H3C S3100-52P Operation Manual page 549

Operation Manual – QoS-QoS Profile
H3C S3100-52P Ethernet Switch
I. Token bucket
The token bucket can be considered as a container with a certain capacity to hold
tokens. The system puts tokens into the bucket at the set rate. When the token bucket
is full, the extra tokens will overflow and the number of tokens in the bucket stops
increasing.
Packets to be sent
through this port
Figure 1-5 Evaluate the traffic with the token bucket
II. Evaluating the traffic with the token bucket
When token bucket is used for traffic evaluation, the number of the tokens in the token
bucket determines the amount of the packets that can be forwarded. If the number of
tokens in the bucket is enough to forward the packets, the traffic is conforming to the
specification; otherwise, the traffic is nonconforming or excess.
Parameters concerning token bucket include:
Average rate: The rate at which tokens are put into the bucket, namely, the
permitted average rate of the traffic. It is generally set to committed information
rate (CIR).
Burst size: The capacity of the token bucket, namely, the maximum traffic size that
is permitted in each burst. It is generally set to committed burst size (CBS). The set
burst size must be greater than the maximum packet length.
One evaluation is performed on each arriving packet. In each evaluation, if the number
of tokens in the bucket is enough, the traffic is conforming to the specification and you
must take away some tokens whose number is corresponding to the packet forwarding
authority; if the number of tokens in the bucket is not enough, it means that too many
tokens have been used and the traffic is excess.
III. Traffic policing
The typical application of traffic policing is to supervise specific traffic into the network
Put tokens in the bucket at the
set rate
Packet
classification
1-11
Chapter 1 QoS Configuration
Continue
to send
Token
bucket
Drop