• Differentiated Services
  • Assured Service
  • Premium Service [Jacobson ’97]
    		•

    Differentiated Service (DS) Field




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    Differentiated Service (DS) Field

    • Version
    • HLen
    • TOS
    • Length
    • Identification
    • Fragment offset
    • Flags
    • Source address
    • Destination address
    • TTL
    • Protocol
    • Header checksum
    • 0
    • 4
    • 8
    • 16
    • 19
    • 31
    • Data
    • IP
    • header
    • DS Filed
    • 0
    • 5
    • 6
    • 7

    Differentiated Services

    Assured Service [Clark & Wroclawski ‘97]

    • Defined in terms of user profile, how much assured traffic is a user allowed to inject into the network
    • Network: provides a lower loss rate than best-effort
      • In case of congestion best-effort packets are dropped first
    • User: sends no more assured traffic than its profile
      • If it sends more, the excess traffic is converted to best-effort

    Assured Service

    • Large spatial granularity service
    • Theoretically, user profile is defined irrespective of destination
      • All other services we learnt are end-to-end, i.e., we know destination(s) apriori
    • This makes service very useful, but hard to provision (why ?)
    • Ingress
    • Traffic profile

    Premium Service [Jacobson ’97]

    • Provides the abstraction of a virtual pipe between an ingress and an egress router
    • Network: guarantees that premium packets (QoS) are not dropped and they experience low delay
    • User: does not send more than the size of the pipe

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