all regions. Please consult your local sales office for the models applicable to your region. Support of the H3C WA series WLAN access points (APs) for features may vary by AP model. For more information, see Feature Matrix. The interface types and the number of interfaces vary by AP model. The term AP in this document refers to common APs, wireless bridges, and mesh APs. 1 QoS Overview This chapter includes these sections: Introduction to QoS Introduction to QoS Service Models QoS Techniques Overview Introduction to QoS In data communications, Quality of Service (QoS) is the ability of a network to provide differentiated service guarantees for diversified traffic in terms of bandwidth, delay, jitter, and drop rate. Network resources are always scarce. The contention for resources demands that QoS prioritize important traffic flows over trivial traffic flows. When making a QoS scheme, a network administrator must consider the characteristics of various applications to balance the interests of diversified users and fully utilize network resources. The subsequent section describes some typical QoS service models and widely-used mature QoS techniques. By appropriately using these techniques, you can improve QoS effectively. Introduction to QoS Service Models This section covers three typical QoS service models: Best-Effort Service Model IntServ Service Model DiffServ Service Model Best-Effort Service Model Best effort is a single service model and also the simplest service model. In the best effort service model, the network does its best to deliver packets but does not guarantee delay or reliability. The best-effort service model is the default model in the Internet and applies to most network applications. It uses the first in first out (FIFO) queuing mechanism. 1-1
IntServ Service Model The integrated service (IntServ) model is a multiple-service model that can accommodate diverse QoS requirements. It provides the most granularly differentiated QoS by identifying and guaranteeing definite QoS for each data flow. In the IntServ model, an application must request service from the network before it sends data. IntServ signals the service request with the Resource Reservation Protocol (RSVP). All nodes that receive the request reserve resources as requested and maintain state information for the application flow. The IntServ model demands high storage and processing capabilities, because it requires that all nodes along the transmission path maintain resource state information for each flow. The model is suitable for small-sized or edge networks, but not large-sized networks, for example, the core layer of the Internet, where billions of flows are present. For more information about RSVP, see MPLS TE in the MPLS Configuration Guide. DiffServ Service Model The differentiated service (DiffServ) model is a multiple-service model that can satisfy diverse QoS requirements. Unlike IntServ, DiffServ does not require an application to signal the network to reserve resources before sending data. DiffServ is easy to implement and extend. All QoS techniques in this document are based on the Diff-Serv model. QoS Techniques Overview The QoS techniques fall into traffic classification, traffic policing, traffic shaping, line rate, congestion management, and congestion avoidance. The following part briefly introduces these QoS techniques. 1-2
Applying QoS Techniques in a Network Figure 1-1 Positions of the QoS techniques in a network As shown in Figure 1-1, traffic classification, traffic shaping, traffic policing, congestion management, and congestion avoidance mainly implement the following functions: Traffic classification uses certain match criteria to assign packets with the same characteristics to a class. Based on classes, you can provide differentiated services. Traffic policing polices flows entering or leaving an AP, and imposes penalties on traffic flows that exceed the pre-set threshold to prevent aggressive use of network resources. You can apply traffic policing to both incoming and outgoing traffic of a port. Traffic shaping proactively adapts the output rate of traffic to the network resources available on the downstream AP to eliminate packet drops. Traffic shaping usually applies to the outgoing traffic of a port. Congestion management provides a resource scheduling policy to determine the packet forwarding sequence when congestion occurs. Congestion management usually applies to the outgoing traffic of a port. Congestion avoidance monitors the network resource usage and is usually applied to the outgoing traffic of a port. When congestion worsens, congestion avoidance actively reduces the queue length by dropping packets. 1-3
