IP Encyclopedia > Traffic policy

What Is a Traffic Policy?

Traffic policy technology is a network traffic management mechanism. A traffic policy classifies packets with the same characteristics into a class and provides the same service for these packets. By configuring traffic policies, you can define traffic classification rules to separately process the traffic matching the rules, reducing the loss caused by network congestion.

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Why Do We Need Traffic Policies?

In daily life, traffic rules are used to classify vehicles and specify the behavior that each type of vehicle needs to comply with to relieve traffic congestion and improve vehicle passing efficiency. For example, a vehicle that turns right must drive on the right, and a vehicle that is on duty can pass first and quickly. These are typical traffic rules. In telecommunications, traffic policy technology is a network traffic management mechanism and belongs to modular quality of service (QoS) command line interface (MQC) in QoS technologies. Traffic policies can be regarded as traffic rules for network traffic. Traffic policies can maintain the traffic transmission order without increasing network bandwidth consumption, effectively relieve network congestion, and safeguard real-time network services.

Traffic rule for vehicle classification and vehicle behavior regulation

The implementation of a traffic policy for network traffic is similar to that of a traffic rule for vehicles. The traffic classification function is used to classify traffic, and then the traffic behavior function is used to customize the behavior to be complied with for each type of traffic. For example, traffic can be classified based on service priority. Traffic of a high-priority service is transmitted first, and traffic of a low-priority service is transmitted later. In this way, the traffic transmission efficiency on the network is maximized.

Traffic policy for traffic classifier and traffic behavior defining

How Is a Traffic Policy Implemented?

To implement a traffic policy, perform the following steps:

Configure a traffic classifier. The prerequisite for effective traffic management is to identify traffic. You can define a group of traffic matching rules to sort out the traffic to be managed. This process is called traffic classification.
Configure a traffic behavior to provide different services for traffic. A service can be defined in the traffic behavior. For example, to provide the VIP service for a certain type of important traffic, you can re-mark the priority of the corresponding packets and assign the highest priority to the packets in the traffic behavior.
Configure a traffic policy, and bind the traffic classifier and traffic behavior to the traffic policy.
Apply the traffic policy in the corresponding view as required.

Implementing a traffic policy

Traffic Classifier

To create a traffic classifier, specify the following:

Name of the traffic classifier, which is bound to a traffic behavior. You can run the traffic classifier command to create a traffic classifier.

Traffic classification rules in the traffic classifier. You can run the if-match command to create a traffic classification rule. The device supports various traffic classification rules, including link-layer rules (Layer 2 rules), network-layer rules (Layer 3 rules), and ACL rules. The following table describes common traffic classification rules.

Table 1-1 Common traffic classification rules

Traffic Classification Rule	Matching Rule
Link-layer rule (Layer 2 rule)	MAC address, VLAN ID, and 802.1p priority
Network-layer rule (Layer 3 rule)	DSCP priority and IP precedence
ACL rule	ACL

Multiple matching rules can be defined in a traffic classifier, and the logical relationships between them can be AND or OR.

OR: A packet matches a traffic classifier as long as it matches any rule in the traffic classifier.
AND: If a traffic classifier contains ACL rules, a packet matches the traffic classifier only when it matches one ACL rule and all the non-ACL rules. If a traffic classifier does not contain any ACL rules, a packet matches the traffic classifier only when it matches all the rules in the traffic classifier.

For example, to create a traffic classification rule for identifying packets with VLAN ID 120, run the following commands:

Step 1  traffic classifier c1   // Create a traffic classifier named c1.
Step 2  if-match vlan-id 120   // Create a rule for identifying packets with VLAN ID 120 in traffic classifier c1.

Traffic Behavior

To create a traffic behavior, specify the following:

Name of the traffic behavior, which is bound to a traffic classifier. You can run the traffic behavior command to create a traffic behavior.

Actions in the traffic behavior. The purpose of classifying packets through traffic classifiers is to provide different services for different types of packets. Different services need to be defined through traffic behaviors. One or more actions can be defined in a traffic behavior. The following table describes common actions in traffic behaviors.

Table 1-2 Common actions in traffic behaviors

Action in a Traffic Behavior	Description
Packet filtering	The device determines whether to discard or forward packets based on traffic classification results.
Packet re-marking	The device re-marks the priority of packets matching traffic classification rules. Packets of services that are sensitive to delay and service quality can be re-marked with a high priority so that they can be preferentially scheduled or forwarded.
Packet redirection or policy-based routing	The device redirects packets matching traffic classification rules to the specified location for processing.
Traffic statistics collection	The device collects statistics on the number of packets and bytes in packets matching traffic classification rules, which facilitates fault diagnosis and troubleshooting.
Traffic policing	The device controls the traffic rate within a bandwidth limit and discards excess traffic when the traffic rate exceeds the limit.

