Quality of service models:
Best-effort service
Integrated services
Differentiated services
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Best-effort service model:
Internet was initially based on a best-effort packet delivery service. Best-effort is the default mode for all traffic. There is no differentiation among types of traffic.Best-effort model is similar to using standard mail service – it will get there when it gets there.
Advantages of best-effort service model:
Highly scalable
No special mechanisms required
Disadvantages of best-effort service model:
No service guarantees
No service differentiation
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Integrated services (intserv model) are a QOS model that is older than QOS / Differentiated services model. Intserv model defines a signaling process by which an individual flow can request that the network reserve the bandwidth and delay needed for the flow.Integrated services model uses RSVP for reserving bandwidth. RSVP is stand for resource reservation protocol. RSVP is used for reserving bandwidth/QOS tools for a particular flow.Here is limitation of intserv model if reserved no other traffic can use it and it is no scalable each flow required separate admin configuration on router.
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Differentiated services model is designed to overcome the limitation of best-effort and intserv models. In diffserv model network traffic is identified by classes and network QOS policy enforces differentiated treatment of traffic classes. You choose the level of service for each class.
Advantages of Differentiated service model:
Highly scalable
Many level of quality possible
Disadvantages of Differentiated service model:
No absolute service guarantee
Complex mechanisms