QoS Processing Flow in an AP Figure 1-2 QoS processing flow... Figure 1-2 briefly describes how the QoS module processes traffic: 1) Traffic classifier identifies and classifies traffic for subsequent QoS actions. 2) The QoS module takes various QoS actions on classified traffic as configured, depending on the traffic processing phase and network status. For example, you may configure the QoS module to perform traffic policing for incoming traffic, traffic shaping for outgoing traffic, congestion avoidance before congestion occurs, and congestion management when congestion occurs. 1-4
2 QoS Policy Configuration This chapter includes these sections: QoS Configuration Approach Overview Configuring a QoS Policy Displaying and Maintaining QoS Policies QoS Configuration Approach Overview Two approaches are available for configuring QoS: Non-Policy Approach and Policy Approach. Some features support both approaches, but some support only one. Non-Policy Approach In non-policy approach, you configure QoS service parameters directly without using a QoS policy. For example, you can use the line rate feature to set a rate limit on an interface without using a QoS policy. Policy Approach In policy approach, you configure QoS service parameters by using QoS policies. A QoS policy defines the shaping, policing, or other QoS actions to take on different classes of traffic. It is a set of class-behavior associations. A class is a set of match criteria for identifying traffic. It uses the AND or OR operator: If the operator is AND, a packet must match all the criteria to match the class. If the operator is OR, a packet matches the class if it matches any of the criteria in the class. A traffic behavior defines a set of QoS actions to take on packets, such as priority marking and redirect. By associating a traffic behavior with a class in a QoS policy, you apply the specific set of QoS actions to the class of traffic. Configuring a QoS Policy Figure 2-1 shows how to configure a QoS policy. 2-1
Figure 2-1 QoS policy configuration procedure Define a class Define a traffic behavior Define a policy Apply the policy to an interface Defining a Class To define a class, specify its name and then configure the match criteria in class view. Follow these steps to define a class: To do... Use the command... Remarks Enter system view system-view Create a class and enter class view Configure match criteria traffic classifier tcl-name [ operator { and or } ] if-match match-criteria Required By default, the operator of a class is AND. The operator of a class can be AND or OR. AND: A packet is considered belonging to a class only when the packet matches all the criteria in the class. OR: A packet is considered belonging to a class if it matches any of the criteria in the class. Required For more information, see the if-match command in QoS in the ACL and QoS Command Reference. Defining a Traffic Behavior A traffic behavior is a set of QoS actions (such as traffic filtering, traffic policing, and priority mapping) to take on a class of traffic. To define a traffic behavior, first create it and then configure QoS actions (such as priority mapping and traffic policing) in traffic behavior view. Follow these steps to define a traffic behavior: To do... Use the command... Remarks Enter system view system-view Create a traffic behavior and enter traffic behavior view Configure a CAR action traffic behavior behavior-name car cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ pir peak-information-rate ] [ red action ] Required 2-2