For example, to create a traffic behavior to perform traffic policing for a certain type of packets, limit the rate to 4096 kbit/s, and collect traffic statistics, run the following commands:

Step 1  traffic behavior b1   // Create a traffic behavior named b1.
Step 2  car cir 4096   // Configure a traffic policing rule in traffic behavior b1.
Step 3  statistics enable   // Enable traffic statistics collection in traffic behavior b1.

Traffic Policy

The previously configured traffic classifier and traffic behavior are independent and must be associated with each other. A traffic policy binds them and the actions defined in the traffic behavior are taken on packets of specific types. Multiple pairs of traffic classifiers and traffic behaviors can be bound to a traffic policy.

Binding multiple pairs of traffic classifiers and traffic behaviors to a traffic policy

For example, to bind traffic classifier c1 to traffic behavior b1, run the following commands:

Step 1  traffic policy p1   // Create a traffic policy named p1.
Step 2  classifier c1 behavior b1   // Bind traffic classifier c1 to traffic behavior b1.

Applying a Traffic Policy

After a traffic policy is configured, determine whether the service traffic to be controlled by the traffic policy passes through a physical interface, a VLAN, a VLANIF interface, the system, or a card, and then apply the traffic policy in the corresponding view.

For example, to apply traffic policy p1 to the VLAN view to implement the traffic policy for packets entering the VLAN, run the following commands:

Step 1  vlan 10   // Enter the view of VLAN 10.
Step 2  traffic-policy p1 inbound   // Apply the traffic policy to the inbound direction of VLAN 10.

Typical Application of a Traffic Policy

As shown in the figure, voice, video, and data services are transmitted on a network. When a large amount of service traffic enters the network, congestion may occur due to insufficient bandwidth. Different bandwidth guarantees must be provided for the voice, video, and data services in descending order of priority. Voice, video, and data services are transmitted in VLAN 120, VLAN 110, and VLAN 100, respectively. A traffic policy can be configured to implement traffic policing and packet re-marking. Voice packets are provided with the maximum bandwidth and highest priority to ensure that voice packets are preferentially forwarded, video packets are provided with the medium bandwidth and medium priority, and data packets are provided with the minimum bandwidth and lowest priority. In addition, Device2 connected to the uplink interface of Device1 processes packets based on their priorities, ensuring the quality of various services.

Using a traffic policy to process different service traffic

The configuration roadmap is as follows:

Configure traffic classifiers on Device1 to classify voice, video, and data packets based on VLAN IDs.
Configure traffic behaviors on Device1 to perform traffic policing and re-mark priorities of different service flows.
Bind the configured traffic behaviors and traffic classifiers to a traffic policy and apply the traffic policy to the inbound direction of Device1.

Step 1 Configure a traffic classifier. traffic classifier c1 // Create a traffic classifier named c1. if-match vlan-id 120 // Create a rule for identifying packets with VLAN ID 120 in traffic classifier c1 to identify voice traffic. traffic classifier c2 // Create a traffic classifier named c2. if-match vlan-id 110 // Create a rule for identifying packets with VLAN ID 110 in traffic classifier c2 to identify video traffic. traffic classifier c3 // Create a traffic classifier named c3. if-match vlan-id 100 // Create a rule for identifying packets with VLAN ID 100 in traffic classifier c3 to identify data traffic. Step 2 Configure a traffic behavior. traffic behavior b1 // Create a traffic behavior named b1. car cir 3000 // Provide the highest bandwidth. remark 8021p 6 // Set the highest priority. traffic behavior b2 // Create a traffic behavior named b2. car cir 2000 // Provide medium bandwidth. remark 8021p 4 // Set a medium priority. traffic behavior b3 // Create a traffic behavior named b3. car cir 1000 // Provide the lowest bandwidth. remark 8021p 2 // Set the lowest priority. Step 3 Configure a traffic policy. traffic policy p1 // Create a traffic policy named p1. classifier c1 behavior b1 // Bind traffic classifier c1 to traffic behavior b1. classifier c2 behavior b2 // Bind traffic classifier c2 to traffic behavior b2. classifier c3 behavior b3 // Bind traffic classifier c3 to traffic behavior b3. Step 4 Apply the traffic policy. traffic-policy p1 inbound // Apply the traffic policy to the inbound interface of Device1.

References

1MQC Configuration Guide (CloudEngine S Series Switches)

2MQC Configuration Guide (CloudEngine Data Center Switches)

3MQC Configuration Guide (NetEngine AR Routers)

4MQC Configuration Guide (HiSecEngine USG Series Firewalls)

5MQC Configuration Guide (AirEngine WAC)