– QoS is Quality of Service
– it’s aims to forward traffic efficiently and perform bandwidth utilization
– QoS used to classify traffic and assign specific priorities and forward the traffic based on priorities
– it helps handling real Time traffic , voice and video efficiently and even data traffic
– QoS works with L2 and L3 frames and packets
– WDM and optical devices L2 cards support Qos protocols
– Qos has 4 processes:
1- classification
2- marking / policing
3- Queing
4- scheduling
– classification means assign forwarding class for each traffic flow depends on types of information carried by packet , we have 8 forwarding class based on importance and type of traffic
– policing means control bandwidth used by each traffic flow, identify whether the income traffic is over , below or within the committed rate
– policing called coloring , we have colors for the packets
1- Red: if the incoming packet bandwidth is greater than the peak Information rate ( in that case we have to discard )
2- Yellow: if the rate of packet is between the peak and committed data rate , in that case we will discard the packet only if congestion occurred
3- Green: if the bandwidth is lower than the committed rate , in that case the packet Forwarded normally
– Queing means put the traffic in it’s specific Queue , FIFO is First in First out , move the packet from ingress to egress Ports
– it’s about how to order packets into the egress buffer memory
– scheduling means select the SLA ( service Level agreement ) for each packet , we have different schedulers types as below
1- strict priority
2- round robin
3- weighted round robin
4- weighted deficit round robin
