H3C S7500 Series Ethernet Switches Operation Manual

Operation Manual – QoS
H3C S7500 Series Ethernet Switches Chapter 1
QoS Configuration
1-7
To
buc
Pac
dr
Packet
classifying
ken
ket
kets
ooped
Packets to be sent through
an interface
Packets sent
te
t
Tokens are input into the
token bucket at a given ra
Figure 1-4 Evaluate the traffic with the token bucke
1) Evaluate the traffic with the token bucket
Traffic specification evaluation is based on whether the number of tokens in the bucket
can meet the need of packet forwarding. If the number of tokens in the bucket is enough
to forward the packets (generally, one token is associated with a 1-bit-forwarding
authority), the traffic is conforming to the specification. Otherwise, the traffic is
nonconforming or excess.
When the token bucket evaluates the traffic, its parameter configurations include:
z 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).
z Burst size: The capacity of the token bucket, namely, the maximum permitted size
of every burst traffic. It is generally set to committed burst size (CBS). The set
burst size must be bigger 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 to forward the packet, the packet is conforming to the
specification and you must take away some tokens whose number corresponds to the
packet forwarding authority; if the number of tokens in the bucket is not enough to
forward the packet, it means that too many tokens have been used and the traffic is
excess.
2) Complicated evaluation
You can set two token buckets in order to evaluate traffic in more complicated
conditions and implement more flexible traffic control policies. For example, the
following 4 parameters are set for TP: