The integrated service (IntServ) model is a multiple-service model that can accommodate diverse QoS requirements. This service model 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 RSVP. All nodes receiving 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 all nodes along the transmission path to maintain resource state information for each flow. This model is suitable for small-sized or edge networks. However, it is not suitable for large-sized networks, for example, the core layer of the Internet, where billions of flows are present.

DiffServ model

The differentiated service (DiffServ) model is a multiple-service model that can meet diverse QoS requirements. It is easy to implement and extend. DiffServ does not signal the network to reserve resources before sending data, as IntServ does.

QoS techniques in a network

The QoS techniques include the following features:

· Traffic classification.

· Traffic policing.

The following section briefly introduces these QoS techniques.

All QoS techniques in this document are based on the DiffServ model.

Figure 1 Position of the QoS techniques in a network

As shown in Figure 1, traffic classification and traffic policing mainly implement the following functions:

· Traffic classification—Uses match criteria to assign packets with the same characteristics to a traffic class. Based on traffic classes, you can provide differentiated services.

· Traffic policing—Polices flows and imposes penalties to prevent aggressive use of network resources. You can apply traffic policing to both incoming and outgoing traffic of a port.

QoS processing flow in a device

Figure 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 can configure traffic policing for incoming traffic.

Figure 2 QoS processing flow

Configuring a QoS policy

About QoS policies

A QoS policy has the following components:

· Traffic class—Defines criteria to match packets.

· Traffic behavior—Defines QoS actions to take on matching packets.

By associating a traffic class with a traffic behavior, a QoS policy can perform the QoS actions on matching packets.

A QoS policy can have multiple class-behavior associations.

QoS policy tasks at a glance

To configure a QoS policy, perform the following tasks:

1. Defining a traffic class

2. Defining a traffic behavior

3. Defining a QoS policy

4. Applying the QoS policy

¡ Applying the QoS policy to an interface

¡ Applying the QoS policy to VLANs

¡ Applying the QoS policy to a user profile

5. (Optional.) Setting the QoS policy-based traffic rate statistics collection period for an interface

Defining a traffic class

1. Enter system view.

system-view

2. Create a traffic class and enter traffic class view.

traffic classifier classifier-name [ operator { and | or } ]

3. Configure a match criterion.

if-match [ not ] match-criteria

By default, no match criterion is configured.

For more information, see the if-match command in ACL and QoS Command Reference.

Defining a traffic behavior

1. Enter system view.

system-view

2. Create a traffic behavior and enter traffic behavior view.

traffic behavior behavior-name

3. Configure an action in the traffic behavior.

By default, no action is configured for a traffic behavior.

For more information about configuring an action, see the subsequent chapters for traffic policing, traffic filtering, priority marking, class-based accounting, and so on.

Defining a QoS policy

1. Enter system view.

system-view

2. Create a QoS policy and enter QoS policy view.

qos policy policy-name

3. Associate a traffic class with a traffic behavior to create a class-behavior association in the QoS policy.

classifier classifier-name behavior behavior-name [ insert-before before-classifier-name ]

By default, a traffic class is not associated with a traffic behavior.

Repeat this step to create more class-behavior associations.

Applying the QoS policy

Application destinations

You can apply a QoS policy to the following destinations:

· Interface—The QoS policy can be applied to the traffic sent or received on an interface.

· VLAN—The QoS policy can be applied to the traffic sent or received on all ports in the VLAN.

· User profile—The QoS policy can be applied to the traffic sent or received by the online users of the user profile.

Restrictions and guidelines for applying a QoS policy

You can modify traffic classes, traffic behaviors, and class-behavior associations in a QoS policy even after it is applied (except that it is applied to a user profile). If a traffic class uses an ACL for traffic classification, you can delete or modify the ACL.

If an action in a traffic behavior cannot take effect, all other actions in the traffic behavior do not take effect.

Applying the QoS policy to an interface

Restrictions and guidelines

A QoS policy can be applied to multiple interfaces. However, only one QoS policy can be applied to one direction (inbound or outbound) of an interface.

The QoS policy applied to the outgoing traffic on an interface does not regulate local packets. Local packets refer to critical protocol packets sent by the local system for operation maintenance. The most common local packets include link maintenance, RIP, LDP, and SSH packets.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Apply the QoS policy to the interface.

qos apply policy policy-name { inbound | outbound }

By default, no QoS policy is applied to an interface.

