3Com Router User Manual

48
TRAFFIC POLICING, TRAFFIC SHAPING 
AND LINE RATE
Traffic Classification 
Overview Traffic classification means classifying packets into multiple priority levels or 
multiple service types according to the ToS (Type of Service) of IPv4 packet header. 
The other two values are reserved for other uses. After the packets are classified, 
QoS will be applied to different classifications respectively.
The network administrator sets the packet classification rules which define the 
specific flow according to...

668CHAPTER 48: TRAFFIC POLICING, TRAFFIC SHAPING AND LINE RATE
■Dropping directly — CAR drops the packets that do not conform to the 
traffic specifications.
■Forwarding after modifying the packet priority level — The packets with the 
estimated result of partial conformance are forwarded after they are marked 
as the lower priority level flows.
■Entering the next level of policing — Traffic policing may be stacked level by 
level, and each level concerns and polices more specific targets. A downstream...

Committed Access Rate (CAR)669
does not have sufficient tokens, it is considered “out of conformance”. 
“Conformance” indicates that the traffic does not exceed the limit--at this 
time, the number of tokens that correspond to the conformance limit can be 
used and “nonconformance” indicates that the number of tokens that are 
being used is beyond the specification.
■Burst size: Indicates the capacity of the token bucket. It is usually set to 
committed burst size (CBS) which is the allowable maximum...

670CHAPTER 48: TRAFFIC POLICING, TRAFFIC SHAPING AND LINE RATE
■Destination IP address
■Destination MAC address
■Application port
■IP protocol type
■Other standards that may be identified through the access list and extended 
access list. 
The packets can also be classified based on the external conditions of the network. 
For example, the client types may classify the packets. After the packet is 
classified, the user can apply the ACL or CARL on a specified interface and set the 
corresponding actions...

Committed Access Rate (CAR)671
By default, no CAR rule of ACL list is established.
For the same carl-index, only one CAR rule can be defined. The later defined CAR 
rule will overwrite the earlier CAR rule. However, multiple CAR rules with different 
carl-index may be defined.
Before the CAR rule is configured, fast forwarding must be disabled.
Applying the CAR Policy on the Interface
The CAR policy can take effect on the incoming and outgoing directions of the 
interface. For the packets conforming to...

672CHAPTER 48: TRAFFIC POLICING, TRAFFIC SHAPING AND LINE RATE
Displaying and Debugging CAR
Ta b l e 713   Display and Debug CAR
CAR Configuration 
ExamplesApplying a CAR Policy to all Packets
■The CAR policy is applied to all the packets that are input to router A 
Ethernet0, directly forwarding the packets that meet the conditions and 
dropping the packets that do not meet the conditions.
■The CAR policy is applied to all the packets that are output from router A 
Ethernet1, directly forwarding the...

Committed Access Rate (CAR)673
Figure 212   Networking diagram of configuring the priority level based CAR policy
1Configure Router A:
The CAR policy is applied to the packet inputted to router A serial interface 0 and 
matching priority level 1.
[RouterA]  qos carl 1 precedence 1
[RouterA]acl 1
[RouterA-acl-1]rule permit source 10.0.0.0 0.0.0.255
[RouterA-acl-1]interface serial 0
[RouterA-Serial0] ip address 10.0.0.1 255.255.255.0
[RouterA-Serial0] qos car inbound acl 1 cir 8000 cbs 15000 ebs 8000...

674CHAPTER 48: TRAFFIC POLICING, TRAFFIC SHAPING AND LINE RATE
Apply a CAR Policy on the Packets that Match ACL
■The CAR policy is applied to the packet that is input to router A serial interface 
0 and that matches the specific ACL rule, directly forwarding the packet that 
meets the conditions and dropping the packet that does not meet the 
conditions.
■The CAR policy is applied to the packet that is output from router A serial 
interface 0 and that matches the specific ACL rule, directly forwarding...

Traffic Shaping675
Figure 215   Schematic diagram of GTS processing
If an interface does not use the rule defined by rule to classify the packet, the 
interface has only one queue. If GTS uses the rule defined by rule to classify the 
packet, it maintains a separate queue for every type of flow. In every interface, 
GTS can select either of the following two methods:
■Processing all the flows of the interface: At this time, if the sending queue of 
this interface is empty, and the traffic of the packets...

676CHAPTER 48: TRAFFIC POLICING, TRAFFIC SHAPING AND LINE RATE
Ta b l e 714   Configure Shaping Parameters for a Specified Flow
By default, the traffic shaping is not performed on the interface.
This command may be repeatedly used to set different shaping parameters for 
different flows.
This command cannot be used together with the qos gts any command in the 
same interface.
Configuring shaping parameters for all flows
Shaping all the flows means shaping all the flows passing this interface.
Please...