The various Quality of Service (QoS) parameters in Computer Network are as follows:

1. Cell Loss Rate (CLR)

   It is the fraction of cells that are lost during transmission.

   CLR = Cell Lost / Total cells transmitted

2. Cell Delay Variation (CDV)

   It defines the difference between the maximum and the minimum cell transfer delay.

3. Cell Transfer Delay (CTD)

4. It is the average time required for cell to travel from source to destination.

5. Cell transfer delay is affected by segmentation reassembly and transmission delay.

6. Cell Error Ratio (CER)

   This parameter defines the fraction of cells that contained errors.

   CER = Error cells delivered / Total cells delivered

7. Cell Mis-insertion Ratio (CMR)

   It is the number of cells inserted per second that are meant for some other destination.

8. It is the ratio of severely error cell blocks to the total transmitted cell blocks.

   SECBR = Severely Error Cell Blocks / Total transmitted cell blocks

The factors affecting the QoS parameters are:

• Propagation Delay

• Capacity of Buffer

• Traffic Load

• Allocation of resources

• Architecture of switch present in network

• Media error statistics

The QoS is determined by four parameters:

i. Reliability

ii. Delay

iii. Jitter

iv. Bandwidth

Technique to achieve Good QoS:

i. Over Provisioning: Excess of router capacity, buffer space and bandwidth is provided so that packets fly through easily.

ii. Buffering: It smooths out jitter and does not affect reliability or bandwidth. It increases delay.

iii. Traffic Shaping: It forces bursty traffic to be transmitted at a uniform rate.

iv. Resource Reservation: In this bandwidth, buffer space and CPU cycles needed for successful transmission are reserved beforehand.

v. Admission Control: In this a router decides, depending on its current load, whether it should accept or reject a new job.

vi. Proportional Routing: In this, traffic is divided equally amongst all routers so that no single router gets overburdened.

Packet Scheduling: Queuing is used so that an aggressive sender does not block all the lines.