Applying the QoS policy to VLANs

About this task

You can apply a QoS policy to VLANs to regulate the traffic on all ports of the VLANs.

Restrictions and guidelines

QoS policies cannot be applied to dynamic VLANs, including VLANs created by GVRP.

Procedure

1. Enter system view.

system-view

2. Apply the QoS policy to VLANs.

qos vlan-policy policy-name vlan vlan-id-list { inbound | outbound }

By default, no QoS policy is applied to a VLAN.

Applying the QoS policy to a user profile

About this task

Restrictions and guidelines

You can apply a QoS policy to multiple user profiles. In one direction of each user profile, only one policy can be applied. To modify a QoS policy already applied to a direction, first remove the applied QoS policy.

Procedure

1. Enter system view.

system-view

2. Enter user profile view.

user-profile profile-name

3. Apply the QoS policy to the user profile.

qos apply policy policy-name { inbound | outbound }

By default, no QoS policy is applied to a user profile.

Parameter	Description
inbound	Applies a QoS policy to the incoming traffic (traffic received by the device from online users).
outbound	Applies a QoS policy to the outgoing traffic (traffic sent by the device to online users).

Setting the QoS policy-based traffic rate statistics collection period for an interface

About this task

You can enable collection of per-class traffic statistics over a period of time, including the average forwarding rate and drop rate. For example, if you set the statistics collection period to n minutes, the system performs the following operations:

· Collects traffic statistics for the most recent n minutes.

· Refreshes the statistics every n/5 minutes.

You can use the display qos policy interface command to view the collected traffic rate statistics.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Set the traffic rate statistics collection period for the interface.

qos flow-interval interval

The default setting is 5 minutes.

Display and maintenance commands for QoS policies

Execute display commands in any view and reset commands in user view.

Task	Command
Display QoS policy configuration.	display qos policy { system-defined \| user-defined } [ policy-name [ classifier classifier-name ] ]
Display information about QoS policies applied to interfaces.	display qos policy interface [ interface-type interface-number ] [ inbound \| outbound ]
Display information about QoS policies applied to user profiles.	display qos policy user-profile [ name profile-name ] [ user-id user-id ] [ inbound \| outbound ]
Display information about QoS policies applied to VLANs.	display qos vlan-policy { name policy-name \| vlan [ vlan-id ] } [ inbound \| outbound ]
Display traffic behavior configuration.	display traffic behavior { system-defined \| user-defined } [ behavior-name ]
Display traffic class configuration.	display traffic classifier { system-defined \| user-defined } [ classifier-name ]
Clear the statistics of the QoS policy applied in a certain direction of a VLAN.	reset qos vlan-policy [ vlan vlan-id ] [ inbound \| outbound ]

Configuring priority mapping

About priority mapping

When a packet arrives, a device assigns a set of QoS priority parameters to the packet based on either of the following:

· A priority field carried in the packet.

· The port priority of the incoming port.

This process is called priority mapping. During this process, the device can modify the priority of the packet according to the priority mapping rules. The set of QoS priority parameters decides the scheduling priority and forwarding priority of the packet.

Priority mapping is implemented with priority maps and involves the following priorities:

· 802.11e priority.

· 802.1p priority.

· DSCP.

· EXP.

· IP precedence.

· Local precedence.

· Drop priority.

About priorities

Priorities include the following types: priorities carried in packets, and priorities locally assigned for scheduling only.

Packet-carried priorities include 802.1p priority, DSCP precedence, IP precedence, and EXP. These priorities have global significance and affect the forwarding priority of packets across the network. For more information about these priorities, see "Appendix C Introduction to packet precedence."

Locally assigned priorities only have local significance. They are assigned by the device only for scheduling. These priorities include the local precedence, drop priority, and user priority, as follows:

· Local precedence—Used for queuing. A local precedence value corresponds to an output queue. A packet with higher local precedence is assigned to a higher priority output queue to be preferentially scheduled.

· Drop priority—Used for making packet drop decisions. Packets with the highest drop priority are dropped preferentially.

· User priority—Precedence that the device automatically extracts from a priority field of the packet according to its forwarding path. It is a parameter for determining the scheduling priority and forwarding priority of the packet. The user priority represents the following items:

¡ The 802.1p priority for Layer 2 packets.

