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User Manual - Configuration Guide (Volume 3)
Versatile Routing Platform
Chapter 2
Traffic Classification and Policing
2-1
Chapter 2 Traffic Classification and Policing
2.1 Traffic Classification and Policing
2.1.1 Introduction to Traffic Classification
Packets can be classified into multiple types of different precedence levels and
services. For example, the user can sort IP packets into 6 types (2 types reserved for
other purposes) according to the ToS (Type of Service) field in IP header. After the
classification, other QoS features, such as congestion management and bandwidth
distribution can be applied to different types.
Network administrator can set the classification policy, which includes physical
interface, source address, destination address, MAC address, IP protocol and the port
number of the application program. Common classification algorithms are limited to IP
packet header, link layer, network layer and transport layer. The content of packet is
rarely used as classification criterion. The range of the classification result is not limited.
The result can be the flow defined by a quin-tuple (source address, source port number,
protocol code, destination address and destination port number), or all the packets in a
network segment.
When classifying packets on network vorder, ToS field in IP header should be set as the
IP precedence which will be used as classification criterion within the network. Queuing
techniques such as WFQ can also handle the packets according to IP precedence. The
classification feature of CAR in QoS can be used to classify the traffic.
Downstream network can select and receive the classification result from Upstream
network or reclassify the traffic according to its own criterion.
I. IP Precedence
The user can specify the service type of the packet with 3 precedence-identifying bits of
ToS field in the IP header. These bits can be used in other features configured in the
network to handle the packets according to the committed services. For example, other
queuing methods such as WFQ can sort the priority order of the traffic according to the
set IP precedence, though IP precedence is not a queuing method.
II. CAR (Committed Access Rate)
CAR is the main feature to support packet classification. CAR performs classification
by using the ToS field in IP header. The user can use CAR classification command to
classify or reclassify the packets.
The following examples show the packet classification rules:
z
The packets received via all the interfaces are set to the highest precedence.
z All the HTTP traffic is classified to medium-level precedence (application
classification).
z
Video traffic from specified IP address is classified to medium-level precedence.
z Traffic to the specified destination address is classified to high-level precedence.