An Architecture For Differentiated Services

Differentiated Services Architectural Model

Example Diff-Service using Assured forwarding PHB with Traffic Conditioning

• The AF PHB group could be used to implement, for example, the so- called Olympic service, which consists of three service classes: bronze, silver, and gold.
  
  
• Packets are assigned to these three classes so that packets in the gold class experience lighter load (and thus have greater probability for timely forwarding) than packets assigned to the silver class.
  
  
• Packets within each class may be further separated by giving them either low, medium, or high drop precedence
  
  
• The bronze, silver, and gold service classes could in the network be mapped to the AF classes 1, 2, and 3.
  
  
• The drop precedence level of a packet could be assigned,at boundary nodes by using a leaky bucket traffic policer.
  
  
• A packet is assigned low drop precedence if the number of tokens in the bucket is greater than the excess burst size,
  
  
• medium drop precedence if the number of tokens in the bucket is greater than zero, but at most the excess burst size, and
  
  
• high drop precedence if the bucket is empty.