¡ The IP precedence for Layer 3 packets.

¡ The EXP for MPLS packets.

Priority maps

The device provides various types of priority maps. By looking through a priority map, the device decides which priority value to assign to a packet for subsequent packet processing.

The default priority maps (as shown in Appendix B Default priority maps) are available for priority mapping. They are adequate in most cases. If a default priority map cannot meet your requirements, you can modify the priority map as required.

Priority mapping configuration methods

You can configure priority mapping by using any of the following methods:

· Configuring priority trust mode—In this method, you can configure a port to look up a trusted priority type (802.1p, for example) in incoming packets in the priority maps. Then, the system maps the trusted priority to the target priority types and values.

· Changing port priority—If no packet priority is trusted, the port priority of the incoming port is used. By changing the port priority of a port, you change the priority of the incoming packets on the port.

Priority mapping process

On receiving an Ethernet packet on a port, the switch marks the scheduling priorities (local precedence and drop precedence) for the Ethernet packet. This procedure is done according to the priority trust mode of the receiving port and the 802.1Q tagging status of the packet, as shown in Figure 3.

Figure 3 Priority mapping process for an Ethernet packet

Priority mapping tasks at a glance

To configure priority mapping, perform the following tasks:

1. (Optional.) Configuring a priority map

2. Configuring a priority mapping method:

¡ Configuring a port to trust packet priority for priority mapping

¡ Changing the port priority of an interface

Configuring a priority map

1. Enter system view.

system-view

2. Enter priority map view.

qos map-table { dot11e-lp | dot1p-lp | dscp-lp | lp-dot11e | lp-dot1p | lp-dscp }

3. Configure mappings for the priority map.

import import-value-list export export-value

By default, the default priority maps are used. For more information, see "Appendix B Default priority maps."

If you execute this command multiple times, the most recent configuration takes effect.

Configuring a port to trust packet priority for priority mapping

About this task

You can configure the device to trust a particular priority field carried in packets for priority mapping on ports or globally. When you configure the trusted packet priority type on an interface, use the following available keywords:

· dot1p—Uses the 802.1p priority of received packets for mapping.

· dscp—Uses the DSCP precedence of received IP packets for mapping.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure the trusted packet priority type.

qos trust { dot1p | dscp } [ override ]

By default, an interface does not trust any packet priority and uses the port priority as the 802.1p priority for mapping.

If the override keyword is configured, the priority derived through priority mapping overwrites the original priority carried in the packet.

4. Return to system view.

quit

Changing the port priority of an interface

About this task

If an interface does not trust any packet priority, the device uses its port priority to look for priority parameters for the incoming packets. By changing port priority, you can prioritize traffic received on different interfaces.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Set the port priority of the interface.

qos priority priority-value

The default setting is 0.

Display and maintenance commands for priority mapping

Execute display commands in any view.

Task	Command
Display priority map configuration.	display qos map-table [ dot11e-lp \| dot1p-lp \| dscp-lp \| lp-dot11e \| lp-dot1p \| lp-dscp ]
Display the trusted packet priority type on a port.	display qos trust interface [ interface-type interface-number ]

Configuring traffic policing

About traffic policing

Traffic limit helps assign network resources (including bandwidth) and increase network performance. For example, you can configure a flow to use only the resources committed to it in a certain time range. This avoids network congestion caused by burst traffic.

Traffic policing, Generic Traffic Shaping (GTS), and rate limit control the traffic rate and resource usage according to traffic specifications. You can use token buckets for evaluating traffic specifications.

Traffic evaluation and token buckets

Token bucket features

A token bucket is analogous to a container that holds a certain number of tokens. Each token represents a certain forwarding capacity. The system puts tokens into the bucket at a constant rate. When the token bucket is full, the extra tokens cause the token bucket to overflow.

Evaluating traffic with the token bucket

A token bucket mechanism evaluates traffic by looking at the number of tokens in the bucket. If the number of tokens in the bucket is enough for forwarding the packets:

· The traffic conforms to the specification (called conforming traffic).

· The corresponding tokens are taken away from the bucket.

Otherwise, the traffic does not conform to the specification (called excess traffic).

A token bucket has the following configurable parameters:

· Mean rate at which tokens are put into the bucket, which is the permitted average rate of traffic. It is usually set to the committed information rate (CIR).

