In this article we discuss about the applications
of the leaky bucket algorithm and the token bucket algorithm.
Applications of Leaky Bucket Algorithm
- The leaky bucket algorithm is implemented in
different versions.
- For example, the generic cell rate algorithm is a version
of this algorithm which is often implemented in the networks using ATM
(asynchronous transfer mode).
- The
algorithm is applied at the user interfaces in the usage/network parameter
control in order to provide protection to the network from the problems of congestive
collapse or excess traffic.
- An algorithm equivalent to the generic cell rate
algorithm might be used in shaping the transmissions made by the network
interface card to a network using ATM.
There are two major applications of the
leaky bucket algorithm.
- The first is using it as a counter only for checking
whether the events or the traffics confirm to the defined limits or not.
- Whenever a packet arrives at the check point, the counter is incremented.
- This
is same as adding water to the bucket in an intermittent way.
- In the same way, the counter is decremented as the water leaks out at a constant rate.
- Because
of this, the conformance of the packet to the burstiness and bandwidth limits
is indicated by the value of this counter whenever a packet arrives.
- Or if an
event occurs, the counter checks whether it confirms to the peak and average
rate limits.
- So, when the packets arrive or an event occurs, water is added to
the bucket and then leaks out. We call this version of the leaky bucket
algorithm as a meter.
- Another application of the leaky bucket algorithm
involves its use as queue implemented for controlling the flow of traffic.
- This
queue maintains a direct control over the flow.
- When the packets arrive, they
are put in to the queue.
- This is same as adding water to the bucket.
- The
packets are then removed in the order they arrived at a constant rate.
- This is
same as water leaking out.
- As a result of this, there is no jitter or burstiness
in the traffic flow.
Applications of Token Bucket Algorithm
- The token bucket algorithm finds its application in
the telecommunications and packet switched computer networks.
- This algorithm is
implemented for checking whether the data transmissions confirm to the
burstiness and bandwidth predefined limits.
- The token bucket algorithm used in
traffic policing and traffic shaping.
- In the former, the packets that are non-conformant are discarded or assigned low priorities.
- This is done for the
management of the downstream traffic.
- On the other hand, the packets are kept
in delay unless they are conformed in traffic shaping.
- Both of these are used
in protecting the network against the burstiness of the traffic.
- Bursty traffic
gives rise to congestion problems.
- These algorithms help in managing the
bandwidth as well congestion of the network.
- Network interfaces commonly use
the traffic shaping process for preventing the discarding of the transmissions by
the network’s traffic management functions.
- This algorithm is based up on the
analogy of a bucket with fixed capacity.
- Tokens are added to this bucket at a
fixed rate and represent a single packet of a fixed size.
- When the packet has
to be checked whether it confirms to the predefined limits or not, first the
bucket is checked if it contains sufficient tokens.
- If sufficient tokens are
there, tokens equal to the number of bytes in the packet are removed and the
packet is transmitted.
- If sufficient tokens are not there, the packet is said
to be non-conformant and the number of tokens in the bucket remain unchanged.