To do... Use the command... Remarks Drop or send packets filter { deny permit } To drop matching packets, select the deny keyword. To permit matching packets to pass through, select the permit keyword. Set the local precedence for packets Set the 802.1p priority for packets Display traffic behavior configuration information remark local-precedence local-precedence remark dot1p 8021p display traffic behavior user-defined [ behavior-name ] Available in any view Defining a QoS Policy and Applying the QoS Policy to an Interface A policy applied to an interface takes effect on the traffic sent or received by the interface. A policy can be applied to multiple interfaces, but only one policy can be applied in one direction (inbound or outbound) of an interface. Follow these steps to apply the QoS policy to an interface: To do... Use the command... Remarks Enter system view system-view Define a QoS policy and enter QoS policy view Associate a class with a behavior in the QoS policy Enter interface view Apply the policy to the interface qos policy policy-name classifier tcl-name behavior behavior-name interface interface-type interface-number qos apply policy policy-name { inbound outbound } Required Required Repeat this step to create more class-behavior associations. Required The QoS policy applied to the outgoing traffic of an interface does not regulate local packets. Local packets refer to the critical protocol packets sent by the local system for maintaining the normal operation of the AP. To avoid drop of local packets, QoS does not process them. Commonly used local packets are link maintenance packets and so on. Displaying and Maintaining QoS Policies To do... Use the command... Remarks Display traffic class information display traffic classifier user-defined [ tcl-name ] Available in any view 2-3
To do... Use the command... Remarks Display traffic behavior configuration information Display the configuration of one or all classes in one or all QoS policies and the associated behaviors of the classes Display QoS policy configuration on the specified or all interfaces display traffic behavior user-defined [ behavior-name ] display qos policy user-defined [ policy-name [ classifier tcl-name ] ] display qos policy interface [ interface-type interface-number ] [ inbound outbound ] Available in any view Available in any view Available in any view 2-4
3 Priority Mapping Configuration This chapter includes these sections: Introduction to Packet Precedences Priority Mapping Overview Priority Mapping Configuration Task List Configuring Priority Mapping Displaying and Maintaining Priority Mapping Priority Mapping Configuration Example Introduction to Packet Precedences IP Precedence and DSCP Values Figure 3-1 ToS and DS fields As shown in Figure 3-1, the ToS field of the IP header contains eight bits, and the first three bits (0 to 2) represent IP precedence from 0 to 7. According to RFC 2474, the ToS field of the IP header is redefined as the differentiated services (DS) field, where a DSCP value is represented by the first six bits (0 to 5) and is in the range 0 to 63. The remaining two bits (6 and 7) are reserved. Table 3-1 Description on IP precedence IP precedence (decimal) IP precedence (binary) Description 0 000 Routine 1 001 priority 2 010 immediate 3 011 flash 4 100 flash-override 5 101 critical 6 110 internet 7 111 network 3-1
Table 3-2 Description on DSCP values DSCP value (decimal) DSCP value (binary) Description 46 101110 ef 10 001010 af11 12 001100 af12 14 001110 af13 18 010010 af21 20 010100 af22 22 010110 af23 26 011010 af31 28 011100 af32 30 011110 af33 34 100010 af41 36 100100 af42 38 100110 af43 8 001000 cs1 16 010000 cs2 24 011000 cs3 32 100000 cs4 40 101000 cs5 48 110000 cs6 56 111000 cs7 0 000000 be (default) 802.1p Priority 802.1p priority lies in the Layer 2 header and is applicable to occasions where Layer 3 header analysis is not needed and QoS must be assured at Layer 2. Figure 3-2 An Ethernet frame with an 802.1Q tag header As shown in Figure 3-2, the 4-byte 802.1Q tag header consists of the tag protocol identifier (TPID, two bytes in length), whose value is 0x8100, and the tag control information (TCI, two bytes in length). Figure 3-3 presents the format of the 802.1Q tag header. The Priority field in the 802.1Q tag header is 3-2
called the 802.1p priority, because its use is defined in IEEE 802.1p. Table 3-3 presents the values for 802.1p priority. Figure 3-3 802.1Q tag header Byte 1 Byte 2 Byte 3 Byte 4 TPID (Tag protocol identifier) TCI (Tag control information) CFI 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 Priority VLAN ID 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 Table 3-3 Description on 802.1p priority 802.1p priority (decimal) 802.1p priority (binary) Description 0 000 best-effort 1 001 background 2 010 spare 3 011 excellent-effort 4 100 controlled-load 5 101 video 6 110 voice 7 111 network-management 802.11e Priority To provide QoS services on WLAN, the 802.11e standard was developed. IEEE 802.11e is a MAC-layer enhancement to IEEE 802.11. IEEE 802.11e adds a 2-byte QoS Control field to the 802.11e MAC frame header. Three bits of the QoS control field represents the 802.11e priority, which ranges from 0 to 7. Figure 3-4 802.11e frame structure Priority Mapping Overview Introduction to Priority Mapping When a packet enters an AP, the AP assigns a set of QoS priority parameters to the packet based on a certain priority field carried in the packet and sometimes may modify its priority, according to certain 3-3