· Burst size or the capacity of the token bucket. It is the maximum traffic size permitted in each burst. It is usually set to the committed burst size (CBS). The set burst size must be greater than the maximum packet size.

Each arriving packet is evaluated.

Complicated evaluation

You can set two token buckets, bucket C and bucket E, to evaluate traffic in a more complicated environment and achieve more policing flexibility. The following are main mechanisms used for complicated evaluation:

· Single rate two color—Uses one token bucket and the following parameters:

¡ CIR—Rate at which tokens are put into bucket C. It sets the average packet transmission or forwarding rate allowed by bucket C.

¡ CBS—Size of bucket C, which specifies the transient burst of traffic that bucket C can forward.

When a packet arrives, the following rules apply:

¡ If bucket C has enough tokens to forward the packet, the packet is colored green.

¡ Otherwise, the packet is colored red.

· Single rate three color—Uses two token buckets and the following parameters:

¡ CIR—Rate at which tokens are put into bucket C. It sets the average packet transmission or forwarding rate allowed by bucket C.

¡ CBS—Size of bucket C, which specifies the transient burst of traffic that bucket C can forward.

¡ EBS—Size of bucket E minus size of bucket C, which specifies the transient burst of traffic that bucket E can forward. The EBS cannot be 0. The size of E bucket is the sum of the CBS and EBS.

When a packet arrives, the following rules apply:

¡ If bucket C has enough tokens, the packet is colored green.

¡ If bucket C does not have enough tokens but bucket E has enough tokens, the packet is colored yellow.

¡ If neither bucket C nor bucket E has sufficient tokens, the packet is colored red.

· Two rate three color—Uses two token buckets and the following parameters:

¡ CIR—Rate at which tokens are put into bucket C. It sets the average packet transmission or forwarding rate allowed by bucket C.

¡ CBS—Size of bucket C, which specifies the transient burst of traffic that bucket C can forward.

¡ PIR—Rate at which tokens are put into bucket E, which specifies the average packet transmission or forwarding rate allowed by bucket E.

¡ EBS—Size of bucket E, which specifies the transient burst of traffic that bucket E can forward.

When a packet arrives, the following rules apply:

¡ If bucket C has enough tokens, the packet is colored green.

¡ If bucket C does not have enough tokens but bucket E has enough tokens, the packet is colored yellow.

¡ If neither bucket C nor bucket E has sufficient tokens, the packet is colored red.

Traffic policing

A typical application of traffic policing is to supervise the specification of traffic entering a network and limit it within a reasonable range. Another application is to "discipline" the extra traffic to prevent aggressive use of network resources by an application. For example, you can limit bandwidth for HTTP packets to less than 50% of the total. If the traffic of a session exceeds the limit, traffic policing can drop the packets or set the precedence of the packets. Figure 4 shows an example of policing outbound traffic on an interface.

Figure 4 Traffic policing

Traffic policing can classify the policed traffic and take predefined policing actions on each packet depending on the evaluation result:

· Forwarding the packet.

· Dropping the packet.

· Forwarding the packet with its precedence re-marked.

Configuring traffic policing

Configuring CAR-list-based traffic policing

1. Enter system view.

system-view

2. Configure a CAR list.

qos carl carl-index { dscp dscp-list | mac mac-address | mpls-exp mpls-exp-value | precedence precedence-value | { destination-ip-address | source-ip-address } { range start-ip-address to end-ip-address | subnet ip-address mask-length } [ per-address [ shared-bandwidth ] ] }

3. Enter interface view.

interface interface-type interface-number

4. Apply a CAR-list-based CAR policy to the interface.

¡ In absolute value:

qos car { inbound | outbound } carl carl-index cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } carl carl-index cir committed-information-rate [ cbs committed-burst-size ] pir peak-information-rate [ ebs excess-burst-size ] [ green action | red action | yellow action ] *

¡ In percentage:

qos car { inbound | outbound } carl carl-index percent cir cir-percent [ cbs cbs-time [ ebs ebs-time ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } carl carl-index percent cir cir-percent [ cbs cbs-time ] pir pir-percent [ ebs ebs-time ] [ green action | red action | yellow action ] *

By default, no CAR policy is applied to an interface.

Configuring ACL-based traffic policing

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure an ACL-based CAR policy on the interface.

