3com 3031 Instruccion De Instalación
936
C
HAPTER
67: T
RAFFIC
C
LASSIFICATION
, P
OLICING
,
AND
S
HAPING
Traffic policing and traffic shaping is a traffic monitoring policy to restrict the traffic
and resources through comparing with the traffic specification. To know whether
the traffic exceeds the specification or not is a prerequisite for traffic policing or
shaping. Then based upon the evaluation result you can implement a regulation
policy. Usually Token Bucket is used to value the traffic specification.
and resources through comparing with the traffic specification. To know whether
the traffic exceeds the specification or not is a prerequisite for traffic policing or
shaping. Then based upon the evaluation result you can implement a regulation
policy. Usually Token Bucket is used to value the traffic specification.
Traffic Evaluation and
Token Bucket
Token bucket features
Token Bucket can be regarded as a container to reserve Token, which has certain
capacity. The system will put Tokens into the Bucket at a defined rate. In case the
Bucket is full, the extra Tokens will overflow and no more Tokens will be added.
capacity. The system will put Tokens into the Bucket at a defined rate. In case the
Bucket is full, the extra Tokens will overflow and no more Tokens will be added.
Figure 228 Measuring the traffic with Token Bucket
Measuring the traffic with Token Bucket
Whether or not the token quantity of the Token Bucket can satisfy the packets
forwarding is the basis for Token Bucket to measure the traffic specification. If
there are enough tokens available to forward packets, it is called traffic
conforming specification (Generally one token is associated with the forwarding
ability of one bit) otherwise, non-conforming or excess.
forwarding is the basis for Token Bucket to measure the traffic specification. If
there are enough tokens available to forward packets, it is called traffic
conforming specification (Generally one token is associated with the forwarding
ability of one bit) otherwise, non-conforming or excess.
When measuring the traffic with Token Bucket, these parameters are included:
■
Mean rate: The rate of putting Token into Bucket, i.e. average rate of the
permitting traffic. Generally set as CIR (Committed Information Rate).
permitting traffic. Generally set as CIR (Committed Information Rate).
■
Burst size: Token Bucket's capability, i.e. the maximum traffic size of every
burst. Generally, it is set as CBS (Committed Burst Size), and the bursting size
must be greater than the maximum packets size.
burst. Generally, it is set as CBS (Committed Burst Size), and the bursting size
must be greater than the maximum packets size.
A new evaluation will be made when a new packet arrives. If there are enough
tokens in bucket for each evaluation, it shows that traffic is within the bound, and
at this time the amount of tokens appropriate for the packets forwarding rights,
need to be taken out. Otherwise it shows that too many tokens have been used,
and traffic specifications are exceeded.
tokens in bucket for each evaluation, it shows that traffic is within the bound, and
at this time the amount of tokens appropriate for the packets forwarding rights,
need to be taken out. Otherwise it shows that too many tokens have been used,
and traffic specifications are exceeded.
Complicated evaluation
Two Token Buckets can be configured to evaluate more complex conditions and to
implement more flexible regulation policy. For example, Traffic Policing (TP) has
three parameters, as follows:
implement more flexible regulation policy. For example, Traffic Policing (TP) has
three parameters, as follows:
incoming packets
outgoing packets
Token Bucket
Tokens enter bucket
at the given speed
classify
Discarded
packets