Traffic shaping
- Traffic shaping, also known as packet shaping, is a network management technique that delays certain types of packets to optimize overall network performance.
- Traffic shaping reduces congestion and thus helps the carrier live up to its guarantees.
- Traffic shaping is about regulating the average rate (and burstiness) of data transmission
- Traffic shaping controls the rate at which packets are sent (not just how many).
- Traffic shaping is about regulating the average rate (and burstiness) of data transmission
Two traffic shaping algorithms are:
- Leaky Bucket Algorithm.
- Token Bucket Algorithm.
The Leaky Bucket Algorithm
- The Leaky Bucket Algorithm used to control the data flow rate in a network. It is implemented as a single-server queue with constant service time. If the bucket (buffer) overflows then packets are discarded.
- Leaky bucket is a bucket with a hole at bottom. Flow of the water from bucket is at a constant rate which is independent of water entering the bucket. If bucket is full, any additional water entering in the bucket is thrown out.
- Same technique is applied to control congestion in network traffic.Every host in the network is having a buffer with finite queue length.
- Packets which are put in the buffer is full are thrown away..\
- The buffer may drain onto the subnet either by some number of packets per unit time,or by some total number of bytes per unit time.
- A FIFO queue is used for holding the packets.
- If the arriving packets are of fixed size,then the process removes a fixed number of packets from the queue at each tick of the clock.
- If the arriving packets are of different size,then the fixed output rate will not be based on the number of departing packets.
Flow rate
- If packets are transmitted in unregulated flow, the router holds the packet and transmits the packet in regulated flow.
- In Leaky Bucket algorithm, router applies a constant output rate regardless of the input flow rate. In networks, packets can arrive faster than router flow rate, cause bucket overflow and packets are dropped.
- The bucket size is important in controlling buffer overflow and reducing maximum number of packets dropped. With small bucket size, number of packets dropped increases. With large bucket size, number of packets dropped decreases.
- Adjustable bucket size, allows the router to release packets into the network according to the burstiness of the network.