¡ In absolute value:

qos car { inbound | outbound } acl [ ipv6 ] acl-number cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } acl [ ipv6 ] acl-number cir committed-information-rate [ cbs committed-burst-size ] pir peak-information-rate [ ebs excess-burst-size ] [ green action | red action | yellow action ] *

¡ In percentage:

qos car { inbound | outbound } acl [ ipv6 ] acl-number percent cir cir-percent [ cbs cbs-time [ ebs ebs-time ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } acl [ ipv6 ] acl-number percent cir cir-percent [ cbs cbs-time ] pir pir-percent [ ebs ebs-time ] [ green action | red action | yellow action ] *

By default, no CAR policy is configured on an interface.

Configuring traffic policing for all traffic

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure a CAR policy for all traffic on the interface.

¡ In absolute value:

qos car { inbound | outbound } any cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } any cir committed-information-rate [ cbs committed-burst-size ] pir peak-information-rate [ ebs excess-burst-size ] [ green action | red action | yellow action ] *

¡ In percentage:

qos car { inbound | outbound } any percent cir cir-percent [ cbs cbs-time [ ebs ebs-time ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } any percent cir cir-percent [ cbs cbs-time ] pir pir-percent [ ebs ebs-time ] [ green action | red action | yellow action ] *

By default, no CAR policy is configured on an interface.

Configuring traffic policing for a user profile

About this task

When a user profile is configured, you can perform traffic policing based on users. After a user passes authentication, the authentication server sends the name of the user profile associated with the user to the device. When any user of the user profile logs in, the authentication server automatically applies the CAR parameters configured for the user profile to the user. When the user logs off, the system automatically removes the CAR configuration without manual intervention.

Procedure

1. Enter system view.

system-view

2. Enter user profile view.

user-profile profile-name

3. Configure a CAR policy for the user profile.

qos car { inbound | outbound } any cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ]

qos car { inbound | outbound } any cir committed-information-rate [ cbs committed-burst-size ] pir peak-information-rate [ ebs excess-burst-size ]

By default, no CAR policy is configured for a user profile.

Display and maintenance commands for traffic policing

Execute display commands in any view.

Task	Command
Display CAR configuration and statistics on an interface.	display qos car interface [ interface-type interface-number ]
Display CAR list information.	display qos carl [ carl-index ]
Display traffic behavior configuration.	display traffic behavior user-defined [ behavior-name ]

‌

Configuring global CAR

About global CAR

Global committed access rate (CAR) is an approach to policing traffic flows globally. It adds flexibility to common CAR where traffic policing is performed only on a per-traffic class or per-interface basis. In this approach, CAR actions are created in system view and each can be used to police multiple traffic flows as a whole.

Global CAR provides the following CAR actions: aggregate CAR and hierarchical CAR. Only aggregate CAR is supported in the current software version.

Aggregate CAR

An aggregate CAR action is created globally. It can be directly applied to interfaces or used in the traffic behaviors associated with different traffic classes to police multiple traffic flows as a whole. The total rate of the traffic flows must conform to the traffic policing specifications set in the aggregate CAR action.

Configuring aggregate CAR

1. Enter system view.

system-view

2. Configure an aggregate CAR action.

qos car car-name aggregative cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ green action | red action | yellow action ] *

qos car car-name aggregative cir committed-information-rate [ cbs committed-burst-size ] pir peak-information-rate [ ebs excess-burst-size ] [ green action | red action | yellow action ] *

By default, no aggregate CAR action is configured.

3. Enter interface view.

interface interface-type interface-number

4. Apply the aggregate CAR action to the interface.

qos car { inbound | outbound } { any | acl [ ipv6 ] acl-number } name car-name

By default, no aggregate CAR action is applied to an interface.

Display and maintenance commands for global CAR

Execute display commands in any view and reset commands in user view.

Task	Command
Display statistics for global CAR actions.	display qos car name [ car-name ]
Clear statistics for global CAR actions.	reset qos car name [ car-name ]

Appendixes

Appendix A Acronyms

Table 1 Appendix A Acronyms

Acronym	Full spelling
AF	Assured Forwarding
BE	Best Effort
BQ	Bandwidth Queuing
CAR	Committed Access Rate
CBS	Committed Burst Size
CBQ	Class Based Queuing
CE	Congestion Experienced
CIR	Committed Information Rate
CQ	Custom Queuing
DCBX	Data Center Bridging Exchange Protocol
DiffServ	Differentiated Service
DSCP	Differentiated Services Code Point
EBS	Excess Burst Size
ECN	Explicit Congestion Notification
EF	Expedited Forwarding
FIFO	First in First out
FQ	Fair Queuing
GMB	Guaranteed Minimum Bandwidth
GTS	Generic Traffic Shaping
IntServ	Integrated Service
ISP	Internet Service Provider
LLQ	Low Latency Queuing
LSP	Label Switched Path
MPLS	Multiprotocol Label Switching
PE	Provider Edge
PIR	Peak Information Rate
PQ	Priority Queuing
PW	Pseudowire
QoS	Quality of Service
QPPB	QoS Policy Propagation Through the Border Gateway Protocol
RED	Random Early Detection
RSVP	Resource Reservation Protocol
RTP	Real-Time Transport Protocol
SP	Strict Priority
ToS	Type of Service
VoIP	Voice over IP
VPN	Virtual Private Network
WFQ	Weighted Fair Queuing
WRED	Weighted Random Early Detection
WRR	Weighted Round Robin

Appendix B Default priority maps

Table 2 Default dot1p-lp priority map

dot1p	lp
0	2
1	0
2	1
3	3
4	4
5	5
6	6
7	7

‌

Table 3 Default dot11e-lp priority map

dot11e	lp
0	2
1	0
2	1
3	3
4	4
5	5
6	6
7	7

Table 4 Default dscp-lp priority map

dscp	lp
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

‌

Table 5 Default lp-dot1p, lp-dot11e, and lp-dscp priority maps

Input priority value	lp-dot1p map	lp-dot11e map	lp-dscp map
lp	dot1p	dot11e	dscp
0	1	1	0
1	2	2	8
2	0	0	16
3	3	3	24
4	4	4	32
5	5	5	40
6	6	6	48
7	7	7	56

‌

Appendix C Introduction to packet precedence

IP precedence and DSCP values

Figure 5 ToS and DS fields

As shown in Figure 5, the ToS field in the IP header contains 8 bits. The first 3 bits (0 to 2) represent IP precedence from 0 to 7. According to RFC 2474, the ToS field is redefined as the differentiated services (DS) field. A DSCP value is represented by the first 6 bits (0 to 5) of the DS field and is in the range 0 to 63. The remaining 2 bits (6 and 7) are reserved.

Table 6 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

Table 7 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. It applies to occasions where Layer 3 header analysis is not needed and QoS must be assured at Layer 2.

Figure 6 An Ethernet frame with an 802.1Q tag header

As shown in Figure 6, the 4-byte 802.1Q tag header contains the 2-byte tag protocol identifier (TPID) and the 2-byte tag control information (TCI). The value of the TPID is 0x8100. Figure 7 shows the format of the 802.1Q tag header. The Priority field in the 802.1Q tag header is called 802.1p priority, because its use is defined in IEEE 802.1p. Table 8 shows the values for 802.1p priority.

Figure 7 802.1Q tag header

Table 8 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. The 3-bit QoS control field represents the 802.11e priority in the range of 0 to 7.

Figure 8 802.11e frame structure

EXP values

The EXP field is in MPLS labels for MPLS QoS purposes. As shown in Figure 9, the EXP field is 3-bit long and is in the range of 0 to 7.

Figure 9 MPLS label structure

15-QoS Configuration Guide

QoS techniques in a network

Defining a traffic class

Defining a traffic behavior

Defining a QoS policy

Restrictions and guidelines

Procedure

Applying the QoS policy to VLANs

About this task

Restrictions and guidelines

Procedure

Applying the QoS policy to a user profile

About this task

Restrictions and guidelines

Procedure

About this task

Procedure

Priority mapping process

Priority mapping tasks at a glance

Configuring a priority map

Procedure

About this task

Procedure

Traffic evaluation and token buckets

Token bucket features

Evaluating traffic with the token bucket

Complicated evaluation

Configuring traffic policing

Configuring CAR-list-based traffic policing

Configuring ACL-based traffic policing

Configuring traffic policing for a user profile

About this task

Procedure

Configuring aggregate CAR

Appendixes

Appendix A Acronyms

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