rules depending on AP status. This process is called priority mapping. The set of QoS priority parameters decides the scheduling priority and forwarding priority of the packet. Priority mapping is implemented with priority mapping tables and involves priorities such as 802.11e priority and 802.1p priority. Introduction to Priority Mapping Tables The AP provides various types of priority mapping table, as listed below. dot11e-lp: 802.11e-to-local priority mapping table. dot1p-lp: 802.1p-to-local priority mapping table. dscp-lp: DSCP-to-local priority mapping table, which applies to only IP packets. lp-dot11e: Local-to-802.11e priority mapping table. lp-dot1p: Local-to-802.1p priority mapping table. lp-dscp: Local-to-DSCP priority mapping table. Table 3-4 through Table 3-7 list the default priority mapping tables. Table 3-4 The default dot1p-lp mapping 802.1p priority Local precedence 0 2 1 0 2 1 3 3 4 4 5 5 6 6 7 7 Table 3-5 The default dscp-lp mapping DSCP Local precedence 0 to 7 0 8 to 15 1 16 to 23 2 24 to 31 3 32 to 39 4 40 to 47 5 48 to 55 6 56 to 63 7 3-4
Table 3-6 The default lp-dot1p and lp-dscp mappings Local precedence 802.1p priority DSCP 0 1 0 1 2 8 2 0 16 3 3 24 4 4 32 5 5 40 6 6 48 7 7 56 Table 3-7 The default port priority-local precedence mapping Port priority Local precedence 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 For the default dot11e-lp and lp-dot11e mappings, an input value yields a target value that is equal to it. Priority Mapping Configuration Task List You can configure priority mapping in two approaches: Configuring priority trust mode. In this approach, you can configure a port to look up the priority mapping tables based on a certain priority such as 802.1p carried in incoming packets. If no packet priority is trusted, the port priority of the incoming port is used. Changing port priority. By default, all ports are assigned the port priority of zero. By changing the port priority of a port, you can change the priority of the incoming packets on the port. It is recommended that you plan QoS throughout the network before making QoS configuration. Complete the following task to configure priority mapping: 3-5
Task Remarks Configuring a Priority Mapping Table Configuring a Port to Trust Packet Priority for Priority Mapping Changing the Port Priority of an Interface Configuring Priority Mapping Configuring a Priority Mapping Table Follow these steps to configure a priority mapping table: To do... Use the command... Remarks Enter system view system-view Enter priority mapping table view Configure the priority mapping table Display the configuration of the priority mapping table qos map-table { dot11e-lp dot1p-lp dscp-lp lp-dot11e lp-dot1p lp-dscp } import import-value-list export export-value display qos map-table [ dot11e-lp dot1p-lp dscp-lp lp-dot11e lp-dot1p lp-dscp ] Required You can enter the corresponding priority mapping table view as required. Required Newly configured mappings overwrite the previous ones. Available in any view Configuring a Port to Trust Packet Priority for Priority Mapping You can configure the AP to trust a particular priority field carried in packets for priority mapping on ports or globally. When configuring the priority trust mode for a port, you can select the following keywords: dot11e: Uses the 802.11e priority of the received packets for mapping. dot1p: Uses the 802.1p priority of the received packets for mapping. dscp: Uses the DSCP value of the received packets for mapping. Follow these steps to configure the priority trust mode for a port: To do... Use the command... Remarks Enter system view system-view Enter interface view interface interface-type interface-number Configure the priority trust mode qos trust { dot11e dot1p dscp } Required Display the priority trust mode and port priority information of the specified interface or all interfaces display qos trust interface [ interface-type interface-number ] Available in any view 3-6
Changing the Port Priority of an Interface If an interface does not trust any packet priority, the AP uses its port priority to look for the set of priority parameters for the incoming packets. By changing port priority, you can prioritize traffic received on different interfaces. Follow these steps to change the port priority of an interface: To do... Use the command... Remarks Enter system view system-view Enter interface view Set the port priority of the port interface interface-type interface-number qos priority priority-value Required By default, the port priority is 0. Displaying and Maintaining Priority Mapping To do... Use the command... Remarks Display priority mapping table configuration information Display the priority trust mode and port priority of the specified interface or all interfaces display qos map-table [ dot11e-lp dot1p-lp lp-dot11e lp-dot1p ] display qos trust interface [ interface-type interface-number ] Available in any view Available in any view Priority Mapping Configuration Example Network requirements As shown in Figure 3-5: All departments access the Intranet through the same AP. Each department is configured with an independent WLAN name. These departments are assigned to different VLANs based on WLAN-BSS interface. It is required that the AP assigns local precedence to incoming packets by mapping the priority of the receiving port. The default priority mapping table of the AP is used. 3-7
Figure 3-5 Network diagram for priority mapping configuration Eth1/0/2 Eth1/0/3 Host A Switch Eth1/0/1 Host B Eth1/0/1 AP ESS 1( WLAN - BSS 1) ESS 2 ( WLAN - BSS 2 ) Configuration procedure 1) Configure the switch # Create VLAN 2 and VLAN 3. <Switch> system-view [Switch] vlan 2 [Switch-vlan2] port ethernet 1/0/2 [Switch-vlan2] vlan 3 [Switch-vlan3] port ethernet 1/0/3 [Switch-vlan3] quit [Switch] interface ethernet1/0/1 [Switch-Ethernet1/0/1] port link-type trunk [Switch-Ethernet1/0/1] port trunk permit vlan all [Switch-Ethernet1/0/1] quit [Switch] 2) Configure the AP # Enter system view. <AP> system-view # Configure a WLAN network for each of the two departments, with the SSID being PART1 and PART2 respectively. Bind the two WLAN networks to WLAN-BSS 1 and WLAN-BSS 2 respectively. [AP] wlan service-template 1 clear [AP-wlan-st-1] ssid PART1 [AP-wlan-st-1] service-template enable [AP-wlan-st-1]quit # Create interface WLAN-BSS1, and configure its port priority as 5. [AP] interface wlan-bss 1 [AP-WLAN-BSS1] qos priority 5 [AP-WLAN-BSS1] quit [AP] interface wlan-radio 1/0/2 [AP-WLAN-Radio1/0/2] service-template 1 interface WLAN-BSS 1 [AP-wlan-st-1] quit [AP] wlan service-template 2 clear [AP-wlan-st-2] ssid PART2 [AP-wlan-st-2] service-template enable 3-8
[AP-wlan-st-2]quit # Create interface WLAN-BSS2, and configure its port priority as 7. [AP] interface wlan-bss 2 [AP-WLAN-BSS2] qos priority 7 [AP-WLAN-BSS2] quit [AP] interface wlan-radio 1/0/2 [AP-WLAN-Radio1/0/2] service-template 2 interface WLAN-BSS 2 [AP-wlan-st-2] quit # Assign interfaces WLAN-BSS 1 and WLAN-BSS 2 to different VLANs, such as VLAN 2 and VLAN 3 respectively. [AP] vlan 2 [AP-vlan2]quit [AP] interface WLAN-BSS 1 [AP-WLAN-BSS1] port access vlan 2 [AP-WLAN-BSS1] quit [AP] vlan 3 [AP-vlan3]quit [AP] interface WLAN-BSS 2 [AP-WLAN-BSS2]port access vlan 3 [AP-WLAN-BSS2] quit # Configure port Ethernet 1/0/1 to use the 802.1p priority of received packets for priority mapping, and configure port Ethernet 1/0/1 as a trunk port. [AP] interface ethernet 1/0/1 [AP-Ethernet1/0/1] qos trust dot1p [AP-Ethernet1/0/1]port link-type trunk # Assign port Ethernet 1/0/1 to VLAN 1 through VLAN 3. [AP-Ethernet1/0/1] port trunk permit vlan 1 to 3 [AP-Ethernet1/0/1] quit With these configurations completed, when you copy files to Host A and Host B or load files to Host A and Host B through the two wireless users connecting to BSS1 and BSS2 respectively, you will find that the loading rate of the wireless user connecting to BSS2 is faster than the loading rate of the wireless user connecting to BSS1. These configurations just apply to the traffic from the wireless network to the wired network. To regulate the traffic from the wired network to the wireless network, you should make port priority configurations on the involved ports on the switch. 3-9